platinum metals review - Johnson Matthey Technology Review

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UK ISSN 0032-1400
PLATINUM METALS REVIEW
A quarterly survey of research on the platinum metals and of
developments in their application in industry
VOL. 28
JULY 1984
NO. 3
Contents
Some Novel Electronic Effects in Hydrogenation Catalysis
Glassy Alloys Containing Platinum Group Metals
Monitoring Thermocouple Usage
The Published Platinum Metal Alloy Systems
The Catalytic Etching of Platinum and Rhodium-Platinum Gauzes
Palladium-Nickel Plating
Combustion in Wood-Burning Stoves
Osmium Doping Improves Recording Media
Electrodeposition of Palladium-Silver Alloys from Ammoniacal Electrolytes
A History of Thermal Analysis
Nineteenth Century Platinum Coins
Abstracts
New Patents
Communications should be addressed to
The Editor, Platinum Metals Review
Johnson Matthey Public Limited Company, Hatton Garden, London E C l N 8EE
Some Novel Electronic Effects
in Hydrogenation Catalysis
T H E SIGNIFICANCE OF ACIDITY AND REDOX POTENTIAL
By J. W. Jenkins
Johnson Matthey Group Research Centre
Recent work at the Johnson Matthey Research Centre has thrown fresh
light upon the electronic effects in hydrogenation catalysis that
underlie the whole nature 0.f the catalytic act and in particular many o,f
the effects that may manifest themselves as support metal interactions. The results show that currently accepted mod& o,f the catalytic
act are incomplete, that ionic intermediates are sometimes important
and that both the relative acidity 0.f the reaction system and thp redox
potential of products and intermediates must be considered.
In the two most commonly accepted models
for a hydrogenation reaction, one or both of the
reactants are adsorbed on the surface, then
reaction takes place and the product desorbs.
These models are referred to as Eley-Rideal and
Langmuir-Hinshelwood
mechanisms,
respectively. Such models frequently give an
excellent representation of experimental results,
but the parameter values so obtained cannot be
confidently extrapolated in a quantitative
manner from one reaction system to another.
In the Eley-Rideal
and LangmuirHinshelwood models two types of parameter are
important: adsorption coefficients representing
the stabilities of the surface intermediates, and
reaction rate constants representing the
reactivity of the adsorbed intermediates.
Naturally, one expects that these parameters
are not uniquely determinable, but are in fact
related, which is to say that the reactivity is in
part influenced by the strength of adsorption.
Thus, for example, in a recent international
symposium on support-metal interactions ( I ) it
was shown (2) that the ratio of adsorption
coefficients for toluene and benzene derived
from competitive hydrogenation via a
Langmuir-Hinshelwood mechanism varied
markedly with the apparent electronic state of
the catalytic metal species when this was varied
by changing the catalyst support or by using
Platinum Metals Rev., 1984, 28, (3), 98-106
ammonia or hydrogen sulphide as catalyst
modifiers. The changes in relative overall
reactivity of these two reactants were, however,
much smaller than expected since the increases
in relative adsorptivity were offset by reduced
relative reactivity.
Similar problems arise in the understanding
of the all-important effects of alloying in
bimetallic catalyst systems and the effects of
metal dispersion on reactivity and selectivity.
In studying catalytic hydrogenation reactions
we are accustomed to using the terms,
“hydrogenation”
and
“reduction”
synonymously. However, in electro-organic
chemistry and other branches of chemistry
“reduction”, is given a more limited definition
as meaning the addition of electrons to a substrate. In such a context hydrogenation involving the addition of a molecule of hydrogen
becomes instead the addition of two electrons
and two protons. Such additions can in
principle be either sequential or in combination.
As a result of the considerations outlined
above, we have studied a number of hydrogenation reactions in which the sequential addition
of electrons and protons could be observed. In
electro-organic chemistry, reactions of this type
are customarily investigated by cyclic
voltammetry in which the potential of the
working electrode is controlled and changed
98
systematically. We chose instead to use a
powdered carbon supported hydrogenation
catalyst as our working electrode and to lower
the reduction potential by the addition of
hydrogen. These changes in the reduction
potential of the reacting system are monitored
by an inert gold sensor electrode operated in
conjunction with a silver/silver chloride
reference electrode. The experimental technique is very similar to that developed by Russian
workers (3, 4) although the way we have used
this technique differs in many other aspects, as
will become apparent later.
Experimental Conditions
Hydrogenations were performed in an
aqueous liquid phase system at ambient
temperature and atmospheric pressure. The
three necked 500ml reaction flask was fitted
with a standard glass electrode, a silver/silver
chloride reference electrode and a gold wire
sensor electrode to follow the potential of the
catalyst. The hydrogen was sparged in at a rate
of too mumin and vented through a bubbler
acting as a gas seal. The reaction flask contents
were stirred by a magnetic stirrer at 600 rpm.
Typically, 0.1 g 1 0 per cent palladium on
carbon catalyst was used. Under these conditions the reactions studied are under gas mass
transfer control where the rate is independent
of the weight of catalyst used. Such conditions
would normally apply in commercial applications of these catalysts. The reaction flask contents were buffered with appropriate combinations of sulphuric acid, acetic acid, sodium
bicarbonate or sodium hydroxide. Standard
phosphate (pH 7), citrate (pH 5.7) and borax
(pH 9) buffers were also used.
In operation we customarily first reduced the
slurried catalyst and equilibrated the reaction
system. The measured redox potential at
equilibrium in general was in good agreement
with the reversible hydrogen potential for that
particular reaction pH. T o this equilibrated
system we then added a known amount of the
substance to be hydrogenated and followed the
change in redox potential with time. Typically,
upon adding the reactant the potential
Platinum Metals Rev., 1984, 28, ( 3 )
99
immediately rose and then began to fall at a
decreasing rate. Eventually, however, the
potential falls at an increasing rate and then
very rapidly back to the original hydrogen
equilibrium potential. The net result is a reduction wave whose half wave potential we can
measure and the total time taken to complete a
reduction can also be measured.
Results and Discussion
Q u i n o n e Hydrogenatinn
Our interest in the quinone hydrogenation
system was two-fold. First, different quinones
have known and well-defined half-wave reduction potentials that are reversible and rapidly
established. Figure I shows the variation in
redox potential with time when a mixture of
various quinones was added to the palladium
catalysed reaction system at pH 7. Several
reduction waves are observed which correspond
to the known half wave reduction potentials of
the different quinones injected. The figure also
shows the reversible nature of these reductions
in that a mirror image is obtained if, at the
completion of the hydrogenation, the oxidation
potential is increased by adding air. It is
important to note that the reduction of a
particular quinone does not commence until all
those with a higher potential have been completely hydrogenated. That is to say, the reduction is under complete control of the reduction
potential of the system. Similar results have
been reported recently in the commercially
important hydrogenation of ethyl anthraquinone which is an intermediate in the
manufacture of hydrogen peroxide ( 5 ) . Here it
was found, in a competitive hydrogenation
experiment using both tetrahydro-2-ethylanthraquinone and 2-ethyl-anthraquinone, that
the former was completely hydrogenated before
the latter began to be hydrogenated in line with
their relative redox potentials. Perhaps an even
more dramatic illustration of redox potential
control is shown in Figure 2. In this series of
experiments we first hydrogenated a known
amount of anthraquinone and to this reaction
mixture then added varying amounts of
benzoquinone. If less than an equivalent
stoichiometric amount of benzoquinone was
added, the only result seen was a rehydrogenation of the anthraquinone. If greater than a
stoichiometric amount of benzoquinone was
added, then reduction waves of both the excess
benzoquinone and the stoichiometric quantity
of anthraquinone produced by the dehydrogenation of anthrahydroquinone are seen.
Our second interest in the quinone system
was in finding out what would happen at a high
pH when hydroquinone, which is a weak acid
(pK, 10.35), dissociates to give an anion and at
even a higher pH a di-anion. Thus:
0
ti
0
0-
Q
0
0
0
H
0-
H
100
If, therefore, we “hydrogenate”
quinone at a high pH we might
form the di-anion by simple
electron transfer without incurring the necessary kinetic
penalty of having to add
molecular hydrogen.
That this is indeed the case is
1
Scheme I
Electrochemical Possibilities for
Quinone Hydrogenation
-
Electron addition
Proton Q
Qaddition
QH+
(QH)'
QH-
QH2'+
QH2
I
(QH2)'
mediates involved to be pH dependent, a low
pH favouring a possible cationic, and a high pH
an anionic intermediate. Furthermore, in the
presence of an active palladium hydrogenation
catalyst we have the following equilibration (6)
H + + e- = HA,)
Q'
suggesting that the electronic potential is
inversely related to the acidity or proton concentration.
Thus variations in the palladium catalysed
hydrogenation rate shown for benzoquinone in
Figure 3 are interpreted as shown in Scheme 2 .
indicated by the results shown in Figure 3. Here
we see the variation in reduction time at
various pH values. It will be recalled that since
we are under hydrogen mass transfer control,
we should have expected that changing the pH
would not have changed the reduction time.
The marked changes observed and in particular
the very high rates at the higher pH show that
the reaction is apparently under electron
transfer control. Adding acid upon the completion of reaction at the high pH gave no further
reaction, showing that indeed reduction was
completed much faster at the high pH under
this electron transfer control. We are therefore
proposing that the hydrogenation of quinone is
better represented in the nomenclature of
electro-organic chemistry, as shown in Scheme
I , in which the possible intermediates include
radical anions and radical cations in addition to
the normally assumed half hydrogenated
neutral radical (QH)'.
One aspect of such a scheme is that we might
expect the reaction mechanism and inter-
Nitrobenzene Hydrogenation
The quinone hydrogenation results discussed
above represent a somewhat special case
because these hydrogenations are reversible and
can yield ionic products. Of more general
interest are irreversible hydrogenations, of
which nitrobenzene hydrogenation is an
example having commercial significance. Since
nitrobenzene is only slightly soluble in water,
these experiments were performed in a 50 per
cent CHJOH/water solvent.
Very pronounced and well defined reduction
waves were obtained upon injection of the
nitrobenzene substrate, as shown in Figure 4.
However, there was little variation in this case
in hydrogenation time, as the pH was changed;
but there were marked changes in the potential
shift of the half wave reduction potential. These
results are best summarised in a potential/pH
plot, as shown in Figure 5.
The first point of interest in Figure 5 is that
the observed half wave potentials are much less
Scheme 2
Effect of Acidity on Quinone Hydrogenation Rate
o
< pH < 3
Hydrogenation is increasingly facilitated by electron transfer
3
< pH < 9
Hydrogenation is increasingly restricted by proton transfer
pH
>9
Hydrogenation is no longer limited by proton transfer but is increasingly
facilitated by electron transfer
101
intermediate pH range 3 to 7 the slope is
-59mV and this in turn corresponds to an
intermediate to which equal numbers of protons
and electrons have been added. Again, in the
formalism of Scheme I , this corresponds to a
neutral free radical or to a species commonly
assumed to represent the half hydrogenated
state. At yet higher pHs above pH 7, the slope
again changes to only -29 mV which
corresponds to the addition of two electrons
for every proton and the anion of Scheme I .
We thus see that in the case of nitrobenzene
hydrogenation, even though the rate of reaction
did not markedly change with pH as in the case
of the benzoquinone, we would seem to have
than the reversible hydrogenation potential.
This can be calculated thermodynamically from
the known change in thermodynamic free
energy as being +826 mV relative to the
reversible potential for I atmosphere hydrogen
using the Nernst expression:
AG = -nF AE
the inference being that these well defined
half wave potentials represent hydrogenation intermediates formed reversibly on the
surface of the catalyst. Of particular interest,
however, are the relative changes in these half
wave potentials as the pH changes as given by
the slopes of the curves shown in Figure 5. At
a low pH, below about three, this slope
approximates to - I I 8 mV, which is what we
should expect from a species formed by the
addition of two protons for each electron. In
the Scheme I presented earlier, such an intermediate corresponds to a radical cation. In the
102
clear evidence of the existence of both anionic
and cationic charged reaction intermediates.
This could affect reaction selectivity, stereochemistry or poison sensitivity of the catalyst.
H y d r o g e n a t i o n of 2-butyne-1,4-diol
T h e palladium catalysed hydrogenation of
butyne-diol is of interest because it proceeds in
two quite clearly defined sequential stages. The
butyne-diol is first selectively hydrogenated to
butenediol and this hydrogenation is virtually
complete before the butene-diol is then
hydrogenated to the butane-diol. This selectivity
is generally ascribed to the much stronger
absorption of the butynediol relative to the
butene-diol with the consequence that the
butenediol intermediate hydrogenation product
is desorbed and virtually excluded from the
catalyst surface. We were curious to see
whether a case might be made for this
selectivity being due to redox potential control,
much in the way as we saw earlier is the case in
the selective hydrogenation of the different
quinones. The reversible redox potential for the
first step of this reaction (est. 625 mV) is considerably higher than for the second (430mV).
Our results are shown in Figures 6, 7 and 8.
In all cases two sequential reduction waves are
clearly in evidence and we can determine both
103
the reduction half wave potentials (Figure 7)
and the reduction times (Figure 8) for each
sequential stage. In all cases, however, the
reductions are irreversible and the half wave
potentials considerably less than those
corresponding to the reversible reaction.
Somewhat surprisingly, we note that the
reduction half wave potential is higher at a low
pH for the second stage of reaction than for the
first. We are not able, therefore, to invoke a
simple explanation of relative redox potentials
to explain the reaction selectivity as we did for
the quinone hydrogenation. The difference
between the two systems lies in the reversibility
of the quinone hydrogenation in contrast to the
irreversibility of the butyne and butene-diol
hydrogenation.
As we discussed earlier in the case of
nitrobenzene hydrogenation, we can obtain
some information on the nature of the surface
intermediates from a consideration of the slope
of the curves of redox potential versus pH.
When we do this (Figure 7) we find that the half
wave reduction potentials for butyne-diol
parallel the hydrogen curve over the whole pH
range, indicating that the active intermediate is
an orthodox half hydrogenated neutral radical
species. For the triple bond hydrogenation we
might speculate that this could be some form of
ally1 radical. Neutral alkyl radicals are also
indicated for butene-diol hydrogenation at a
high pH. Under acidic conditions (pH < 7),
however, the slope increases and again a radical
cation is suggested as becoming the surface
intermediate. We shall return to this point later.
At a high pH the half wave potential for formation of the allylic surface radical is higher than
Selective Lead Poisoning o f a Palladium Catalys~
0.4 g 5% Pd/C paste
Normal acetic acid (DH 2.3)
Half wave potential
mV R.H.E.
Reduction time
minutes
Lead added
0.2 g 2-butyne-1 ,4-diol
Concentration
x 1O5 moles
Pb : Pd mole
ratio
0
0
14
11
+145
+195
1.o
0.06
17
16
+140
+165
2.0
0.12
20
24
+125
+110
2.7
0.1 6
25
70
+90
+30
3.0
0.18
34
>180
+60
+20
C',
+
c,-
c,=
104
+
co
,
C',
+
c,o
-
that for the alkyl surface radical, that is to say
the former is more stable in line with what we
might expect from a consideration of the relative free radical stabilities.
The reduction times for the different reduction stages are correlated in Figure 8. Although
for a given pH the alkene hydrogenation is in
all cases more rapid than that for the alkyne,
the relative difference changes with pH. In
particular we note that the rates in both cases
go through a maximum (that is reduction times
are a minimum) as the pH is varied, but that
the optimum pH for alkyne hydrogenation is
lower than that for alkene hydrogenation. Such
maxima in the rate are implicit in our Scheme
I , given the relative promoting effects of proton
and electron concentration and the inverse
relationship between them.
Effect of Lead Poisoning on Palladium
Catalyst Selectivity
In catalysts of the Lindlar type, lead acetate
is used to selectively poison a palladium
catalyst. Such a poisoned catalyst may still be
effective for hydrogenating triple bonds and yet
is ineffective for hydrogenating double bonds.
We were therefore interested in studying the
effect of lead addition to our palladium
catalysed butyne-diol hydrogenation system.
The lead was added as a very dilute solution of
lead nitrate to the reduced catalyst slurry. We
found no apparent effect of these modest lead
additions either at a low or a high pH. In the
pH range 2 to 5, however, marked effects were
observed, as shown in the Table. Although the
addition of lead decreased the half wave reduction potentials and increased the time taken for
reduction for both the first and second stages of
the butyne-diol reduction, the effect on the
butenediol hydrogenation was much greater. So
much so, in fact, that with the addition of 0.I 8
moles lead per mole palladium reduction was
not completed within the three hour duration
of the experiment.
The lead poisoning of a palladium catalyst
is generally assumed to be due to an alloy
containing metallic lead on the palladium
surface. However, in o u r conditions
(pH 2.3 [Pb’’]
I O - ~ Mthe
) redox potential for
metallic lead formation at - I 50 mV relative to
the reversible hydrogenation potential is considerably more cathodic than we can achieve in
our reaction system. It only becomes zero at or
above pH 5 (7). Indeed we ascribe the absence
of a poisoning effect above pH 5 to deposition
of metallic lead and conversely the selective
poisoning of the palladium surface to the
adsorption of a divalent lead cation.
Remembering that, as we showed earlier, the
surface intermediate in butenediol hydrogenation is a cationic species under these low pH
conditions we conclude that it is the more
favourable adsorption of the dicationic lead ion
that poisons the sites normally active in
forming the monocationic butene-diol
hydrogenation intermediate. The relative
reductions in the stabilities of these intermediates are reflected in the relative reductions
in their half wave redox potentials.
Conclusions
It has been our purpose in this article to
indicate the effectiveness of the electrochemical
technique when applied to a real working
catalytic system. We think it is important to
recognise the distinction that must be made
between electronic reduction and hydrogenation even in the case of simple double bond
saturation reactions. We have stressed comparative studies of compounds having different
redox potentials and studies made under
different acidity conditions. Although these
conditions are relatively easy to specify in liquid
phase hydrogenation systems, we believe that
the same parameters apply in gas phase
hydrogenation reactions and that if we are to
understand properly support-metal interactions
both the acidity and redox potential of the
whole catalytic system must be taken into
account. Our results indicate that in some conditions ionically charged reaction intermediates
occur on the catalyst surface and that at least in
the case of a lead poisoned palladium catalyst
this has been invoked to explain the observed
selective poisoning of the mono olefin
hydrogenation reaction.
105
The ability to quantify the free energy of
formation of the surface reaction intermediates
by means of the half wave reduction potential
presents us with a powerful tool for comparing
catalysts of different metals and the effects of
alloying and multimetallic composite catalysts.
Finally, there is much useful background
information in this area contained in a recent
review (8) and in the results obtained by
Russian workers who originated and developed
the electrochemical tichnique that has been
publicised by D. V. Sokolskii (3, 4). Particularly
we would refer the reader to the latter for information on how different metals affect the half
wave reduction potential and for some of the
linear free energy correlations between half
wave reduction potentials and activation energy
on the one hand and the effects of electrophilic
benzene substituents in hydrogenation substrates on the other.
References
“Studies in Surface Science and Catalysis; I I .
Metal-Support and Metal-Additive Effects in
Catalysis”, ed. B. Imelik et al., Elsevier,
Amsterdam, 1982
Tran Mahn Tri, J. Massardier, P. Gallezot and B.
Imelik, ibid., pp. 141-148
D. V. Sokolskii, “Hydrogenation in Solutions”,
Akademii Nauk Kazahkskoi SSR, Alma-Ata I 962,
translated by the Israel Program of Scientific
Translations, Jerusalem, I 964
‘Catalysis. Heterogeneous and Homogeneous”, ed.
B. Delmon and G. Jannes, Elsevier, Amsterdam,
I
1975
T. Berglin and N.-H. Schoon, Ind. Eng. Chem.,
ProcessDes. Dew., 1983, Z Z , ( I )150-153
,
F. Beck, Ber. Bunsenges Phys. Chem., 1965,69, (3),
I 99-206
7 M. Pourbaix, “Atlas of ElectrochemicalEquilibria
in Aqueous Solutions”, Pergamon, Oxford, I 966
8 M. D. Birkett, A. T. Kuhn and G. C. Bond,
“Catalysis, Volume 6”, a Specialist Periodical
Report, Royal Society of Chemistry, 1983, pp.
61-89
Glassy Alloys Containing Platinum Group Metals
Amorphous Metallic Alloys, EDITED BY F. E. LUBORSKY
Butterworth & Co. (Publishers) Limited, London, 1983, 534 pages, E35
Amorphous metallic alloys have great
scientific and technological importance in the
field of materials science. The above-named
book, one of the Butterworth’s Monographs in
Materials series, brings together much of our
basic knowledge and understanding of the
atomic, electronic and structural behaviour of
such materials with emphasis on magnetic,
superconducting, thermal and chemical
properties and techniques of production.
In the section dealing with chemical
properties of amorphous metallic systems, a
series of palladium-phosphorus alloys are
mentioned which have been specifically designed as anode materials for the electrolysis of
sodium chloride solutions. These materials have
shown high catalytic activity for chlorine evolution with low activity for oxygen evolution
while maintaining good corrosion resistance in
the hot aqueous environment. Surface-activated
amorphous palladium-phosphorus alloys for use
as fuel cell electrodes are also described where it
has been observed that these systems show
higher catalytic activity for the oxidation of
methanol and its derivatives than either
platinised
platinum or surface-activated
crystalline palladium.
Refractory metal-metalloid superconducting
glasses, particularly those of molybdenumruthenium-phosphorus
and molybdenumrhodium-phosphorus, show unusually high
transition temperatures compared with their
crystalline counterparts which is in contrast to
normally expected behaviour. In the readily
formed glass systems of the early transition-late
transition alloys where the late transition metal
is one of the platinum group elements, eutectic
temperatures are generally high (> I 5ooOC).
However, with devitrification temperatures in
excess of 725°C it is surprising that few systems
have been investigated; those reported include
5s niobium-45 iridium and 55 tantalum-45
rhodium.
The book contains references to 193
amorphous metallic alloys of which 39 involve
one or mort of the platinum group metals. It is
evident, however, that glassy alloys which
contain a platinum group metal are still at the
level of scientific interest with few systems
being examined for technological application.
With the knowledge that a great deal of work
is continuing in this field, our increasing
understanding of amorphous alloy behaviour
I.R.M.
should lead to novel products.
106
Monitoring Thermocouple Usage
NEW DEVICE INDICATES WHEN RE-CALIBRATION REQIJIRKI)
The precise control of temperature during
manufacturing processes has assumed an
increased importance in recent years.
Particularly within the semiconductor industry,
this has arisen as more complex devices and
higher product yields have been sought. For
example, during the processing of silicon wafers
the stages of diffusion and epitaxial growth are
carried out under very strictly controlled conditions. Diffusion furnaces used during these
stages require not only accurate control to
within narrow limits, but also the maintenance
of temperature profiles. In the past, the
measurement of profiles was carried out using
single junction thermocouples, although the use
of multi-junction assemblies is increasing and
more recently such assemblies are being used
for direct furnace control.
To achieve the precise control of
temperatures, noble metal thermocouples are
generally employed because of the accuracy to
which they can be calibrated and their stability
in service. While both these factors are
important, stability presents users with the
greater imponderable. Calibrations can be
carried out to high degrees of accuracy in
laboratories approved by the British Calibration
Service, such as the Calibration Laboratory of
Johnson Matthey Metals Limited, where
standards are traceable to those of the National
Physical Laboratory. The stability of thermocouples, on the other hand, is relative, as all
thermocouple types are subject to drift during
use as shown in Figure I and therefore require
re-calibration from time to time.
In the past obtaining a reliable guide to the
need for re-calibration has proved difficult, not
only because the rate of drift is dependent upon
the environment, although this variable can be
much reduced by the use of a suitable sheath,
but also because of the problems associated with
monitoring temperatures and lengths of time of
thermocouple usage. Such problems have led
the operators of processes depending upon
precise temperature control to adopt one of two
practices. Either thermocouple usage is
monitored continuously by sampling the
temperature at frequent intervals under computer control and processing this information to
give an estimate of accumulated drift, or
thermocouples are re-calibrated or replaced at
pre-set intervals of time. The first approach is
expensive and requires an extensive knowledge
of drift characteristics under conditions of time
and temperature, while the second is somewhat
arbitrary.
To help overcome the problems of deciding
when to re-calibrate thermocouples, Johnson
107
:I
750'C
++
f
+
+
+ +
+
t
-31
-6.
4+*
+
Fig. 1 The drift characteristics of
platinum versus 10 per cent rhodiumplatinum thermocouples in air at
temperatures of 750 and 1000°C.The
points represent individual calibrations
and the blue lines are a least squarcs f i t
Fig. 2 The DeltaLog drvicv, shown fitied t o
a modified Lemo connector or a :$-junction
profiling thermocouple, is battery driven and
eompletrly self contained
Matthey Metals have developed a small
electronic device named DeltaLog which can
form an integral part of their range of quartz
sheathed multi-junction thermocouples. Housed
within the end connector, the device monitors
the time and temperature of thermocouple
usage and indicates when re-calibration is
necessary.
The indicator consists of a small dot within a
glass tube which moves along an adjacent scale
at a rate determined by the temperature of
usage. When the dot has reached full scale
deflection, thermocouple re-calibration is
recommended.
A DeltaLog device fitted to a modified Lemo
connector of a 3-junction profiling thermocouple is shown in Figure 2. It is completely
self contained, being driven by a battery
inserted into the device immediately prior to
despatch, giving an active life of approximately
one year. Thermocouples returned to the
Calibration Labratory of Johnson Matthey
Metals Limited are checked and re-calibrated
while the DeltaLog indicator is re-set to zero
and a new battery inserted in preparation for
R.A. B.
further use.
Acknowledgement
Deltalog is a Trademark of Johnson Matthey,
registration and patents have been applied for.
The Published Platinum Metal Alloy Systems
Phase Diagrams of Precious Metal Alloys, COMPILED BY H E CHUNXIAO, MA GUANGCHEN,
WANG WENNA, WANG YONGLI AND ZHAO HUAIZHI, The Metallurgical Industry Press, People’s
Republic of China, I 983, 301 pages, U.S. $6.66
Knowledge is of only limited value to society
unless it is accessible to all those who can
understand and make use of it; indeed it was to
make information on the fundamental
properties and industrial applications of the
platinum group metals more readily available
that Platinum Meials Review was founded by
Johnson Matthey in 1957.Since that time many
studies of these metals have been made but,
unfortunately, much of the established data still
remains widely, and inconveniently, dispersed
throughout the literature.
T o overcome this difficulty in a particularly
important area of materials science a group of
colleagues under the guidance of Professor Tan
Qinglin, Director of the Institute of Precious
Metals, at Kunming in the People’s Republic of
China, has collected together the phase
diagrams of all alloy systems containing the socalled precious metals published up to the end
of 1975. Over 500 systems are presented in
this book, including I 99 binary, I 15 ternary and
five quarternary systems that contain a
platinum group metal.
In view of the rate of progress in this aspect
of physical metallurgy none of the diagrams has
been evaluated or reviewed; despite this the
publication is a most useful addition to the
literature on the platinum group metals.
Although nominally in Chinese, English
translations are given wherever this is required.
The contents pages list systems in
alphabetical order according to the chemical
symbols of the component elements. Interestingly, the compilation has enabled gaps in the
knowledge to be identified; even among binary
systems phase diagrams of rhodium, iridium,
osmium and ruthenium are still rather scarce.
This important work may be obtained from
the China National Publishing Industrial
Trading Corporation, P.O. Box 614, Beijing,
People’s Republic of China.
I.E.C.
108
The Catalytic Etching of Platinum
and Rhodium-Platinum Gauzes
CRYSTALLOGRAPHIC CHANCES DURING AMMONIA OXIDATION
By J. Pielaszek
Institute of Physical Chemistry of the Polish Academy of Sciences, Warsaw, Poland
Surface morphological and X-ray examinations have been carried out
on catalyst gauzes exposed to the conditions encountered during the
oxidation of ammonia. A model, based upon observations of platinum
and rhodium-platinum single crystals is proposed to explain the
structural changes that occur on rhodium-platinum alloys during
industrial use.
A major concern during the process of
ammonia oxidation is the loss of platinum from
the rhodium-platinum catalyst gauze, which
occurs simultaneously with its deactivation.
The use of rhodium-platinum or palladiumrhodium-platinum alloys causes a noticeable
rise of mechanical strength of the gauze,
without a significant loss of catalytic efficiency.
Previous studies have shown that the wires of
a new catalyst gauze are essentially smooth
(1-8). During use they become roughened and
etching occurs along grain boundaries. The
process spreads into the interior of the grains
and ultimately well developed facets appear, the
character of which varies from grain to grain.
After a prolonged period of use deep etch-pits,
often with very regular shape and developing
into channels which penetrate the interior of
the grains, are also observed. Finally irregular
cauliflower-like growths appear on the surface.
During catalyst use, segregation of the components and enrichment of the surface layers
with rhodium occurred on rhodium-platinum
gauzes, and X-ray examination revealed the formation of rhodium oxide (I, 4, 7,9, 10).This
rhodium oxide layer can form a very compact,
thick envelope which can be separated from the
gauze wire core ( I I , I 2).
The facets observed on the surface of the
grains have a very regular form. This suggests
that they are crystallographically oriented and
Platinum Metals Rev., 1984, 28, (3), 109-1 14
it is reported that their character depends on
local structural features (2,6, 8, I 3).
Experiments with single crystals in the form
of small diameter balls have shown that faceting
depends upon the local orientation of the
surface, its curvature and the flow velocity of
the reactant gases (14, I 5).
In the present paper results are presented of
studies with scanning electron microscopy
(SEM) of surface morphology, and X-ray
examinations of platinum and rhodiumplatinum alloys exposed to industrial conditions
for ammonia oxidation. To explain the
structural changes observed in commercially
used rhodium-platinum gauzes a model is
proposed, based on the observed changes
of surface morphology of single crystals
of platinum and rhodium-platinum alloys.
All the samples were exposed in an experimental reactor designed to follow industrial
practice. The samples were placed between the
first and second gauzes in a pack of four with
the examined surface facing the reaction gas
stream. The experiments were performed at
pressures of 3.5 to 4.8 atm, the concentration of
the ammonia in the gas being 6.3 to 6.8 wt. per
cent. The average gas temperature was 820 to
9oo0C, and the catalyst gauze loading was
either 24.5, or more generally 49N cubic metres
109
not allow the formation of large mosaic blocks.
The characteristic feature of any wire is the
longitudinal structure (texture) resulting from
directional plastic deformation during wire
production. This structure is usually nonuniform, and changes with the distance from
the longitudinal axis of the wire. Wires of face
centred cubic metals generally exhibit an axial
structure with axes (16).
Using CuK,, X-ray radiation, the half
penetration depth for platinum is about 1.6pm.
Thus by dissolution it was possible to study
changes in the structure as a function of the
distance from the surface.
>
>
Fig. 1 4 platinuni ( 1 I I ) surface. which had
hc-c-n shielded by the gauzc, showing an early Observations and Results
stagr o f catalytic- etching
x :$400
As produced platinum wires had an axial
<I I I
texture in the surface layer but in the
of nitrogen per hour while the exposure times interior there was a mixed axial texture of the
were 5 to loo hours (for single crystals 5, 10 type. X-ray photographs of
and loo hours), except for gauzes obtained the surface layers of pure platinum wire after
treatment in the reactor for 10 hours showed a
directly from industrial plant.
High purity platinum and rhodium-platinum polycrystalline image. However, hardly any
polycrystalline wires of 1 5 0 and 60 pm changes occurred at the interior of the wire.
Before treatment in the reactor the rhodiumdiameter, respectively, were used; the 60 pm
wires being in both the as-produced condition platinum wires had a mixed I I I ) + I oo>
and as taken from catalyst gauzes. In addition axial texture near the surface. However, after
flat polycrystalline samples, with surface dimen- the treatment the samples exhibited a
sion 5 x 5 mm, were cut from rods used in the
production of gauzes.
Single crystals of platinum and 1 0 per cent
rhodium-platinum with surface orientation
( I oo), ( I I I), ( I I 0) were cut by spark-erosion
from randomly oriented single crystal rods of 4
to 6 mm diameter. The samples were polished
with diamond paste and then annealed in
vacuum by an electron beam at a temperature
of about
I 200OC.
Berg-Barrett
X-ray
topographs of the cut and annealed samples
displayed a highly developed mosaic structure,
which, in the case of the platinum single
crystal, was noticeably reduced only after the
third annealing treatment.
The 1 0 per cent rhodium-platinum samples
were annealed at much lower temperatures and Fig. 2 A platinum (100) surface showing an
early stage o f catalytir etching. The relief
for shorter periods of time than the platinum. developed on t h e surface corresponds t o its
x 3500
This reduced segregation of rhodium, but did symmetry
>
>
<
110
<
polycrystalline structure with a simultaneous
increase of the type of texture when
examined by X-ray diffraction. The degree of
 crystallographic orientation was greater
in the 1 0 per cent rhodium-platinum than in
the 5 per cent rhodium-platinum wire. The
observed changes in the interior of the wires
were those expected after a purely thermal
treatment of the sample. The thick 150 pm
diameter wires behaved similarly, except that
after an initial I o hours exposure, recrystallisation of the interior was less pronounced.
The platinum and rhodium-platinum wires
obtained from catalytic gauzes behaved in the
same manner. However, the curvature of the
wires made X-ray identification of the texture
more tedious.
T h e single crystal samples were treated
under the same conditions as the wires. Before
treatment the surfaces were optically smooth,
except for a few scratches remaining from the
mechanical polishing. After the treatment
however, both the oriented platinum and
rhodium-platinum single crystal samples
exhibited some common features. Platinum
crystals with surfaces parallel to ( I I I), (100)
and ( I 1 0 ) planes and also the 1 0 per cent
rhodium-platinum crystals with ( I I I ) and (100)
faces, when treated for 2 0 hours, exhibited only
a few pits; these were mostly along the
Fig. 3 A platinum (100) surface after 100
hours exposure to the direct influence of the
reactant gases. Crystallites with well defined
faces are visible, as are cauliflower-like
x3400
growths
Fig. 4 A 10 per cent rhodium-platinum ( 1 0 0 )
surfare after treatment for 1 0 0 hours. The
surface is not as deeply etched as platinum
after the same treatment time
X.7400
mechanical scratches produced during the
handling of the samples after preliminary SEM
examinations. After 100 hours treatment, the
whole surface of the samples exposed directly to
the reactant gases was heavily etched. T h e
places shielded by the gauze were attacked less
and show the earlier stages of the etching
process, see Figures I and 2. The analysis of the
relief showed that the edges of the etch-pits are
oriented along the directions of intersection of
low-index planes with the single crystal surface.
In the heavily etched areas, shown in Figures 3
to 6, the surface was covered with crystallites of
varying regularity and, in the case of platinum,
cauliflower-like growths occurred in some
places, see Figure 3. For the same treatment
time, the surfaces of the platinum crystals were
more deeply etched than those of rhodiumplatinum crystals, as can be seen by comparing
Figure 3 with Figures 4 and 5 .
The relief developed on each surface
corresponded to its symmetry. This is especially
evident at the earlier stages of catalytic etching
of the platinum crystals, illustrated in Figures I
and 2. The relief observed on (100)and ( I I I )
rhodium-platinum crystals was not as regular as
that seen on pure platinum crystals. This
results from the partial recrystallisation of the
rhodium-platinum single crystals, the crystals
having a highly developed mosaic structure.
111
are the most stable. An analysis of SEM
photographs indicates that on platinum (100)
crystals the etching takes place with the
exposure of ( I I 0)planes and to a lesser degree
( I I I ) planes. On the ( I I I ) oriented surface the
pits have edges parallel to the intersection of
( I 00)and ( I I I ) or ( I I 0)planes, and the exposed
planes are probably (100) and ( I 10) because
they form more acute angles with respect to the
( I I I ) plane than the other ( I I I ) planes. For
identical treatment conditions the (100)plane is
etched more quickly than the ( I I I ) plane and
this results in the better developed relief
observed on the former plane. The 1 0 per cent
Fig. 5 A 10 per cent rhodium-platinum ( I I I )
rhodium-platinum crystals are more resistant to
surface treated for 100 hours
x 3400
etching than the platinum crystals.
Both the 5 and 10 per cent rhodiumThe relief observed on both the platinum and
platinum alloys exhibited the same surface rhodium-platinum crystals is very regular only
features. Grains with different orientations over short distances, although its character
were etched in different ways, as can be seen in remains the same all over the surface. This
Figure 6, and some preferential etching at grain probably results from the highly developed
boundaries took place. Prolonged exposure mosaic structure in these crystals and the fact
resulted in very pronounced etching of the that in some cases the misorientation between
interior of the grains, with a distinct relief on subgrains can be as large as several degrees.
different grains. On the surface of some grains, Figure 7(left) shows Berg-Barrett X-ray
regular square pits occurred (shown in the left topographs of a platinum (100) crystal before
hand photomicrograph in Figure 6) similar to annealing, and Figure 7(right) after the third
those observed on the platinum ( I 00)face at the I hour anneal. In the case of the rhodiumbeginning of the etching process. On the grains platinum alloy such an annealing treatment was
of the 5 per cent rhodium-platinum alloy, some precluded to avoid segregation of rhodium and
cauliflower-like growths were present. It should recrystallisation. This is why the relief observed
be noted that these growths were not apparent on these crystals is more confused and is only
on the I o per cent rhodium-platinum alloy after roughly similar to that observed on platinum
the same loo hours of treatment.
single crystals. As suggested elsewhere the loss
of material probably proceeds through the forDiscussion and Conclusions
mation of volatile platinum oxide (5, I 0,I 3,17),
The morphology of the oriented platinum and results in the enrichment of the surface
and rhodium-platinum single crystal surfaces layer with rhodium. The volatile component
exposed to reactant gases during the ammonia probably condenses on other parts of the crystal
oxidation process indicates that catalytic and, together with smaller crystallites detached
etching takes place along crystallographically from the bulk of the crystal and carried by the
defined plans. This explains why pits with four- reactant gas stream until randomly deposited
fold symmetry on (100)surfaces and with three- elsewhere, forms the observed cauliflower-like
fold symmetry on ( I I I ) surfaces were observed, growths. These do not have as regular a form
whereas the pits on the ( I 10)plans exhibited a on a large scale as the etched crystallites, but in
linear form.
some cases their general shape is parallel to the
It seems reasonable to assume that the planes low index directions of substrate crystals.
exposed during the process of catalytic etching
The results show that all the examined low-
112
Fig. 6 T w o areas on a flat polycrystalline sample of 5 per cent rhodium-platinum after treatment for 100 hours in the reactor. The relief produced by etching depends upon the orientation
of the grains. Regular square pits can be observcd on one of the grains
x1130
index planes are stable. However their stability
depends on the number of points at which the
etching process starts.
It is reasonable to assume, as in the case of
chemical etching, that the sites of preferential
etching are places of high stress concentration,
grain boundaries, impurity segregation and
other kinds of defects. Once activated, catalytic
etching proceeds to expose the nearest lowindex planes. This process spreads until new
points of preferential etching develop on the
newly exposed planes. New low-index planes are
then exposed at these points. In this way the
etching process proceeds not only at right
angles to the crystal surface, but also in other
directions. Some parts of a crystal may be
etched from all sides and the crystallites formed
in this way will be moved away from the bulk of
the crystal by the stream of reactant gases. This
model should also be valid for polycrystalline
material, where every crystal grain is behaving
in the same manner. For such polycrystalline
material the existence of grain boundaries
makes the number of sites of preferential
Fig. 7 Berg-Barrett X-ray topographs of a ( 100) oriented platinum crystal showing, on the left,
the sample after annealing for 1 hour at 12OO0C, and on the right after the third period of I
hour annealing a t 1200OC. (Reflex (31 1 ), CuK,, radiation). The same low-angle boundary is
marked tl on both topographs. T h e increase in size of the micromosaic blocks after repeated
annealing is clearly shown
approx. x 8 5
113
References
C.lLC3
etchinp much hieher and the random orientation of grains causes more non-stable highindex planes to be exposed at the surface of the
sample.
The rhodium-platinum wires have a high
degree of longitudinal texture of the (100) type
in their surface layers. This means that a higher
than average number of grains have the <roo>
direction parallel to the wire axis. The <roo>
planes are stable. Thus, etching on these planes
will be much slower than on any other adjacent
plane, and etching along the planes
perpendicular to the wire axis will be even
slower. As a result, grains with a longitudinal
texture close to I oo> will be more stable. T h e
other grains will be attacked more readily and
some of them will be separated from the matrix
and removed by the stream of reactant gases.
The SEM studies (18) of post-reaction dusts
revealed crystallites with the dimension of a few
pm and with habit planes looking very similar
to the crystallites developed on oriented single
crystal planes, as shown in Figure 3. As a result,
the relative number of grains
in the surface
layer with an orientation of the (loo) type is
increased. This was actually observed.
l,lz,.=X
I
2
(41,' 3 '
3 J. P. Contour, G. Mouvier, H. Hoogewys and C.
3 J.Leclers,
P. Contour,
G. Mouvier, H. Hoogewys and C.
3. Catal.,
I 977,48, ( I /3), 2 I 7
Leclers, 3. Catal., I 977,48, ( I /3), 2 I 7
4 F. Sperner and W. Hohmann, Platinum Metals
4 F.
Sperner
and W. 1Hohmann,
Platinum Metals
Rev.,
1976,20,(1),
2
Rev., 1976,20,(1), 1 2
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(41, ‘35
6 R. W. McCabe, T. Pignet and L. D. Schmidt, 9.
Catal., 1974, 3 4 (11, I 14
7 N. H. Harbord, Platinum Metals Rev., 1974, 18,
(31397
8 L. D. Schmidt and D. Luss, 3. Caral., 1971, zz,
(I), 269
9 J. A. Busby and D. L. Trimm, 3. Caral., 1979,
60, (3L 430
1 0 M. Chen, P. Wang and L. D. Schmidt, 3. Catal.,
1979, 60, (3)> 356
I I M. Pszonicka and T. Dymkowski, Pol. 3. Chem.,
1978, S Z , ( I ) , 121
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1 3 R. T. K. Baker, R. B. Thomas and J. H. F.
Notton, Platinum Metals Rev., 1974, 18, (4), I 30
14 M. Flytzani-Stephanopoulos and L. D. Schmidt,
Prog. Surf. Sci., I 979,9, 83
I 5 M. Flytzani-Stephanopoulos, S. Wong and L. D.
Schmidt, 3. Caral., 1977,49, ( I ) ,5 I
16 G. Wasserman and J. Grewen, “Tekstury
metakzeskich materiallov”, Moscow, 1969
I 7 G. C. Fryburg and H. M. Petrus, 3. Elecrrochem.
SOC.,
I.,-.,
96 I , 108,
-__.,
---,(6),
,-,,496
~~-
<
The etching processes observed on platinum
and rhodium-platinum
rhodium-platinum wires
and
wires and
and single
single
crystals, presented above, can explain the
crystallographic features observed on catalytic
gauzes used in ammonia oxidation. It can also
explain why well developed crystallites are
found in post-reaction dust (18). However, it
does not account for the way the loss of
material takes place, although it seems that the
most effective way for the described model to
operate will be through the formation of
volatile products.
18
l,lz,.=X
The economic advantages of palladiumnickel as a replacement for electrodeposited
gold in the electronics industry have been
demonstrated many times during recent years
and an extended study of their relative performance recently reported by K. J. Whitlaw of
LeaRonal U.K. (Trans. Insr. Met. Finish., 1984,
62, ( I ) , 9-12) serves to substantiate the
potential value of these deposits.
The experimental work shows that a duplex
layer of 2.5 to 3.opm 70 palladium-30 nickel
followed by 0.1 to 0.25 pm of acid hard gold is
to be recommended as a replacement f o n . 5 pm
gold deposited on a copper substrate such as a
printed circuit board. This combination offers
freedom from porosity, stability of contact
resistance, excellent resistance to wear and to
corrosion, and also resistance to copper diffusion at elevated temperatures.
These properties, while being identical to
those secured with a conventional gold deposit,
offer savings in cost of as much as 65 per cent.
C.lLC3
G.J.K.Acres,PlarinumMetalsRev., I 980,24,( I),14
h4etals
2 A. G. Knapton,Platinum
Platinum
MetalsRev.,
Rev.,1984,28,
1978, 22,(3)
(41,' 3 '
3 J. P. Contour, G. Mouvier, H. Hoogewys and C.
Leclers, 3. Catal., I 977,48, ( I /3), 2 I 7
4 F. Sperner and W. Hohmann, Platinum Metals
Rev., 1976,20,(1), 1 2
M.Pszonicka, private information
Palladium-Nic kel Plating
Acknowledgements
The rhodium-platinum gauzes were kindly
supplied by Dr. M. Pszonicka, Technical University,
Warsaw. The platinum-rhodium single crystal was
made by Metals Research Limited, England.
Exposures of all the samples were done at the experimental reactor in Instytut Nawoz6w Sztucznych,
Pulawy, where substantial help of Mr. Kozlowski is
greatly appreciated.
This work was carried out with the Research
Project 03.10.
I
G.J.K.Acres,PlarinumMetalsRev., I 980,24,( I),14
A. G. Knapton, Platinum Metals Rev., 1978, 22,
114
Combustion in Wood-Burning Stoves
PLATINUM CATALYST INCREASES THERMAL EFFICIENCY
A N D GREATLY REDUCES POLLUTION
The use of wood as a residential heating fuel
has always been popular in the Scandinavian
countries. More recently there has been a significant increase in the use of wood-burning
stoves in many other parts of the world,
especially in the United States of America. This
trend was initiated by the escalating costs of
fossil fuels and electricity and, to a certain
extent, public concern about the reliability of
future supplies of these fuels.
Heating with wood fuel can be less costly
than heating with coal, oil or electricity,
especially in rural and some suburban areas
where wood is relatively inexpensive and plentiful. Furthermore, modern wood-burning stoves
are at least as efficient as oil and gas fires. Tests
have shown that radiant, damped-draught
wood-burning stoves deliver from 50 to 70 per
cent of the energy available in the wood to the
surrounding living area.
Despite all its advantages the wood-burning
stove does present some problems, not the least
of which is smoke.
T h e main difficulty is that there is no
economical method of continuously feeding a
measured amount of wood into the stove to
control the heat output. Large amounts of fuel
are loaded into the stove and the combustion
rate is controlled by the amount of air available.
T h e unburned wood is heated to the point at
which combustible volatile components are
distilled off. These components comprise
hydrocarbons (including polycyclic aromatic
hydracarbons), aldehydes, phenols and carbon
monoxide and are often incompletely burned in
the stove because there is insufficient air available for combustion. Even when sufficient air is
available, temperatures are often too low to
bring about any significant degree of burning.
The nett result is that these volatile components
can be released from the stove to either condense in the chimney or be emitted to the
atmosphere. The condensed materials contribute to the danger of chimney fires while the
smoke emissions can cause significant air pollution. Furthermore, the overall effect is a significant loss of potential heating value.
The application of new technology in the
design of wood-burning stoves can now largely
overcome the basic problems associated with
their operation. The requirement is for a
method of operation which enables smoke to be
Fig. I The plalinuni nietal catalyst is located
in the secondary Combustion chamber of the
stove. The three-tier design provides a large
surface area and hence efficient heat exchange
115
burned at the temperatures existing in a stove
operating under damped conditions. These
temperatures are typically in the range 200 to
4ooOC. The use of platinum group metal
catalysts supported on ceramic honeycomb substrates is now a well established method of controlling emissions of unburned hydrocarbons
and carbon monoxide from motor vehicle
exhausts. The catalyst reduces the combustion
temperature of the hydrocarbons and carbon
monoxide so that they start oxidising at
temperatures around 250°C.The catalytic reaction increases until the system reaches an
equilibrium between the inlet gas temperature,
the gas-flow rate and the amount of combustible material in the gas stream. The
equilibrium temperature can be as high as
about 800°C for an optimum sized catalyst
system and at this temperature essentially complete oxidation of the combustibles in the gas
stream proceeds very rapidly.
During the course of the past few years the
application of catalytic oxidation to promote
secondary combustion has led to the appearance
on the market of a new generation of wood-
burning stoves. One such product has recently
been launched by Trolla Brug, a long
established Norwegian company. Appropriately
named the Pioneer, it combines the traditional
appeal of a cast iron stove with the modern
technology of catalytic secondary combustion.
The stove is a three-tier design comprising a
primary combustion chamber, a secondary combustion chamber incorporating the catalyst and
a third storey which acts solely as a heat
exchanger. The catalyst, which was specifically
developed by Johnson Matthey Chemicals
Limited for wood-burning stove applications
comprises platinum metal dispersed on a low
cell density ceramic honeycomb support. T h e
multi-storey design provides a large surface
area for maximum heat exchange efficiency.
The incorporation of the catalytic afterburner
is claimed to result in a 30 per cent reduction in
wood consumption for the same useful heat
output compared to the non-catalytic version of
the same stove. In addition smoke emission
levels are greatly reduced and the potentially
dangerous accumulation of inflammable conA.E.R.B.
densates in the chimney avoided.
Osmium Doping Improves Recording Media
'I'tllN FILMS H A V E HIGH COERCIVI'I'Y A N D COERCIVK S Q U A H K N K S S
In magnetic recording the continuing
demand for ever increasing recording density
has stimulated research on thin films of continuous magnetic materials suitable for the
production of high capacity storage discs.
Sputtered y-Fe203 thin films are attractive for
this application in view of their high coercivity
and high remanent magnetisation, combined
with their resistance to corrosion and wear, and
a y-Fe203 film containing small amounts of
cobalt, copper and titanium has been developed.
The function of these additions is to increase
the coercivity of the film, to improve coercive
squareness, to widen and lower the temperature
range of the a-Fe203 to F e 3 0 4 reduction-so
making it possible to obtain uniform magnetic
properties-and
also to suppress grain growth
during heat-treatment.
Now workers at the Ibaraki Electrical Communication Laboratory in Japan report that
remarkable improvements have been made to
the magnetic properties and microstructure of
sputtered y-Fe203 thin films when osmium is
used as an additive element (0. Ishii and I.
Hatakeyama, J . Appl. Phys., 1984, 55, (6),
2269-2271).
Films 0.1 to o.2pm thick have been prepared
by reactive magnetron sputtering, the target
being an iron plate to which osmium pellets
were attached. Coercivity and coercive
squareness increased with osmium content, to
maximum values of 2100 Oe and 0.81,
respectively. Osmium doping also brought
about field-induced anisotropy which greatly
increased the coercive squareness parallel to the
easy axis, a figure of 0.96 being obtained with
0.88 to 5.2 atomic per cent osmium. Osmium
also suppressed grain growth during preparation, giving crystallites about 400 A in diameter
which improves the signal to noise ratio, an
advantage for increasing recording density and
read back amplitude.
116
Electrodeposition of Palladium-Silver
Alloys from Arnrnoniacal Electrolytes
By B. Sturzenegger
Department of Chemical Engineering, Swiss Federal Institute of Technology, Zurich
and J. C1. Puippe
Werner Fluhmann A.G., Diibendorf, Switzerland
A viable technique f o r the electrodeposition of palladium-silver alloys
could find application during the manufacture of electrical contacts.
Previously such a process has not been available but some alloys with
useful physical properties can now be deposited from an ammoniacal
system, while a better understanding of the mechanisms involved has
been gained during the work reported here.
Applications of palladium and palladium
alloys in the electrical contact field have
recently been reviewed by Antler (I). Among
these materials,
palladium-silver alloys,
particularly the 60 per cent palladium-40 per
cent silver composition, are well established in
the wrought form, as claddings, weldments or
inlays, with advantages over the pure metal in
terms of cost and durability. More recently,
interest has extended in the direction of
electrodeposited coatings of palladium and
alloys as economic substitutes for gold plating,
and in this context it is clearly attractive to consider the possibilities of producing palladiumsilver alloys by electrodeposition, a technique
which would permit, for example, the application of coatings to pre-formed contact fingers
and other components in cases where the inlay
technique is not practicable. While, however, a
considerable amount of research work has been
carried out to this end, notably from Russian
sources, it would appear that no viable process
has yet been developed.
Early attempts used a solution based on
cyanide complexes of the two metals (2,3), but
the alloys produced, with a palladium content
of 2 0 to 2 2 per cent, were of poor appearance
and the cathode efficiency was very low.
Improvements were later obtained in terms of
increased cathode efficiency by optimising
process parameters and bath formulation (4-6).
Deposits from thiocyanate-based electrolytes
showed a broader compositional range, up to 70
per cent palladium (2, 7-12), the best coatings
from this type of bath containing 2 to 10 per
cent palladium. A bath formulation based on
palladium and silver ammino-hydroxy salts
gave semi-bright deposits with palladium contents from 15 to 85 per cent and good cathode
efficiency of 85 to 95 per cent (13-16),while
bright coatings have been reported from an
electrolyte based on amino-acid complexes
(17, 18). Solutions of palladate and argentate
salts have been stated to give semi-bright coatings with palladium content between I o and 60
per cent, with thicknesses up to 15,um being
obtainable ( I 9).
Work has also been carried out using concentrated halide baths with lithium chloride to
permit increased solubility of silver (20-22).
This type of solution is very aggressive to base
metals due to vigorous displacement reactions;
however, good deposits were reported, with
palladium contents ranging from 30 to 60 per
cent. Attempts to deposit alloys from
ammoniacal solutions of nitrito-complexes were
unsuccessful (2), but when nitrate complexes
are employed it has been reported that the full
range of alloy compositions can be obtained
simply by adjustment of the current density
(23). Later reports claim the production of
bright, pore-free deposits from this type of
117
PVC jacket-Cathode
Anode
__
__
ENLARGED VIEW ON A-A
Outlet
DIMENSONS IN rnm
Teflon sleeve
Fig. I The elrctrolytes were studied in the cell shown here. Deposits were
made onto a rotating cylindrical copper cathode, the anode being a concentric platinised titanium cylinder
solution, with thicknesses up to 20 pm (24).
The object of the present work was to study
the mechanism in palladium-silver alloy deposition in order to gain a better understanding of
the influence of process and compositional
parameters on alloy composition and properties.
For this purpose the ammoniacal solution with
palladium and silver nitrates was selected in
view of the possibility of obtaining a wide range
of alloy compositions.
was prepared for plating by an initial polish
with I pm alumina paste, followed by cathodic
degreasing at I o mA/cm’ in an alkaline cyanide
solution, and a final activating dip in concentrated sulphuric acid, with intermediate
water rinses. Immersion in the electrolyte was
made under an applied voltage.
Deposition was carried out at room
temperature (22OC) for times selected to
produce coating thicknesses in the order of
2pm. The applied current density (j&I was
varied between 5 and 40mA/cm2, and the
cathode rotational speed between o and 1 0
revolutions per second.
The electrolyte compositions studied are
given in the Table opposite.
Deposition was made on a copper cylinder
Deposition Mechanism Studies
( 1 0mm diameter, 10 mm high) attached to a
Polarisation curves for (a) a solution containTeflon shaft, the rotational speed (a)of which
could be continuously adjusted from o to 10 ing 20 g/l of palladium only, and*(b) a solution
revolutions per second. The anode was a con- containing 20g/l of palladium and 2 g f l of
centric cylinder of platinised titanium, which silver are shown in Figure 2. From these it is
was itself provided with a further jacket of PVC seen that silver begins to deposit at potentials
for temperature stabilisation. The electrolytic less negative than for palladium, and that
cell is shown as Figure I . The cathode surface palladium deposition occurs when silver is
118
being deposited under limiting current conditions. T h e large plateau of curve (b) is
associated with the limiting current of silver
deposition, as will be quantitatively evidenced
later. T h e fact that palladium, a more noble
metal than silver, is deposited only at more
negative potentials than the latter, is explained
by the much greater stability of the palladiumammino complex, the relevant stability constants being as follows ( 2 5 ) :
-200
-400
-600
-80C
ELECTRICAL POTENTIAL, Ev,,*p,A,c,,rnV
The influence of current density and
rotational speed of the cathode on the composition of the alloys was studied for electrolytes
containing I and 2 g / l of silver. The results,
shown in Figures 3 and 4, are consistent with
the hypothesis of a mass transport-controlled
codeposition of silver, in that the silver content
increases with agitation rate at constant current
density, and decreases with increase in current
density at constant agitation rate. As shown by
comparison of Figure 3 with Figure 4, the
increase in the silver content of the deposit is
proportional to the increase in silver concentration in the electrolyte, which is again consistent
with the mass transport model for silver
incorporation.
Figures 3 and 4 also show the experimental
conditions under which bright, semi-bright,
and matt deposits are obtained. The thickness
of the deposits was 2pm. In general, deposits
with a silver content below 25 atomic per cent
are bright, while higher silver contents are
associated with semi-bright or matt coatings.
This may be explained on the basis that at low
silver incorporation rates the deposit structure
is essentially governed by the crystallisation
Fig. 2 Polarisation curves for palladium
and palladium-silver electrolytes.
Voltage scanning speed: I mV/s
( a ) Palladium: 20 g/l
( b ) Palladium: 20 g/I; silver: 2 g/l
r
40
2
4
6
8
1
0
ROTATIONAL S P E E D . n , r e v / s
1
2
Fig. 3 Silver content of deposits a5 a
function of rotational speed of cathode
and current density for electrolyte 1 .
0 bright deposits; 0 semi-brighl
deposits; matt deposits
mode for palladium, while at higher rates of
silver incorporation the morphology of the
deposit is progressively affected by the
crystallisation of silver. Since silver deposition
takes place under mass transport controlled
Electrolyte Compositions
Palladium, as Pd(NH,l,(NO,),
Silver, as Ag(NH,),(NO,)
pH (adjusted by gaseous NH,)
1
2
3
20 911
2 0 911
2 911
11.5
2 0 911
3 gA
11.5
1 911
11.5
119
that the current is under full mass transport
control, providing a quantitative demonstration
of the fact that similar conditions apply to the
incorporation of silver in the palladium-silver
alloy. This being so, a model may be derived for
the calculation of alloy composition as a function of deposition parameters, as given below.
During the electrodeposition of palladiumsilver alloy, the total current density is due to
contributions from the deposition of palladium,
silver and hydrogen.
conditions, there is a tendency for the formation of dendrites and powder, leading to
rougher deposits. The morphology of matt,
semi-bright and bright deposits with various
silver contents is illustrated in the scanning
electron micrographs of Figure 5.
The variation of current efficiency with
silver content is shown in Figure 6. The
decrease in efficiency with increasing silver
content can be explained by the increasing
roughness of the deposits, leading to enhancement of hydrogen evolution at asperities and
hence to a decrease in current efficiency for
metal deposition. The current efficiency was
calculated on the basis of Faraday's law from
the metal contents of deposits, as determined by
atomic adsorption on solutions prepared by
dissolution in nitric acid, as follows:
it01
=
[ivl
iPd + j A g + i H
The molar-ratio of silver in the deposit is:
xAg
=
jAg/bAg
+
[VI
112 jl'dd)
Assuming a I 00 per cent current efficiency and
combining Equations [iv] and [v],
where
J
xAg
= 2
XAg
= 2/(I +
iAg/(iAg
+
jd
J)
=&
=
LA^ 85.5 nn'ss9.
CAg
'to'
[Vil
[vii]
[viii]
With Equation [vii] one can thus predict the
silver content in the deposit for different total
= 100
[ii]
current densities, different silver concentrations
110,
in the electrolyte and different hydrodynamical
where IAg and I,, are partial currents for silver conditions.
and palladium, Ilo, is total current, mAgand mPd
For not negligible drops in current efficiency,
are weights of silver and palladium deposited, Equation [vii] has to be rewritten as follows:
AAg and A,, are the atomic weights of the
X A ~ =2/( I + J . CE)
[vii']
metals, F is the Faraday constant and t is the
electrolysis time.
From the silver content of deposits, and on
the assumption that silver is deposited under
mass transport control, the limiting current
density for silver deposition can be calculated
from the results of Figures 3 and 4, and is
plotted as a function of rotational speed of the
cathode in Figure 7. The limiting current
density values so obtained fit the following
relationship:
4
j h g = 85.5 f2n.sr9. C A ~ [iii]
That is to say, the limiting current density is
directly proportional to the silver concentration
CAgin the electrolyte and is a function of 12°.ss9.
An exactly similar relationship between limiting
current density and rotational speed was found
in separate experiments with a ferriferrocyanide system, where it is well known
120
2
4
6
8
1
0
ROTATIONAL SPEED, n, rev/s
1
2
F i g . 4 Silver content of deposits as a
function of rotational speed of cathode
and current density for electrolyte 2.
0 bright deposits; 0 semi-bright
Fig. .5 Scanning electron
micrographs of palladiumsilver alloy deposits from
rlectrnlytc 3 (palladium 20
g/l; silver 3 g / l ) .
( a ) R = 0 rev/s;
mA/cm2; Ag = 52.5
(matt)
,i= 5
at.%
( b ) R = 0 rev/s; ,i= 15
mA/cm2; Ag = 29.3 at.%
(srmi-bright )
( c ) 0 = 0 rev/s; .i = 3 0
mA/cm*; Ag = 20.8 at.%
(bright)
( d ) 0 = 3 rcv/s; ,i = 30
mA/cm2; Ag = 33.0 at.%
( semi-bright)
121
+
treatment at 280mV in a solution of 200g/l
copper sulphate, 50 g/l sulphuric acid, to leave
an isolated foil for measurements. A series
of foils was produced in this way under the
following conditions:
100.
W
U
K
W
90.
>
. O
U
$80-
-
.. ...
.
0
0
m
u
LL
,“ 70.
10
20
30
Electrolyte I : jlOl= 5 , to, IS,ZO d c m ’
Electrolyte 2: j,,,=
10, 1 5 , 2 0 mNcm2
.
40
ATOMIC PER CENT SILVER
Fig. 6 Current efficiency for metal
deposition as a function of silver
content of deposits.
0 bright deposits; 0 semi-bright
Equation [vii] and the experimental results for
R > 2/s are plotted in Figure 8. Agreement
between calculated and measured values was very
good. Only small deviations occur for experimental values corresponding to matt deposits.
Physical Property Measurements
For measurement of properties such as
hardness and specific resistance it was necessary
to produce alloy coatings of thickness at least
I o pm and of good surface finish, both on flat
substrates (for hardness) and as isolated foils
(for specific resistance). Since, at thicknesses in
excess of about 2pm, coatings tended to
develop cracks due to internal stress associated
with hydrogen occlusion, and also to deteriorate
in surface finish, a multi-layer technique was
adopted for this purpose, in which coatings
were built up in successive increments of 2 pm,
with intermediate polishing of the cathode with
I pm alumina. Thus it was possible to produce
bright, crack-free coatings up to I 2 pm thick.
Deposition was made on both sides of brass
plate cathodes (20 x 70 mm), which were
masked to expose a total area of 16cm’ and
suspended between platinised titanium anodes
in an open vessel, with stirring by natural convection. To produce unsupported foils as
required, the coating was removed from one
side of the plate by grinding, and the supporting substrate was then dissolved by anodic
A l l o y Composition
Alloy composition as a function of current
density under the above conditions is shown in
Figure 9, together with analogous results
pertaining to coatings produced on the copper
electrodes used in the earlier work, with zero
rotational speed. From the results it is clear that
the change from the one type of cathode to the
other has no significant influence on the
composition-current density relationship.
Hardness
The Knoop hardness of coatings was determined as the mean of five measurements at
various locations on the surface of 1 2 p m
deposits at a load of 1 5 p, with indentation
period of 30 seconds. It has been experimentally
determined that the alloy thickness of I 2 pm
was sufficient to avoid any influence of the brass
substrate on the Knoop-hardness values. Figure
1 0 shows the hardness of deposits from the two
electrolytes as a function of composition. Since
both curves are more or less parallel, it appears
that the hardness is independent of deposition
conditions and increases with increasing silver
content.
Specific Resistance
Results of measurements of specific
resistance by the four-point probe method
(ASTM F390-78) are shown in Figure I I . As
for hardness, this property increased with
increasing silver content, being practically
independent of electrolyte composition and
bath conditions.
Contact Resistance
Contact resistance measurements were made
on 2 p m coatings by the method according to
the ASTM B667 specification, the test surface
122
>
I
1
2
3
4
5
6 7 8 9 1 0
ROTATIONAL SPEED,IL. mv/s
4
8
12
16
20
CURRENT DENSITY, J , dimensionless
Fig. 7 Limiting current density for silver
as a function o f the rotational speed of
the cathode.
( I ) Electrolyte I ;( 2 ) Electrolyte 2
24
Fig. 8 Silvrr content in the deposit as a
funrtion of the dimensionless current
density J.
according to equation [ vii] ;
0 experimental values
-
4 50
VI
9
x
I400
v;
W
z
E
2 350
20
30
CURRENT DENSITY, 1. mA/cm2
10
40
300
5
Fig. 9 Silver content o f deposits as a
function o f current density f o r
cylindrical ( 0 ) and vertical plate
( x ) electrodes by natural convection.
( I ) Eleclrolyte I ;( 2 ) Electrolyte 2
20
10
15
25
Fig. I 0 linoop hardness of deposits as a
function o f silver content.
( I ) Elertrolylc- I ; ( 2 ) Electrolyte 2
4
5401
a
?
/
/
10
15
20
C
E
w
Y3
I-
2
W
a2
I-
u
2
81
25
10
15
20
Fig.
I I Electrical resistivity of
electrodeposited palladium-silver foils
as a function of the silver content.
( I ) Elertrolyte I ;( 2 ) Electrolyte 2
25
Fig. 12 Conlact resistance of palladiumsilver alloy deposits as a function of
silver content, for different loads
123
being flat, and the contact partner being a gold
hemisphere of diameter 3.2 mm. T h e results,
for loads between 1 0 and IOO g, are shown in
Figure 12, indicating that, in contrast to
hardness and resistivity, contact resistance is
relatively little affected by alloy composition,
but does depend strongly o n the test load.
Concluding Remarks
T h e present investigation has resulted in a
better understanding of the mechanism governing electrodeposition of palladium-silver alloys
from an ammoniacal system, in particular in
the clear demonstration that silver incorporation occurs under mass transport controlled
conditions. On this basis it is possible t o predict
the silver content of deposits as a function of
the experimental conditions. T h e palladiumsilver system from ammoniacal baths provides,
in fact, a very good example of the “regular”
type of alloy deposition, according to the
classification of Brenner (26).
Results of pulsed current plating studies, to
be reported elsewhere, are also consistent with
the mass transport model, but this technique
permitted no increase in the silver content for
bright coatings as compared t o d.c. conditions.
From the applicational viewpoint, alloy
deposits so far obtained show useful physical
properties, despite the limitation of the silver
content. From the process viewpoint, the very
high ammonia content of the bath may constitute a potential disadvantage, certainly
necessitating effective ventilation. However, it
appears to have no adverse effect, as might have
been expected, on the adhesion of deposits to
copper and copper alloys, and, in total, provides
a system of good stability, with very simple and
easily monitored bath chemistry.
Acknowledgements
The work described in the present paper was
started under the direction of the late Professor Dr.
Norbert Ibl, and was later supervised by Dr. 0.
Dossenbach. Thanks are due to Mr. F. H. Reid for
helpful advice at various stages of the work, and for
assistance in the preparation of this paper, and to the
firm of Werner Fliihmann AG, Dubendorf, for the
provision of financial support and facilities for
analytical work.
References
M. Antler, Platinum Metals Rev., 1982, 26, (3), 14 N. T. Kudryavtsev, 1. F. Kushevich and N. A.
I 06
Zhandarova, Russian Patent 291, 988; 1971
2 G. Grube and D. Beischer, Z. Elektrochem., I 933,
1 5 I. F. Kushevich and N. T. Kudryavtsev,
Elektrokhim. Osazhdenie Primen. Pokrytii
39, (31, 1 3 1
Dragorsennymi Redk. Metal., I 972
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Met., 1 9 7 4 , m 78
4 N. P. Fedotev, P. M. Vyacheslavov, B. Sh.
Kramer and V. V. Ivanova, Zh. Prikl. Khim.
1 7 J. Culjkovic and R. Ludwig, German Patenr
(Leningrad), 1967, 40, (7) I474
29 445,538; I974
18 H. J. Schuster and K. D. Heppner, German
5 Nippon Mining Co. Ltd., Japanese Parent 81,
Patent 2,657,925; 1976
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19 N. T. Kudryavtsev, I. F. Kushevich, L. P.
6 Z. G. Stepanova, Russian Parent 425,98 I ; I 974
Vladimirova and L. V. Galkina, Russian Parent
7 N. P. Fedotev, P. M. Vyacheslavov, B. Sh.
379Y 676; 1973
Kramer and G. K. Burkat, Russian Patent 22 I ,
2 0 Extended Abstracts No. 309, Electrochem. SOC.
452; 1968
Fall meeting, Denver, Oct. I 98 I , I I
8 B. M. Kramer, Zh. Prikl. Khim. (Leningrad),
21 A. K. Graham, S. Heiman and H. L. Pinkerton,
I 973,469 (61, 1242
Plating, I 948,35, ( I 2), I 2 I 7
2 2 Bell Telephone Laboratories Inc., US. Parent
1973,469 ( 1 0 h 2326
432699671; 1981
2 3 V. E. Medina, US.Parent 3,053,741; 1961
1 9 7 5 ~ 4 8( ,I ) , 226
24 A. Ya. Pronskaya, S. I. Krichmar and S. D.
I I B. Sh. Kramer, Obmen Opytom Radioprom., 197 I ,
Okhrimets, Dokl. Akad. Nauk S S S R ,
( I 1)
Elekrrokhim., 1 9 7 1 , 7 ,(6), 778
I 2 Kumamoto Prefecture, Japanese Patent 82, 076,
2 5 R. M. Smith and A. E. Martell, “Critical Stability
196; 1982
Constants”, Volume 4, Plenum, New York, I 98 I
1 3 N. T. Kudryavtsev, I. F. Kushevich and N. A. 26 A. Brenner, “Electrodeposition of Alloys”,
Zhandarova, Zashch. Met., 1971,7,206
Volume I, Academic Press, New York, 1963,76
I
.Platinum Metals Rev., 1984, 28, ( 3 )
124
A History of Thermal Analysis
PLATINUM IN T H E MEASUREMENT OF HIGH TEMPERATIJRES
For thousands of years man has been slowly
learning how to regulate fire to yield the degree
of heat required for individual purposes. No
method of temperature measurement was available to him, however, until early in the
seventeenth century and then only u p to about
300°C~ and the measurement of higher
temperatures had to await the discovery and use
of platinum.
In a Special Issue of Thermochimica Acta
devoted to the history of thermal analysis Dr.
R. C. Mackenzie, of the Macaulay Institute for
Soil Research in Aberdeen, has presented two
most interesting papers that together form a
monumental and scholarly survey of the whole
subject from the earliest times to the present
day ( 1 984,73, (31,249-3671.
The first of many applications of platinum in
the measurement of higher temperatures was
due to Guyton de Morveau who designed a
pyrometer in 1803 that employed a platinum
rod supported in a refractory groove with its
free end in contact with the short arm of a bent
lever, the longer arm serving as a pointer
moving over a graduated scale, all made in
platinum. Some years later, in 1 8 2 1 ,Professor
J. F. Daniell, of King’s College, London,
devised an improved form that overcame the
deficiencies of de Morveau’s instrument and in
which the temperature was determined by the
difference in expansion of a platinum rod and
an earthenware tube.
Neither of these instruments was capable of
measuring really high temperatures, nor were
they of appreciable accuracy. A discovery was
now made, however, as Dr. Mackenzie clearly
brings out, that was to lead to one of the two
reliable and accurate methods of temperature
measurement that are still in extensive use in
both the manufacturing industry and scientific
research. It was in Berlin in 1 8 2 1 that Thomas
Johann Seebeck described the deflection of a
magnetic needle caused by the electric current
Platinum Metals Rev., 1984, 28, (3), 125
generated when one of the junctions of two
dissimilar metals was heated. While it did not
occur to Seebeck to make use of his discovery
for the measurement of temperature, this
invaluable effect was employed five years later
by Antoine C h a r Becquerel who decided that
the most suitable combination of metals was a
circuit consisting of platinum and palladium.
With this combination he was able to arrive at
the determination of temperatures up to
I 350°C by extrapolation.
An iron-platinum thermocouple was then
used by Professor C. S. M. Pouillet of Paris,
while Henri Regnault, making use of the same
couple, found such irregularities that he
roundly condemned the whole idea of the
thermoelectric method, his troubles arising, of
course, from the use of iron as one element.
Later, in I 862, Becquerel’s son Edmond, again
using platinum and palladium “as these two
metals are not altered by the action of heat”,
succeeded in rehabilitating the reputation of the
thermocouple, but it was not until 1872 that
Professor Peter Tait of Edinburgh, using
platinum against iridium-platinum, devised a
sound relationship between e.m.f. and
temperature, so making possible the development of accurate pyrometry.
But the successful practical use of the thermocouple was mainly due to the work of Henri
Le Chatelier, Professor of Metallurgy at the
h o l e des Mines in Paris, who in 1885 concluded that platinum against rhodium-platinum
gave the most consistent results.
Dr. Mackenzie’s fascinating account of the
history of these and other developments,
including the later work of Roberts-Austen and
the concept of the platinum resistance thermometer proposed by Sir William Siemens in
1 8 7 1 , will be of immense interest to all
physicists and metallurgists concerned in any
way with the control and measurement of
L.B.H.
temperature.
125
Nineteenth Century Platinum Coins
AN EARLY INDUSTRIAL USE OF POWDER METALLURGY
By Hans-Gert Bachmann and Hermann Renner
Degubsa AG, Frankfurt am Main, West Germanv
Powder metallurgy is the metallurgist’s
answer to the production of ductile metals of
high melting point by methods differing from
conventional melting and casting. The history
of platinum, extensively and vividly recorded
by McDonald and Hunt (I), gives examples of
how platinum was worked into objects from
earliest times onwards. However, the first real
melting of platinum was achieved only as late as
I 782, when Lavoisier successfully reached the
temperature of 1769OC necessary to melt this
metal on a very small scale with the aid of an
oxygen torch (2). Three years earlier, Franz
Karl Achard (1753--1821), whose contributions
to metallurgy have only recently been fully
realised (3), made use of the property of
platinum to form low-melting point alloys with
elements such as phosphorus, mercury and
arsenic. A mixture of 13 weight per cent of
arsenic and 87 per cent of platinum (equivalent
to 28 atomic per cent of arsenic) gives a eutectic
with a melting point of 597OC (4, 5). Achard
melted this mixture of arsenic and platinum
with the addition of potash as flux, and after
evaporation of the volatile arsenic he obtained
platinum sponge which he was able to shape
into objects, such as crucibles. This process
remained in use until I 8 10.
In the meantime Wollaston produced the first
malleable platinum by a “wet” method. As early
as I 80I he solved the problem of how to get rid
of the impurities normally accompanying
naturally occurring placer platinum. By careful
adjustment of the proportions of hydrochloric
and nitric acid in aqua regia, and later by using
more dilute mixtures, he separated platinum
from its associated palladium and rhodium. The
solution, containing only hexachloroplatinate,
H2FtCI6, was subsequently treated with sal
ammoniac, resulting in a precipitate of
ammonium hexachloroplatinate, (NH4)dPtC16].
On heating this decomposed to platinum
sponge, and thus an economical method was
found to produce the pure metal in sufficiently
large quantities for industrial use (6).
On a limited scale platinum was already
turned into commemorative coins and
medals-ften
surface-gilded-in
Spain in
1780 and in France in 1799. About 1825 a new
source of platinum group metals was discovered
Fig. I Russian 3-rouble
coins minted in 1829 and
1843, respectively. Retween
1828 and 1845 many
hundreds of thousands of
platinum coins were struck
in the m i n t at S t .
Petersburg
126
Fig. 2 Modern platinum
coins w e r e strurk between
1977 and 1980 to commemorate the 0lymp.k
Games held in Mosrow in
1980. ‘I’hc obverse shown
here (left) is common to
the five coins. In addition to
the
runners
illustrated,
other coins show the
Olympir emblem, discus
throwing, wrestling and
chariot racing
in the Russian Urals, these extensive and rich
placer deposits making large quantities of
platinum available. As there was no significant
industrial use for the metal in those days, it was
decided to employ it for coinage purposes. By
imperial decree of Tsar Nicholas I (1825-1 8 5 5 ) ,
dated April 24, I 828, the platinum coinage was
initiated for circulation, starting with 3-rouble
denominations, followed in 1829 by coins of
6-roubles, and finally in 1830 by those of
I 2-rouble
denomination (7). The person
responsible for introduction of the Russian
platinum coinage was Count Georg von
Cancrinus ( I 775- I 845), Minister of Finance
to Tsar Nicholas I from 1824 to 1844. He
belonged to a famous mining family that had
immigrated to Russia from Germany (8).
The crude metal was refined by a “wet” method
developed by the chemist Peter Grigorievich
Sobolevsky (1781-1841) at St. Petersburg (9),
and the resulting platinum sponge was compressed under high pressure to circular blanks.
After sintering, they were again compressed,
heated and struck into coins (10). Between 1828
and 1844 some 485,000 ounces of platinum
were thus converted into coins, employing for
the first time in history powder metallurgical
methods on a large scale. The platinum roubles
were intended to be circulated in lieu of the
traditional silver and gold coinage and the
Russian law fixed the ratio between platinum
and silver at 1:5.21459 (11). The 3-, 6- and
12-rouble platinum coins weighed 0.333, 0.666
and 1.332 ounces troy each, respectively.
Examples of 3-rouble pieces, minted in 1829
and I 843, are illustrated in Figure I .
However, the platinum coins met with little
approval by the public. They came to be known
as the “little grey ones” (in Russian: serenkije,
cepemwie , also meaning “little donkey”) and
the acceptance of these coins was more and more
refused, the Russian government finally having
to call back all the coins still in circulation. T h e
full story of the introduction and the cessation
of platinum coining in Russia has been recorded
in detail by McDonald and Hunt ( I 2), and need
not be repeated here.
The whole stock of demonetised roubles was
stored in the vaults of the Imperial State Bank
until I 872, when George Matthey’s partner,
John Sellon, managed to secure the whole lot,
then amounting to 378,000 ounces. This bulk
wasdistributed among the three refiners: Johnson
Matthey in London, Desmoutis Quennessen in
Paris and Heraeus in Hanau, near Frankfurt,
West Germany (13). Today, very few of
these Russian platinum coins still exist,
they are collectors’ items and fetch high prices
at coin auctions. At the time, when the large
shipments of the Russian stock were distributed
among the refineries mentioned, the small
establishment of Wilhelm Siebert (I 862-1 927),
like Heraeus also situated in Hanau, was able to
secure a share of the Russian coinage from
Johnson Matthey, and after 1884 Wilhelm
Siebert travelled to Russia and as a result was
able to acquire additional raw material
(platinum “sand” and nuggets) for his refinery.
From this time-either through purchase from
Johnson Matthey or through his own
dealings-a few cherished platinum coins and
platinum nuggets were salvaged from the
127
m
L
h)
5
e
Pdnn'mn2 Me.taEs Rev., 1984, 28, (3)
77.14 12.13 0.22
42
Rh
Ir
Cu
2.74 5.10 0.34
-
-
0.57
1.38
3.87
2.56
3.75
0.32
1.89
3.85
2.30
2.87
-
0.93
0.50
2.10
1.96
2.30
0.36
0.86
0.70
5.20
1.30
1.13
0.64
1.16
1.47
1.59
0.28
0.21
0.50
1.98
3.72
0.30
-
3.17
2.50
0.96
0.86
1.15
0.59
2.14
2.35
3.61
3.12
3.30
2.79
2.19
3.46
2.26
2.76
2.48
trace
trace
0.98
4.97
2.35
1.91
2.42
1.21
1.03
1.15
1.34
5.32
1.00
1.15
0.83
1.18
4.73
2.35
0.50
?
1.40
2.80 1.45 2.15
0.30 4.30 4.10
?
?
1.04
1.15 - 0.45
-
(Ir, 0s)
98.65
98.51
98.75
98.70
98.75
97.86
99.72
99.38
99.50
98.92
98.88
98.07
98.98
99.20
98.07
97.76
98.40
98.37
97.70
100.50
90.43
98.92
98.83
Sum
6.36 insoluble,
including (Ir, 0 s )
0.98 insoluble,
including (Ir, 0 s )
1.80 insoluble
0.54 0 s
? Au, 1.OO sand
0.40 Au, 1.40 sand
1.45 insoluble
0.79 S, 0.1 1 residue
Remarks
Weight per rent. after Hintze (111
Nishne-Tagilsk
Kushvinsk,
Blagodat
(coinage metal1
Locality
Osann
Muchin
Claus
Berzelius
Muchin
Frenzel
Berzelius
Deville & Debray
Osann
Analyst
(Reference)
( a ) A n n Phys. lfoggendorffl 1826 8 510.lb) Ann. chim. phys., 1859. 56. 4 4 9 : A r n . J . Sc.. 1860 29 3 7 9 Id NeuesJahrb. Minera/.,l874.684.~dlAk.Hand/.Stockh..l828.1
13:Ann.Phys./Poggendodf~,
1828.13, 5 6 4 . (el Kokshardv’s Mi;. Ross/., 5. 183.If1 Plafinmet. Dorpar. 1854.60 (91Ann. Phvs. {Pogqendodfl, 1828.13.286
1.94
1.87
0.75
0.28
0.30
0.26
0.30
0.23
0.20
0.23
0.21
0.17
0.25
0.18
0.18
0.14
0.20
8.98
17.30
6.54
11.04
12.98
10.79
11.48
11.23
18.90
16.65
18.93
11.72
11.50
17.73
15.54
15.79
15.58
83.49
76.22
85.97
78.94
73.58
83.07
81.34
82.46
70.15
73.70
68.95
78.38
82.16
71.20
74.67
71.94
68.72
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
~
77.50 9.60 0.85
76.40 11.70 1.40
?
76.97 10.97
86.50 8.32 1.10
Pd
2.30 1.64 11.07 trace 2.05
~~
Fe
21
22
23
24
Pt
80.87
~
20
Analysis
Number
Tabla I
Analysis of Platinum from Russian Placer Deposits
Fig. 3 These two platinum
n u g g e t s from placer
deposits in the Urals are
reproduced
here
at
approximately twice actual
size. The results of an
analysis made on the
smaller nugget are given in
Table I1
dissolving acid baths and kept in the company’s
archives. In I 906, Degussa (Deutsche Goldund Silberscheideanstalt vormals Roessler) became a shareholder in the Siebert plant and in
I 930 its sole owner. Fortunately, a few coins and
nuggets even survived this transaction and all
other events of time and we were thus able to
carry out the non-destructive investigations
described below.
After an interval of more than a century,
Russia again issued platinum coins as legal
Table II
Analyses of a Platinum Nugget
and a 3-Rouble Coin
(atomic prr criit)
Element
Platinum
Palladium
Iridium
Rhodium
Ruthenium
Osmium
Iron
Chromium
Nickel
Titanium
Lead
Rhenium
Tungsten
Vanadium
Specific gravity
Jugget from the
3-rouble coin
Urals, exact
ocality unknowr dated 1 8 2 9
-
85
- 2
trace
0.5
trace
trace
- 2
10
trace
trace
-
-
99
0.1
0.1
0.5
0.2
-
-
<0.1
trace
trace
trace
-
16.44 g/cm3
20.72 g/cm3
-
tender of the Union of Soviet Socialist Republics.
The I go-rouble coin commemorating the 1980
Olympic Games in Moscow, shown in Figure 2 ,
was struck at the State Mint of Goznak from
999.3 pure platinum, as stated on the certificate
accompanying each coin.
To bring the story of platinum coinage up to
date, mention must be made of the attempts to
introduce a “Platirand” in the Republic of
South Africa during 1983, while Ayrton Metals
Ltd., the London bullion dealer, successfully
launched a platinum coin, known as the
“Noble” on November 3rd, 1983, accepted as
legal tender on the Isle of Man.
To return to the 19th century, the raw
material for the production of early Russian
platinum coinage came entirely from placer
deposits in the Urals. The most complete
summary of analyses of placer platinum from
this area is found in Hintze (14), together with
a comprehensive description of the nature of
the numerous placer deposits known up to the
beginning of this century. Hintze’s compilation
of Russian sites is reproduced in Table I
together with the original references.
To appreciate the technique of refining
placer platinum and the multi-step production
method at the commencement of platinum
coining, we have investigated a 3-rouble piece
minted in 1829. The results of nondestructive
X-ray fluorescence analysis of this coin, compared with that of a platinum nugget, shown in
Figure 3, are given in Table 11. While the overall composition of the nugget is comparable
with the data given for coining metal in Table I
129
Fig. 4 This set of scanning electron mirrnscope photographs taken of a 3-rouble coin, minted in
1829, at progressively higher magnificatinns clearly shows the many irregularities in the surface
that resulted in the dull, unattractive appearance. As reproduced here, the magnifications are
approximately: ( a ) x 17, ( b ) x55, ( c ) x 1 7 0 , ( d ) ~ 5 . 5 0(, e ) x1700,and ( f ) ~ 5 . 5 0 0
130
(with the exception of a high chromium content
in our specimen), the coin itself is of
remarkably pure platinum. T h e purity as well
as the successful production of the blank by
powder metallurgical procedures is further
reflected by the specific weight of the coin; with
a value of 20.72g/cm3 it approaches that of
pure, massive platinum, that is 2 1.43 g/cm’.
T h e coin analysed, shown in Figure I , has a
somewhat striated surface, obviously not the
influence of wear, but of production. A set of
micrographs, taken under a scanning electron
microscope, from low to very high magnifications (Figures 4a-f) clearly reveals the limits
and shortcomings of early powder metallurgy.
Despite the efforts to compact the platinum
sponge by various stages of pressing and sintering, it was not possible to eliminate small
vesicles and voids. Particularly at high magnifications the pitted surface with holes and
cavities, separating individual metal grains, is
clearly visible. No wonder that the resulting
dull appearance of the coins made them less
attractive compared t o silver coins, thus
attributing to their seemingly inferior quality in
public opinion. Though the issues of later years
I
2
were of much better quality (Figure I, right),
this could not prevent their rejection. The
reason for the final withdrawal of the Russian
platinum coinage from circulation was,
however, a rapid fall in the price of platinum.
The nominal value of the coins was exceeding
their metal value, and fears of counterfeiting
were imminent, though perhaps-in
view of
the complicated process of coining-not
fully
justified.
Considering the numerous modern technical
applications of platinum-the
latest being its
role as one of the active constituents in
automobile exhaust gas catalysts-modern
platinum coinage is but another attempt to
interest investors. We should, however, remember that abundant supplies of the then
practically useless metal and the intention to
introduce it as a substitute for silver (!) helped
to initiate what came t o be known as powder
metallurgy.
AcknowledRements
For advice and information we have to thank Mrs.
Helene Dittmer, Maintal, and Professor Franz
Pawlek, Berlin. Mr. Hajo Everts expertly made the
SEM-micrographs.
References and Notes
Donald McDonald and Leslie B. Hunt, “A
the province of Hessia. He died in 1768. His two
History of Platinum and its Allied Metals”,
sons, Franz Ludwig and Johann Philipp followed
Johnson Matthey, London, 1982
in their father’s footsteps. Franz Ludwig became
L. B. Hunt, “The First Real Melting of’ Platinum”,
supervisor of all the mines in the county, while
Johann Philipp succeeded his father as head of
the Bieber mines. After serious disagreements
LShberg, 6GFranzKarls Achard,s Beitrag zur
with his employer, Franz Ludwig left the services
Legierungskunde aus dem Jahre 1788”, Zeits
of the Count of Hessia and went to Russia, where
Fcrdmm d. Bhgbaus
u.d. Hiirlenwesens an
he was put in charge of the salt works of Staraja
Techn. Universitat Berlin e.V., 1981, 15, 1-2
Russa. Later he rose to high ranks as Counsellor
M. Hansen, “Constitution of Binary Alloys’’,
to the Imperial Court. He died at St. Petersburg
McGraw-Hill, New York, Toronto, London,
in 1816. His son Georg too became a Russian
1958, P. 174-175
civil servant and was subsequently promoted to
H. Quiring, “Die Metallischen Rohstoffe”, 16
Minister of Finance.]
Band, Platin-Metalle, Stuttgart3J962,P.39and 61
9 D. McDonald and L. B. Hunt, op. cit., Ref, I, p.
D. McDonald and L. B. Hunt, op. cit., Ref. I , p.
237-239
159-160
I o R.
Kieffer, “Metallkeramisch hergestellte
Kontaktwerkstoffe”,Z.tech. Phys., I 940,21,35-40
H. M. Severin, “Gold and Platinum Coinage of
Imperial Russia from 1701 to 191I”, Crown and I I xaverF~~~ and C. ~
l “M“nzbuch
~
~ oder~
cO.y
New
‘95% p. S2-54J
Abbildung der kursirenden Geldsorten”, Bern,
distributed by the Numismatic Review
1856, p. 225-226
E.-L’ Hofmann, Geschichte der Berg- und 1 2 D. McDonald and L. B. Hunt, op. cit., Ref, I , p.
Huttenwerke zu Bieber, Natur und Museum,
241-247
1969, 99, 3,177328.[The minister’s grandfather,
Johann Helnrlch cancrinus
was made director 13 D. McDonald, “One Hundred and Fifty Years”,
Phtinum Metals Rm.9 19673 IIY
(117 18-29
(“Bergmeister”)ofthe silver mines near Bieber in
the Northern Spessart Mountains, at that time 14 C. Hintze, “Handbuch der Mineralode”, 1.
Band, I . Abt., Leipzig, 1904, p. 147-148
under the jurisdiction of the Counts of Hanau in
di
4
5
6
7
13 1
~
,
ABSTRACTS
of current literature on the platinum metals and their alloys
PROPERTIES
Thermal Diffusion of PI in Silicon from
Interaction of 0 2 with Pt( l O O ) . l .
Equilibrium Measurements. 11. Kinetics
and Energetics
s. MANTOVANI, F.
PtSi
NAVA, c. NOBILI, M. C o N n and G .
PIGNATEI.,A~PI. Phys. Lett., 1984, 44, (3), 3 2 8 - 3 3 0
K. GRIFFITHS, T. E. JACKMAN, J. A. DAVIES and P. R.
NORTON; P. R. NORTON, K. GRIFFTTHS, and P. E.
BINDNER, Surf. Sci., 1 9 8 4 , 138, ( I ) , 1 1 3 - 1 2 4 ;
17-5-147
Two newly discovered phases on the Pt(Ioo) surface
produced by the adsorption of 0 have been
investigated. One phase is associated with the 0saturated surface, where a very complex LEED
pattern is seen; the other is observed at an average
coverage of 0.44 & 0.05 monolayers and gives rise to
a (3 x I ) LEED pattern. Rutherford backscattering
experiments indicate large Pt atom displacements.
( I 9 Refs; 2 0 Refs.)
Inhibition of Acid Etching of Pt by
Pre-exposure to Oxygen Plasma
M. J. KIM, I.. A. GRUENKE, R. J. SAIA and s. s. COHEN,
APPl. P ~ Y skr~.,
.
1984,44, (419 4 6 2 - 4 6 4
The characteristics of Pt etching in aqua regia have
been studied. Prior exposure to an 0 2 plasma
inhibited the dissolution of the Pt. 02;which is more
abundant in the exposed than the unexposed Pt
helps to form an inhibition layer, such as PtO2,
which prevents CI- attack. This inhibition layer
appears to retard Pt etching effectively in C1- based
etch solutions.
Isothermal Section of Phase Diagram of
the Gold-Platinum-Rhodium System at
1 ooooc
G. P. ZHMURKO, E. M. SOKOLOVSKAYA, M. V. RAEVSKAYA
and YU. A. BRAUER, Vestn. Mosk. univ., Ser. Khim.,
1 9 8 4 , 2 5 9 ( I ) , 107-108
Microstructural and spectroscopic studies were made
of the character of phase equilibrium in the Au-PtRh system at IOOO~C.
Boundaries for reciprocal
solubility of components at iooo0C and for permeation of separation iwliquid state in ternary systems
are obtained.
Phase Diagrams of Platinum-KutheniumRhodium, Platinum-Ruthenium-Palladium
and
Platinum-Ruthenium-Iridium
Systems at 14OOoC
M. v. RAEVSKAYA, v. v. VASEKIN, YU. I. KONOBAS and T.
A. CHEMLEVA, Vesrn. Mosk. Univ., Ser. Khim., 1 9 8 4 ,
25, ( I ) , 109-1 10
Physico-chemical studies of ternary systems Pt-RuRh, Pt-Ru-Pd and Pt-Ru-Ir were made and a region
of phase equilibrium was established at 14ooOC.
Pt diffusion in n-type Si was measured using various
spectroscopic techniques for deep energy levels. Pt
acts as an acceptor which captures electrons. An
energy level of 0 . 2 3 i- 0.02 eV was found for the
trap.
In Situ Study of Film Stress and Kinetics
of Platinum Silicide Formation on Silicon
and I. A. BLECH, Thin Solid Films, 1 9 8 4 , 113,
34
In situ studies of the film stress and film reflectivity
were performed when samples of Pt film on Si were
sintered in an inert gas ambient. The reflectivity of
the film dropped in two stages when the reaction
between Pt and Si transformed the Pt film to a Pt 2Si
film and then to a PtSi film.
J. T PAN
(2), 129-1
PI-Ni
Bilayers on
n - l y p e Silicon.
Metallurgical and Electrical Behaviour
S. MANTOVANI, F. NA\'A, C. NOBILI, G. QUEIROLO
C E L o r r 1 , J . Appl. Phys., 1 9 8 4 , 5 5 , (4), 899-908
and
G.
Silicide formation in Pt/Ni/Si and Ni/Pt/Si structures
has been investigated. Pt and Ni films were deposited
on < l o o > n-type Si. The reaction starts by formation of Ni2Si or PtzSi where metal meets Si and
proceeds until all the inner metal film is silicide.
When held at -300°C for 30 mins the outer metal
diffuses through this silicide and builds up at the Si
surface. When heated at 400°C for 30 mins Nisi
forms and pushes out the Pt from the Si surface.
NilSi changes to Nisi and the structures become non
uniform. The PtzSi --t PtSi transformation at 5ooOC
is accompanied by Pt transport through the Nisi.
The Investigation of Hydrogen Diffusion
in Palladium by the Chemichromic Effect
s. J. TAKERIS, A. R. LUSS and J. P.
P h p . Starus Solidi, 1 9 8 4 , 81, (2),
K I ~ I - K I ~ ~
The chemichromic effect in WO3 was used to
investigate H2 diffusion in Pd by the differential cell
method enabling visual control of the H2 in, for
instance, the walls of metallic pipelines for chemical
transport to be checked for corrosion. Half of a thin
I'd foil was covered with a r p n film of wo3 and the
sample was fixed into a differential cell, with a laser
beam and photoelectron multiplier. H2 was
generated and the change in potential recorded by
Ag/AgCI electrodes. The reflected laser light
recorded changes in optical density. The appearance
of H Z at the PdhyIo3 interface causes a colourless +
blue transition.
J. 1. KLEPERIS,
STRADINS,
132
SAXS Study on Crystallisation of an
Amorphous PdihAu6Si 1 8 Alloy
R. 0. SUZUKI and K. OSAMURA, J. Muter. Sci., 1984,
19, ( 5 ) > 1 4 7 6 I 4 8 5
The crystallisation behaviour of a Pd76Au6Si18 alloy
was studied by means of small angle X-ray scattering
technique. The amorphous alloy crystallised to form
MS-I phase with composition Pd78Au22 in the
amorphous matrix, which later crystallised as MS-11.
The remarkable increase of the scattering intensity
corresponded to the growth of MS-I phase,
the kinetics of which were found to be controlled
by the diffusion mechanism. The interdiffusion
constant was obtained from D = 6.0 x 1 0 ”
exp (- 420kJ/mol/RT)m2/s.
Superconductivity and Atomic Ordering
of Pd-Cu-H Solid Solutions
V. E. ANTONOV, 1’. E. ANTONOVA, 1. T. BELASH, V. YU.
MALYSHEV and V. I. RASHUPKIN, Phys. Srarus Solidi,
198481, (2), K185-Kl90
The superconducting transition temperature TK(n)
dependences on the H : metal atomic ratio, n, for
ordered and disordered Pd-Cu-H solutions containing I ~ 4 at.%
0 Cu were studied. Pd-Cu samples were
hydrogenated for 24h at roo T < 300OC and H2
pressures 8 GPa. X-ray analyses of the alloys under
various H2 pressures were performed and the
structural results are discussed. Replacing Pd by Cu
resulted in no essential changes in the TK(n)
dependence of the Pd-H y-solutions for hydrogenation under conditions close to thermodynamic
equilibrium.
<
Change of Electrical
Properties of Pd-W
Hydrogenation
<
and Magnetic
Alloys during
F. N. BERSENEVA, N. V. VOLKENSHTEIN, E. V.
GALOSHINA, v. I. GROMOV, N. I. TIMOFEEV and T. s.
SHUBINA, Fiz. Mer. Metalloved., 1984, 57, (2),
283-287
Studies were made of magnetic susceptibility and
electroresistivity of hydrogenated solid solutions in
Pdioo-.W, systems ( x = o , I , 7 and 8) with
H < Pd 0.5). Both the temperature coefficients of
resistance and the susceptibility of Pd-W alloys
decreased with the increase of W concentration.
Magnetic susceptibility of the alloys decreases
linearly with the increase of H concentration during
hydrogenation.
<
High-pressure Magnetic Susceptibility
of the Intermediate Valence System
Eu Pd 2 Si 2
s. SRINIVASAN, s. USHA, E. v. SAMPATHKUMARAN and R.
VIJAYARAGHAVAN,~.
Phys. F, 1984,14, (3), L33-L35
Studies of the pressure dependence of the magnetic
susceptibility of the intermediate valence system
EuPd2Si2 at 77-3ooK and ~ 7 k b a showed
r
that the
thermally induced valence transition became more
gradual on application of pressure. The characteristic
fluctuation temperature was pressure dependent.
Activation
Volume
for
Hydrogen
Diffusion in Palladium Hydride
B. BARANOWSKI and S. MAJOROWSKI, 3. Less-Common
Met., 1984, 98, (2), L27-L.q
A method for measuring activation volume for H 2
diffusion in Pd hydride, which consists of parallel
measurements of Fick‘s diffusion for pure gaseous
H Z and for a mixture of H2 and He is reported. H2
occupies the octahedral interstitial sites in the Pd
lattice. The number of sites available is independent
of the pressure and therefore the volume of activation measured relates to the kinetic part only. It
involves the dilatation of the lattice during the intermediate step and the numerical value indicates that
this dilatation is comparable with the partial molar
volume of H2. The activation volume in the system
may be a function of the composition and the
pressure (at a given temperature).
SQUID-Magnetometer
Combined with
Ion Implantation
M. HITZFELD, Z. ZIEMANN and W. BUCKEL,3. Phys. E ,
1984317, (41, 291-295
A magnetron is presented which allows the in situ
determination of the magnetic susceptibility of PdFe
and InMn samples produced by low temperature
(T < IOK) ion implantation into corresponding Pd
and In foils. The superconducting transition
temperature of InMn and the ferromagnetic transition temperature of PdFe samples are used in studies
of the performance of the instrument. The operatinp
principle is based on a superconducting quantum
interference device (SQUID) detecting changes in the
magnetisation as a function of the temperature of a
sample positioned within a static magnetic field.
Thermal Stability of Crystalline and
Amorphous ZrzPdH,
R. c. BOWMAN, J. s. CANTRELL and D. E. ETTER, Scr.
Metall., 1984, 18, (I), 6 1 - 6 6
Differential scanning calorimetry and powder X-ray
diffraction have been used to study the phase transitions and decompositions of the a-Zr2Pd alloy, aZr2PdH2.9 and several crystalline c-Zr2PdH 1.94 compositions. The H-free alloy undergoes low energy
exothermic transitions that are very similar to
crystallisation behaviour in other metallic glasses,
however the lower exothermic peak may be due to
the formation of a metastable phase. A strongly
endothermic peak is observed for a-Zr2PdH2.9.
The Structure of [ Er( 1 ) I - ~ ,Sn( 1 ).I
Er( 2 ) & h & n ( 2 ) ~ S n (3 ) 1zSn(4)2,
A
Ternary Reentrant Superconductor
J. L. HODEAU, M. MAREZIO and J. P. REMEIKA, Acra
Crystallogr., Sect. B, 1984,40, ( I ) , 26-38
The crystal structure of phase I1 of the above compound, which has re-entrant superconductivity
(T,= 0.97 and T ~ = o . s 7 K )has been solved, and
refined from single crystal X-ray diffraction data.
The space group is Iqdacd, with eight formulae per
unit cell of dimensions a = I 3.73 and c = 27.42A.
133
CHEMICAL COMPOUNDS
Phase Diagram and High-Resolution
Photoemission Study of the Superconducting and Magnetic PseudoBody-Centered-Tetragonal
ternary
Ho(Rh I - , R u , ) rB,r System
R. KNAUF, A. THOMA, H. ADRIAN and R. L. JOHNSON,
Phys. Rev. B, 1984,29, ( 5 ) , 2477-2482
Interaction of Hhodiuni
Anthranilic Acid
(Ill)
with
and B. E.
Neorg. Khim., 1984, 29, (3), 764-767
Chemical, thermogravimetric and spectroscopic
The phase diagram for b.c.t. superconducting studies of the interaction of Rh(II1) with anthranilic
acid showed, for the first time, formation of complex
pseudoternary
system
Ho(Rh I - ~ R U , ) ~ B ~
[Rh(C7H 602N)zCI.H 2 0 1
and
(0.07 x I ) is reported for temperatures above compounds
[Rh(C,H602N)3].H20.
The
prepared
compounds
are
1 .3K, showing an abrupt drop in T, near the critical
concentration xcr z 0.40, characteristic for this class not soluble in H20, ethanol, acetone, etc., but
[Rh(C7H602N)3].H 0 dissolved in HNO3.
of compound. T o clarify the origin of this
phenomenon, high resolution photoemission spectra
have been taken of samples with x = 0.07, 0.37 and ELECTROCHEMISTRY
0.90. The analysis of the valence band data near Ef Electrocatalysis
by
Electrodeposited
shows a shift of Ef to lower energies with increasing Spherical Pt Microparticles Dispersed in
x relative to the transition metal d-electron structure. a Polymeric Film Electrode
\', M. BLOKHINA, V. I. IVI.IE\'A, A. K. MOLODKIN
zAITSEV,Zh.
< <
Crystal
Structure
of
New
Superconducting Materials LaIrSi3 and
LaRhSi.3. Structural Relation between
LaRhzSiz, LajRhjSis and LaRhSia
W-H. KAO
and
T. KW'ANA,
3. Am.
Chem. SOC., 1984,
106,(31,473-476
Electrochemical methods for the dispersion of Pt
microparticles at microgram levels in polymeric
matrices of poly(viny1acetic acid) glassy C electrodes,
Pt-PVAA/GC are described. Cyclic voltammetry and
single and double potential step electrolysis were
applied to form Pto particles on PVANGC from an
acidic hexachloroplatinate solution. The Pt particles
were randomly dispersed in the polymer and were
spherically shaped. This electrode had high activity
toward the electrochemical generation of H2 and
reduction of 02. The electrodes have a large surface
area at low loading levels, high catalytic efficiency
and excellent stability.
P. LEJAY, 1. HIGASHI, B. CHEVALIER, J. ETOURNEAU and
P. HAGENMULLER, Mater. Res. Bull., 1984, 19, ( I ) ,
I 15-123
Two new superconducting silicides LaRhSi 3 and
LaIrSi3 have been prepared by arc melting the elements and annealing for ten days at 9ooOC. A single
crystal study shows these materials to have
tetragonal symmetry and to be isostructural with
BaPtSn3. Their T, = I 4-2.7K depends strongly on
stoichiometry and thermal treatment. The structures
are compared to those of superconducting LaRh2Si2
and La2Rh3Si~.The superconductivity seems to be
related to the presence of similar coordination
polyhedra for Rh or Ir and Si atoms.
Methanol Electrooxidation on Platinum
Directly Bonded to a Solid Polymer
Electrolyte Membrane
and M. w.
JOHNSON, Nucl. Instrum. Methods Phys. Res., I 984,
220, (2, 3), 288-292
0 s targets 2-40 mg/cm2 sandwiched in graphite by
centrifuging and hot-pressing in Ar have been prepared for electron scattering experiments. The elastic
and inelastic electron scattering cross sections could
then be determined. The target needs to endure
temperatures up to 500°C for
iooh without
showing chemical or mechanical change.
A. ARAMATA and R. OHNISHI, 3. Electroanal. Chem.
Interfacial Electrochem., 1984, 162,(1/2), I 53-162
Methanol electrooxidation was performed in perchloric acid solution on Pt directly bonded to a solid
polymer electrolyte ( W E ) membrane. After an initial
sharp deactivation in a short time at the polarisation,
the Pt-SPE was found to retain high activity for a
long duration, whereas the platinised Pt showed a
considerable decrease in activity during the polarisation. A surface mediator action of Pto and Pt2' was
essential for the durability of a high catalytic activity.
Mossbauer Evidence for Ru(1V) and
Ru( 11) in Ti02
Adsorption and Oxidation of Phenol on
Platinum and Graphite Anodes
P. TRIGGS, F. LEVY and F. E. WAGNER, Mater. Res.
T. A. KHARLAMOVA, G. A. TEDORADZE and I.. T.
GOROKHOVA, Akad. Nauk SSSR, Elektrokhim., I 984,
Thick Osmium Targets
w. REUTER, 1. c. GURSKY, E.
B. SHERA
-
Bull.,
1984, 199 (2), 97-200
The Mossbauer absorption of the 89.4 keV line of
99Ruhas been measured at 4.2K for samples of Ru in
Ti02 and in Ti02 doped with Ta. It is deduced that
Ru replaces Ti substitutionally in Ti02 as Ru(1V)
and that no delocalisation of the four Ru(1V) 4d
electrons occurs. If the donor T a is added to the
system, the Ru(I1) ion is formed, showing that Ru
behaves as an acceptor in Ti02.
*
Platinum Metals Rev., 1984, 28, (3)~
2% (4), 490-493
Studies were made of the anodic behaviour of phenol
on Pt and graphite anodes under potentiodynamic
and galvanostatic regimes; and the dependence of the
values of phenol adsorption on the potential in acid,
neutral and alkali media was established. The reaction order for the oxidation of phenol was I for
phenol concentration of 1.10-3-1.10-4M at pH 7.
134
<
Cyclic Voltammetric Investigation
Platinum-Rhodium Alloys
of
M. K. ASTON, D. A. J. RAND and R. WOODS,J.
Eleccroanal.
Chem. lncerfacial Electrochem., 1984, 163, (1/2),
199-207
Cyclic voltammetric studies were performed on PtRh alloys in a wide range of pH value solutions. The
potential of the 0 desorption peak on the voltammogram was found to vary linearly with alloy composition. At lower or higher pH values, preferential
dissolution of Rh results in Pt concentration at the
alloy surface. At pH I 3.0, a hydrated Rh oxide layer
develops on the electrode, and changes in the
stoichiometry of this oxide give rise to anodic and
cathodic current peaks.
Study of the Composition of the Surface
of Platinum, Rhodium and Their Alloys
after Anodic Polarisation at High
Potentials by X-Ray Electron and Auger
Spectroscopy
A. A. YAKOVLEVA, 1. L. KUVINOVA, A. M. KLESHCHEVNIKOV, E. N. LUBNIN and Y. A. M. KOLOTYRKIN, Akad.
Nauk SSSR, Elektrokhim., 1984,20, (3), 398-401
X-ray electron and Auger spectroscopy studies of the
surface of Pt, Rh and 1+2owt.% Rh-Pt alloys after
anodic polarisation at high potentials showed a PtO
formation with a thickness range of 8A and also of
Pt02.HzO oxide, depending on the polarisation and
on the concentration of solution on the surface.
Thermochromatographic Behaviour of
O x y g e n - C o n t a i n i n g I r i d i u m and
Platinum Compounds in Ultra Small
Quantities
v. P. DOMANOV, B. AIKHLEV and I. ZVARA
Radiokhimiya, I 984,26, (I), 66-76
Radioactive Ir and Pt compounds were prepared in
air at 725 _+ 25°C by isolation in a S i 0 2 thermochromatographic column. Both elements formed
two adsorption zones and adsorption zone centres
were at 265 k 2ooC and 175 & 20°C for Ir and at
280 & 2ooC and 5 5 k 15°C for Pt. It is suggested
that M e 0 3 oxides are adsorbed at the higher
temperature zones and compounds are fixed to oxides
at the lower temperature zone.
Structure and Electrical Properties of
Pd-Ag-H Alloys Synthesised a1 High
Hydrogen Pressures
v. E. ANTONOV,
PONYATOVSKII,
and E. G.
Fiz. Mer. Metalloved., 1984, 57, (4),
T. E. ANTONOVA, I . T. BELASH
671-679
Studies of the behaviour of electrical resistivity, composition and crystal structure of solid hydrogen solutions Pd-Ag-H were performed on Pd-Ag alloys containing 0,20, 50, 78 and looat.% Ag prepared under
a H Z pressure of 67kbar at up to 35Ooc. New phase
conversions in the systems PdjoAgjo-H and
Pd22Ag78-H were obtained. The results showed that
the conversion in the PdjoAgjo-H system occurred by
atomic ordering in the metallic matrix of its solution.
Electrochemistry
in Liquid
Sulfur
Dioxide. 5. Oxidation of Bipyridine and
Phenanthroline Complexes of Osmium,
Huthenium, and Iron
I.
G. GAUDIELLO, P. G. BRADLEY, K. A. NORTON, W. H.
WOODRUFF and A. J. BARD, horg. Chem., 1984%
23, (I),
3-10
The electrochemical oxidation of bipyridine and
phenanthroline complexes of Ru, 0 s and Fe in liquid
SO2 was investigated by cyclic voltammetry and
coulometry. Os(bpy)$+ and Os(phen)j+ undergo two
successive one-electron oxidations to form stable 3 +
and 4 + species. Fe(phen):+ and Ru(phen):' when
oxidised to the 4 + form, produce an electroactive
layer on the electrode surface.
Hydrogenation of Acetylene and Ethylene
Alcohols in the Liquid Phase on
Membrane Catalysts Made of Binary
Alloys of Palladium with Nickel and
Ruthenium
A. N. KARAVANOV and V. M. GRYAZNOV, Akad. Nauk
SSSR, Kinec. Karal., 1984, 25, (I), 69-73
Studies of the hydrogenation of a number of
unsaturated aliphatic alcohols in the liquid phase
over H2 permeable Ru-Ni membrane catalyst showed
that most active and selective were membrane
catalysts made of 6wt.%Ru-Ni alloy. Capacity of the
surface of the membrane catalyst during hydrogenation of acetylene alcohol was almost loo times higher
than those of supported and skeletal catalysts.
Novel Effect of Neighboring Croups on
the Quenching of the Excited State of a
Polymer-Pendant Ru( bpy)$+ by Methylviologen
M. KANEKO, A. YAMADA, E. TSUCHIDA and Y. KURIMURA,
J . Phys. Chem.,1984, SS,(6), 1061-1062
A
polymer-pendant
tri~(2,2'-bipyridine)Ru(II)
complex was prepared from the copolymer of 4methyl-4'-vinyl-2,2'-bipyridine and acrylic acid, and
the quenching of its excited state by methylviologen
was studied. The quenching rate showed a great pH
dependence and was an order of ma nitude larger
than that of the monomeric Ru(bpy),+
8 in alkaline
medium.
PHOTOCONVERSION
Photolysis
Catalysts
of
Water
over
Pt/TiOz
and s. SATO, N + p n Kagaku Kaishi,
19849(2), 253-263
The quantum efficiency was measured for the
photolysis of gaseous H2O over NaOH-coated
Pt/Ti02 catalysts and was maximised by selection of
crystal structure and source of Ti02. The catalysts
could be activated by illuminating them in a wet
state and then in a dry state in the presence of
gaseous water. A maximum quantum efficiency of
17%occurred when MCB anatase was used.
K. YAMAGurl
135
Resin-Immobilized
Photocatalyst for
Visible Light-Induced Hydrogen
Evolution
ELECTRODEPOSITION AND
SURFACE COATINGS
N. T O S H I M A , Y. YAMADA, J. I S H I Y A M A and H. H I R A I ,
Nippon Kagaku Kaishi, 1984, (z), 368-371
Resin-immobilised colloidal Pt catalysts were prepared by refluxing an anion-exchange resin and
chelate resin hexachloroplatinate complexes in
ethanol-water. The catalysts were active for visible
light
induced
H2
evolution
in
an
E D T A / [ R U ( ~ ~ ~ ) ~ ] ~ ' / Maqueous
V~'
solution.
Ternary photocatalysts were prepared by further
immobilisation of Ru(bpy):+ and MV2+ on the
chelate resin-immobilised Pt catalyst by electrostatic
means. Irradiation of this ternary photocatalyst in an
aqueous solution of disodium EDTA resulted in H2
evolution.
Electrochemical
Deposition
Conducting Ruthenium Oxide Films from
Solution
Photocatalyzed
Benzene in the
conductors
Hydroxylation
of
Presence of Semi-
or
and L. F. \Y'ARREN,J. Electrochem. SOC.,
1984,1313 (219347-349
A new method of electrodepositing conducting
hydrated Ru oxide films from stable aqueous solutions containing a Ru(I1) complex is described. The
films slowly dissolve in aqueous electrolyte upon
potential cycling, yet appear to be catalytic during
water oxidation.
D. P . ANDERSON
LABORATORYAPPARATUS
AND TECHNIQUE
Sputtered Platinum Films on Colloidal
Gold Particles: A Calibration Specimen
S. TERATANI, Y . TAKAGI, M. TAKAHISHI, H. NODA, A.
I K U O and K. TANAKA, Nippon Kagaku Kaishi, 1984,
for Quartz Film Thickness Monitors
R. v. JOHANSEN and E. NAMORK, 3. Microsc. (Oxford),
(z), 283-291
1 9 8 4 > 1 3 3 > ( 183-87
),
A method for calibrating quartz crystal thickness
monitors is described, which makes use of zonm Pt
sputtered colloidal Au particles. The actual thickness
is measured on TEMs of Au particles protruding
from the edge of fractured, rolled up, C films.
Ti02 was loaded with Pt, I'd, Cu, RuO., PdO., IrOx,
Rho, and PtO, to try to enhance the yield of phenol
during the photocatalytic hydroxylation of benzene
and other aromatic compounds. Benzene hydroxylation was conducted at 3ooC under I arm 0 2 by
irradiation with a SOOW Xe lamp. The above
catalysts had quite high relative activities ranging
from 3.0 to 4.3 when used in H2SO4-added solution.
The highest relative activity (4.8) was obtained with
the RuOJTi02 catalyst in the H2SOq-acidified solution containing 4-methyl-2-pentanone.
H ydrogen-Evolving Solar Cells
Use of Arsenic Resonance Line of
197.2nm and Matrix Modification for
Determination of Arsenic in Environmental Samples by Graphite Furnace
Atomic Absorption Spectrometry Using
Palladium as a Matrix Modifier
A. HEI.LER,&ience, 1984, 223, (4641), I 141-1 148
A review is given of H 2-evolving photochemical cells
with semiconductor electrodes where sunlight is
directly converted to chemical energy. In H2evolving photoelectrodes,
electron-hole pairs
photogenerated in the semiconductor are separated
at electrical microcontacts between the
semiconductor and group VIII metal, including Pt
group metal, catalyst islands. Their Gibbs free
energy efficiency solar-to-hydrogen conversion of
I 3.3%) approaches the solar-to-electrical conversion
efficiency of the best p n function cells. ( I23 Refs.)
SHAN XIAO-QUAN, NI ZHE-MING and %HANG LI, At.
Spectrosc., 1984,5, ( I ) , 1-4
An atomic absorption spectrometer with a graphite
furnace was used to measure As absorbance at
I 97.znm. The As-containing river sediment solutions
were injected into the heated graphite furnace along
with the same volume of aqueous Pd solution. When
a L'vov platform with matrix modification by Pd was
used the tolerable charring temperature for As was
raised to I soo"C, and the peak absorbance sensitivity
increased. This can be used with biological samples
to determine As levels.
Luminescence
and
Triplet-Triplet
Absorption Spectra of Rhodium (111)
Porphyrins
Impregnation of Biological Material by
Zn12-0s0 t , K I - 0 s 0 I and N a I - 0 s 0 I
Mixtures
for
Electron Microscopic
Observations: Chemical Interpretaiion of
the Reaction
K. KALYANASUNDARAM, Chem. Phys. Lett., 1984, 104.
(41,357-362
Photophysical studies of four Rh(II1) porphyrins
RhTPPS(H 2 0 ) 1 - , RhTPP(CI)(L), RhOEP(CI)(L) and
RhMesoPME(C1XL) showed them to be characterised
by a moderate phosphorescence ((p I O - ~ ) and a
very weak fluorescence ((p Q 5 x I O - ~ ) in solution at
room temperature. TPP derivatives also have
moderately intense triplet-triplet absorption.
>
Platinum Metals Rev., 1984, 28,
(3)l
I;. CARRAPISO, F. MADALENA-COSTA and M. S. S. PAIS,3.
Microsc. (Oxford), 1984, 134, (z), 193-202
Alkaline iodide-Os04 mixtures were used in the
electron microscopic study of plant cells and gave
better results in the preservation of the cell structure,
in contrast to the cell structure observed when ZnI2Os04 mixtures are used.
136
Osmium Tetroxide: A New Probe for
Site-Specific Distortions in Supercoiled
DNAs
G. c. GLIKIN, M. VOJTISKOVA, L. RENA-DESCALZI and E.
PALECEK,NUCI.
Acids Res., 1984, 12, (3), 1725-1735
oso4 has been shown by gel electrophoresis to bind
to supercoiled DNA, to induce its relaxation without
nicking, and to form single-stranded regions at
specific sites which are recognisable by nuclease S I ,
and visualised as a denaturation “bubble” in the
electron microscope. The amount of 0 s bound to the
DNA increases with the extent of DNA relaxation.
The “bubble” remains stable, yielding the possibility
of site mapping. Thus 0 s may represent another
probe for local distortions in the DNA structure.
Spectrophotometric Determination of
Carbon Monoxide with Ruthenium (11)
Octaet hylporphyrin
A. CORSINI, A. CHAN and H. MEHDI, Talanra, 1984, 31,
( 1 1 3 33-38
A novel spectrophotometric method for estimating
CO at levels from 2-250 ppm is presented. It is based
on the formation of a carbonyl complex of Ru(I1)
octaethylporphyrin and measurement of the
difference in absorbance at 393.5nm between this
complex and the porphyrin reagent. 0 2 and N2 do
not interfere and up to 300ppm of SO2 and
- I 500 ppm C02 can be tolerated to determine CO at
the 4-10 ppm levels. H2S interferes and must be
eliminated before determination.
HETEROGENEOUS CATALYSIS
Studies of the Deactivation Processes of
Platinum Catalysts during Burning up of
Exhaust Gases in the Internal Combustion Engine
R. A. GAZAROV, S. A. SAFONOV, G. M. PLAVNIK, V. P.
MOISSEV, v. I. PANCHISHNYI and V. V. MATVEEV, Zh.
Prikl. Khim. (Leningrad), I 984,57, ( 2 ) , 262-266
Studies of the deactivation processes were performed
on 1wt.X Pt/A120, catalyst prepared by saturation
with H2PtC16 followed by drying and reduction in
Hz at 850-900°C. The results showed that continuous exposure of Pt catalyst to exhaust gases in
the combustion engine leads both to the sintering of
the active Pt particles and to sulphating of the
support, causing change in its phase state.
Optimization of an n-Pentane Isomerisation Reactor
M. CLILPAZ, J. AKYURTLU and Z. AKTAS, Chem. Eng. J . ,
19849 2% (11, 39-48
The optimisation of the operating variables in a
pentane isomerisation reactor was studied during
isomerisation on Pt/A120 3 reforming catalyst where
there is the problem of catalyst decay due to the carbonaceous deposits. The improvement obtained with
optimal operation ranges from an increase of 7% to
an increase of 36% in the production rates.
I. Kinetics of Catalytic Hydrocracking
of n-Decane, n-Undecane and n-Dodecane
on Platinum/Alumina Catalyst. 11. Composition of the Products of Hydrocracking
of n-Decane, n-Undecane and n-Dodecane
on Platinum/Alumina Catalyst
YU. YA. GOL‘DFARD, YA. R. KATSOBASHVILI, E. A.
KULIKOVA, A. L. ROZENTAL and 1. G. SIROTKINA, Akad.
Nauk SSSR, Kinet. Karal., 1984, 25, (2), 363-369,
370-378
Studies of the kinetics of catalytic hydrocracking and
the composition of hydrocracking products were
performed during hydrocracking of n-decane, nundecane and n-dodecane over Pt/A1203 catalyst at
450°C. Relative constants of the rate of isomerisation
and cracking reactions of the initial organic compounds are reported.
Radial Profiles in Pt/AlzOS, Re/AlzOa
and Pt-Re/AlzO:$
S. R. DE MIGUEL, 0. A. SCELZA, A. A. CASTRO, G. T.
BARONETTI, D. R. ARDILES and J. M. PARERA, Appl.
Car& I 984,9, (3), 309-325
The competitive effect of HCI on H2PtCI6 andor
HRe04 deposition on y - A I 2 0 3 was studied by determining HCl, HzPtC16 and HRe04 adsorption
isotherms and by obtaining their radial distribution
profiles. The results show that the three components
compete for the same surface sites and the number of
occupied surface sites per adsorbed molecule of HCI,
HRe04 and H2PtC16 is I , 2 and 4, respectively. The
adsorbate-support interactions were strong and the
shape of the radial profiles indicated that the
H2PtCI6, HCI and HRe04 adsorption was more
rapid than the interparticle diffusion.
Aromatisation of n-Heptane on Platinum
Catalysts
n. DIMITROV, M. GANCHEVA, L. KOZOVA and V.
PENCHEV, Akad. Nauk SSSR, Neftekhim., 1984, 24,
(2), 196-200
Studies of the effect of thermal treatment on the
activity and selectivity of Pt containing zeolite, PtKL
and PtNaX type catalysts were performed during
dehydrocyclisation of n-pentane. The most active
and selective were catalysts thermally treated in air,
then in an A r atmosphere and then reduced in H2. It
is suggested that the inert gas removes adsorbed
oxygen in zeolites thus inhibiting the local thermal
effects.
Valence State Platinum and Catalytic
Activity of Palladium/Support Catalysts
N. S. KOZLOV, L. YA. MOSTOVAYA, A. F. YANCHUK, G. A.
ZHIZHENKO and L. I. TITOVA, Vestn. Akad. Nauk
BSSR, Ser. Khim. Nauk, 1984, ( I ) , 14-18
Studies were made of Pt supported catalysts prepared
by impregnation of y-A1203, MgO and Si02 with
anionic and cationic Pt complexes, (NH4)2PtC14,
(NH4)2PtC16 and Pt(NH3)4C12. The nature of the
initial Pt complex determines the catalytic properties
of the catalysts.
137
Kinetics of Isomerisation of n-Pentane on
Aluminum-Platinum-Lead Catalyst
Catalytic Chemistry of Oxide Bound
Transition Metal Complexes
I. A. VARTANOV, M. S . KHARSON, M. M. KOSTYUKOVSKII,
V. G. LIPOVICH and s. L. KIPERMAN, Akad. Nauk SSSR,
Kinet. Katal, 1984,25, (I), 142-146
B. M. POSIN, Ph.D. Thesis, Princeton University, 1983,
Diss. Abstr. Int. B., 1984,44, (8), 2420-B
New electrophilic oxide-bound catalysts were
investigated using high oxidation state
organometallic compounds on high surface area
oxides. Systems investigated were tris(ally1)Rh on
A1203 or zeolite X and bis(ally1) Pd on zeolite X,
zeolite Y and SiO2. Treatment of the supported ally1
Pd species with H Z resulted in Pd metal formation.
Methanol carbonylation, methane chlorination and
heteroatom oxide reduction using CO as reducing
agent were tested. Pd complexes were better than Rh
complexes for the last reaction. All the Pd complexes
reacted quickly with C12 to give similar species. The
selectivity in product formation suggested that
electrophilic attack by the Pd complex on an alkane
was the key activating interaction.
Studies of the kinetics of isomerisation of n-pentane
were made on Pt-Pb/Al203 catalysts prepared by
saturation of a 0.55% Pt-3.5% F/A1203 catalyst
with Pb acetate, dried in air at 12ooC for 4h and
reduced in H2 at 450°C for 6h. The Pt-Pb/Al203
catalyst contained 25% Pb and studies were performed at 40o-48o0C.
Selectivity of Hydrogenation in an
Alkyne-Alkene System on Palladium
Catalysts Modified with Inorganic Salts
L. C E R V E ~ N.
, T. THANH and v. R ~ J . ~ E K ACollect.
,
Czech. Chem. Commun., 1984,49, (3), 592-596
Studies were made of the competitive catalytic
hydrogenation of 2-octyne and I-heptene in
methanol over 3% Pd/activated C and I'd black
catalysts modified with NH,CI, KCI, KzCO3 and
CaCO3. The rates of hydrogenation of the two substrates and the rate of isomerisation of r-heptene were
measured. The effect of inorganic salts on the
activity and selectivity of the catalysts is discussed.
Spectroscopic Studies on Adsorbed Metal
Carbonyls. Part
1 . Interaction of
[ Rht( CO) 1 2 1 and [ Rhh(C0) I,,] with
Alumina, Silica and Titania
and G. s. McNULTY, 3. Chem. soc., Dalton
Trans., 1984, (41, 587-j94
Spectroscopic studies of the interaction of
[Rh,(CO),,] ( I ) and [Rh6(cO)16] (2) with Alz03,
Ti02, Ti02 and Si02 using isotopic substitution and
spectrum simulation techniques showed conversion
of ( I ) into (2) on A1203 and Ti02. Isolated Rh'(C0)2
sites were considered to exist on all three oxides after
oxidative fragmentation of ( I ) or (2).
J. EVANS
Adsorption and Catalytic Behaviour of
Palladium Dispersed on Rare Earth
Oxides
M. D. MITCHELL and M. A. VANNICE, Ind. Eng. Chem.,
Fundam., 1984,23, (I), 88-96
Studies of adsorption of H2, CO and 0 2 and of
catalytic activity of Pd dispersed on La203, Ce02,
Pr6011, Nd203, Sm203 and Eu203 showed that
large fractions of the Pd surface were blocked by the
oxide support. Turnover frequencies for both CH,
and C02 formation varied by an order of magnitude
and for both reactions activity maxima at Pr or Nd
occurred when plotted vs. atomic number. Mainly
oxygenate formations occurred in these catalysts.
Rhodium( I )
and
Ruthenium( 1 1 )
Complexes of Sulphonated Triphenylphosphine Immobilised on Ion-Exchange
Materials
Enhanced Activity of Pd/TiOZ Catalysts
for the CO/H2 Reaction in the Absence of
Strong
Metal-Support
Interactions
(SMSI)
and R. BURCH, 3 . Catal, 1984, 86, (2),
384-391
The dispersion of the Pd in Pd/TiO2 and Pd/SiOz
catalysts was studied during H2 and CO adsorption,
and catalytic activity was determined for the
hydrogenolysis of ethane and for the CO/H2 reaction. It is found that the Pd/SiO2, and Pd/TiOZ
catalysts reduced at low temperature, show normal
chemisorption and catalytic properties. For the
CO/H2 reaction it is found that all the Pd/TiOz
catalysts have enhanced activity, irrespective of
whether or not SMSIs are operative. It is concluded
that the high activity of Ti02-supported catalysis in
the CO/H2 reaction is not due to SMSI. It is
proposed that the role of the support is to create new
active sites at the interface between metal and support.
J. D. BRACEY
106 and M.T. BECK, 3. Mol. Catal., 1984, 24, (2),
135-145
Complexes of sulphonated triphenylphosphine with
Ru(I1) and Rh(1) were immobilised on strongly basic
anion exchanges. The heterogenised complexes were
successfully applied to the hydrogenation of various
olefins in solution and in the gas phase at 6ooC and
IZOOC,respectively, and at 0.1 MPa total pressure.
The results suggest that the anchored RuClZ(mSPq), exerts its catalytic effect via the same
molecular pathway as in homogeneous solutions.
F.
Stoichiometric and Catalytic Homologation of Olefins on the Fischer-Tropsch
Catalysts Fe/Si02, Ru/SiOz, Os/SiO1 and
Rh/SiOz. Mechanistic Implication in the
Mode of C-C Bond Formation
M. LECONTE, A. THEOLIER, D. ROJAS and J. M. BASSET,J.
Am. Chem. SOC.,1984,106, (4), I 141-1 142
With the above catalysts C.H2. olefins can be
stoichiometrically or catalytically (under H 2)
homologated to higher and lower olefins, and there is
evidence that the mode of the C-C bond formation is
the same in Fischer-Tropsch and in homologation.
138
HOMOGENEOUS CATALYSIS
Chemisorption and Catalysis by Metal
Clusters. 1. Chemisorption of Carbon
Monoxide and of Oxygen Supported
Osmium Clusters Derived from
Osa( CO) 1 2 and from Osb( CO) 1 8
Application of Ultrafine Metal Particles
to Organic Syntheses
H. HIRAI
Palladium Compounds with Some
Azocompounds and Their Catalytic
Properties
and J. E. GOODWIN, zeolites,
198494, (11, 56-60
Ru catalysts prepared using Na-X, Na-Y, K-L and
Na-mordenite as supports were characterised by H 2
and CO chemisorption. Significant suppression of H2
chemisorption was found for the ion-exchanged
catalysts as the Si : Al ratio increased. Chemical
interactions between the metal and support are the
main cause of the H chemisorption suppression.
L. A. SAFRONOVA, A. D. SHEBALDOVA and M. L.
KHIDEKEL‘, Z h . Obshch. Khim., 1984, 54, ( 2 ) ,
Catalytic Oxidation of Carbon Monoxide
over Ru/SiOs. An in Situ Infrared and
Kinetic Study
j. ‘ I . KISS and R. D. GONZALEZ, J . P h y s . C h e m . , 1984,
88, ( 5 1 9 892-897
A spectroscopic study of the partial deactivation of a
series of Ru/SiOl catalysts during the CO oxidation
reaction showed that partial deactivation occurs as
the result of the formation of a more tightly bound
0 2 species, perhaps lattice 0 2 which reacts more
slowly with adsorbed CO than 0 2 in the reactant gas
mixture. The results of a temperature-programmed
reduction study showed that the CO species
responsible for the CO adsorption band at zoIo/cm
reacts preferentially with H2 to form CH4.
s. DAVIDSON,
A. c . TSEUNG, M. GRATZEL
org. C h e m . ,
ap lication of ultrafine metal particles
diameter to organic syntheses are
reviewed. Ultrafine particles of Pt, Pd, Rh, Ru, Cu
and others show high catalytic activity and selectivity
in various organic syntheses. Catalytic reactions
involve: hydrogenation of C = C double bonds, nitro
groups and aromatic rings; hydrogenation of dienes
to the corresponding monoenes; hydrogenolysis of
cystine to cysteine; hydration of acrylonitrile to
acrylamide, and hydration of C = C double bond
followed by dehydrogenation of the alcohol. (5 I Refs.)
H. T. WANG, Y. W. CHEN
P. BALTZER, R.
3. S y n r h .
1 0 - I O O Oin
~
Hydrogen Chemisorption Suppression in
Ru-Zeolite Catalysts
and J. KIWI, J . Am. C h e m . SOC., 1984, 106, (5),
1504-1506
The paramagnetic behaviour of Ru02 islands on
Ti02 was studied since the paramagnetic properties
of surfaces have a profound effect on chemical reactions.
In
the
reaction
4Ce4++ H 2 0
+
4Ce3++ 4H’ + 0 2 , catalysed by RuO2, the
paramagnetic species are responsible for the catalysis
since the observed reaction goes through isolated
RuO2 islands on the catalyst surface. A 6%
Ru02/Ti02 loading represented the minimum concentration for maximum contact.
M. KOMIYAMA,
The
Studies of CO and 0 2 chemisorption on the highnuclearity carbonyl protected clusters os3(co) 12 or
O S ~ ( C O )impregnated
I~
on Si02, A1203 and Ti02
were performed at q 3 K . It is suggested that CO and
0 2 each adsorbs molecularly in both the primary and
the secondary regions. In the primary region CO
adsorption occurs at 0 s sites on the cluster whereas
in the secondary region it occurs at ligandsarbon
bonded to 0s.
Quantitative Studies on the Paramagnetic
RuOz-Ti02
(Anatase)
Behavior of
Powders Catalytically Active in Water
Oxidation
and
JPn., 1984,42, ( I ) , 32-38
D. J. HUNT, S. D. JACKSON, R. B. MOYES, P. B. WELLS and
R. WHYMANJ. Catal., 1984, 86, (z), 333-341
285-288
Studies were made of the reaction of K2PdC14 with
azocompounds in hydro-alcoholic media and
Pd : azocompound molar ratio of I : I using orthosubstituted
a z o c o m p o u n d s o f 4-(2pyridylazo)rezorcyl, 142-pyridylaz0)-2-naphthol and
I ~z-naphtholazo>4-sulphobenzene.
The Pd(I1) complexes yielded by the reaction were highly stable and
catalytically active during hydrogenation of
nitrobenzene under mild conditions.
Synthesis of Aryltrimethyltins by the
Reaction of MeaSnSnMea with ArI
Catalysed by “Ligandless” Palladium
N. A. BUMAGIN, I. G. BUMAGINA and I. P. BELETSKAYA,
D o k l . A k a d . Nauk SSSR, I 984,274, (s), I 103-1 I 06
The dependence of the nature of various solvents on
the final product yield made during the reaction of
M e s h 2 with 2,4dinitrobenzene in the presence of I
mole % of ( Z - C ~ H J P ~ CatI )25OC
~
showed a strong
dependence on the solvent. The solvent depended on
its donor ability behaviour as ligand, and stabilised
Pd intermediates ArPdL2 and ArPdSnMe3L2. The
increase of the donor properties increased reactive
ability of Me6Sn2 and also affected its rate of
disproportionation.
Homogeneous Asymmetric Catalysis by
Means of Chiral Rhodium Complexes
l . O J I M A , P u r e A p p l . Chem., 1984,56,(1),99-110
Synthetic and mechanistic aspects of homogeneous
asymmetric hydrogenation and hydrosilylation
catalysed by Rh complexes with chiral phosphine
ligands are described. A sample of the reactions
discussed include: asymmetric reduction of t i , /Ienones and keto esters via hydrosilylation, asymmetric reduction of rr-keto esters and ketopantoyl
lactone by hydrogenation, remarkable effects of H I
pressure on the stereoselectivity and efficiency of
typical chiral diphosphine ligands. (45 Refs.)
139
Hydroformylation of Unsaturated Fatty
Acids
E. H. PRYDE, J . Am. Oil Chem. Soc., 1984, 61, (2),
Homogeneous Hydrogenation of (r, pUnsaturated Aldehydes Catalyzed by
Ruthenium and Osmium Complexes
4 19-425
A review is given of hydroformylation of unsaturated
fatty materials in the presence of Rh catalyst. With
Rh, the reaction can be carried out at pressure as low
as zoo psi, at double bond location in a polyunsaturated fatty acid and in high yield and conversion. The reconstituted catalyst is more active than
the original catalyst and can be recycled. (74 Refs.)
A. ANDRIOLLO and N
Mol. Calal., 1 9 8 4 ~ 2 4(2),
, 217-220
The Ru and 0 s hydridophosphine and carboxylatophosphine complexes were found to be effective
catalysts for the homogeneous hydrogenation of (t, Dunsaturated aldehydes. The activity and selectivity of
the reaction may be controlled by suitable choice of
reaction conditions and by small variations in the
catalyst structure. High selectivity C = C bond
reduction is achieved with Ru complexes, while for
the more difficult selective reduction of the C = C
bond, the use of 0 s complexes is more suitable.
Chemistry of Continuous
Hydroformy lation
R. A. SANCHEZ-DELGADO,
VALENCIA,J.
Rhodium
A. E. OSUC‘ALD, D. E. HENDRIKSEN, C. S. HSU,
E. J.
MOZELESKI and 1. c . REISCH,
Book of Abstracts, I 87th
ACS Natl. Meeting, St. Louis, Missouri, Apr. 8-13,
I 984, Division of Industrial and Engineering
Chemistry, Abstract No. 1 0 6
Novel alkyldiphenylphosphine based Rh complex
catalysts were found to increase thermal and
operational stability over known commercial Rh
complex systems based on triphenylphosphine,
during continuous r-olefin hydroformylation. In the
product flash-off mode of the commercial process the
low pressure operation, gaseous HJCO and
propylene or I-butene reactants were continuously
introduced into a well stirred homogeneous solution
of catalyst complex plus excess phosphine ligand.
However, the use of a large excess of
alkyldiarylphosphine ligand with the novel Rh
catalyst allowed a stable continuous operation at
increased temperature ( I 4ooC).
Ruthenium Complexes of
1,3-Bis
(2-pyridylimino) isoindolines as Alcohol
Oxidation Catalysts
R. R. CACNE and D. N. MARKS, Inorg. Chem., 1984, 23,
(1),65-74
The complex ( I ,3-bis(4-methyl-2-pyridylimino)
isoindoline) trichlororuthenium(II1) catalyses the
autoxidation and electrochemical oxidation of
alcohols in basic alcoholic solutions. Primary and
secondary alcohols are oxidised, with the principal
products being aldehydes and ketones. The best
results were obtained with Na ethoxide as base. Turnover numbers of 10-30 per day were observed in
iatm 02 at ambient temperatures. But >200 turnovers were observed in the oxidation of ethanol at
ambient temperature with no loss of catalytic activity.
Hydrogen Transfer Reactions Catalyzed
by Neutral Rhodium(1) Schiff Hase
Complexes
R. SARIEGO, I. CARKOVIC, M.
VALDERRAMA, Transition Met.
106-108
MARTINEZ and
Chem., 1 9 8 4 , 9 ,
M.
(3),
HI transfer reactions from z-propanol to acetophenone or cyclohexene are catalysed by neutral
Rh(1) complexes of the type [Rh(COD)L] and
[Rh2(COD)2L1] where L and L’ are Schiff base
ligands and COD = cycloocta-r,S-diene. A
dependency of the catalytic activity on the electronic
and steric properties of the ligands was found.
Hydroformylation
of
Cyclohexene
Catalysed by Homogeneous Bimetallic
Systems
and Y. UCHIDA, 7.
Chem. SOC.,Chem. Commun., I 984, (8), 5 I 6-5 I 7
Homogeneous bimetallic systems, such as Co2(C0)8Ru3(C0)1~ and [Et4N] [FeCo,(CO)12] show high
catalytic activity for the hydroformylation of
cyclohexene compared with C o z ( C 0 ) ~alone. As
more R u ~ ( C O ) Iwas
Z added to C o ~ ( C 0 ) 8the initial
rate for the conversion of cyclohexene to
cyclohexanecarbaldehyde increased until at a
Ru : Co ratio of 9.9 : I it approached 100% and the
initial rate was 27 times faster than with Co~(C0)8.
M. HIDAI, A. FUKUOKA, Y. KOYASU
FUEL CELLS
Electrocatalytic Oxidation of CO in a
CWOz Fuel Cell
J. w’u and c. I? KIJBIAK,Book of Abstracts, 187 ACS
Natl. Meeting, St. Louis, Missouri, Apr. 8-1 3, I 984,
Division of Inorganic Chemistry, Abstract No. I 3 I
A laboratory scale fuel cell was constructed with
2mM [Rh1(C0)2Br2]- as anodic electrocatalyst which
oxidised CO to COz at glassy C electrodes with a
turnover of I 5.I , and produced I .2 I mmol CO 2 and
2 6 2 C of electric charge.
CHEMICAL TECHNOLOGY
Ruthenium Tetroxide-A
Reagent with
the Potential for the Study of Oxygen
Functionalities in Coal
N. MALLYA and R. A. ZINGARO, Fuel, 1 9 8 4 , 63, (3),
423-425
The oxidation of coals by RU04 gives a variety of
products. Among these are the esters formed by the
oxidation of ether linkages. Infrared spectra were
taken of the neat coals, their oxidation products and
two ether soluble fractions. These initial observations
justify further studies on the behaviour of R u 0 4
towards known organic substrates having typical coal
(oxygen) functionalities.
140
Chemical Vapor Deposition of Huthenium
and K. J. SCHNOES,
Extended Abstracts, 84-1, Spring Meeting, Cincinnati, Ohio, May 6-1 I , 1984, Abstract No. 1 0 1 ,
'499'50
A low temperature organometallic chemical vapour
deposition process for Ru is described. Three
organometallic Ru compounds were tested as sources
for chemical deposition of the metal on Si and Si02
substrates at low temperature and pressure. The
decomposition of Ru~(C0)12in vacuum produced the
most uniform metallic films. During runs at
temperatures 250-450°C, the film thickness and
grain sizes decreased. Resistivity values of the Ru
films increased with
increasing deposition
temperature. Samples deposited at 250-300°C
compare favourably with pure Ru. Ru from
Ru~(C0)12
deposited on a device wafer at 3ooOC gave
excellent conformal step coverage. This Ru was subsequently oxidised to Ru02.
M. E. GROSS, L. E. PAPA, M. L. GREEN
ELECTRICAL A N D ELECTRONIC
ENGINEERING
A Hydrogen Sensitive Pd-MOS Structure
Working over a Wide Pressure Range
H. M. DANNETUN, L.X. PETERSSON, D. SODERBERG and
I. LUNDSI'ROM, Appl. Surf. Sci., 1984, 17, (3),
259-264
A Pd-MOS structure, made of pdoped Si wafer,
thermally oxidised to an oxide thickness -ioonm,
with Pd evaporated to a thickness of -ioonm, has
been developed. It is sensitive to H2 both in air at
atmospheric pressures and in UHV. It is sensitive to
H Zpressure from 5 x 10-l' to z Tom. It has applications in studying catalytic reactions involving H on
metal surfaces, leak detection on underground telephone cables and water tubing, and monitoring H in
breath for medical diagnosis. Under different experimental conditions the H pressure range could be
extended by at least two orders of magnitude.
NEWPATENlS
METALS A N D ALLOYS
Palladium
Complexes
Silver-Plastic Moulded Body
U.S. Paten1 4,410,475
JOHNSON MAITHEY P.L.C.
Articles such as jewellery may be fabricated by
moulding under pressure and at elevated
temperature a mixture of metallic particles and thermoplastic particles. The metals may be platinum
group metals, Au, Ag and base metals such as Ni, Cu,
Zn or Sn.
US.Parent 4,4 16,709
An alloy highly resistant to corrosion for use in the
core of a magnetic head has a composition of formula
(Fe,Co,Ni,).M&r,M',jX,
where M is Ru alone or a
mixture with Pt, Pd, Ir and/or Rh, M' is a transition
metal other than those in the formula, X is a
vitrification
element,
p + q + r = roo%,
a + b + c + d + e = 100% and e is 20-2670. A typical
alloy is (Fe~.sCo94,4),04RuzCr(SiloB90)2~.so.~Ti.
Sulphur
A l X ' DER D.D.R.
East German Patent 203,054
Complexes L*M, where L is a dithiobenzil, are made
by reacting a HC1 acid solution of the metal with a
corresponding diketone or acyloin and P
pentasulphide. M is Pt, Pd, or Ni.
ELECTROCHEMISTRY
ENERGY CONVERSION DEVICES INC.
European Appls. 99,866167
An improved anode or cathode is formed by a transition metal host matrix incorporating one or more
modifier elements, such as Ru co-sputtered with Ti
or material with the composition N ~ ~ ~ C O ~ J R U ~ .
Electrocatalytic Energy Conversion
MASSACHUSSETTS INS'ITI'U'TE OF TECHNOLOGY AND
W.R. GRACE & CO.
European Appl. 99,894
Electrochemical reactions for energy and chemical
production give improved yields when carried out in
a solid-state cross-flow monolith reactor. The
monolith may be made from yttria-stabilised 21-02
with screen printed Pt electrodes.
CHEMICAL COMPOUNDS
Amorphous Zirconium Phosphosilicate
1)AIICHI KIGENSO KAGAKU KOGYO CO. LTD.
New ion exchange agents of increased resistance
have the formula Zr(P04)2,(Si02~,.n'H20 or
M2/lZr(P04)2y(Si02),.n'H20 where 1 is the valence
of the cation M, y is 0.02-2, z is 0.05-16.00 and n' is
0-100. The cation may be derived from Groups IA,
IB, IIA, IIB, IIA, IIIB, VA, VIA, VIIA and VIII.
Platinum group metals, Ag and the lanthanides are
among the cations proposed.
Platinum
Electrolytic Cell Electrodes
Amorphous Magnetic Alloy
T.D.K. ELECTRONICS CO. LTD.
and
Water Photolysis Cell
CENTRE NATIONAL DE LA RECHERCHE SCIENTIFIQUE
European Appl. I 00,695
In a new form of cell the separate 0 2 formation and
H2 formation catalysts are held apart by depositing
them on different supports. The cell may use a Ru
bipyridyl photosensitiser and the catalysts are usually
platinum group metal or Ag.
141
using an acetylene iminr or aminoalcohol brightener.
The U.S.Patent 4,416,741 describes the use of acetylene alcohols and/or their ethers as brighteners.
Electrodes for Brine Electrolysis
OLIN CORP.
US.Patent 4,409,085
Reticulate cathodes for use in brine electrolysis are
felts of plastics filaments coated with an
electroconductive metal such as Ni, Mo, Co or a
platinum group metal or alloy. The corresponding
anodes are preferably of Ti mesh coated with Ru
oxide.
Black or Blue Rhodium Electrodeposits
NIPI’ON MINING CO. LTD.
co. 1 . m .
and
NIPPON METAL PLATING
V.S. Patent 4,416,742
Electroplated coatings with a black or blue colour are
obtained using a conventional Rh plating bath with
an added organic carboxylic acid, aromatic sulphonic
acid, amine, gelatin, butynediol and/or a hypophosphite, such as ethylenediamine.
Electrolytic Ozone Production
BBCBROWN BOVERI & co.
U.S. Patent 4,416,747
Water saturated with 0 2 is used to produce 0 3 in a
cell where the electrolyte is solid. The electrolyte,
such as a membrane, is coated on the cathode side
with Pt and on the anode side with Pb02.
LABOHATOHY APPARATUS
AND TECHNIQUE
Raney Alloy Coated Cathode
OLIN CORP.
U.S. Patent 4,419,208
Catalytic Gas Detector
1. & S. SIEGER LTD.
British Appl. 2,125,554A
A sensing element for a catalytic flammable-gas
detector has an electrically resistive heating element,
such as a Pt or Pt alloy coil, embedded in a bead
having a Pd, Pt, Rh or Ir catalyst dispersed over
particles of a metal oxide support material prior to
formation of the bead.
A low overvoltage electrode for use as a H2 evolution
cathode in an electrolytic cell has a conductive metal
core with a Raney metal surface layer derived from
an adherent (Ni-Ru)Al3 beta-phase alloy containing
5-15S”o Ru.
Polarographic Electrode
I’HOTO\’OI.T CORP.
US.Patent 4,419,210
A membrane electrode for polarography comprises
an auxiliary electrode preferably of pure Ag, a
working electrode, preferably made of a noble metal
such as Pt and a reference electrode, such as a
Ag/AgCl electrode.
ELECTRODEPOSITION AND
SURFACE COATINGS
Hydrogen Isotopes Separation
KERNFORSCHUNGSZENTRUM KARISRUHE G.m.b.H.
British Appl. 2, I 26,204A
Apparatus for separating the gaseous H isotopes
protium, deuterium and tritium from a gas stream
uses a membrane, such as a Pd membrane, which is
permeable to the H isotopes and impermeable to the
gas stream.
Vapour Source-Holding Container
KONISHIROKU PHOTO INDUSTRY CO. CI‘D.
Palladium Electroplating
TECHNIC INC.
Brirish Appl. 2,127,315A
A low emissivity wall material used in the construction of a vapour source-holding container may be of
mirror-ground Pt or Au. The container is for an
evaporative material such as Se-Te, Se-S, Fe-Ni or
AgBr-I.
US.Patent 4,406,755
Bright coatings free from microcracks are obtained
from electroplating baths containing succinimide,
pyridine or a pyridine derivative and an
organopalladium complex such as PdL2S04 where L
is preferably ethylene diamine or propane-I ,3diamine.
Blood Gas Sensors
Palladium Electroplating
DEGUSSA A.G.
US.Patent 4 4 I I ,743
Good quality Pd coatings are obtained from an
electroplating bath which is not corrosive to the substrate metal. The bath contains, per litre, 2-5og Pd
of which 80-9570 is present as sulphate and the
remainder as sulphite, 40-ioog H2S04 and/or
phosphoric acid and no HNO3 acid.
Palladium-Nickel Alloy Plating
LANGBEIN-PFANHAUSER WERKE A.G.
US.Patents 4,4 I 6,74014 I
Baths containing 5-30 g/l Pd, 5-30 g/l Ni and a
Pd : Ni ratio of 30-90 : 70-10 are known to give
alloy coatings able to replace Au. Their brightness
and mechanical properties are now improved by
DIAMOND SHAMROCK CORP. European Appl. I 00,667
A new solid state transcutaneous blood gas sensor is
constructed from a noble metal electrode (Ag or a
platinum group metal), a Ag/Ag halide reference
electrode and an 02-permeable polymeric membrane
electrolyte.
Carbon Monoxide Gas Detector
TOKYO SHIBAURA DENKI K.K. European Appl. 102,067
A gas detector for CO consists of a gas sensor and a
reference sensor. The gas sensor is based on Sn oxide
or another oxide semiconductor whose resistance
changes on contact with the reducing gas, a pair of
electrodes, of Pt-Au, and a layer of Pt, I‘d or Rh
deposited on an A1203, Si02 or Zr02 support. The
reference sensor electrode is similar, except that the
catalyst is Ag.
142
Thermal Flow Meter
Diesel Engine
European Appl. I 03,2 I 2
The current flowing through a Pt or other thermosensitive element is amplified and the signal
processed to indicate the required parameter for the
fuel intake required.
Particles in diesel engine exhaust gas are oxidised
using an interstitial catalyst system comprising a
catalyst such as Pt, Rh, Pd or their alloys, a layer of
refractory metal oxide and a support comprising
filamentary metallic material in a knitted or woven
form. The gas is made to execute a sharp change in
direction.
HITACHI L I D .
Determining
Membrane
Hydrogen
Flux
JOHNSON MATTHEY P.L.C.
through
HELLESENS AJS
Steel components are susceptible to H2 attack in
corrosive environments. The extent of such attacks
on steel is now measured electrochemically on a steel
member, coated with a Pd film, using the
Devanathan principle.
Methanol Production
BRITISH PETROLEUM CO. P.L.C.
British Appl. 2 , 125,400A
Methanol is produced by passing CO and H2 over a
supported Pd metal catalyst containing a Group I A
metal, Group I I A metal or lanthanide element as
promoter and supported on a C support with defined
surface area characteristics.
Oxygen Sensor
NISSAN MOTOR CO. LTD.
U.S. Patent 4 4 I 9,2 I 3
For installation in a vehicle exhaust system, an 0 2
sensing element has a solid electrolyte concentration
cell formed as a laminate of thin layers on a ceramic
substrate in which a heater is embedded and to which
lead wires are attached. A conductive cermet paste
prepared by dispersing a mixture of 65 parts Pt
powder and 5 parts of a ZrO2-yttria powder (95 : 5
mole ratio) in 30 parts of an organic liquid vehicle
may be used in its production.
Heat Recovery Process
BARCOCK & K’ILCOX CO.
Waste gases from a combustion process, such as a
boiler, are passed through a recovery heat-exchanger
which has a catalyst-coated surface to oxidise the
combustion products and increase heat recovery. The
catalyst may be Pt, Pd or Ni deposited on the surface
by sputtering.
I.C. Engine Exhaust Gas Treatment
STE. FRANCAISE DES PRODUTTS POUR CATALYSE PROEuropean Appl. I 00,267
CATALYSE
JOINING
A multimetal catalyst is produced from
A 1 2 0 3 or
another support by several treatment stages: the
impregnation with I’d and at least one base metal
(includes lanthanide metals), activation, impregnation with a platinum group metal other than Pd and
finally reduction. In one example Pd is used with Fe
and Ce.
Ihctile Brazing A l l o y
G.T.I!. PRODUCTS CORP.
European Appl. I 04,623
An alloy for brazing ceramics, other non-metals and
metals contains 0.25-5% of Ti, V and/or Zr, 25-85%
Au and/or Pd and I 5-70% Cu andor Ni. The noble
metal gives ductility to the alloy. Cr may also be
optionally present in small amounts.
Olefin Hydroxylation Catalyst
Brazing Foil
ALLIED CORP.
EXXON RESEARCH & ENGINEERING CO.
US.Patent 4,403,391
An homogeneous, ductile foil, useful for brazing Fe,
Ni and Co alloys, contains 1-41 at.% Pd, 0-20 at.%
Cr, I 1-20 at.% B, remainder Ni.
Brazing Alloy
European Appl. I 02,I 54
Olefins are hydroxylated with a watedoxidant
mixture in the presence of a supported 0 s catalyst,
such as Os~(C0)12on MgO, optionally together with
NaI. Typically isobutylene glycol is produced using
this type of catalyst.
GENERAL EI.ECTRIC CO.
U.S. Patent 4,414,178
An improved brazing alloy, particularly suitable for
Nitrilotriacetonitrile Production
use in high temperature gas turbine engines, consists
of 20-80% Pd, 2-1 3% Cr, 1-4% B, remainder Ni.
A gas stream containing HCN is produced, by react-
HETEROGENEOUS CATALYSIS
ing NH3 and a hydrocarbon on a Pt-Rh gauze, and is
scrubbed out of the gas stream with nitrilotriacetonitrile mother liquor. The liquor is fed to a unit for
the production of nitrilotriacetonitrile.
Lead Tolerant Catalyst Containing &ria
JOHNSON MATTHEY
P.I..~.
British Appl. 2,122,9 I 2A
A Pb-tolerant spark-ignition engine exhaust gas
purification catalyst comprises Pt, Ru andor Pd on
ceria which is supported as a refractory oxide coated
support. The combination of the Pt, Rh andor Pd
with ceria results in improved Pb tolerance.
MONSANTO CO.
Hydrogen Peroxide Production
EKA A.B.
A new form of catalyst for the well known anthra-
quinone process consists of one or more thin-walled
coherent solid catalyst bodies forming parallel channels through which the working solution and H2
143
Osmium H ydroxylation Catalysts
pass. The platinum group metal catalyst preferably
forms a thin layer on the walls.
1:XXON RI?SEARCH & ENGINEERING CO.
U.S. Parenr 4,4 I 3, I 5 I
The hydroxylation of olefins to diols is catalysed by
an 0 s carbonyl cluster complex supported on a
carrier such as Alz03, with NaI co-catalyst.
Metallisation of Polyarylene Sulphide
Printed Circuit Boards
I’HII.I.IPS PETROLEUM CO.
European App!. 103, I49
The adhesion of conductive metals to polyarylene
sulphide surfaces after pretreatment with a Pd-Sn
catalyst is increased by allowing the metallised board
to age.
Multimetal
Catalyst
Hydrocarbon
Oxidation Catalyst
‘TOKYOSHIHAK!RA IIENKI K.K.
U.S. Patent 4,414,139
A catalyst for the oxidation of CO, especially in the
waste gases from domestic cookers or heaters, is
made by calcining a Li aluminosilicate clay, coating
with A1203, and impregnating the A1203 coating
with a platinum group metal, preferably Pt.
Ht4orniing
A new catalyst contains 0.05-58 each of Pt, Ir and
Re uniformly dispersed throughout a porous
refractory oxide support, instead of being deposited
on the surface as before.
MOBIL OIL CORP.
Naphtha Hydroreforming
EXXON RESEARCH & ENGINEERING CO.
US.Putenr 4,415,441
In a process for producing a high-octane hydrocarbon from naphtha and H Z over a supported Repromoted Pt catalyst, the H2 is at first added at no
more than 75[$ of the rate required to maintain an
optimum yield of hydrocarbons with over five C atoms.
I.C. Engine Exhaust Catalyst
AIR PR0I)UCrS &CHEMICALS INC.
US.Parent 4,407,738
A specified single step impregnation method is used
to impregnate a carrier consisting of A1203 spheres
containing minor amounts of La oxide, Nd oxide and
C e oxide with Pd, Pt and R h so as to obtain a desired
distribution of the metals in the carrier particles.
Internal Coating o f ‘lubes w i t h (:atalyst
DECI‘SSA A.G.
U S . Parent 4,415,485
An internal coating of catalyst is provided on contact
Catalyst Packaging
I)EGI!SSA A.G.
U S . Parenr 4,409, I 85
Pyrophoric Fe or Ni catalysts which may emit H2
during storage or transport are packed in containers
having a safety closure which is a hollow stopper
provided with a relief valve and containing a recombination catalyst such as Pt and/or Pd supported on
A1203.
I.C. Engine Exhaust-Gas Purification
U S . Patent 4 4 I 0,454
U O P INC.
A catalyst for the oxidative purification of I.C.E.
exhaust gases consists of a metallic support such as a
Ni-Cr alloy electroplated with a mixture of platinum
group and lanthanide metals, preferably Pd and Pt,
and La or Ce.
tubes in a simplified mechanised way by filling the
inside of the tube with catalyst liquid and heating the
surface of the liquid as it is drained from the tube. In
an example an A1203 tube is filled with a Pt solution
which was heated to 250°C as it was drained at a rate
of 8cdminute.
Effluent Gas Purification
RICOHCO. i . m .
U.S. Paieni 4,415,533
Malodorous exhaust gas from an electrophotographic
machine is purified by passing it over a heated porous
honeycomb oxidation catalyst in which the active
material may be Pd or Pt, among others.
Catalytic Combustor
I!NI~Tl~I~~TI~CHNOI.OC.IES
CORP. U.S. PUrenl 4,415,537
A catalytic combustor for use with solid-fuel stoves
consists of a carrier which is stable at high
temperatures, such as La-stabilised A1203, supporting an active, S-tolerant catalyst such as Rh.
Selective Hydrogenation Catalyst
IMPERIAL CHEMICAL INDUSTRIES P.L.C.
U S . Patent 4,4 I 0,455
A catalyst for the selective hydrogenation of acetylenic impurities in an olefin stream to olefins is
made by calcining shaped pieces of a Ca aluminate
cement at 900-1050~Cand impregnating with a Pd
salt solution below pH I .3.
Diesel Oil Production
Gt!I.F RESEARCH & DE\’ELOPMENT CO.
US.Parenr 4,413,064
A catalyst for the conversion of synthesis gas to diesel
oil is made by impregnating A1203 with an aqueous
solution of a Co salt and a mixture of T h or La
nitrate and Ru acetylacetocate in an organic solvent
such as acetone-ethanol.
Syngas Catalyst
SHELL 011. CO
US.Patents 4,415,675176
A catalyst for the conversion of synthesis gas to
paraffins, alcohols and aldehydes is made by calcining a Ru-exchanged fauiasite zeolite in Nz and then
in H2, treating with a borane solution and again
calcining successively in N I and H2.
Homologation Catalyst
ETHYI. CORP.
US.Parent 4,415,749
A catalyst for the formation of ethanol and methyl
acetate from methanol and synthesis gas consists of
[-lo% Rh and I-Io‘Z, Fe supported on A1203
modified with Na or Ca.
144
Nitrobenzene Hydrogenation
HOMOGENEOUS CATALYSIS
E. 1.D11PONT DE NEMOIJRS & CO.
US.Patenr 4,415,754
Crude nitrobenzene is hydrogenated over a Pd-PtFe/C catalyst, and aniline is separated from the tarry
residue.
Hydrocarbon Conversion Catalyst
U.S.Patent 4,416,804
A variety of conversion processes, particularly gasoline fraction reforming, are catalysed by an acidic
multimetal composite containing 0.01-2% Pt or
another platinum group metal, 0.05-5%, Co,
0.01-57r Sn, o.o1-5~$~
P and 0.1-3.58 halogen.
IlOP INC.
Oxidation Apparatus
DAlKlN KOGYO K.K.
US.Patent 4,4 I 8,046
In a process for the catalytic oxidation of CO, formaldehyde andor methanol, a cylindrical honeycomb catalyst carrier is designed so that it can be
regenerated in sections by the passage of hot air. The
active component is finely divided Pd.
Oxygen Scavenging
Anaerobiosis
System
for
BI~CTONDICKINSON CORP.
U.S. Patent 4,419,45 I
A system for producing an atmosphere for culturing
anaerobic microorganisms comprises, in a sealable
container, a metal-metal salt couple (a) capable of
reacting with 0 2 and a catalyst for the reaction of 0 2
with gas generated in the container. In (a) the metal
salt may contain Pt or Pd and the catalyst may be a
supported Pd catalyst.
Hydrodesulphurisation Catalyst
INSTI'IIJT FRANCAIS DLI PETROLE
French Appl. 2,521,448
If a natural gas stream, possibly containing small
amounts of 0 2 and odorised with tetrahydrothiophene, is to be used as a chemical feedstock, the S
compound should first be removed to prevent
catalyst poisoning. This is done by mixing the gas
with H2 at elevated temperature and passing the
mixture over a o.I-~%, Pd catalyst supported on
A1203 or Si02.
Ruthenium Catalyst
INSTll'LlT FRANCAIS DU PETROLE
French Appl. 2,523,955
A catalyst for the production of C H 4 from CO, and
H2 in aqueous media is obtained by impregnating a
vegetable carbon of high specific surface area with
Ru acetylacetonate and reducing it in a stream of HI.
Three-Way Catalyst
DEGUSSA A.G.
German Offen. 3,223,500
A three-way catalyst for the purification of I.C.E.
exhaust gases consists of a carrier which is
particulate A1203 or a ceramic honeycomb coated
with A1203 impregnated with Ce oxide or a mixture
of Ce oxide and Fe oxide in the ratio Ce : Fe of 9 : 2
to I : 8, and the ratio Pd : Rh of 2-20 : I .
Carboxylic Acid and Ester Co-Production
SHELL ~NI'EKNATIONALERESEARCH Mij. B.V.
British Appl. 2, I 23,404A
Carboxylic acid and related carboxylic esters are
produced simultaneously by the reaction of different
carboxylic esters with CO and H2 at elevated
temperature and pressure using a catalyst system
containing a Ru compound, a Group VIII metal compound and an organic bromide or iodide. Other
Group I1 metal and transition metal salts must be
absent. Thus ethyl acetate and acetic acid may be
produced from methyl acetate in the presence of Rh
and Ru chlorides and CH3I.
Alcohol Production from Synthesis Gas
BRITISH PEI'ROLEUM CO. P.I..C.
Saturated straight-chain alcohols are produced from
synthesis gas using a catalyst, especially a mixed
oxide catalyst, containing Co, one or more of Cu, Ag,
Ga, Zr, Zn and Th; one or more of Pt, Pd and Ni and
one or more Group IA metals, in specified ratios. A
typical catalyst is CuCoPdo.o~K.0, where x is about
1.5%and y satisfies the valence requirements.
Acetic Acid Production Catalyst
CHEMISCHE WERKE HULS A.C. European Appl. 105,132
Acetic acid is produced by the rearrangement of
methyl formate in the presence of a catalyst consisting of Rh, Rh salt or a Rh complex (but specifically
excluding Group VA ligands), a Group VIB metal
compound, (preferably Cr carbomyl and/or halide)
and a halogen promoter such as CH3I. At least
o.ojmg atom, preferably o.i-Img atom, of Rh is
used per mol of methyl formate.
Hydroformylation Catalyst
SLlN TECH. INC.
T h e hydroformylation of propylene to
n.butyraldehyde is catalysed by the complex
Pt(acac)2.5(SnC12.2H20).5(PPh3).
Rhodium Complex Catalysts
MONSANTO CO.
US. Patent 4,405,814
The hydroformylation of formaldehyde to glycol
aldehyde is catalysed by Rh-tertiary phosphine complexes, such as (CO)ClRh(PPh3)2 and a t.amine.
Rhodium Complex Catalyst
NAI'IONAL DISTILLERS &CHEMICAL CORP.
US.Patent 4,405,82 I
The hydroformylation of formaldehyde in liquid
organic media to glycol aldehyde is catalysed by
ClRh(PPh3)j and Bu3PO.
Platinum Complex Catalyst
SHELL OIL CO.
US.Patent 4,408,078
The hydroformylation of olefins to aldehydes is
catalysed
by
complexes
of
the
type
{(PPh3)2PtH(OPPh2)J.
145
hydrogenation. The hydroformylation catalyst may
be a compound of ruthenium, Ir, Rh o r 0s.
Hydrogenation Catalysts
SHELL 011. CO.
US.Patent 4,409,397
Specified asymmetric hydrogenation reactions are
preferably catalysed by a system consisting of a
complex (LRhC1)z where L is cyclooctadiene or norbornadiene and a chiral ferrocenyl phosphine ligand.
FUEL CELLS
Nuclear Fuel Processing
G.m.b.H.
European Appl. I 00,94 I
Spent fuel rods are heated to expand the sheathing.
The fuel released is dissolved in an 0 2 atmosphere
where Ru and other platinum group metals are lost
as volatile compounds with 0. They are recovered in
a cold trap.
ALKEM
Rhodium and Ruthenium Catalysts
NATIONAL DISTILLERS & CHEMICAL CORP.
US.Paten1 4,4 I 3, I 46
Catalysts for the water-gas shift reaction and various
organic hydrogenation and hydroformylation reactions consist of a lamellar material such as graphite, a
clay or Zr dihydrogen phosphate intercalated with a
Rh or Ru carbonyl cluster complex.
Fuel Cell Electrode
In an improved, stabilised, gas-diffusion electrode for
a fuel cell, a conductive permeable substrate is coated
with a catalyst consisting of colonies of primary
metal particles uniformly distributed on a carrier
powder. The metal is a platinum group metal.
HITACHI LTD.
Rhodium and Iridium Hydrosilylation
Catalysts
MINNESOTA MINING & MANUFACTURING CO.
U.S. Parent 4,414,376
The hydrosilylation curing of vinyl siloxane
polymers is catalysed by complexes (L)MX(L')2 or
(L)(RhX(CO)212 where L is a N heterocycle such as
pyridine, phenazine or pyrazine, L' is CO or L'2 is
cyclooctadiene and M is Ir o r Rh.
Fuel Cell Electrode
Hydrogen Transfer Catalysts
MONTEIXSON S.P.A.
US.Patent 4,414,417
H transfer between alcohols and unsaturated ketones
is catalysed by complexes of formula (M(L)(cod)JX
where M is Ir or Rh and L is a phenanthroline or
bipyridyl ligand. Mainly Ir complexes are used.
Binder for Solid Fuels
UNITED TECHNOLOGIES CORP. U.S. Patent 4,4 I 6,7 I 0
Norbornene polymerised using a Ru chloride catalyst
provides a useful binder for gasoline and other
liquids to give solid fuels.
W ' R . GRACE & CO.
U.S. Patent 4,4 I 3,04 I
A fuel cell reactor consists essentially of a stack of
ribbed solid electrolyte sheets (ZrO2 stabilised with
CaO or Y oxide) coated with a catalyst such as Pt or
Pt-Rh alloy.
Corrosion Protection System
1EXAS INSI'RUMENI'S INC.
U.S. Paten1 4,407,7
DU P O N I DE NEMOURS & CO.
I I
In an impressed-current corrosion-protection system
for hot-water tanks, the electrochemically active nonsacrificial anode consists of a strand of Ti, Nb or T a
coated with Pt, Ir and/or Ru.
US.Parenr 4,4 I 6,801
The oxidative carbonylation of toluene with C O and
0 2 to toluic acid is catalysed by a mixture of
1.5-95 mol %
platinum
group metal and
perfluorinated polymeric sulphonic acid or its salts
(5-98.5 mol%). The two components may be combined, in Pd-exchanged Nafion resin. The text
discloses a wider range of S oxyacids as co-catalysts.
CHEMICAL TECHNOLOGY
Hydrogen Purification Apparatus
CONSOLIDATED TECHNOLOGY CORP.
H ydrosilylation Catalysts
'I'H. GOI.I)SCHMIIlT A.G.
Fuel Cell Reactor
CORROSION PROTECTION
Toluic Acid Production
E. 1.
U S . Parent 4,407,906
An improved catalytic electrode for use in a
phosphoric acid fuel cell consists of a graphitised C
substrate coated with a Pd-Pt alloy in a hydrophobic
binder.
~1.s
IIEPARTMENT 01: ENERGY
The hydrosilylation of compounds containing
olefinic double bonds is catalysed by compounds of
general formula M(NH))zX2, where X is CI, Br, I or
NO2 and M is Pd or Pt.
An apparatus for safely purifying Hz gas and a
method for preventing explosions in laboratory scale
H Z gas diffusion purification units, which may use a
series of Ag-Pd tubes, are described.
Colour Photographic Material
Hydrocarbon Processing
MOBIL OIL CORP.
KONISHIROKU PHOTO INIXISTRY CO. LTII.
US.Patent 4,417,973
Hydrocarbon stocks of high olefin content are
upgraded by sequential hydroformylation and
Ag halide colour photographic material has a lightsensitive Ag halide emulsion layer containing at least
146
one cyan-forming coupler and optionally Au
sensitisers, such as K chloroaurate, or sensitisers of
water-soluble salts of Ru, Rh, Ir, Pt or Pd, such as
ammonium chloropalladate or K chloroplatinate. A
Pd/C catalyst is used as a hydrogenation catalyst in
the production of the couplers.
Metals Recovery
NATIONAL RESEARCH DEVELOPMENT CORP.
US.Patent 4,4 I 2,893
In a method for recovering metals more noble than
Fe by electrolysis of their salt solutions in the presence of ferrous ions, relative motion is maintained
between the solution and the anode which is of graphite, Pt, platinised Ti, Ti coated with Ir oxide or Pt
coated with Ir oxide.
Thermal Treatment of Semiconductor
Powders
CIBA-GEIGY A.G.
The photoredox properties of a wide variety of
chalcogenide semiconductor powders (among them
Ag sulphide) are improved by heat treatment at up to
150°C under pressure. The products may be coated
with metal, especially Pt.
Microcircuit Assembly
HUGHES AIRCRAFT CO.
US.Patent 4,410,874
A large area hybrid microcircuit assembly includes
thick film leads preferably made from pastes of Pt-Ag
or Pt-Au alloy.
Sparking Plug
NGK SPARK PLUG co. LTD.
US.Parenr 4,4 I 4,483
In a specified powder metallurgy process spark plug
electrodes are made from alloys of Ag and Au with
each other and/or Pt, Pd and/or Cr.
GLASS TECHNOLOGY
Metallised Glass-Ceramics
CORNING GLASS WORKS
US.Patent 4,4 I 4,28 I
Machinable glass-ceramics having an integral surface
layer of Cu or Ag are made by fusing specified
mixtures of Si02, Mg oxide, Mg fluoride, K oxide or
Ba and Sr oxides, Al203, B2O3 and Cu oxide or Ag
oxide in a Pt crucible, shaping, and heating in a
reducing atmosphere.
U.S. Patent 4,414,282
Glass ceramic compositions for making seals to
Inconel are made by fusing specified oxide mixtures
in a Pt or Pt-Rh crucible.
V.S. DEPARTMENI' OF ENERGY
Flat Glass Manufacture
PATENT
US.PHILIPS CORI'.
US.Patent 4,415,486
A resistor paste consists of an organic vehicle, a glass
frit and one of a rhodite, Ag.Pdl-xRh02 or its alloy
with Ag and Pd, or Ag-Pd alloy particles coated with
the rhodite.
Thick Film Inks
Glass Ceramics
EGLASSTREK
Rhodite Resistor Paste
PROMOI'ION
&
AWARDING
c;.m.b.H.
In a process for making flat glass, a stream of molten
glass is drawn across a flat refractory or Pt alloy
surface by a Pt alloy or stainless steel device.
ELECTRICAL AND ELECTRONIC
ENGINEERING
Permanent Magnet
British Appl. 2,1 24,033A
Radially directed internal magnetisation, for
instance in a bearing, is obtained by forming a
magnet from axial slices which are stacked to form a
cylinder with a central bore. Pt-Co and lanthanideCo magnet alloys are preferably used.
LIT7'ON SYSTEMS INC.
Magnetic Recording Medium
HITACHI LTD.
A recording medium free from spike noise has a high
permeability
magnetic
material film, an
antiferromagnetic material film and
a
perpendicularly oriented magnetic film. The high
permeability film may be made of a Co-Ru alloy.
R.C.A. CORP.
US.Patenr 4,415,624
Thick film resistor or conductor inks based,
respectively, on Ru02, and a precious metal and Bi
oxide, can be fired in air when the frit used is a Ca Ba
borosilicate glass.
Electrode for Printing
INTERNATIONAI. BUSINESS MACHINES CORP.
US.Patent 4,415,905
The wear resistance of an electrolytic printing
electrode is considerably increased by coating the
substrate tip with a thin layer of T i 0 2 and Ru oxide.
Iridium Oxide Electrochromic Devices
BELL TELEPHONE LABORATORIES INC.
A new combination of an electrochromic Ir oxide
electrode and a T a oxide counter electrode produces
a device which has a short circuit memory, colouration threshold and response time.
Thick Film Conductor
8.1. DU PONT DE NEMOURS & CO.
US.Parent 4,4 I 6,932
A thick film conductor composition suitable for use
in terminations for hermetic ceramic capacitors consists of a mixture of 30-8070 finely divided noble
metal or alloy (preferably a mixture of Ag, Pt and
Pd), 1-2070 finely divided low-viscosity glass,
0.1-1070 metal oxide capable of reacting with A1 2 0 3
to form a spinel and 0 . 1 ~ 2 %organotitanium
complex, especially an alkoxy complex.
147
throughs in an implantable medical prosthetic
Package which includes a
in the tube Of biocompatible material, preferably Pt.
Magnetic Recording Medium
U.S. Parent 4,416,943
Super high density recordings can be made by using
a thin layer (up to 5ooA) of an alloy containing at
least 50% Co, and one or more of Zn, R h and Ir.
~ r . 1 1 . ~EI,ECTRON~CS
.
c o . L1-11.
wound Dressings
LINIVERSITY OF sTRATHCLYDE European Appl. 99,758
In a multilayer wound dressing, especially for use in
combination with the application of electrical
EMI-VARIAN rrm.
4’4r7y173 stimuli, a biodegradable tissue interface layer such as
Thermionic electron-emitters consist of a porous collagen is preferably coated on to a layer of fabric
matrix of w, impregnated with a Group
plated with Ag, Au or Pt, for example, protected on
activator, coated with I pm of a sigma Phase alloy its other side with a semipermeable membrane of
such as an alloy of Os, Ir or Rh with M o , T a or Nb.
collagen or Ca alginate.
Thermionic Cathodes
Electrical Hesistors
C I S CORP.
Biological Electrorhemical Sensor
US.Patenr 4,4 I 8,009
HEI.I.IGE c.m.b.H.
An electrochemical sensor for the transcutaneous
measurement of C 0 2 partial pressure in a living
body uses an Ir/lr oxidehembrane measuring
electrode in contact with a buffer solution mounted
on a Cu or Ag base.
Shaped electrical resistors are made by mixing
powdered glass with a finely divided refractory oxide
filler and a thermally decomposable resinate of Pt
a n d o r Ru, heating to decompose the resinate, and
then shaping and firing at a temperature sutlicient to
fuse the glass but below the softening point of the
refractory oxide.
Dental Jacket Crown
Magnetic Recording Material
N.\’. PHILII’S’ GI.O~II,AMPENFABRIEKEN
German Offen. 3,32 I ,944
An improved magnetic recording material consists of
a non-magnetic substrate coated with a film of Co
containing I 5-30 at.%Cr and 1-5 at.%%.
1. SHOHER
The crown is prepared from a thin metal foil substrate coated with a noble metal composition of low
melting point, for example a Pt foil coated with Au.
The foil is folded into a number of triangular flaps or
pleats to form the jacket on a die.
Pacemaker Electrode
r n . LTD.
US.Patent 4,408,604
A procedure for fabricating a porous Pt electrode tip
WI.ECTRONICS
TEMPERATURE
MEASUREMENT
for a cardiac pacemaker is claimed.
Heater Control Device
British Appl. 2,124,4 I OA
A heater control device in which energy consumption
by the control circuit is largely reduced includes a
temperature sensor, such as a Pt resistor.
H. SUGIMORI
Platinum Diamine Complexcbs
Nli~THERLANIIST N O
US.Parent 4,410,544
Complexes of Pt with a large number of diamines
may be used in the treatment of tumours and are
considerably less toxic than cisplatin.
Fast-Response Thermocouple Probe
Dental A l l o y s
ARMSI’RONG WORLD INDUSTRIES INC.
JliNERlC INDUSTRIES INC.
In a passive fast-response insulated-foil thermocouple
probe, the metal pairs forming the thermocouple
junctions may be made of Pt-Rh alloys.
U.S. Parent 4 4 1 9,325
A dent21 alloy for use in porcelain-fused-to-metal
restorations includes Pd, Ga and optionally Cu, Au,
Al, Co, R u or Re. The Ru or Re provides grain
refining for the alloy to increase its elongation,
tensile strength and thus toughness.
MEDICAL USES
Platinum Dioxopyrimidine Complexes
US.Parent 4,4 I 9,023
Oxygen Sensor
POLYSTAN (GREAT BRITAIN) LTD.
A polarographic 02 sensor intended primarily for
measuring levels of O 2 in blood during by-pass
surgery may include a Ag anode and a Pt cathode.
RESEARCH CORP.
US.Patenr 4 4 I 9,35 I
Blue or green Pt<2,4-dioxopyrimidine) complexes,
useful as anti-tumour, anti-bacterial and anti-viral
agents, are prepared by reacting a 2,4dioxopyrimidine with cis-diaquodiammine Pt(I1) at
0-55’C and pH 3-8.
Kadiodiagnostic Agents
Prosthetic Package
Twenty two metallic tubes, preferably Pt, are placed
in small holes in a ceramic plate to form feedTELECTRONICS PTY. LTD.
Useful agents for examining adrenal activity are
labelled
metallocenes
of
general
formula
C ~ Z M C H ~ N H C Hwhere
~ R , M is Ru, 0 s o r Fe.
M. W’ENZEL
148

platinum metals review - Johnson Matthey Technology Review

Transcription

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