Catalytic Detonation of RDX/TNT Blend Explosives for the

Catalytic Detonation of RDX/TNT Blend Explosives for the
Assembly of Carbon Nanostructures
Yeuh-Hui Lin* and Yi-Ming Su
Chemical & Biochemical Engineering Department, Kao Yuan University, 821, Kaohsiung, Taiwan, ROC
*Email: [email protected]
Abstract
1. Introduction
Nano-structured materials have been synthesized by a
Due to their unique properties, carbon nanotubes
self-heating detonation process using a RDX/TNT blend
(CNTs) are an extremely attractive raw material for
explosive (i.e. B explosive) for providing the need of high
functional as well as structural applications. In recent years,
temperatures, high shock waves, and parts of carbon
dramatic advances have been accomplished, especially
sources in the presence of metallic-containing catalysts.
concerning the use of CNTs in nano-electronics. For this
The products of carbon nanomaterials are characterized by
field of application comparatively small amounts of highly
SEM, EDX and TEM techniques. The systematic
determined CNTs are sufficient to serve valuable functions,
experiments
that mixture of
which makes relatively high prices tolerable. However, as
RDX/metalcene with or without carbon source as a
traditional CNT synthesis like arc-discharge, CVD or laser
molecular precursor can be employed to produce transition
ablation is energy- and setup-intensive, routes to cheap
metals (Fe, Co and Ni) nanoparticles encapsulated in
mass production of CNTs are highly demanded [1-3],
concentric layers of graphitic carbon. Moreover, various
especially for their utilization in structural materials, where
pure carbon or metal nanostructures can be simply obtained
large amounts are required. The novel structure of
from the detonation of the desired molecular precursors.
encapsulating second phase inside carbon shells can
Therefore, catalytic detonation of carbon-rich explosives
immunize the encapsulated species against environmental
can be designed as a useful method and with the potential
degradation effects while retaining their intrinsic properties,
application for the production of nano-structured materials
and can also offer an opportunity to investigate
of
dimensionally
graphitic
carried out indicate
carbon-encapsulated
nanoparticles
and
confined
system.
The
synthesis
of
carbon-nanotubes. The experimental results show that the
carbon-encapsulated metal nanoparticles has attracted
metal compounds can be converted into metallic
much attention for their wide promising applications,
nanoparticles due to the fast decomposition with a
especially in information technologies and biomedicines.
reduction reaction after the detonation and this will play an
There are many differences among these methods in
important role for the growth of different size of carbon
technique as well as in chemical and physical principles,
capsules. The systematic of experiments indicate that it is
the common base is that nanostructures always grow under
possible for a cheaper process and can be as an alternative
high temperature conditions. However, these processes are
compared to these high energy and hardware intensive
both high energy and hardware intensive, which lead to
processes to assemble nano-sized carbon nanomaterials
high cost of nanostructures and therefore constrains their
under catalyzed-blast process.
practical application [4-6].
Keywords: Detonation, Nanostructures, Explosives
Explosive decomposition-experiments and shock wave
synthesis of nanoscale materials have been described in
literature. These include e.g. the preparation of binary
nitrides such as c-BN, CNx-materials and GaN. Even the
typical XRD result of the sample obtained from the
commercial fabrication of diamond nanopowders is
detonations of RDX-Fe mixture. XRD characterization is
performed by shock wave methods [8-11]. In this way,
performed to further validate the corresponding structure of
uniform iron nanoparticles well encapsulated within
the core and shell. No signals of iron carbide or iron oxide
graphitic shells can be obtained, with crystalline structure
are observed. Although it is difficult to completely rule out
of parent ones. Therefore, a laboratory self-heating
the presence of very small oxide and carbide particles from
detonation process has been designed in-house and a more
the XRD pattern because the particles possessing a
effective synthesis of CNTs using nitro-amine CHNO
scattering region smaller than 2 nm cannot be registered
explosives as an energetic materials and the metal
with the X-ray technique. TEM observation shows that the
containing material as a catalyst. Here we report that
size of the particles are larger than 5 nm, suggesting the
individual carbon nanostructures, both unfilled and
containing metal nanocrystals in a string-by-string
bead-like arrangement, can be obtained reproducibly by
detonative decomposition of a RDX/TNT explosive.
cores will be bcc-Fe. The diffraction peak at about 26.2°
can be assigned to the (002) planes of hexagonal graphite
structure with an interlayer spacing of 0.34 nm,
corresponding to the encapsulating carbon shells. The peak
is rather asymmetry, broader and lower than that of the
well-crystallized graphite, indicating a relatively small
2. Experimental
crystalline dimension. Amorphous carbon background in
The chemical reagents used were RDX/TNT energetic
materials (B explosive), transition metal catalysts (Co, Ni,
and Fe containing compounds) and anthracene (C14H10).
The use of this specially system to study the
catalysis-ssisted detonation process, the relationship
between
the
experimental
conditions
and
product
distribution and roles of the catalyst types. Before the
detonation experiments, the starting materials were mixed
in desired ratios. The detonation was performed in a sealed
stainless steel vessel connected with vacuum and inert gas
control system, and induced external heating to ignition
temperature. After the detonation, the reactor was cooled in
air to room temperature. The gaseous products were vented
and the solid products were collected for further
characterizations. The reactor and various units of the
collection system were weighted before and after the runs
to determine the mass balance. Scanning Electron
Microscopy with detection ) SEM equipped with EDX and
Transmission electron microscopy (TEM) were employed
to investigate the as-synthesized solid products.
the products contributes to the broad diffraction peak in
proximate to the graphite peak. A typical TEM image of the
resulted material showing that the Fe–C core–shell
structures with the carbon shells show relatively defective
structure observed can be effectively protect the iron cores
against the environmental degradation (Fig. 2). The iron
cores are crystal and have lattice fringe spacing of 0.20 nm),
related to the (110) plane of the bcc-Fe crystal or the (121)
plane of the Fe7C3 crystal. The identification of the phase
can be realized in virtue of XRD measurements (Fig. 1).
As shown in Fig. 3, it indicate that the mixture result in
catalytic detonation reaction and produce nanostructures
under the condition. The above data show that the
detonation-induced Co pyrolysis is able to controllably
produce well-constructed Co–C core–shell nanostructures.
In this process, since the detonation of RDX is induced by
temperature-programmed heating. The hot gases (N2, CO,
CO2, H2O) generated from the detonation collide with the
gaseous molecules and make latter quickly decompose into
small carbon (Cn) and Co species, which subsequently
condense into solid materials when cooling. The
3. Results and discussion
simultaneous condensation of the Co clusters and the Cn
An individual metal catalyst was mixed with explosives
species leads to the likely formation of a (Co, C) alloy,
(RDX) before the detonation experiments. The materials
whose carbon content varies with the system temperature.
used in this study can be formulated, including explosive,
When the carbon dissolution in the Co nanoparticles
carbon
reaches saturation, a precipitation of pure carbon around
source,
and
catalyst,
from
which
carbon
nanomaterials can be effectively synthesized. Fig. 1 is a
the nanoparticles would start in the form of graphite.
Fig. 4 shows typical TEM patterns of the
show that it is possible for a cheaper process and can be as
as-synthesized samples obtained from the detonations of
an alternatives compared to these high energy and
RDX/Nickelocene/C14H10 mixture. The presence of Ni
hardware intensive processes to assemble nano-sized
catalyst is necessary for the nanostructures growth in this
carbon nanomaterials under catalyzed-blast process.
system, at least under the experimental used in this study.
TEM image of this sample presents the effect of C14H10
4. Conclusion
addition on the formation of carbon nanotubes. Elemental
The detonation of nitro amine-containing CHNO
analyses by EDX show that the products mainly consist of
explosive as common as a RDX/TNT composite can be
carbon and catalyst with very little amount of detectable
used to synthesized carbon nanomaterials in the presence
oxygen and nitrogen. Both of the recipe RDX/
of a catalyst. The approach has the potential ability to
Nickelocene/C14H10 and RDX/cobaltcene/C14H10 of the
convert waste energetic explosives to form highly valuable
TEM micrograph in Figs. 4 and especially in Fig. 5 show
materials. This method represents a novel and low cost
that the length of the tubes can reach more than a dozen
process towards metal–carbon encapsulating structures, in
microns and that they are segmented. The term
which the needed high-temperature environment is self
‘‘bamboo-like nanotubes’’ has been introduced for this
provided by the energy emitted from the RDX/TNT
nanostructures morphology. Based on theoretical studies it
detonation. sing this special system prticulate products are
was supposed that nitrogen substitution of carbon in
generated. Similar results were obtained when the reaction
graphite develops buckled structures and enhances the
was performed in a certain outward flow of gaseous
compartmentization of nanostructures. However, a detailed
reaction products and intermediate pressure decline rates,
and possibly quantitative experimental investigation of the
and in the presence of iron, nickel or cobalt, various
influence of nitrogen incorporation on the morphology of
nanostructures are formed. Uniform carbon-encapsulated
carbon nanostructures remains to be conducted in the
Fe nanoparticles are successfully synthesized through the
future. The segment of long tube in Fig. 5 has diameters of
detonation of RDX/TNT and metalcene mixture. For the
about 50 to 100 nm (right). Similar to the left figure shown
controlling formation of carbon-encapsulated metal
that all produced materials the tube diameters vary between
nanoparticles and carbon nanotubes, it is clear that C:metal
100 and 150 nm. All tubes prepared with Co transition
ratio in the starting materials is considerable controled to
metal and carbon sources (C14H10) were multi-walled with
obtain tme majority of high yields of encapsulated metal
the
nanoparticles
said
dimensions.
The
morphology
and
the
without
the
formation
of
carbon
nanostructures yield varied depending on the metal. As can
nanostructures. A further increase in caobon nanostructures
be seen in Fig. 6, in the formation of the nanostructures of
yield and tailoring of structure defects may be available in
nanoparticles of nanoencapsule (right) and nano-sized
relation to the optimization of reaction conditions.
metal particles (Left), the explosive detonative plays an
important role with the heat and the carbon species
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Fig. 5. TEM images for the catalyzed-blast of RDX/TNT
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10 nm
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