Synthesis of intermetallic compounds LaNi5 and NdNi5 from mixed basic carbonates of lanthanum or neodymium and nickel

Article abstract of DOI:10.1023/A:1026365118722

The possibility of obtaining powdered LaNi₅ and NdNi₅ intermetallic compounds by reaction of mixed basic carbonates La ₂Ni₁₀(CO₃)₈(OH)₁₀· 54H₂O and Nd₂Ni₁₀(CO₃) ₈(OH)₁₀ ·14H₂O with calcium hydride in a hydrogen flow at 1073 K and 10⁵ Pa was studied.

Full text of DOI:10.1023/A:1026365118722

Russian Journal of Applied Chemistry, Vol. 76, No. 6, 2003, pp. 1008 1010. Translated from Zhurnal Prikladnoi Khimii, Vol. 76, No. 6, 2003,
pp. 1036 1038.
Original Russian Text Copyright
2003 by Burlakova, Volkov, Shilkin.
BRIEF
COMMUNICATIONS
Synthesis of Intermetallic Compounds LaNi and NdNi
5
5
from Mixed Basic Carbonates
of Lanthanum or Neodymium and Nickel
A. G. Burlakova, L. S. Volkov, and S. P. Shilkin
Institute for Problems of Chemical Physics, Russian Aacademy of Sciences, Chernogolovka, Moscow oblast, Russia
Received January 17, 2003
Abstract The possibility of obtaining powdered LaNi and NdNi intermetallic compounds by reaction
5
5
of mixed basic carbonates La Ni (CO ) (OH)
hydride in a hydrogen flow at 1073 K and 10 Pa was studied.
54H O and Nd Ni (CO ) (OH)
14H O with calcium
2
10
3 8
10
2
2
10
3 8
10 2
5
Powdered intermetallic compounds of rare-earth
and 3d-transition metals are used as hydrogen-sorbing
materials [1] and materials for fabrication of magnets
with high magnetic characteristics [2]. The production
of such materials includes the stage of alloying of
appropriate metals in electric-arc or vacuum induction
furnaces with the subsequent grinding of the alloys
under the action of hydrogen [1, 3, 4] or under ex-
ernal mechanic action in various ball-type activating
mills [5, 6].
a solution of Na CO to the filtrate in the ratio
2 3
Ln : CO2 = 1 : 4, and added, in the course of 0.5 h
3+
3
under conditions of vigorous stirring, a 1.2 N solution
of NaOH in the amount corresponding to the ratio
3
+
Ln : OH = 1 : 5. The suspension was allowed to
settle for 15 20 h, then filtered, and the precipitate
was dried in air at room temperature for 20 30 h.
The powders obtained were X-ray-amorphous. Ac-
cording to IR spectral and chemical analysis data,
their empirical composition corresponded to the for-
mulas: La Ni (CO ) (OH)
(H O) (x
54) and
2
10
3 8
10
10
2
x
Presently, attention is attracted in laboratory and
industrial practice to reduction-diffusion methods for
obtaining intermetallic compounds containing rare-
earth and 3d-transition elements. These techniques
include reduction of mixtures of metal oxides, hy-
roxides, chlorides, carbonates with various reducing
agents in hydrogen or an inert medium [2, 7, 8]. The
advantage of this method is that it yields powdered
intermetallic compounds with narrow fraction distri-
bution and controlled chemical composition without
stages of alloying and mechanic grinding of the alloys.
Nd Ni (CO ) (OH)
(H O) (y
14).
2
10
3 8
2
y
To elucidate the role of molecular hydrogen and
calcium hydride in reduction of mixed basic carbo-
nates of La(III) [or Nd(III)] and Ni(II) with the above-
mentioned composition, we carried out the reaction
in two stages. In the first stage, we placed a molybde-
num container with a weighed portion of a mixed
basic carbonate in a quartz reactor 20 mm in diameter
and 600 mm in length, the reactor was purged with
argon, the temperature in the hot zone of the reactor
was raised to 1023 K for La(III) and Ni(II) basic car-
bonate and to 873 K for Nd(III) and Ni(II) basic car-
bonate, and the reactor was kept at these tempera-
tures with flowing hydrogen for 2.5 3 h. The comple-
tion of the reaction was judged from termination of
water drop formation in the cold part of the reactor.
Thereafter the heating was switched off and the reac-
tion mixture was cooled to room temperature in flow-
ing hydrogen, then the reactor was purged with argon
for 0.25 h, and the reaction products were discharged
in an inert atmosphere. According to the results of
X-ray phase analysis, the powders obtained were mix-
This communication describes synthesis of ba-
sic carbonates La Ni (CO ) (OH)
(H O)x and
2
10
3 8
10
2
Nd Ni (CO ) (OH) (H O)y and their reduction
2
10
3 8
10
2
with calcium hydride in hydrogen with the aim of
obtaining the intermetallic compounds LaNi5 and
NdNi5.
To prepare mixed basic carbonates of lantha-
num(III) [or neodymium(III)] and nickel(II), we dis-
solved starting Ni(OH) in a solution of LnCl +10HCl
2
3
(
Ln La, Nd) in the ratio Ln : Ni = 1 : 5 under heating
without boiling. Then we filtered the solution, added
1
070-4272/03/7606-1008 $25.00 2003 MAIK Nauka/Interperiodica

SYNTHESIS OF INTERMETALLIC COMPOUNDS LaNi5 AND NdNi5
1009
tures of nickel with lattice constant a = 0.3521 nm
The powders of intermetallic compounds, obtained
by the above procedure absorb about 6 mol of hy-
drogen per 1 mol of intermetallic compound in the
reaction with hydrogen. The enthalpies of hydrogena-
tion of the samples under study in the region of the
transition, calculated from the experimental
0
and hexagonal modifications of La O with a =
2
3
0
0
0
.4000, c = 0.6340 or Nd O with a = 0.3963, c =
.6301 nm, which is in good agreement with pub-
0 2 3 0 0
lished data and points to the absence of reaction
between these compounds in the solid phase.
dependence of log(P[H ]) on inverse temperature, are
2
In the second stage, powders of Ni and La O or
kJ mol 1 H2): H = 33.0 for LaNi ( H = 32.9
2
3
(
5
Ni and Nd O were mixed with CaH , placed in the
2
3
2
for a molten alloy) and H = 30 for NdNi ( H =
5
same reactor, and kept in flowing hydrogen for 2.5 3 h
at 1273 K. After cooling the reaction mass first in
flowing hydrogen and then in argon, the reactor was
discharged. In the case of lanthanum, the powder
was washed first with distilled water cooled to 273 K,
and then with ethanol and diethyl ether. The resulting
dried powder was composed of the intermetallic com-
3
0.1 for a molten alloy).
Thus, the reactions of mixed basic carbonates of
composition La Ni (CO ) (OH)
54H O and
2
10
3 8
10
2
Nd Ni (CO ) (OH)
14H O with calcium hydride
2
10
3 8
10
2
in flowing hydrogen yield LaNi and NdNi powders
5
5
without stages of alloying of the corresponding metals
or their mechanic grinding.
pound LaNi . According to the results of chemical
5
analysis:
EXPERIMENTAL
Found (wt %): La 31.95, Ni 68.00.
LaNi5.
In this study, we used commercial pure-grade
Calculated (wt %): La 32.12, Ni 67.88.
Ni(OH)2 0.25H O, basic nickel carbonate containing
2
4
7.6% nickel(II), chemically pure-grade Na CO ,
2 3
An X-ray phase analysis of the powder indicated
that only a single phase is present, which corresponds
NaOH, hydrochloric acid, metallic lanthanum of
9.9% purity, 99.85% pure neodymium, 99.99% pure
9
to the intermetallic compound LaNi crystallizing to
5
nickel, and calcium hydride of purity 99.9% with
give hexagonal crystals with lattice constants a =
0
respect to H . Hydrogen-sorption characteristics of
LaNi and NdNi powders were studied on a high-
2
0
.5010 and c = 0.3970 nm.
0
5
5
pressure installation by plotting isotherms of hydro-
gen pressure against the composition of the hydride
phase at various temperatures [11].
According to the results of reaction gas chromatog-
raphy, the content of oxygen in the sample obtained
was 0.2 wt %; a chemical analysis demonstrated that
the content of calcium and chlorine did not exceed
We used a metal-hydride battery [12] as a source
of high-purity hydrogen. The composition of the hy-
dride phases formed in the reactions of intermetallic
compounds with hydrogen, calculated from pressure
changes in a calibrated system, was refined by a stan-
dard procedure of sample combustion in flowing oxy-
gen. The thermodynamic characteristics of hydride
formation were determined from the dependence of
0
.1 wt %.
Since neodymium salts are more susceptible to
hydrolysis than lanthanum salts, the desired com-
pound was isolated from the reaction mixture using
magnetic separation [9]. According to the results of
chemical analysis:
the equilibrium pressure of H in the regions of the
Found (wt %): Nd 32.87, Ni 66.96.
NdNi5.
2
transition on inverse temperature.
Calculated (wt %): Nd 32.95, Ni 67.05.
We prepared the reference intermetallic compounds
LaNi5 and NdNi by alloying calculated amounts
5
As indicated by reaction gas chromatography, the
content of oxygen in the sample obtained was about
of La or Nd with Ni in an electric arc furnace with
a permanent tungsten electrode in the atmosphere of
high-purity argon. The alloy samples were subjected
to threefold remelting and then to homogenizing an-
nealing at 950 1000 K for 500 h with the subsequent
quenching in water at 273 K. The X-ray studies were
carried out using the powder technique on an ADP-1
diffractometer (CuK radiation) equipped with a micro-
computer controller. The error in determining the
lattice constants did not exceed 0.0004 nm. The el-
emental chemical analysis of mixed basic carbonates
0
.2 wt %. The compound NdNi crystallizes to give
5
hexagonal crystals with lattice constants a = 0.4963
0
and c = 0.3974 nm, which is in reasonable agreement
0
with published data for the reference intermetallic
compound NdNi obtained in an electric arc furnace
5
(
a = 0.4926 and c = 0.3957 nm) [10].
0
0
The size of powder particles, calculated in the ap-
proximation of their spherical shape, is about 220 nm
for LaNi and 400 nm for NdNi .
5
5
RUSSIAN JOURNAL OF APPLIED CHEMISTRY Vol. 76 No. 6 2003

1010
BURLAKOVA et al.
of La(III) or Nd(III) with Ni(II) and analysis of the
4. Fokin, V.N., Tarasov, B.P., Korobov, I.I., Shilkin, S.P.,
final products of their reactions with CaH and H2
et al., Koord. Khim., 1992, vol. 18, no. 5, pp. 526 534.
2
were carried out by the standard procedures.
5
6
7
8
. Andrievskii, R.A., Tarasov, B.P., Korobov, I.I., et al.,
Zh. Neorg. Khim., 1996, vol. 41, no. 8, pp. 1295 1289.
All the operations involving loading and discharg-
ing of reactors, including sampling for analysis, were
carried out in the atmosphere of argon.
. Chu, B.-L., Lee, S.-M., and Perng, T.-P., Int. J. Hy-
drogen Energy, 1991, vol. 16, no. 6, p. 413.
. Wang, X. and Wang, G., Z. Phys. Chem. (BRD), 1989,
vol. 164, no. 2, pp. 1207 1212.
CONCLUSION
. Tarasov, B.P., Burlakova, A.G., Volkova, L.S., et al.,
Zh. Neorg. Khim., 1997, vol. 42, no. 2, pp. 209 212.
Powders of the intermetallic compounds LaNi and
5
NdNi were obtained without stages of high-tempera-
5
9. Karmazin, V.V. and Karmazin V.I., Magnitnye metody
obogashcheniya (Magnetic Methods of Enrichment),
Moscow: Nedra, 1984.
ture alloying and mechanic grinding of alloys. The
compounds crystallize to give hexagonal crystals with
lattice constants a = 0.5010, c = 0.3970 and a =
0
0
0
1
1
0. Gladyshevskii, E.I. and Bodak, O.I., Kristallokhimiya
intermetallicheskikh soedinenii redkozemel’nykh me-
tallov (Crystal Chemistry of Intermetallic Compounds
of Rare-Earth Metals), Lvov: Vysshaya Shkola, 1982.
0
.4963, c = 0.3974 nm, respectively.
0
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3
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