Tuesday Invited 8

In situ studies of hydrogen desorption
from metallic hydrides by neutron diffraction
M. Latroche,
V. Paul-Boncour, F. Cuevas
Institut de Chimie et des Matériaux de Paris Est
ICMPE - UMR 7182 - CNRS
Thiais, France
Outline
9 Short introduction to metallic hydrides (MH)
9 Neutron diffraction for MH investigation
o Steady state structural analysis
o Out of equilibrium study by coupled TDS/ND
9 The peculiar cases of TiNiHx and YFe2Hx
9 Conclusions
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Short introduction to metallic hydrides
Metallic hydride for solid gas storage
ª Solid gas route ( Peq , C(x) , T)
α
ln(PH )
ln(PH )
2
2
M + x/2 H2 ↔ MHx
T4
ln(PH ) = ΔH/RT - ΔS/R
2
Tc
T3
Peq
β
T2
T1
αmax
Introduction
Neutrons for MH
x(H/M)
Case of TiNiHx
Peq
2
Peq
α+β
α
3
β min
1
1/T
Case of YFe2Hx
Conclusions
Short introduction to metallic hydrides
Metallic hydride for electrochemical storage
ª Electrochemical route ( Eeq ,Q(x), T)
E
=−
eq
MH
x
RT
ln
nF
P
H2
↔ MHx +
− 0 . 926
[in
E (V) vs Cd/Cd(OH)2
M + x H2O + x
e-
-0,05
xOH-
V vs Hg/HgO
]
+x
0,10
0,15
0,20
0,30
300
250
200
150
100
50
Q (mAh.g-1)
e-
↔ M + x LiH
4000
TiH2
ZrV2H4.9
3000 TiFeH2
MgH2
Mg2NiH4
Ah/L
MHx + x
0,05
0,25
ª Non aqueous electrochemical route
Li+
0,00
2000
Li
AB5H5
1000
graphite
Y. Oumellal, W. Zaïdi, J-P Bonnet,F. Cuevas, M. Latroche, J. Zhang,
J-L Bobet, A. Rougier and L. Aymard. IJHE, 37 (2012) 7831-7835
Introduction
Neutrons for MH
Case of TiNiHx
0
0
500
1000
1500
2000
0
Ah/Kg
Case of YFe2Hx
Conclusions
4000
Some successful applications of hydrides…
MgH2
Mg
HEV Toyota Prius
NiMH traction batteries for Nice trams
Other applications - emergency light units, telecommunications, cordless vacuum...
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Neutron diffraction for MH investigation
9 Crystal structure determination
- Quantification and location of H(D) content
- Evidence of phase transitions as a function of H(D) content
Inner Ni counter-electrode
ti m
e
Example: In-situ ND of LaNi5-type electrodes
β β
β
Hydride electrode
Silica cell
αα
outer Ni counter-electrode
γ
2θ
Latroche et al. JALCOM 293-295 (1999) 673
9 Practical advantages of using ND as diffraction tool:
- Bulk analysis (high penetration depth of neutrons)
- Adaptable sample environment (furnace, cryostat, electrochemical cell…)
- Adapted time resolution for thermal desorption
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Thermal desorption spectroscopy (TDS)
Gas release measurement (H2) while heating in a low pressure atmosphere
T (K)
Heating ramp
t (s)
dn/dt (α P)
T
Potential energy diagrams
b
(K/s)
TDS Spectrum
T (K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Thermal desorption spectroscopy (TDS)
• TDS: Experimental method
dn V dP
=
dt KT dt
+
S
P
KT
dn/dt
P
V, T
Variation of P in Removal of gas by
the chamber
pumping
S
(QMS)
Pump
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Thermal desorption spectroscopy (TDS)
• TDS: Experimental method
dn V dP
=
dt KT dt
+
dn/dt
S
P
KT
P
V, T
S
Variation of P in Removal of gas by
the chamber
pumping
Pump
Small volume (V)
High pumping rate (S)
TDS Spectrum
dn/dt α P
dn
α P
dt
(QMS)
T (K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
TDS: what information can be obtained ?
9 Temperature assessment of discrete desorption “states” (TDS peaks)
9 Populations (integrated areas) and related activation energies (Kissinger plots)
9 Determination of rate limiting steps (surface, trapping, diffusion, phase
transformation) with a valid kinetic model : full spectra description.
Example: TDS from PdHx
Measured
Stern et al. J. Phys. F: Met. Phys. 14(1984)1625
Simulated
PCT isotherms for simulation
c)
α+β
β
β
α+β
α
α
H/M
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
TDS vs. ND
• TDS
• ND
Amount of desorbed H2
Amount and location of H in bulk
Desorption mechanism
Crystal structure
Surface recombination
Phase transformation vs H-content
H – Diffusion
Order-disorder transitions
Phase transformation
Amorphisation
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Combined measurements TDS – ND
Silica container
Vacuum and T connections
Neutron beam line ILL – D1B
4OO Detectors
Thermocouple
Neut
ro n b
Furnace
eam
MH sample
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
The case of TiNi-H2
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Sorption properties of the TiNi-H2 system
Absorption by solid gas reaction: T = 150°C, PD2 = 4 MPa, t = 2 weeks
Measured concentration: TiNiD1.35
y
10
PH2 (bar)
Ti
Ni
PCT
(
β-phase
Temperature (°C)
1
Pm m
Vol/TiNi = 27 Å3
)
α-phase
0.1
0.0
0.2
77
152
0.4
127
0.6 0.8
H / TiNi
52
102
1.0
1.2
1.4
Burch and Mason, J. Chem. Soc. Faraday Trans. I 75 (1979) 561
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Structural properties of the α phase
Pm m
3.057 Å
D/TiNi = 0.29
Vol/TiNi = 28.7 Å3
3.057 Å
Ti
Ni
H(D)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Ti
I4/mmm
Ni
D/TiNi = 1.14
Soubeyroux et al., JALCOM 196 (1993) 127
Introduction
Neutrons for MH
H(D)
Case of TiNiHx
3.093 Å
Structural properties of the β phase
3.122 Å
Case of YFe2Hx
Conclusions
Hydrogen desorption from TiNiH1.4
9
8
TDS
7
One–step desorption
P (μbar)
6
β → α transformation
5
4
3
2
1
0
0.0
400
500
600
700
T(K)
DSC
-0.1
Three–step desorption
-0.2
Exo
Heat flow (W/g)
300
-0.3
0
100
200
300
400
500
T(°C)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
?
Conclusions
Coupled TDS-ND experiment
9
8
α
6
P (μbar)
ND
TDS
7
5
4
3
2
β
1
0
300
400
500
600
700
T(K)
T (K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
α-TiNi
Crystallization
Amorphisation
β-TiNiH1.4
Introduction
Neutrons for MH
Intermediate
phase (γ)
Case of TiNiHx
Case of YFe2Hx
Conclusions
Phase content (wt% )
Results of Rietveld refinement
100
80
60
α phase
β phase
γ phase
40
20
0
300
350
400
450
500
550
T (K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
β
I4/mmm
Ti
D/TiNi = 1.14
Vol/TiNi = 30.1 Å3
Ni
H(D)
γ
P4/mmm
α
3.122 Å
Introduction
D/TiNi = 0.29
Vol/TiNi = 28.7 Å3
3.057 Å
3.001 Å
3.093 Å
D/TiNi = 0.7
Vol/TiNi = 29.4 Å3
Pmm
3.129 Å
Neutrons for MH
Case of TiNiHx
3.057 Å
Case of YFe2Hx
Conclusions
Comparison of ND and TDS H-contents
Deuterium content (D/TiNi)
1.4
TDS (spectrum integration)
ND (ΣD-occupancies)
1.2
1.0
0.8
0.6
0.4
0.2
0.0
300
Introduction
400
Neutrons for MH
500
T(K)
Case of TiNiHx
600
Case of YFe2Hx
700
Conclusions
Comparison of ND, TDS and DSC
ND
0.2
Exo
Crystallisation
0.0
-0.2
Desorption H2
-0.4
9
TDS
8
7
-0.6
100
6
200
300
400
500
T(°C)
P (μbar)
Heat Flow (W/g)
DSC
5
4
3
2
1
0
300
400
500
600
700
T(K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
The case of YFe2-H2
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Motivation
Multi-peak TDS spectra of Laves C15 hydrides attributed to
H-desorption from energetically different interstitial sites
ErFe2
HfV2
Park et al. Scr. Metall. 23 (1989) 1525
Stern et al. JALCOM 88 (1982) 431
AB2Dx
ND: Only 2 types of site occupied !
A2B2 x ≤ 3
A
B
Introduction
Neutrons for MH
AB3 x > 3
Case of TiNiHx
Case of YFe2Hx
Conclusions
-1
-1
-dx/dt (H u.f. s )
Coupled TDS-ND experiment for YFe2D4.2
4.0x10
-4
3.5x10
-4
3.0x10
-4
2.5x10
-4
2.0x10
-4
1.5x10
-4
1.0x10
-4
5.0x10
-5
0.0
300
350
400
450
500
550
600
650
T(K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Coupled TDS-ND experiment for YFe2D4.2
Phase
transformations
Order-disorder
transitions
C15
380K
monoclinic
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Thermodynamic & crystal structure for YFe2–D2
- Multi-plateau isotherms
α'3 / α'4
α / α'1
-2
10
α'2 / α'3
400
α'1 / α'2
-3
10
408 K
0
450
2
3
x (D/YFe2)
Introduction
T=300 K
0
373 K
1
cubic 2a
Tetragonal
3
10
500
Cubic C15
V (Å )
P (bar)
-1
Tetragonal
550
Neutrons for MH
4
triclinic
0
10
Cubic C15
473 K
monoclinic
600
Orthorhombic
1
10
1
2
3
x (D/f.u.)
4
5
V. Paul-Boncour, JSSC 142 (1999) 120
Case of TiNiHx
Case of YFe2Hx
Conclusions
Simulation of the TDS spectrum
Successive phase transformation: Johnson-Mehl-Avrami (JMA) equation
{
ηi
Fi = 1 − exp − ( k i t )
}
⎛ Ei ⎞
exp
=
k
k
⎟ , Ko ~ hT/K ~10-13 s-1
⎜−
, i
o
⎝ RT ⎠
⎧
RT 2 ηi ⎫
Fi ≈ 1 − exp⎨− (ki
) ⎬
β Ei ⎭
⎩
J. Farjas, P. Roura, "Modification of the
Kolmogorov-Johnson-Mehl-Avrami rate equation for
non-isothermal experiments and its analytical
solution", Acta Mater., 54 (2006) 5573-5579
dFi
(η −1) / ηi
= ηi ki (1 − Fi )[− ln(1 − Fi )] i
dt
⇒ Fit of TDS spectrum to i-phase transformations
n
dx
dF
−
= ∑ Δxi i
dt i=1
dt
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Fit of the TDS spectrum
-4
4.0x10
TPi
Fit ΣTPi
-4
Data
23
-1 -1
-dx/dt (H f.u s )
3.0x10
-4
2.0x10
1
-4
1.0x10
0.0
300
Peak
Ea
(kJ/mol)
n
Δx
(D/f.u.)
1
123.4
1.5
0.34
2
127.5
1.1
0.73
3
133.5
1.1
0.78
4
139.8
0.7
0.40
5
148.1
0.7
0.35
6
158.9
0.7
0.37
7
171.4
0.7
1.22
7
4 5 6
350
400
450
500
550
600
650
T (K)
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Δx (D/f.u.)
Assigned Phase Transformation
1
0.34
YFe2D4.2 → YFe2D3.85
2
0.73
YFe2D3.85 → YFe2D3.15
3
0.78
YFe2D3.15 → YFe2D2.35
4
0.40
YFe2D2.35 → YFe2D1.95
5
0.35
YFe2D1.95 → YFe2D1.60
6
0.37
YFe2D1.60 → YFe2D1.20
7
1.22
YFe2D1.20 → YFe2
Orthorhombic
Peak
0
Introduction
Neutrons for MH
Case of TiNiHx
2
3
x (D/f.u.)
Case of YFe2Hx
monoclinic
→ 4.2
triclinic
→ 3.3
→ 3.5
→ 2.5
cubic 2a
Tetragonal
Tetragonal
1
→ 1.75
→ 1.95
400
→ 1.2
450
Cubic C15
500
→0
3
V (Å )
550
Cubic C15
600
T=300 K
4
5
Conclusions
500
3
V (Å )
480
xPD (ΣD-occupancies)
xTDS (spectrum integration)
C15-Volume
4
3
460
2
440
Superstructure
1
420
0
400
350 400 450 500 550 600 650
Deuterium content (D/f.u.)
Comparison of ND and TDS H-contents
T (K)
T. Leblond et al., IJHE, 34(2009) 2278
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Conclusions (I)
9 Thermal desorption from TiNiD1.4 hydride occurs through an
intermediated hydride phase of medium H-content: γ-TiNiD0.7.
9 γ→α phase transformation generates compound amorphisation.
9 DSC measurements are explained by the combined effects of
endothermic hydrogen desorption and exothermic alloy
crystallization.
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Conclusions (II)
9 Multi-peak TDS spectrum for YFe2 hydride is well-described by
consecutive phase transformations.
9 Multiple C15 Laves phases have been evidenced by ND and XRD
diffraction measurements .
9 Same description may account for multi-peak TDS spectra
observed for many C15 Laves phases.
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Conclusions (III)
9 TDS set-up can be easily implemented in ND beam-line
9 Coupling of TDS - ND techniques is a very powerful
tool to characterize hydrogen desorption from solids,
particularly when phase transformations take place
Introduction
Neutrons for MH
Case of TiNiHx
Case of YFe2Hx
Conclusions
Acknowledgments
V. Paul-Boncour
T. Leblond
F. Cuevas