Hydrogenation of the intermetallic compound Zr2Ni

Article abstract of DOI:10.1134/S0020168514010063

We have determined conditions for the preparation of hydride phases with the composition Zr₂NiH_～5 by reacting the intermetallic compound Zr₂Ni with hydrogen or ammonia and identified the products of the reaction between th

Full text of DOI:10.1134/S0020168514010063

ISSN 0020ꢀ1685, Inorganic Materials, 2014, Vol. 50, No. 1, pp. 19–22. © Pleiades Publishing, Ltd., 2014.
Original Russian Text © V.N. Fokin, E.E. Fokina, B.P. Tarasov, 2014, published in Neorganicheskie Materialy, 2014, Vol. 50, No. 1, pp. 24–27.
Hydrogenation of the Intermetallic Compound Zr Ni
2
V. N. Fokin, E. E. Fokina, and B. P. Tarasov
Institute of Problems of Chemical Physics, Russian Academy of Sciences,
pr. Akademika Semenova 1, Chernogolovka, Moscow oblast, 142432 Russia
eꢀmail: fvn@icp.ac.ru
Received May 21, 2013
Abstract—We have determined conditions for the preparation of hydride phases with the composition
Zr NiH by reacting the intermetallic compound Zr Ni with hydrogen or ammonia and identified the prodꢀ
2
~5
2
ucts of the reaction between the intermetallic compound and ammonia in the temperature range 150—
00°C in the presence of NH Cl as an activator. The results demonstrate that the use of ammonia at 500°C
5
4
leads to decomposition of the intermetallic compound and formation of zirconium hydride, zirconium
nitride, and metallic nickel.
DOI: 10.1134/S0020168514010063
INTRODUCTION
tively. The hydride phase ZrNiH3 decomposes at 260–
80 to give a monohydride, which isolated hydroꢀ
gen only when heated to above 400 [10].
2
°C
The application field of metal hydrides and interꢀ
metallic hydrides is very multifaceted [1–3]. For this
reason, improvement of existing processes and a
°
C
The most hydrogenꢀrich zirconium hydride
search for new approaches for the preparation of metal ZrH1.7–2.0 crystallizes in a tetragonally distorted
hydrides and polymetallic hydrides, as well as studies CaF2 structure with unitꢀcell parameters
a
= 0.4977–
of their properties, continue to attract great interest 0.4981 nm and
c = 0.4449–0.4451 nm [11, 12].
and remain important scientific and technological
Since, as mentioned above, published data on the
problems and challenges in material science.
The zirconiumꢀrich region of the binary system
Zr–Ni contains two intermetallic compounds: Zr Ni
hydrogenation of the intermetallic compound Zr Ni
2
are contradictory, we have examined and demonꢀ
strated the possibility of preparing a hydride phase
based on this compound through direct hydrogenation
with highꢀpurity hydrogen and through hydronitriding
2
(
tetragonal structure,
and ZrNi (orthorhombic structure,
= 0.9937 nm, c = 0.4101 nm). Nickel solubility in
a
= 0.6477 nm,
c
a
= 0.5241 nm)
= 0.3268 nm,
b
(
ammonia treatment), compared the results of reacꢀ
α
ꢀZr is below 0.5 wt % [4].
The Zr Ni compound absorbs hydrogen under varꢀ
ious conditions to the composition Zr NiH
but available data on the phase composition of hydroꢀ
genation products are contradictory. For example, Van
Essen and Buschow [7] reported that, when exposed
to hydrogen at a pressure of 4 MPa and a temperature
tions with hydrogen and ammonia in the initial stage
of the reaction with the intermetallic compound,
investigated the reaction of the intermetallic comꢀ
2
[5, 6],
2
1.5–5
pound with ammonia at temperatures of up to 500°C,
and identified and characterized the reaction prodꢀ
ucts.
of 50°C, this intermetallic compound underwent
hydrogenolysis to form ZrNiH2.5 and ZrH2, whereas
Akopyan et al. [6] observed that, reacting with hydroꢀ
gen even under selfꢀpropagating highꢀtemperature
EXPERIMENTAL
Starting materials. The intermetallic compound
synthesis conditions in the range 120–400°C, Zr Ni Zr Ni was prepared by melting a mixture of
2
2
formed a hydride phase with the composition 99.97%ꢀpure Zr and 99.99%ꢀpure Ni in an arc furnace
Zr NiH4.4–5.0, which had an expanded tetragonal latꢀ using a nonconsumable tungsten electrode under a
2
tice (a = 0.6860 nm, c = 0.5657 nm) derived from that purified argon atmosphere (0.2 MPa). The resultant
of the parent intermetallic compound.
After activation between 700 and 800°
alloys were annealed at 800
°C for 250 h in quartz
C, ZrNi ampules sealed off under vacuum and were then
reacts with hydrogen to form two hydride phases with quenched in cold water. To prevent reaction with
the compositions ZrNiH and ZrNiH3 [7–11], which quartz during annealing, the alloy was wrapped in
have the following unitꢀcell parameters:
a
=
=
=
molybdenum foil. According to Xꢀray diffraction data,
0
0
0
.3367 nm,
b
= 1.0313 nm,
= 1.004 nm,
= 1.048 nm,
c
= 0.4063 nm [9] (or
a
a
the alloy was singleꢀphase and had a tetragonal Zr Ni
2
.328 nm,
.353 nm,
b
b
c
c
= 0.424 nm [10]) and
= 0.430 nm [8, 9], respecꢀ
structure with unitꢀcell parameters
c = 0.5278 nm.
a = 0.6490 nm and
19

20
FOKIN et al.
For hydrogenation, the alloy was ground to a partiꢀ
The specific surface area S of the samples was evalꢀ
cle size of several millimeters. Prior to the hydronitridꢀ uated by Brunauer–Emmett–Teller analysis from lowꢀ
ing step, Zr Ni powder was prepared by grinding a temperature krypton adsorption measurements after
2
–
3
piece of the alloy in a metallic mortar, followed by degassing the solid phase in a vacuum of 1.3
sieving to a particle size of 100 m2. The specific surꢀ 300 for 5 h. The error of determination was
face area of the powder was 0.04 m /g.
×
10 Pa at
µ
°C
±
10%
.
The composition of the forming phases was deterꢀ
The alloy was hydrogenated in highꢀpurity mined by gas volumetry and chemical analysis. The
(
99.99%) hydrogen produced by heating a LaNi5
based metal hydride accumulator [13].
ꢀ
hydrogen and nitrogen contents of the reaction prodꢀ
ucts were determined on a Vario Micro Cube
Ammonium chloride (reagent grade) was vacuumꢀ CHNS/O elemental analyzer, and chlorine was deterꢀ
dried at 150
for 9 h. The purity of the ammonia after mined turbidimetrically.
drying over sodium metal was 99.99%.
°
C
The thermal stability of the reaction products was
Experimental procedure. The hydrogenation and assessed with a Netzsch STA 409 Luxx simultaneous
hydronitriding of the alloy were carried out in a stainꢀ thermal analyzer (TG–DTA/DSC) in an argon atmoꢀ
lessꢀsteel container mounted in a reactor (autoclave) sphere at a heating rate of 10
°
C/min.
of a 60ꢀmL laboratoryꢀscale highꢀpressure apparatus.
Before hydrogenation, the alloy was activated by brated pressure gage of accuracy class 0.4.
evacuation at 300°C for 1 h. Next, the autoclave was
The hydrogen pressure was monitored with a caliꢀ
charged with hydrogen to a pressure of 2.5 MPa.
Hydrogen absorption began with no induction period.
When the pressure stopped decreasing, heating was
terminated, and the autoclave and sample were equilꢀ
ibrated at room temperature for several hours. In a
number of cases, to prevent disproportionation of the
intermetallic compound during hydrogenation we
used soꢀcalled mild synthesis: hydrogen was introꢀ
duced into the autoclave at room temperature in small
portions and was given time to be absorbed [14, 15].
This prevented intense heating of the intermetallic
compound, thereby inhibiting the chemical reaction.
RESULTS AND DISCUSSION
The intermetallic compound Zr Ni was hydrogeꢀ
2
nated under various conditions, which determined the
composition of the reaction products. In particular, at
room temperature in the presence of excess hydrogen
at an initial pressure of 3.5 MPa, which resulted in
rapid hydrogenation (~5 min) and considerable heatꢀ
ing, the reaction products identified by Xꢀray diffracꢀ
tion included, in addition to an intermetallic hydride
with the composition Zr NiH (
a
= 0.6858 nm,
.5742 nm), a new intermetallic hydride with the
composition ZrNiH3 ( = 0.3520 nm, = 1.0475 nm,
= 0.4310 nm) and zirconium dihydride ZrH2 (
= 0.4458 nm), which resulted from
c =
2
4.9
0
The reaction between the Zr Ni powder and
2
a
b
ammonia was studied at an initial ammonia pressure
c
a =
of 0.6–0.8 MPa, using NH Cl (10 wt % relative to the 0.4962 nm,
c
4
intermetallic compound) as an activator of the proꢀ hydrogenolysis of some of the parent intermetallic
cess. A weighed amount (0.8–1.0 g) of the starting compound. Products of similar composition were
powder mixture was pumped to a residual pressure of obtained by reacting the intermetallic compound
0
.13 Pa over a period of 30 min at room temperature. Zr Ni with hydrogen (20–25 MPa) at 300
°C
and then
2
The autoclave was then charged with ammonia and maintaining the reactor at this temperature for 2 h.
left standing for 30 min. Next, the reactor was heated
to a preset temperature, held there for 3 h, cooled to
When hydrogenation was carried out at room temꢀ
perature under hydrogenꢀdeficient conditions (hydroꢀ
gen was introduced into the reactor in small portions
at a pressure of 0.04 MPa and was given time to be
absorbed; the total synthesis time was 6 h), which minꢀ
20°C
, and heated again. Since the pressure in the
system increased during the reaction (to no more than
.5 MPa), the process was considered to reach comꢀ
1
pletion when the pressure stopped varying. After an
appropriate number of heating–cooling cycles, the
ammonia was discharged to a buffer tank, and the
reaction products were drawn from the reactor in an
inert atmosphere and analyzed.
imized heating, no Zr Ni hydrogenolysis was
detected, and the only reaction product was a hydride
2
phase with the composition Zr NiH (2 wt % hydroꢀ
2
4.9
gen).
According to Xꢀray diffraction data, this hydride
phase ( = 0.6866 nm, = 0.5736 nm) had the same
The NH Cl was removed from the reaction prodꢀ
4
a
c
ucts by two procedures: by washing with absolute ethꢀ
anol for 1 h while stirring the mixture at room temperꢀ
ature (the procedure was repeated twice) and by evacꢀ
symmetry as the parent intermetallic compound, but
hydrogen absorption increased the unitꢀcell volume by
2
7.5%. The lattice parameters of the hydride phase
uating the reaction products to
a period of 3 h.
ꢀ
1.3 Pa at 300°C over
slightly exceeded those reported by Akopyan et al. [6]
for a phase of similar composition. During heating to
Characterization techniques. Xꢀray diffraction patꢀ 500
°C Zr NiH decomposes in one step, with an
2 4.9
terns were collected on an ADPꢀ1 diffractometer endothermic peak at 300
°C, to the composition
(
Cu
K
radiation). Lattice parameters were determined Zr NiH2.8, which also has the same symmetry as the
α
2
with an accuracy of 0.0005 nm or better.
parent intermetallic compound.
INORGANIC MATERIALS Vol. 50
No. 1
2014

HYDROGENATION OF THE INTERMETALLIC COMPOUND Zr Ni
21
2
Products of the reaction between the intermetallic compound Zr Ni and ammonia in the range 150–500
°
C
2
2
Sample
tsynthesis
,
°C
Phase composition
a
, nm
b
, nm
c
, nm
S
, m /g
1
2
3
4
150
200
250
300
Zr Ni
0.6482
0.6479
0.6858
–
–
–
–
0.5284
0.5283
0.5676
0.2
0.3
0.6
1.1
2
Zr Ni
2
Zr NiH
2
4.7
Zr NiH
0.6862
0.3515
0.4758
0.5698
0.4291
0.5081
2
4.7
ZrNiH3
ZrH1.2
1.0504
–
5
6
350
400
Zr NiH N
y
0.6834
0.3533
0.4758
–
1.0513
–
0.5670
0.4288
0.4981
3.2
3.3
2
x
ZrNiH Ny
x
ZrH1.2
ZrNiH Ny
0.3485
0.4968
0.4560
0.3524
1.0532
0.4474
0.4427
–
x
ZrH2
ZrN
Ni
–
–
–
–
7
8
450
500
ZrNiH Ny
0.3547
0.4968
0.4545
0.3523
1.0471
0.4297
0.4436
–
2.1
5.2
x
ZrH2
ZrN
Ni
–
–
–
–
ZrH2
ZrN
Ni
0.4967
0.4562
0.3522
–
–
–
0.4457
–
–
Another example of the mild synthesis of intermeꢀ reaction with hydrogen, which is supported by chemiꢀ
tallic hydrides is ammonia treatment of a metallic cal analysis data. Increasing the reactor temperature to
phase in the presence of NH Cl as a promoter. Heatꢀ 250
ing ( 250°C
°
C
(sample 3) leads to hydrogen absorption and
) a powder mixture in an ammoniaꢀfilled formation of an intermetallic hydride with the compoꢀ
reactor leads to gradual hydrogen and nitrogen accuꢀ sition Zr NiH (1.9 wt % hydrogen), which has the
4
≤
2
4.7
mulation, that is, the reaction takes place under parent crystal lattice with increased unitꢀcell parameꢀ
hydrogenꢀdeficient conditions and, as a consequence, ters ( = 0.6858 nm, = 0.5676 nm). Hydrogenation
a
c
no selfꢀheating or hydrogenolysis of the alloy occurs.
The activation effect of ammonium chloride stems
from the fact that raising the temperature leads to the
reversible reaction
reduces the particle size of the metallic phase and
increases the specific surface area of the product to
2
0
.6 m /g, which corresponds to an average particle
size of about 2 m (under the assumption that the parꢀ
ticles are spherical in shape).
µ
NH Cl
4
↔
NH + HCl.
3
(1)
When the intermetallic compound is exposed to
It seems likely that the released hydrogen chloride ammonia at 300
°C (sample 4), Zr Ni hydrogenation
2
reacts with surface zirconium or zirconium oxide (to Zr NiH4.7) is accompanied by a competing reacꢀ
2
atoms to form a chloride, thereby facilitating the tion of disproportionation with formation of the interꢀ
hydrogenation of the metallic phase. Since the dissoꢀ metallic hydride ZrNiH3 and zirconium hydride
ciation and recombination processes according to ZrH1.2
.
reaction (1) in an ammonia atmosphere occur very
rapidly, the amount of forming metal chlorides is very
small and they cannot be detected by Xꢀray diffracꢀ
tion.
At a hydronitriding temperature of 350°C
sample 5), the hydrogenation and disproportionation
of the alloy are accompanied by nitriding, that is,
incorporation of a small amount of nitrogen atoms
(
The temperature of the ammonia treatment of the into the metallic lattice of the hydride phase. This proꢀ
intermetallic compound Zr Ni and the results cess was confirmed by chemical analysis data, but
2
obtained are summarized in the table. The treatment since it is characteristic not only of the Zr Niꢀbased
2
time was 28–32 h.
phase but also of the forming intermetallic compound
ZrNi, the nitrogen content of each product cannot be
quantitatively determined.
It follows from the table that, according to Xꢀray
diffraction data, heating powder Zr Ni in ammonia at
2
1
50 and 200
°
C
(samples 1, 2) causes no significant
In the range 400–450°C (samples 6, 7), the
changes in the unitꢀcell parameters of the parent interꢀ reaction of Zr Ni with ammonia yielded the same
2
metallic compound; that is, there is essentially no products: in addition to the hydride nitride phase
INORGANIC MATERIALS Vol. 50
No. 1 2014

22
FOKIN et al.
ZrNiH Ny, which was first identified at a reaction
temperature of 350°C, we obtained stoichiometric
3. Tarasov, B.P., Fokina, E.E., and Fokin, V.N., Chemiꢀ
cal techniques for dispergation of metallic phases, Izv.
Akad. Nauk, Ser. Khim., 2011, no. 7, p. 1228.
4. Diagrammy sostoyaniya dvoinykh metallicheskikh
sistem: Spravochnik (Phase Diagrams of Binary Metalꢀ
lic Systems: A Handbook), Lyakishev, N.P., Ed., Mosꢀ
cow: Mashinostroenie, 1996, vol. 1.
x
zirconium hydride ZrH2, zirconium nitride (ZrN),
and Ni. As shown earlier [3, 16], zirconium nitride
forms from zirconium hydride and the amount of
forming metallic nickel is sufficient for Xꢀray difꢀ
fraction identification. At the reaction temperaꢀ
tures in question, the hydride nitride phase
Zr NiH N does not exist.
5
. Pebler, A. and Gulbransen, E.A., Thermochemical and
structural aspects of the reaction of hydrogen with
alloys and intermetallic compounds of zirconium,
Electrochem. Technol., 1966, vol. 4, nos. 5–6, p. 211.
2
x
y
The hydronitriding of the intermetallic comꢀ
pound Zr Ni at 500 yields zirconium hydride,
°
C
2
6
. Akopyan, A.G., Dolukhanyan, S.K., Karapetyan, A.K.,
and Merzhanov, A.G., Combustion synthesis of Zr–Ni
intermetallic hydrides, Izv. Akad. Nauk SSSR, Neorg.
Mater., 1983, vol. 19, no. 6, p. 881.
zirconium nitride, and nickel (sample 8).
The products of the reaction between the interꢀ
metallic compound and ammonia have the form of
black powders with a specific surface area in
7
. Van Essen, R.M. and Buschow, K.H.J., Hydrogen
absorption in various zirconiumꢀ and hafniumꢀbased
intermetallic compounds, J. LessꢀCommon Met., 1979,
vol. 64, no. 2, p. 277.
2
the range 0.6–5.2 m /g (see the table). The
S of
2
sample 8 (5.2 m /g) indicates that this material is
finely dispersed powder.
The lattice parameters of the synthesized mateꢀ
rials (table) agree with earlier data.
8. Peterson, S.W., Sadana, V.N., and Korst, W.L., Neuꢀ
tron diffraction study of nickel zirconium hydride, J.
Phys., 1964, vol. 25, no. 5, p. 451.
9
. Westlake, D.G., Shaked, H., Mason, P.R., et al., Interꢀ
stitial site occupation in ZrNiH, J. LessꢀCommon Met.
1982, vol. 88, no. 1, p. 17.
CONCLUSIONS
,
We have proposed procedures for the preparation
of an intermetallic hydride with the composition 10. Padurets, L.N., Chertkov, L.A., and Mikheeva, V.I.,
Zr NiH
by hydrogenation with ammonia or
Synthesis and properties of ternary hydrides in the Zr–
M–H (M = V, Cr, Mn, Fe, Co, Ni) systems, Izv. Akad.
Nauk SSSR, Neorg. Mater., 1978, vol. 14, no. 9, p. 1624.
2
4.7–4.9
hydrogen and identified conditions for obtaining
finely dispersed ZrH2–ZrN–Ni chemical composiꢀ
tions.
11. Metal Hydrides, Mueller, W.M., Blackledge, J.P., and
Libowitz, G.G., Eds., New York: Academic, 1968.
1
2. Fokin, V.N., Fokina, E.E., and Shilkin, S.P., Synthesis
of coarsely crystalline metal hydrides, Russ. J. Gen.
Chem., 1996, vol. 66, no. 8, p. 1210.
ACKNOWLEDGMENTS
This work was supported by the RF Ministry of
Education and Science through the federal targeted 13. Fokin, V.N., Fokina, E.E., and Tarasov, B.P., Hydride
program The Scientists and Science Educators of Innoꢀ
vative Russia, state contract no. 14.140.11.1103.
and Ammonia Dispersion of Metals, Russ. J. Inorg.
Chem., 2010, vol. 55, no. 10, pp. 1536–1540.
14. Burnasheva, V.V. and Ivanov, A.V., CeCo hydrogenaꢀ
2
tion in excess argon, Zh. Neorg. Khim., 1985, vol. 30,
no. 1, p. 257.
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2
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2014