ISSN 0020ꢀ1685, Inorganic Materials, 2011, Vol. 47, No. 3, pp. 267–272. © Pleiades Publishing, Ltd., 2011.
Original Russian Text © V.M. Chumarev, V.P. Mar’evich, A.V. Larionov, A.Ya. Dubrovskii, 2011, published in Neorganicheskie Materialy, 2011, Vol. 47, No. 3, pp. 317–322.
Reactions of V2O5, Nb2O5, and Ta2O5 with AlN
V. M. Chumareva, V. P. Mar’evicha, A. V. Larionova, and A. Ya. Dubrovskiib
a Institute of Metallurgy, Ural Division, Russian Academy of Sciences, ul. Amundsena 101, Yekaterinburg, 620016 Russia
eꢀmail: pcmlab@mail.ru
b OAO Uralredmet, ul. Petrova 59, Verkhnyaya Pyshma, Sverdlovsk oblast, 624092 Russia
eꢀmail: uralredmet@uralredmet.ru
Received February 19, 2010; in final form, August 16, 2010
Abstract—Reactions of vanadium, niobium, and tantalum pentoxides with aluminum nitride have been
studied using Xꢀray diffraction. At temperatures from 1000 to 1600°C, we have identified various V, Nb, and
Ta nitrides. The composition of the niobium and tantalum nitrides depends on the reaction temperature. The
tendency toward nitride formation becomes stronger in the order V2O5 < Ta2O5 < Nb2O5
.
DOI: 10.1134/S0020168511030071
INTRODUCTION
Phase transformations were explored by Xꢀray difꢀ
fraction (XRD) of reaction products obtained by heatꢀ
ing compacted mixtures of the Group VꢀB metal penꢀ
toxides and aluminum nitride in an inert atmosphere.
The starting mixtures were prepared by a conventional
ceramic processing technique and were compacted at
a pressure of 10 MPa. The compacts were fired in a
heliumꢀfilled SShVLꢀ0,6.2/16I2 furnace. The heating
Data on reactions between refractory rareꢀmetal
oxides and aluminum nitride may be of scientific and
technological interest. It is worth noting that alumiꢀ
num nitride can be used as a nitriding agent in the
preparation of nitrided vanadium–aluminum alloys
via aluminothermic smelting. A literature search
revealed no data on phase transformations in systems
formed by refractory rareꢀmetal oxides and aluminum
nitride. V, Nb, and Ta are known to form stable
nitrides. In particular, the Ta–N system contains two
stable nitrides: Ta2N and TaN. The stable nitrides in
the Nb–N system are NbN, Nb2N, and Nb3N, and
rate was 7–10 C/min, and the isothermal hold time
°
was 0.5–1 h. The starting materials used were analytiꢀ
calꢀgrade vanadium pentoxide, pureꢀgrade niobium
and tantalum pentoxides, and SVS TChꢀ1 aluminum
nitride (produced at the Institute of Structural Macroꢀ
kinetics and Materials Science, Russian Academy of
Sciences, Chernogolovka, Russia).
those in the V–N system are VN and V2.15N
.
In this paper, we present our findings on the reacꢀ
tions in mixtures of vanadium, niobium, and tantalum
pentoxides with aluminum nitride.
RESULTS AND DISCUSSION
Figure 1 illustrates the modeling results for reacꢀ
tions of vanadium, niobium, and tantalum pentoxides
with AlN. Below 1000 С, the condensed metallic
EXPERIMENTAL
°
Phase relations in the М2О5–AlN systems were first
modeled using detailed thermodynamic analysis [3]
with the HSCꢀ6.1 software [4]. The starting mixture
composition was taken to correspond to the reaction
stoichiometry
product of the reaction between V2O5 and aluminum
nitride consists only of VN. Above this temperature,
less AlN is involved in the reduction of vanadium. For
t
> 1250
together with VN. For
products are V3Al2 and elemental aluminum. Near
2500 , the VN content may drop to 26 wt % and the
°
С
, elemental vanadium is likely to form
t
> 2000 , the likely reaction
°
С
(1)
3M2O5 + 10AlN = 6MN + 5Al2O3 + 2N2,
°
С
vanadium, aluminum, and V3Al2 contents may
increase to 53.0, 3.0, and 12.0 wt %, respectively.
which was selected based on preliminary analysis of
phase equilibria at AlN : М2O5 weight ratios from 0 to
3 and temperatures below 1500
°
С
. The possible reacꢀ
Therefore, according to the thermodynamic modꢀ
tion products included elemental metals, their nitrides eling results, during heating of a stoichiometric
(VN, NbN, Nb2N, NbN0.88, Nb3N, TaN, Та2N) and 3V2O5 + 10AlN mixture the degree of vanadium
aluminides (VAl3, V5Al8, V2Al3, NbAl3, Nb2Al, Nb3Al), nitriding should decrease monotonically from 57.0%
and condensed and gaseous metal oxides and nitrogen for
t
≤
1000
°
С
to 9.5% at 2500 С. Al2O, AlO, and VO
°
oxides (NO, NO2) represented in the HSCꢀ6.1 dataꢀ vaporization is insignificant. The equilibrium NO and
base. The amount of the inert gas (helium) was NO2 concentrations in the gas phase do not exceed
0.1 kmol.
10–3% up to 2500
С. The oxide product consists
°
267