Reaction of the intermetallide ZrV2 with ammonia

Article abstract of DOI:10.1134/S0036023612010081

The reaction of the intermetallic compound ZrV₂ with ammonia within a temperature range of 150-500°C in the presence of NH₄Cl as an activator of the process was studied. Depending on the reaction temperature, intermetallide hydrides and compositions of metal hydrides and nitrides or metal nitrides were obtained in the form of finely dispersed powders with particle sizes of less than 1.0 μm. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S0036023612010081

ISSN 0036ꢀ0236, Russian Journal of Inorganic Chemistry, 2012, Vol. 57, No. 1, pp. 21–23. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.N. Fokin, E.E. Fokina, B.P. Tarasov, 2012, published in Zhurnal Neorganicheskoi Khimii, 2012, Vol. 57, No. 1, pp. 24–26.
SYNTHESIS AND PROPERTIES
OF INORGANIC COMPOUNDS
Reaction of the Intermetallide ZrV with Ammonia
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 December 5, 2010
Abstract—The reaction of the intermetallic compound ZrV with ammonia within a temperature range of
2
1
50–500°C in the presence of NH Cl as an activator of the process was studied. Depending on the reaction
4
temperature, intermetallide hydrides and compositions of metal hydrides and nitrides or metal nitrides were
obtained in the form of finely dispersed powders with particle sizes of less than 1.0 µm.
DOI: 10.1134/S0036023612010081
A small grain size in finely dispersed particles of a cles in the ZrV –NH3 system at different
2
material causes the material to manifest physical, temperatures.
chemical, and mechanical properties that considerꢀ
ably differ from those of a compact sample and thereby
attract the attention of scientists and specialists in difꢀ
EXPERIMENTAL
ferent science and engineering fields. In this connecꢀ
Initial intermetallide samples were prepared by
tion, it is extremely important to develop, optimize, alloying a mixture of metals with a purity of 99.97%
and put into practice treatment methods that lead to (zirconium) and 99.98% (vanadium) in an electric arc
the dispersion of the material down to a desired size.
furnace with a nonꢀconsumable tungsten electrode
under purified argon of 0.2 MPa. Alloys were annealed
in quartz vacuumꢀsealed ampoules at 800°C for 250 h
with subsequent quenching in cool water. Xꢀray difꢀ
fraction confirmed a MgCu2ꢀtype structure with the
The foregoing relates first of all to the treatment of
metals and polymetallic phases, which play an imporꢀ
tant part in industry and, in particular, to intermetallic
compounds, one representative of which is the interꢀ
metallide ZrV2. Among the diversified methods for the
dispersion of intermetallic compounds, a chemical
unit cell period a = 0.7441 nm for ZrV2.
ZrV2 powders were prepared by grinding alloy regꢀ
ulus in a metal mortar with subsequent screening of
(
hydride or ammoniac) pounding method based on
the fraction with a particle size of less than 160 m.
µ
the ability of intermetallides to be hydrided or dehyꢀ
drided with a dispersion effect under variable condiꢀ
tions plays an especially important part.
2
The specific surface of such a powder is 0.03 m /g.
Ammonium chloride (chemically pure grade) was
dried in vacuo for 9 h at 150 . Ammonia dried by
°
C
According to a handbook [1], the Zr–V system
contains an only intermetallic compound ZrV2, which
metallic sodium had a purity of 99.99%.
Xꢀray diffraction studies were performed on an
has a cubic MgCu2ꢀtype structure (
is formed by a peritectic reaction at 1300
pound ZrV2 reacts with hydrogen with the formation
of ZrV H = 0.7930 [2] or 0.7956 nm [3]) retaining
a
= 0.7439 nm) and
ADPꢀ1 diffractometer (Cu
K radiation). The error in
α
°C. The comꢀ
the determination of unit cell parameters did not
exceed 0.0005 nm.
(a
4.8
2
Specific surfaces (Ssp) were derived from lowꢀtemꢀ
perature adsorption of krypton after the elimination of
volatile products from the solid phase in a vacuum at
the structure of the initial metal matrix. According to
Pebler and Gulbransen’s data [2], the thermal decomꢀ
position of the hydride proceeds by scheme (1) and is
finished by the complete elimination of hydrogen from
the intermetallide hydride:
–3
1 × 10 Pa and 300°C for 5 h and calculated by the
.3
Brunauer–Emmett–Teller (BET) method. The meaꢀ
surement error was ±10%
.
1
37−142°C
ZrV H ⎯⎯⎯⎯ ⎯→ ZrV H
The amount of hydrogen and nitrogen in the reacꢀ
tion product was determined on a Vario Micro Cube
Elementar CHNS/O elemental analyzer. Chlorine
2
4.8
2
4.6
(1)
2
02−207°C
237−267°C
⎯
⎯⎯⎯ ⎯→ ZrV H ⎯⎯⎯⎯ ⎯→ ZrV .
2 4.05 2
The present work continues the series of studies on was determined turbidimetrically.
the reactions of metals [4, 5] and intermetallic comꢀ
The reaction of ZrV2 with ammonia (soꢀcalled
pounds [6, 7] with ammonia in the presence of ammoꢀ hydronitriding process) was studied at an initial
nium chloride as an activator and is devoted to studyꢀ ammonia pressure of 0.6–0.8 MPa with the use of
ing the formation conditions of finely dispersed partiꢀ ammonium chloride (10% by weight of the amount of
21

22
FOKIN et al.
Conditions and results of reaction of ZrV with ammonia
2
Synthesis conditions
Reaction products
Sample
no.
unit cell parameters, nm
2
Ssp, m /g
T
,
°
C
time, h
phase composition
а
с
1
2
3
4
150
200
250
300
33
29
31
31
ZrV H
2
0.7463
0.8018
0.7948
0.7808
0.7779
0.3020
0.4986
0.3018
0.4996
0.2944
0.3058
0.4073
0.4976
0.4531
0.4142
0.4546
–
–
1.0
2.4
2.6
4.0
~1
ZrV H
2
1.3
ZrV H
2
–
2.2
ZrV H N
2
–
0.7 1.0
ZrV H N
y
–
2
x
5
6
350
400
35
33
VHх
0.3425
0.4450
0.3420
0.4502
0.4527
–
3.3
3.9
4.1
2.5
ZrH2
VHх
ZrH2
VN0.35
V
VN
–
7
8
450
500
33
31
ZrH2
ZrN
VN
0.4456
–
–
ZrN
–
the intermetallide introduced into the reaction). A
RESULTS AND DISCUSSION
mixture of ZrV2 and NH Cl powders was subjected to
vibromilling at room temperature for 30 min. A preꢀ
cisely weighed portion of the thusꢀprepared mixture
4
A distinctive feature of the intermetallide ZrV2 is
the ability of its constituent metals to form hydride
phases when brought in contact with hydrogen. As
known [8], hydride phases are converted into nitride
(
0.8–1.0 g) was placed into a stainless steel container,
loaded into a 60ꢀmL autoclave reactor of a highꢀpresꢀ phases in the presence of ammonia, in some cases
sure laboratory unit, vacuumized down to ~1 Pa for hampering the identification of products of ammoniac
treatment of alloys.
3
3
0 min at room temperature, and allowed to stay for
0 min after ammonia was added. The reactor was furꢀ
The results of the reaction of the intermetallic
ther heated up to required temperatures, allowed to compound ZrV2 with ammonia in the presence of
NH Cl at different temperatures are given in the table.
As follows from these data, the treatment of the interꢀ
stay for 3 h, cooled down to ~20
°
C
, and heated again.
4
Since the pressure in the system increased in the
course of the reaction (no higher than 1.5 MPa), the
end of the process was determined by the moment at
which the pressure stopped to change. After the
required number of heating–cooling cycles was perꢀ
formed, ammonia was released into a buffer vessel.
The reaction products were unloaded in an inert
atmosphere and analyzed.
metallide with ammonia at 150°C and a contact time of
3
3 h leads to the formation of a ZrV H hydride phase
2
~1
(sample 1) with an expanded lattice (a = 0.7463 nm).
2
The specific surface of such powders is ~1 m /g.
Rising ammoniac treatment temperature to 250°C
considerably increases the hydrogen concentration in
the ZrV2 matrix: a ZrV H phase (sample 2) and a
2
1.3
ZrV H phase (sample 3) are formed at 200 and
2
2.2
2
50°C, respectively, and contact times of 29–31 h.
NH Cl was removed from the reaction products by
4
The specific surfaces of the products also increase to
the following two methods: the treatment with absoꢀ
lute ethanol under mechanical stirring of the mixture
for 1 h at room temperature (the procedure was
2
2
.6 m /g, thus indicating an increased dispersity of
formed powders. Really, the average particle size
determined on the assumption of their spherical shape
repeated twice) or the vacuumization of the product is 0.9
mixture at ~1 Pa for 3 h at 300
treatment temperature of 150
µ
m for the particles obtained at an ammoniac
°C
.
°C
and 0.3 µm for the
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012

REACTION OF THE INTERMETALLIDE ZrV2
23
particles which are the products of the reaction at
50
All the synthesized reaction products are black
powders.
2
°C.
The use, instead of the intermetallide, of the interꢀ
It should be noted that, in the measurements of the
metallide hydride ZrV H , which is prepared by
2
4.8
specific surface of ZrV2ꢀbased hydrides, we in fact
determine the specific surface of the intermetallide
itself, as its hydride phases are unstable, and the
ZrV H hydride completely evolves hydrogen at
direct synthesis in the form of a 50ꢀ
the use of highꢀpurity hydrogen, as an object of
hydronitriding at 450–500 leads, as expected, to
µ
m powder with
°C
2
4.8
the formation of metal hydride and metal nitride mixꢀ
tures similar to those obtained in the hydronitriding of
ZrV2. In this case, the specific surface of the product
2
60°C, as already mentioned earlier [2].
The product obtained at 300°C is a hydridonitride
2
phase and has the composition ZrV H N (sample 4),
2
0.7 1.0
amounts to 4.7–5.2 m /g, which is slightly higher than
i.e., nitrogen is introduced into the lattice of the interꢀ
metallide. Such a product is characterized by a develꢀ
the specific surface of the products obtained in the
ammoniac treatment of the intermetallide.
2
oped specific surface (4.0 m /g) and is a finely disꢀ
In summary, the reaction of the powdery intermetalꢀ
lic compound ZrV2 with ammonia in the presence of
ammonium chloride at different temperatures has been
studied for the first time, and the possibility of the synꢀ
thesis of variableꢀcomposition hydride phases of interꢀ
metallide and finely dispersed compositions of zirconium
and vanadium hydrides and nitrides or metal nitrides
persed powder with particle sizes of ~0.5
The increase in ammoniac treatment temperature
up to 350 reduces the stability of the hydridonitride
µ
m.
°
C
phase. Upon the decomposition of the latter, the
reflections of metal hydrides (vanadium monohydride
VHх and zirconium dihydride ZrH2) appear in the
Xꢀray diffraction patterns of ammoniac treatment
products. The hydridonitride phase is still observed in
2
with a considerable specific surface up to 4.0 m /g has
been shown.
the products of the reaction conducted at 350°C (samꢀ
ple 5), but is completely absent in the products
obtained in the reaction of the intermetallide with
ammonia at 400°C (sample 6). The conversion of
vanadium hydride into VN0.35 nitride begins at this
temperature, and the conversion of zirconium dihyꢀ
dride into zirconium nitride begins at a reaction temꢀ
REFERENCES
1
.
Binary Metal Phase Diagrams: Handbook, Ed. by
N. P. Lyakishev (Mashinostroenie, Moscow, 2001),
Vol. 3, Book 2, 448 p. [in Russian].
. A. Pebler and E. A. Gulbransen, Trans. Metall. Soc.
AIME 239 (10), 1593 (1967).
2
perature of 450
°
C
(sample 7). Moreover, the temperaꢀ
3
. S. V. Mitrokhin, V. N. Verbetskii, E. Yu. Snegov, and
K. N. Semenenko, Vestn. Mosk. Univ.: Khim. 21 (6),
ture of 450
°
C is sufficient for a deeper nitriding of
vanadium with the formation of the nitride VN.
Hence, a mixture consisting of metal hydrides and
nitrides is formed at this temperature. A mixture of
metal nitrides is the reaction product at an intermetalꢀ
lide ammoniac treatment temperature of 500°C (samꢀ
ple 8).
608 (1980).
4
5
6
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sov, Neorg. Mater. 44 (2), 184 (2008).
7. V. N. Fokin, E. E. Fokina, and B. P. Tarasov, Neorg.
°C
2
Mater. 45 (8), 926 (2009).
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2
2.5 m /g.
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 57 No. 1 2012