Metal sulfide synthesis by self-propagating combustion of sulfur-containing complexes

Article abstract of DOI:10.1023/A:1020508817410

Coordination compounds of thiourea with cadmium(II), zinc(II), bismuth(III), and indium(III) nitrates were synthesized. The self-sustained combustion of these complexes, as well as that of thiosemicarbazide coordination compounds of nickel(II), cobalt(II)

Full text of DOI:10.1023/A:1020508817410

Inorganic Materials, Vol. 38, No. 10, 2002, pp. 985–991. Translated from Neorganicheskie Materialy, Vol. 38, No. 10, 2002, pp. 1173–1180.
Original Russian Text Copyright © 2002 by Tukhtaev, Boldyrev, Gavrilov, Larionov, Myachina, Savel’eva.
Metal Sulfide Synthesis by Self-Propagating Combustion
of Sulfur-Containing Complexes
R. K. Tukhtaev*, V. V. Boldyrev*, A. I. Gavrilov*, S. V. Larionov**,
L. I. Myachina**, and Z. A. Savel’eva**
Institute of Solid-State Chemistry and Mechanochemistry, Siberian Division, Russian Academy of Sciences,
ul. Kutateladze 18, Novosibirsk, 630128 Russia
*
*
* Institute of Inorganic Chemistry, Siberian Division, Russian Academy of Sciences,
pr. Akademika Lavrent’eva 3, Novosibirsk, 630090 Russia
e-mail:tukhtaev@solid.nsc.ru
Received June 15, 2001
Abstract—Coordination compounds of thiourea with cadmium(II), zinc(II), bismuth(III), and indium(III)
nitrates were synthesized. The self-sustained combustion of these complexes, as well as that of thiosemicarba-
zide coordination compounds of nickel(II), cobalt(II), iron(II), copper(II), lead(II), and zinc(II) nitrates, was
studied in an inert atmosphere. All these compounds burn to yield metal sulfides. The particle size and morphol-
ogy of the product depend on the pressure at which the process is carried out. For cadmium(II) and zinc(II) sul-
fides, which are capable of subliming at the combustion temperatures of their precursors, these parameters can
be varied in wide ranges.
INTRODUCTION
mium nitrate–ethylenediamine complex produces chro-
mium oxide, while the analogous copper, cobalt, nickel,
and zinc complexes decompose to pure metals [4].
As found earlier [7–9], the combustion of coordina-
tion compounds of nickel(II) and copper(II) nitrates
with hydrazine derivatives (semicarbazide, ami-
noguanidine, and oxalyldihydrazide) affords pure met-
als in the form of porous skeletons. Their microstruc-
ture and morphology depend on the reaction pressure.
More recently [10, 11], the combustion of dithi-
osemicarbazidecadmium nitrate was found to yield
CdS in the form of well-faceted crystals with a hexag-
onal structure. The crystal size could be controlled by
varying the pressure.
In the synthesis of metal sulfides for various appli-
cations, it is often very important to obtain the product
as particles with certain morphology and size. There-
fore, finding simple and convenient methods affording
powder sulfides and allowing their particle size and
morphology to be controlled is a challenging problem.
Here, we report sulfide synthesis by combustion of
coordination compounds at a controlled inert-gas pres-
sure. The objects of our study were coordination com-
pounds of metal nitrates with thiosemicarbazide (TSC)
and thiourea (Thio).
Until recently, metal nitrate complexes with ammo-
nia and hydrazine and with their organic derivatives
attracted researchers' attention only because of their
capacity for self-sustained combustion in an inert atmo-
sphere [1–6]. Their combustion may yield a variety of
solid products. Therefore, these compounds are candi-
date precursors for the synthesis of solids with con-
trolled composition and properties.
In this work, we demonstrate that it is possible to
obtain other sulfides by the combustion of coordination
compounds of metal nitrates with S-coordinated
ligands, specifically, sulfur-containing derivatives of
ammonia and hydrazine. To do this, we synthesized
TSC, NH NHC(S)NH , and thiourea, (NH ) CS, com-
2
2
2 2
plexes of various metal nitrates, tested them for com-
bustibility, determined the composition of the solid
products, and found out whether it is possible to control
the morphology and particle size of the resulting sul-
fides by varying combustion conditions.
The composition of the solid combustion product of
these compounds is determined primarily by the chem-
ical properties of the metal, the composition of the
ligand, and the proportions of oxygen and oxidizable
elements in the molecule.
The combustion of diamminecopper(II) and diam-
minenickel(II) nitrates yields copper and nickel oxides,
respectively [1]. More ammonia-rich complexes, such
EXPERIMENTAL
Synthesis of the starting compounds. Most of the
as tetraamminecopper(II), tetraamminenickel(II), hexa- TSC complexes were synthesized by standard proce-
amminenickel(II), and hexaamminecobalt(III) nitrates, dures. Cu(TSC) (NO ) was synthesized as described
burn to give pure metals. The combustion of the chro- in [12], and [Ni(TSC) ](NO ) was obtained in a simi-
2
3 2
2
3 2
0
020-1685/02/3810-0985$27.00 © 2002 MAIK “Nauka/Interperiodica”

9
86
TUKHTAEV et al.
Table 1. Elemental analysis of thiourea complexes
In(Thio) (NO ) . A mixture of In(NO ) · 4.5H O
3 3 3 3 3 2
(
3.82 g, 0.01 mol) and thiourea (2.28 g, 0.03 mol) was
Found/calculated, wt %
Complex
dissolved in acetone (30 ml), and the solution was
boiled as in the synthesis of the cadmium(II) complex.
After hot filtration, the solution was transferred to a
beaker, and most of the solvent was evaporated to
obtain a viscous substance. Successively adding etha-
nol and pentane to this substance resulted in a white
precipitate, which was then washed with pentane and
dried in air. Yield: 2.7 g (50%).
M
C
H
N
Zn(Thio) (NO ) 19.3/19.2 7.0/7.0 2.3/2.4 24.4/24.6
2
3 2
C H N S O Zn
2
8
6
2
6
Cd(Thio) (NO ) 29.0/29.0 6.2/6.2 2.0/2.0 21.9/21.7
2
3 2
C H N S O Cd
2
8
6
2
6
Pb(Thio) (NO ) 43.3/42.9 4.7/5.0 1.5/1.7 16.9/17.3
2
3 2
The elemental analysis of the thiourea complexes is
presented in Table 1.
C H N S O Pb
2
8
6
2
6
Bi(Thio) (NO ) 31.1/31.5 5.9/5.8 2.0/1.9 19.9/20.2
3
3 3
The compounds to be burnt were pressed at
50 MPa into pellets 8 mm in diameter and 5 to 10 mm
C H N S O Bi
3
12
9
3
9
2
In(Thio) (NO ) 21.8/21.7 6.7/6.8 2.3/2.3 23.0/23.8
3
3 3
in height. Combustion was carried out in a nitrogen
atmosphere in a constant-pressure bomb. The gas pres-
sure was varied between 0.1 and 3 MPa. The combus-
tion temperature and rate were measured using piles
glued from three pellets. W/Rh thermocouples welded
from wires 30 or 100 µm in diameter were glued
C H N S O In
3
12
9
3
9
lar way. The complexes [CÓ(TSC) ](NO ) · 3H O,
3
3 3
2
[
Zn(TSC) ](NO ) , and Fe(TSC) (NO ) · 2H O were
2 3 2 2 3 2 2
prepared by the procedures reported in [13–15]. The between the first and second and between the second
compounds were analyzed for metal content by titra- and third pellets. The signals from both thermocouples
tion with Trilon B.
were continuously recorded with an N-117 loop oscil-
lograph to determine the combustion temperature, the
time it took for the combustion front to travel the dis-
tance between the thermocouples, and the linear com-
bustion rate. The combustion of the complexes gener-
ally yielded an easily grindable porous solid in the
shape of the original pellet. Solid combustion products
were identified by x-ray diffraction (XRD) on a
DRON-4.0 diffractometer and chemical analysis and
Most of the synthetic methods reported for thiourea
complexes yield compounds that contain two thiourea
molecules per nitrate ion. Such complexes are incapa-
ble of self-sustained combustion because of the lack of
oxygen. We developed synthetic procedures for cad-
mium(II), zinc(II), bismuth(III), and indium(III) thio-
–
urea complexes with Thio : NO = 1. These com-
3
pounds are richer in oxygen and are combustible in an were examined under electron microscopes (JSM-T20,
inert atmosphere. The complex Pb(Thio) (NO ) was JEM-2000 FX-II).
2
3 2
obtained by the procedure reported in [16].
Cd(Thio) (NO ) . A mixture of Cd(NO ) · 4H O
3.09 g, 0.01 mol) and thiourea (1.52 g, 0.02 mol) was
2
3 2
3 2
2
RESULTS AND DISCUSSION
(
The main results concerning the combustion of the
TSC complexes—linear combustion rate and combus-
tion temperature as functions of the combustion-bomb
pressure p, as well as composition and particle-size
data for the combustion products—are presented in
Table 2.
All the TSC complexes examined burn to give sul-
fides. However, each of them shows its specific com-
bustion behavior. For example, some of the complexes
are incombustible at atmospheric pressure. The
zinc(II), iron(II), and nickel(II) complexes are combus-
tible starting at p = 0.25, 0.3, and 0.7 MPa, respectively.
dissolved in acetone (50 ml) in a flask fitted with a
backflow condenser and heated on a water bath. The
solution was boiled for 30 min, filtered while hot,
reduced by half on the water bath, and left to stand in
air for a few hours for crystallization. The resulting
white precipitate was vacuum-filtered, washed with
pentane, and dried in air. Yield: 2.7 g (70%).
Zn(Thio) (NO ) . This complex was synthesized
2
3 2
by the same procedure as the cadmium(II) thiourea
complex except that the solvent was isopropanol.Yield:
6
0%.
Bi(Thio) (NO ) . A mixture of Bi(NO ) · 5H O
3
3 3
3 3
2
According to XRD data, the combustion product of
(
4.85 g, 0.01 mol) and thiourea (2.28 g, 0.03 mol) was the nickel(II) complex consisted largely of NiS (ASTM
ground in a mortar to obtain a homogeneous yellow card 2-1280) and contained a minor amount of nickel
paste. The paste was transferred to a beaker, and 5 ml of disulfide. No other Ni–S phases were found in this
ethanol was added. The reaction mixture was heated on combustion product. All reflections in the XRD pattern
a water bath with stirring until it boiled up, and then were rather broad, indicating that the crystallites were
5
ml of acetone was added. The resulting yellow pre- small. Furthermore, they broadened as the pressure was
cipitate was filtered after cooling the mixture, washed raised. The mean crystallite size was 30 nm, as esti-
with acetone and pentane, and dried in air. Yield: 5.7 g mated by the Scherrer formula. This result was con-
(92%).
firmed by electron microscopy, which demonstrated
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METAL SULFIDE SYNTHESIS BY SELF-PROPAGATING COMBUSTION
987
Table 2. Combustion parameters of TSC complexes and composition and crystallite size of the combustion products
Composition
Original complex
Ni(TSC) ](NO )
p, MPa
v, mm/s
t, °C
d, µm
of the combustion product
[
[
0.7
0.6
0.9
0.3
1.8
0.6
0.9
1.1
0.5
3.2
0.6
0.9
2.4
4.4
700
770
NiS + NiS2
0.03*
0.03*
0.02*
0.05*
0.04*
0.04*
0.08*
0.07*
0.12*
0.5
2
3 2
1
.5
0.1
.5
0.3
Co(TSC) ](NO ) · 3H O
500
CoS + CoS
3
3 3
2
2
1.097
1
850
Fe(TSC) (NO ) · 2H O
600
Fe7S8
2
3 2
2
0
1
.5
.0
600
700
Cu(TSC) (NO )
0.1
.5
0.25
400
Cu1.8S
2
3 2
1
650
[
Zn(TSC) ](NO )
1300
1320
1400
1560
α-ZnS
2
3 2
0
0
3
.3
.5
.0
5**
2
1
*
The crystallite size is estimated from XRD peak widths.
*
* Length of needle crystals.
that the product consisted of aggregates up to 1 µm in nal zinc sulfide (wurtzite). At 0.25 MPa, we obtain pris-
size, formed largely by 10- to 50-nm particles. Some of matic ZnS crystals ~1 µm in size; at 0.3 MPa, the crys-
the particles attained 200 nm in size.
tals have the shape of needles up to 5 µm in length and
up to 2 µm in thickness; at 0.5 MPa, we obtain prisms
The solid combustion product of the cobalt(III)
complex consisted of two phases: CoS and the nonsto-
1
to 3 µm in size; combustion at 3 MPa results in
2
rounded particles measuring 1–2 µm (Fig. 1). In the last
case, the round shape of the particles may be due to par-
tial fusion, even though the combustion temperature
ichiometric monosulfide CoS1.097. The proportions of
these phases depended on pressure. At atmospheric
pressure, the reflections from the disulfide dominated
and all the reflections were very broad. At 1.5 MPa, the
reflections from the monosulfide were much stronger of zinc sulfide.
than the reflections from the disulfide and all the reflec-
(Table 2) is considerably lower than the melting point
A somewhat different combustion behavior is
exhibited by thiourea complexes (Table 3). At a given
tions were narrower. The mean crystallite size was esti-
mated from XRD data to be 20 nm for the product
obtained at atmospheric pressure and 50 nm for the one
obtained at 1.5 MPa. According to electron microscopy
data, the product synthesized at 1.5 MPa consisted of
NO : ligand ratio, the thiourea complexes burn at a
3
lower temperature and at a considerably higher rate
than their TSC analogs. Although their combustion also
2
0- to 60-nm particles, forming aggregates up to 0.5 µm yields sulfides, the composition and structure of the
in size.
solid product depend on the combustion temperature
and the residence time in the flame zone.
The combustion of the iron(II) or copper(II) com-
plex yields a single sulfide. The iron(II) compound
For example, at 0.25 MPa, Zn(Thio) (NO ) burns
2
3 2
burns to form pyrrhotite, Fe S . The copper(II) com-
7
8
to yield cubic ZnS and traces of hexagonal ZnS. As the
pressure and combustion temperature are raised, the
proportion of the hexagonal phase increases. Above
plex yields digenite, Cu S. The other compounds in
1
.8
the Fe–S and Cu–S systems are unstable at high tem-
peratures. The reflections from both sulfides were very
broad. With increasing pressure, they broadened but did
not shift.
0
.7 MPa, hexagonal ZnS dominates over the cubic
phase. Starting at 1.5 MPa, only hexagonal ZnS is
formed.
The strongest pressure effect on the morphology and
particle size of the product was observed for the zinc(II)
A similar situation is observed for the cadmium(II)
complex. In this respect, the behavior of this complex is complex. Over the p range 0.1–0.5 MPa, the product
identical to that of [Cd(TSC) ](NO3)2 [10, 11]. consists largely of cubic CdS; above 1 MPa, it is domi-
2
Throughout the pressure range examined, the only nated by the hexagonal phase; starting at 2 MPa, hexag-
combustion product of the zinc(II) complex is hexago- onal CdS is the only phase in the product.
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TUKHTAEV et al.
1
0 µm
1 µm
(
a)
(b)
1
0 µm
10 µm
(
c)
(d)
1
0 µm
(
e)
Fig. 1. Micrographs of zinc sulfide powders obtained by [Zn(TSC) ](NO ) combustion at p = (a, b) 0.25, (c) 0.3, (d) 0.5, and
2
3 2
(e) 3 MPa.
Thus, by varying p in the combustion of the zinc(II) combustion temperature is as high as the melting point
and cadmium(II) thiourea complexes, one can control of the sulfide.
the structure of the resulting ZnS and CdS.
The complex Pb(Thio) (NO ) differs in the compo-
2
3 2
The bismuth(III) and indium(III) complexes burn to sition of the solid product from the other complexes
examined. Its combustion gives not only PbS but also
lead(II) sulfate.
form Bi S and In S , respectively. Bi S is the only bis-
2
3
2
3
2 3
muth sulfide existing in the solid state. By contrast,
solid sulfides other than In S are known in the In–S
2
3
Our data demonstrate that the pressure in the system
may have different effects on the particle size and mor-
system. Nevertheless, only In S , the most thermally
2
3
stable indium sulfide, results from combustion. At phology of the product, from very strong to insignifi-
2
.5 MPa, the process yields fused In S , because the cant. If the effect of pressure is strong, as in the cases of
2 3
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METAL SULFIDE SYNTHESIS BY SELF-PROPAGATING COMBUSTION
989
Table 3. Combustion parameters of thiourea complexes and composition and crystallite size of the combustion products
Composition
Original complex
Zn(Thio) (NO )
p, MPa
v, mm/s
t, °C
d, µm
of the combustion product
0.25
1.9
6.7
29
480
1290
1360
1440
400
β-ZnS, traces of α-ZnS
α-ZnS, traces of β-ZnS
α-ZnS
0.02*
3
2
3 2
1.0
2.0
3.0
20**
2
8.8
0.3
22
α-ZnS
Cd(Thio) (NO )
0.1
β-CdS, traces of α-CdS
α-CdS, traces of β-CdS
α-CdS
0.02*
0.07*
0.7
2
3 2
1.0
2.0
3.0
800
10
1010
1240
380
16
α-CdS
3
Bi(Thio) (NO )
0.1
0.4
1.0
1.6
2.7
0.7
2.0
10
Bi2S3
0.07*
0.12*
0.12*
2
3
3 3
1
2
3
.0
.0
.0
440
470
600
In(Thio) (NO )
0.1
420
In2S3
0.02*
0.02*
0.04*
3
3 3
0
1
2
.5
.0
.5
510
580
2.2
0.8
1.6
0.9
1.1
1060
500
Pb(Thio) (NO )
0.5
PbS + PbSO4
0.1*
0.1*
0.1*
0.1*
2
3 2
1
2
3
.0
.0
.0
530
540
560
*
The crystallite size is estimated from XRD peak widths.
*
* Length of tubular crystals.
the cadmium(II) and zinc(II) complexes, we obtain sulfide resulting from the thermal decomposition of the
well-faceted crystals, which provides clear evidence of complex recrystallizes as the high-temperature front
vapor-phase growth. Therefore, the finding that the travels along the sample.
effect of p on the particle size of the product varies from
The micrographs in Fig. 2 illustrate the pressure
complex to complex can apparently be explained by the
effect on the morphology and particle size of ZnS
fact that the resulting sulfides differ in volatility at the
obtained from Zn(Thio) (NO ) . This complex is com-
combustion temperatures of their precursors. In the
case of nonvolatile sulfides, such as nickel, cobalt, iron,
and copper sulfides, the particle size is under 1 µm and
depends only slightly on p. If the resulting sulfide is
volatile, as in the case of the lead(II) and bismuth(III)
complexes, but its vapor pressure at the combustion
temperature is insufficient to ensure a considerable con-
centration of the sulfide (or its dissociation products) in
the gas phase [17, 18], the effect of p on the grain size
is again weak.
2
3 2
bustible starting at 0.25 MPa, and its combustion tem-
perature at this pressure is as low as 475°C. Under these
conditions, there is no sublimation and zinc sulfide
forms in the condensed phase, yielding a spongy sub-
stance consisting of submicron-sized grains. Elevating
p to 1 MPa raises the combustion temperature to
1
290°C. Under these conditions, the sulfide is fairly
volatile, the zinc + sulfur vapor pressure is several thou-
sand pascals [17], and the product appears as separate
crystals 1 to 3 µm in size. At 2 MPa, the combustion
The most interesting situation is observed for the temperature reaches 1360°C, causing a further increase
cadmium(II) and zinc(II) complexes, which vaporize in vapor pressure, and the sulfide crystallizes as hexag-
dissociating to the metal and sulfur [18]: the total vapor onal tubes up to 20 µm in length. Further increase in
pressure at the combustion temperature may be as high temperature caused by raising p to 3 MPa reduces the
4
as a few times 10 Pa [17, 18]. As a consequence, the size and changes the morphology of the crystals.
INORGANIC MATERIALS Vol. 38 No. 10 2002

9
90
TUKHTAEV et al.
1
0 µm
10 µm
(
a)
(b)
1
0 µm
10 µm
(
c)
(d)
Fig. 2. Micrographs of zinc sulfide powders obtained by Zn(Thio) (NO ) combustion at p = (a) 0.25, (b) 1, (c) 2, and (d) 3 MPa.
2
3 2
1
0 µm
10 µm
(
a)
(b)
Fig. 3. Micrographs of cadmium sulfide powders obtained by the combustion of a Cd(Thio) (NO ) –NH NO (1 : 1) mixture at p =
2
3 2
4
3
(a) 0.3 and (b) 0.5 MPa.
Similar pressure and temperature dependences of 1010°C, sublimation is possible, and the mean particle
the crystal size are observed in the combustion of size of the product is 0.7 µm. If the combustion temper-
Cd(TSC) (NO ) [10, 11].
2
3 2
ature is raised by adding ammonium nitrate (extra oxi-
dizer) to the precursor, the formation of large, well-fac-
eted crystals starts at substantially lower pressures. The
combustion temperature of the mixture containing
The combustion temperature of Cd(Thio) (NO3)2
2
below 2 MPa is comparatively low (Table 3) and is
insufficient for sulfide volatilization [17, 18]. As a con-
sequence, the product consists of submicron-sized equimolar amounts of the complex and ammonium
crystallites. At 2 MPa, the combustion temperature is nitrate is 1100°C at 0.3 MPa and 1230°C at 5 MPa. In
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METAL SULFIDE SYNTHESIS BY SELF-PROPAGATING COMBUSTION
991
the former case, we obtain misshapen prisms up to
−6 µm in size. In the latter case, the prisms are better
shaped, their diameter is up to 10 µm, their length is up
to several tens of micrometers, and some of them have
the shape of tubes (Fig. 3).
3. Shidlovskii, A.A., Gorbunov, V.V., and Shmagin, L.F.,
Combustion of Transition-Metal Ammine and Hydra-
zine Complexes with Picrate, Styphnate, and Nitrate
Anions, Izv. Vyssh. Uchebn. Zaved., 1978, vol. 21, no. 9,
pp. 1249–1251.
5
4
. Gorbunov, V.V., Shidlovskii, A.A., and Shmagin, L.F.,
Combustion of Transition-Metal Ethylenediamine Com-
plexes with Nitrate Anions, Fiz. Goreniya Vzryva, 1983,
vol. 19, no. 2, pp. 46–47.
Of great significance is the purity of the resulting
sulfides. According to chemical analysis data, the sul-
fides obtained from TSC complexes are very pure. For
example, ZnS synthesized at 1 MPa contains 0.096%
5
. Sinditsky, V.P., Fogelzang, A.E., Egorshev, V.Y., et al.,
Catalysis and Combustion Mechanism of Coordination
Compounds, Proc. 21st Int. Pyrotechnical Sem., Mos-
cow, 1995, pp. 747–761.
ZnO, 0.088% ZnSO , and less than 0.002% free sulfur.
4
No carbon, hydrogen, or free metal was found in this
product. Cadmium sulfide prepared under the same
conditions is even purer: it contains 0.032% CdO,
6. Sinditskii, V.P. and Fogel’zang,A.E., Energy-Rich Mate-
rials Based on Coordination Compounds, Ross. Khim.
Zh., 1997, vol. 41, no. 4, pp. 74–80.
7. Gavrilov, A.I., Tukhtaev, R.K., Larionov, S.V., et al.,
Preparation of Fine-Particle Nickel with Controlled
Morphology by Combustion, Dokl. Akad. Nauk, 1996,
vol. 348, no. 2, pp. 201–204.
0
.014% CdSO , and less than 0.005% free sulfur.
4
Again, no carbon, hydrogen, or free metal was found in
this product.
The combustion of thiourea complexes affords less
pure products. These complexes burn incompletely, as
indicated by the finding that the actual weight of the
combustion residual exceeds the weight calculated
under the assumption that the solid combustion product
consists of sulfide only. At low pressures, the excess
weight is 10–40% of the calculated sulfide weight. As p
and the combustion temperature are increased, the
complex-to-sulfide conversion grows and, accordingly,
the resulting sulfide gains in purity. However, this ten-
dency is not equally strong for different complexes.
8
. Tukhtaev, R.K., Gavrilov, A.I., Larionov, S.V., et al.,
Formation of Dispersed and Porous Metals by Combus-
tion of Complex Compounds of Nickel and Copper, J.
Mater. Synth. Process., 1997, vol. 5, no. 5, pp. 371–377.
9
. Boldyrev, V.V., Tukhtaev, R.K., Gavrilov, A.I., et al.,
Combustion of Coordination Compounds of Nickel and
Copper Nitrates with Hydrazine Derivatives as a Method
for Preparation of Fine-Particle and Porous Metals, Zh.
Neorg. Khim., 1998, vol. 43, no. 3, pp. 362–366.
Zinc(II), cadmium(II), and bismuth(III) sulfides almost 10. Tukhtaev, R.K., Gavrilov, A.I., Savel’eva, Z.A., et al.,
free of incomplete-combustion products are obtained
starting at pressures of 1.5, 2, and 3 MPa, respectively.
By contrast, indium(III) sulfide produced even at the
highest pressure (Table 3) contains ~2.5% carbon,
nitrogen, and hydrogen.
Effect of Pressure on Cadmium Sulfide Synthesis by
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2
2 2
3 2
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pp. 21–24.
The combustion of coordination compounds of
metal nitrates with sulfur-containing organic ligands
proved to be a suitable method for metal sulfide synthe-
sis. The morphology and particle size of the sulfides
that are capable of subliming at the combustion temper-
ature can be controlled in wide ranges by varying p and
the combustion temperature.
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ACKNOWLEDGMENTS
This work was supported by the Russian Foundation
for Basic Research, project no. 02-03-33333.
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INORGANIC MATERIALS Vol. 38 No. 10 2002