Synthesis of Fine-Particle α-LiAlO2 via Heat Treatment of a Mechanically Activated Mixture of Gibbsite and Lithium Carbonate

Article abstract of DOI:10.1134/S0020168519030099

Abstract—: We have found conditions for the synthesis of fine-particle phase-pure α-LiAlO₂ via heat treatment of a mechanically activated mixture of gibbsite and lithium carbonate in air. The results demonstrate that, to synthesize α-LiAlO₂, the mechanical activation of the reaction mixture should cause no gibbsite amorphization and heat treatment in air should be performed in the range 650–700°C.

Full text of DOI:10.1134/S0020168519030099

ISSN 0020-1685, Inorganic Materials, 2019, Vol. 55, No. 3, pp. 256–262. © Pleiades Publishing, Ltd., 2019.
Russian Text © V.P. Isupov, I.A. Borodulina, R.N. Niyazova, N.V. Eremina, 2019, published in Neorganicheskie Materialy, 2019, Vol. 55, No. 3, pp. 283–289.
Synthesis of Fine-Particle α-LiAlO via Heat Treatment
2
of a Mechanically Activated Mixture of Gibbsite
and Lithium Carbonate
a,
a
a, b
a
V. P. Isupov *, I. A. Borodulina , R. N. Niyazova , and N. V. Eremina
a
Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch, Russian Academy of Sciences,
ul. Kutateladze 18, Novosibirsk, 630128 Russia
b
Novosibirsk State Technical University, pr. Marksa 20, Novosibirsk, 630073 Russia
*e-mail: isupov@solid.nsc.ru
Received May 12, 2018; revised October 4, 2018; accepted October 15, 2018
Abstract—We have found conditions for the synthesis of fine-particle phase-pure α-LiAlO via heat treat-
2
ment of a mechanically activated mixture of gibbsite and lithium carbonate in air. The results demonstrate
that, to synthesize α-LiAlO , the mechanical activation of the reaction mixture should cause no gibbsite
2
amorphization and heat treatment in air should be performed in the range 650–700°C.
Keywords: aluminum hydroxide, lithium carbonate, mechanical activation, thermal interaction
DOI: 10.1134/S0020168519030099
INTRODUCTION
Later, gamma-aluminum oxide was used as an alumi-
num compound. It was reacted with lithium carbonate
in the presence of a eutectic mixture of lithium car-
bonate and potassium carbonate at a temperature of
Fine-particle lithium monoaluminates (α-LiAlO
2
and γ-LiAlO ) are of interest as matrix electrolyte
2
materials for molten carbonate fuel cells [1]. The abil-
600°C for 24 h [7, 8]. After the synthesis, the residual
ity to produce materials with high phase purity (≥98%)
eutectic was removed using a mixture of acetic acid
and acetic anhydride, and the solid phase was washed
with ethanol. Despite the decrease in the heat treat-
ment time needed for obtaining the desired product,
the necessity to remove the alkali carbonates from the
2
and large specific surface area (≥10 m /g) is critical for
this application. At present, high-temperature lithium
monoaluminate, γ-LiAlO , is used for these purposes
2
[
(
2]. According to recent work, however, prolonged
20000 h) holding of γ-LiAlO in a eutectic Li CO +
2
2
3
α-LiAlO thus synthesized adds complexity to the syn-
2
Na CO carbonate melt leads to a phase transition of
2
3
thesis of the desired product.
γ-LiAlO to the low-temperature phase α-LiAlO [3].
2
2
It is promising to use aluminum trihydroxide in the
This transformation can disturb the operation of a
form of gibbsite as an aluminum compound for the
matrix cell, so the question arises whether it is reason-
synthesis of fine-particle α-LiAlO . In particular, as
2
able to use fine-particle α-LiAlO instead of γ-LiAlO
2
2
shown by Kharlamova et al. [9] interaction of coarse
gibbsite powder with lithium carbonate at a tempera-
ture of 650°C for 2 h in air leads to the formation of
as a matrix electrolyte material for molten carbonate
fuel cells [3, 4].
Fine-particle α-LiAlO can be synthesized by alpha-lithium aluminate containing unreacted lithium
2
several techniques, among which ceramic processing carbonate as an impurity phase. Raising the reaction
route is of most interest. This approach is based on temperature to 700°C allows one to obtain lithium
heat treatment of a starting mixture containing alumi- monoaluminate without lithium carbonate impurities,
num compounds (oxides or hydroxides) and lithium but the solid phase then contains not only α-LiAlO
2
carbonate at temperatures below 700°C (the tempera- but also γ-LiAlO as an impurity phase, whose con-
2
ture of the α → γ phase transition) [5]. In particular, in centration rises with increasing heat treatment tem-
the first studies concerned with α-LiAlO synthesis, a perature. To increase the rate of the reaction between
2
mixture of corundum and lithium carbonate was lithium carbonate and gibbsite and obtain phase-pure
reacted in air at 600°C for 200 h with intermediate α-LiAlO , Choi et al. [10] prehomogenized the start-
2
grindings of the sintered material [5, 6]. The α-LiAlO
ing mixture in an aqueous medium and then dried the
2
thus synthesized has a small specific surface area and material at 110°C for 24 h. The dried mixture was cal-
requires further prolonged grinding in a ball mill. cined in air for another 24 h at temperatures from 600
256

SYNTHESIS OF FINE-PARTICLE
257
to 800°C. The reaction products obtained at 600 and mined by X-ray diffraction on a D8 Advance diffrac-
7
00°C consisted of phase-pure α-LiAlO ranging in tometer (CuK radiation). Intensity data were col-
2
α
2
specific surface area from 9 to 11 m /g. One drawback lected in the angular range 2θ = 10°–70° at a scan step
to this approach is that it is necessary to prehomoge- of 0.02° and counting time of 35 s per data point. In
nize the mixture of starting reagents in water, dry the situ high-temperature X-ray diffraction measurements
resultant material in an additional step, and then heat- were performed using an HTK 1200N chamber
treat it for a long time.
(Anton Paar, Austria) equipped with a corundum
holder. The chamber was heated in air from room tem-
perature to 100°C at a rate of 12°C/min, and then an
X-ray diffraction pattern was collected at this tem-
perature. Next, the temperature was raised to 200°C
and measurements were again made, etc. The percent-
age of X-ray amorphous aluminum hydroxide (A, %)
in the activated mixture was evaluated as A (%) =
Another way to accelerate the reaction between
gibbsite and lithium carbonate is to use preliminary
mechanical activation (MA) of a mixture of these
reagents in a planetary activator mill, followed by heat
treatment of the activation products in air [9, 11]. In
particular, activation of a mixture of gibbsite and lith-
ium carbonate in an AGO-2 planetary activator mill at
a centrifugal acceleration of 40g for several minutes
leads to an appreciable increase in the specific surface
area of the reactants, defect accumulation in the crys-
tal structure of these compounds, their micron-scale
mixing, and structural changes [11]. Subsequent heat
treatment of the mechanically activated mixture in air
for 4 h at a temperature of 700°C leads to the forma-
tion of a mixture consisting of γ-LiAlO and α-LiAlO
1
00(I – I )/I , where I is the integrated intensity of a
0 0 0
particular reflection from the gibbsite in the mixture
τ
before activation and I is the integrated intensity of
this reflection after activation of the mixture for time τ
τ
(
min). To follow the variation in the phase composi-
tion of the mechanically activated mixture during heat
treatment, we measured the integrated intensity of the
(
112) reflection from gibbsite and the (110) reflection
2
2
2
from lithium carbonate. For the forming reaction
products, we used the (020) reflection from boehmite,
with a specific surface area above 10 m /g. The per-
centage of γ-LiAlO in the mixture is directly propor-
2
(
003) reflection from α-LiAlO , and (101) reflection from
2
tional to the percentage of X-ray amorphous aluminum
hydroxide formed in the MA step [12]. After activation
for 1 min, the mixture consists of 16% X-ray amorphous
γ-LiAlO . Since the strongest reflections from γ-Al O and
2
2
3
χ-Al O , resulting from aluminum hydroxide decompo-
sition, overlap with reflections from α-LiAlO and lith-
2
3
aluminum hydroxide, content of α-LiAlO —80%,
2
2
ium carbonate, their integrated intensity was not mea-
γ-LiAlO —20% [11]. Previous results suggest that MA
2
sured.
of a mixture of gibbsite and lithium carbonate in a
planetary activator—without formation of a consider-
The mechanically activated mixture was heat-
able amount of X-ray amorphous aluminum hydrox- treated in air in an SNOL muffle furnace at a heating
ide—followed by heat treatment in air at a temperature rate of 10°C/min. After a desired temperature was
below the α-LiAlO → γ-LiAlO phase transition can reached, the mixture was held there for a preset time.
2
2
The quantitative composition of the lithium alumi-
nates was determined by fitting X-ray diffraction line
profiles by the Rietveld method with the Topas 4.2
program (Bruker AXS, Germany). The specific sur-
face area of the samples was determined from argon
desorption measurements with the use of a specific
surface standard.
be used to synthesize fine-particle α-LiAlO .
2
The purpose of this work was to optimize conditions
for the MA of a mixture of gibbsite and lithium carbonate
in an AGO-2 planetary activator (milling time and cen-
trifugal acceleration) and subsequent heat treatment in
air so as to obtain phase-pure α-LiAlO with characteris-
2
tics meeting requirements for matrix electrolyte materials
for molten carbonate fuel cells.
EXPERIMENTAL RESULTS
Influence of the milling time and centrifugal acceler-
ation during the MA of a mixture of gibbsite and lithium
EXPERIMENTAL
The starting chemicals used in our experiments carbonate on aluminum hydroxide amorphization. As
were analytical-grade Al(OH) (gibbsite) and reagent-
3
mentioned above, data available in the literature sug-
grade Li CO with specific surface areas of 0.2 and gest that a necessary condition for the synthesis of
2
3
2
1
m /g, respectively. A starting mixture was mechani- fine-particle α-LiAlO without considerable γ-LiAlO
2 2
cally activated in air in an AGO-2 laboratory planetary impurities (under a few percent) is that the MA of a
centrifugal mill in 100-mL steel vials at an acceleration mixture of gibbsite and lithium carbonate in a plane-
of 10g, 20g, or 40g (rotor rotation rate of 420, 590, or
30 rpm) for 1 to 5 min. For activation, we used
-mm-diameter steel balls. The powder-to-ball weight
tary activator be not accompanied by the formation of
a considerable amount of X-ray amorphous aluminum
hydroxide. Because of this, in the first step of this
study we examined the influence of the centrifugal
8
5
ratio was 1 : 20.
The phase composition of the mechanically acti- acceleration and milling time of a mixture of gibbsite
vated samples and heat treatment products was deter- and lithium carbonate on the percentage of X-ray
INORGANIC MATERIALS Vol. 55 No. 3 2019

2
58
ISUPOV et al.
А, %
00
(а)
(b)
1
8
70
0
1
3
2
1
80
60
40
20
6
5
4
3
2
0
0
0
0 3
2
0
4
0
10
0
1
2
3
4
5
600
650
700
Milling time, min
Temperature, °C
Fig. 1. (a) Influence of the MA time and centrifugal acceleration on the percentage of X-ray amorphous aluminum hydroxide
(
A, %): (1) 10g, (2) 20g, (3) 40g. (b) Influence of heat treatment temperature on the specific surface area of the products obtained
by heat-treating the starting mixture of aluminum hydroxide and lithium carbonate (1) and the mixtures mechanically activated
for 1 (2), 3 (3), and 5 min (4) (heat treatment time, 4 h).
amorphous aluminum hydroxide in the activation tions from lithium carbonate begins to decrease in the
products (Fig. 1). It is seen in Fig. 1a that reducing the temperature range from 500 to 600°C. At 700°C, the
centrifugal acceleration from 40g to 10g at a given mill- reflections from lithium carbonate almost completely
ing time allows the percentage of X-ray amorphous disappear and only reflections from α-LiAlO are
2
aluminum hydroxide to be considerably reduced (by observed (Fig. 5). Heating to 800°C causes weak
several times). In view of this, in our subsequent reflections from gamma-lithium monoaluminate to
experiments we used samples prepared at a centrifugal emerge. After cooling to room temperature, the X-ray
acceleration of 10g and milling times of 1, 3, and diffraction pattern of the sample is dominated by
5
min, which had specific surface areas of 2.7, 5.7, and reflections from α-LiAlO , and there are weak reflec-
2
2
7
.6 m /g, respectively. The average particle size in the tions from γ-LiAlO , without reflections from lithium
2
mixture, evaluated as D = 6/(ρS), where ρ is the average
carbonate.
3
density of the mixture (2.3 g/cm ) and S is its specific sur-
The sequence of phase transformations during heat
face area, is 1.0, 0.46, and 0.34 μm, respectively.
treatment of the mixtures activated for 3 and 5 min is
Effect of heat treatment conditions of the mechani- qualitatively similar to that at τ = 1 min. We observe
MA
cally activated mixture of gibbsite and lithium carbonate
on α-LiAlO formation. Heat treatment of the unacti-
vated mixture above 200°C leads to gibbsite decompo- an increase in the intensity of the reflections from
sition and the formation of χ-Al O and boehmite α-LiAlO , forming at 600°C; and an increase in the
a further reduction in the percentage of boehmite
resulting from aluminum hydroxide decomposition;
2
2
3
2
(
Figs. 2, 3). In the range from 400 to 600°C, boehmite intensity of the reflections from γ-LiAlO , forming on
2
decomposes to form γ-Al O . At temperatures above
2
3
heating to 800°C.
6
00°C, lithium carbonate reacts with χ-Al O and
2 3
Thus, in situ X-ray diffraction data demonstrate
γ-Al O to form α-LiAlO . At a temperature of 800°C,
2
3
2
that optimal temperatures for α-LiAlO formation
2
along with reflections from α-LiAlO those from
γ-LiAlO begin to emerge. After cooling the sample to
2
from both the unactivated and activated mixtures lie in
2
the range from 600 to 700°C. Heating to temperatures
room temperature in a solid phase, we observe not only below this range leads to incomplete reaction between
reflections from α-LiAlO and γ-LiAlO but also weak the starting materials, whereas heating to higher tem-
2
2
reflections from lithium carbonate, indicating that the peratures leads to the formation of the high-tempera-
reaction did not reach completion.
ture polymorph γ-LiAlO as an impurity phase.
2
Heating the mixture activated for 1 min to 300°C
also leads to the formation of boehmite and χ-Al O
In the next step of our study, we examined the
effect of heat treatment conditions on the phase com-
2
3
(
Figs. 4, 5). The amount of boehmite resulting from position and specific surface area of α-LiAlO . To this
2
aluminum hydroxide decomposition in the mechani- end, we used samples prepared by calcining the start-
cally activated mixture is smaller than that in the unac- ing and mechanically activated (1, 3, and 5 min) mix-
tivated mixture. Boehmite decomposition also begins tures of gibbsite and lithium carbonate at temperatures
in the range from 400 to 500°C (Fig. 5) and is accom- of 600, 650, and 700°C for 4 h (Fig. 6). Throughout
panied by γ-Al O formation. The intensity of reflec- the temperature range studied, heat treatment of the
2
3
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SYNTHESIS OF FINE-PARTICLE
259
α
α
γ γ α
γ
8
00°C
α C C
CC C
C
α
α
7
00°C
α
α γ
γ
C
C
800°C
700°C
C
α
C
C
C
α, G
α, G
600°C
α α, χ, G
C
C
α
C
C
C
C
B
B
C
B
B
α, χ, G
5
00°C
C
α
C
C
C
600°C
400°C
C
C
C
χ, G
C
C
500°C
400°C
C CB
C
B
3
00°C
00°C
0°C
C
χ
C
C C C
B B
300°C
2
2
00°C
H H
H
H
H
C
H
HH H
H
C
H
HH
H
C
H
H
H
C
C
H CCC
C
C
C H
C
H
C
2
0°C
2
10
15 20 25 30 35 40
θ, deg
45 50 55 60 65 70
2
2θ, deg
Fig. 2. In situ X-ray diffraction results for the starting mixture of aluminum hydroxide and lithium carbonate in air: H = Al(OH)3,
C = Li CO , B = AlO(OH), χ = χ-Al O , G = γ-Al O , α = α-LiAlO , γ = γ-LiAlO .
2
3
2
3
2
3
2
2
2
unactivated mixture leads to the formation of α-LiAlO2 650 to 700°C ranges from 10 to 15 m /g, which meets
containing unreacted lithium carbonate as an impurity the requirements for matrix electrolyte materials for
phase (Fig. 6a). Preliminary MA of the mixture for molten carbonate fuel cells.
1
min accelerates the reaction between the reagents
and allows essentially phase-pure α-LiAlO to be
2
DISCUSSION
obtained in the range 650–700°C (Fig. 6b). Increasing
According to the literature, heat treatment of a
the activation time to 3 and 5 min leads to the forma-
mixture of gibbsite and lithium carbonate leads to α-
tion of γ-LiAlO as an impurity phase, together with
2
LiAlO formation at temperatures above 600°C
2
α-LiAlO . The amount of the former phase increases
2
through chemical interaction of the lithium carbonate
with increasing heat treatment temperature and MA
time (Figs. 6c, 6d; Table 1). The percentage of the
impurity phase γ-LiAlO in α-LiAlO is an essentially
with crystalline γ-Al O and χ-Al O forming by the
2
3
2
3
reactions (1)–(3) [11, 13]
2
2
T >200°C
linear function of the percentage of X-ray amorphous
aluminum hydroxide (Table 1). For the content of the
impurity phase γ-LiAlO in α-LiAlO not to exceed a
Al(OH) (cr) ⎯ ⎯ ⎯ ⎯ ⎯→ AlOOH(cr) + H O↑, (1)
3
2
2
2
few percent, the percentage of the X-ray amorphous
hydroxide in the mechanically activated mixture
should be at the same level.
α-LiAlO2
2500
1000
The specific surface area of the lithium aluminate
depends on the activation time of the reaction mixture
and heat treatment temperature (Fig. 1b). The largest
specific surface area is offered by the products
obtained by heat-treating the starting mixture of gibb-
site and lithium carbonate at 600°C. Raising the heat
treatment temperature reduces the specific surface
area (Fig. 1b, curve 1). A similar temperature depen-
AlO(OH)
Li CO3
2
500
Al(OH)3
γ-LiAlO2
0
dence of the specific surface area for α-LiAlO is
2
0
200
400
600
800
observed during heat treatment of the mechanically
activated samples (Fig. 1b, curves 2–4). At a given
heat treatment temperature, the specific surface area
decreases with increasing MA time. The specific sur-
Temperature, °C
Fig. 3. Effect of heat treatment temperature on the inte-
grated intensity of reflections from the phases formed
during heat treatment of a mixture of lithium carbonate
and gibbsite.
face area of the phase-pure α-LiAlO synthesized at
2
τ
= 1 min and heat treatment temperatures from
MA
INORGANIC MATERIALS Vol. 55 No. 3 2019

2
60
ISUPOV et al.
ꢀ
ꢀ
ꢀ
ꢂ
ꢂ ꢀ
ꢀ
ꢀ
ꢀ
8
00ꢄC
ꢂ
ꢀ
ꢀ
8
00ꢄC
00ꢄC
ꢀ
C
ꢀ
700ꢄC
00ꢄC
ꢀ
ꢀ
ꢂ
C
C C C C
C
C
C
7
6
ꢀ
, G
ꢀ, ꢃ, G
ꢃ, G
C
C
C
C
ꢀ
C
C
B
B
B
5
4
00ꢄC
00ꢄC
600ꢄC
00ꢄC
400ꢄC
G
C
C
C
C
5
C
C
C
B
C C
B
C
3
00ꢄC
00ꢄC
C
ꢃ
C
B
C C
B
3
00ꢄC
00ꢄC
2
2
H
H
H
H
H
H
HH
H H
H
H
C
H
C
C
H
C
C
CH
H
H
H
C
C
C
C C
C
CH
C
20ꢄC
2
0ꢄC
10
20
30
40
45 50 55 60 65 70
2ꢁ, deg
2ꢁ, deg
Fig. 4. In situ X-ray diffraction results for a mixture of aluminum hydroxide and lithium carbonate mechanically activated for
1
min in air: H = Al(OH) , C = Li CO , B = AlO(OH), χ = χ-Al O , G = γ-Al O , α = α-LiAlO , γ = γ-LiAlO .
3
2
3
2
3
2
3
2
2
T >250°C
aluminum hydroxide and the formation of crystalline
Al(OH) (cr) ⎯ ⎯ ⎯ ⎯ ⎯→χ-Al O + H O↑, (2)
3
2
3
2
aluminum oxides and X-ray amorphous π-Al O as an
2
3
T >450°C
impurity phase, whose reaction with lithium carbon-
AlOOH(cr) ⎯ ⎯ ⎯ ⎯ ⎯→γ-Al O + H O↑ .
(3)
2
3
2
ate is responsible for the formation of γ-LiAlO impu-
2
The crystalline χ-Al O and γ-Al O oxides form a
2
3
2
3
rities in α-LiAlO [11, 14]. This point of view is sup-
2
pseudomorph after spherulite-like intergrowths of
parent gibbsite crystals, whose size in the case of a
macrocrystalline material lies predominantly in the
range from 60 to 150 μm. Because of the large size of
the forming aluminum oxide particles, the rate of their
ported by the above-mentioned linear correlation
between the γ-LiAlO concentration in α-LiAlO and
2
2
the amount of X-ray amorphous aluminum hydroxide
after MA. At heat treatment temperatures above
interaction with lithium carbonate under the experi- 700°C, the formation of γ-LiAlO as an impurity
2
mental conditions of this study (600–700°C, 4 h) does phase may be due as well to the phase transition of
not ensure complete interaction between the reac- α-LiAlO to γ-LiAlO .
2
2
tants. The reaction products contain both α-LiAlO
2
and unreacted lithium carbonate and aluminum
oxides. A brief activation of the reaction mixture at a
centrifugal acceleration of 10g for 1 min leads to a
reduction in the average size of the gibbsite and lith-
ium carbonate particles by about one order of magni-
tude, essentially without gibbsite amorphization. The
appreciable decrease in the particle size of the gibbsite
and forming crystalline aluminum oxides leads to an
increase in the rate of the reaction between the oxides
and lithium carbonate, which yields essentially phase-
α-LiAlO2
6
000
5500
500
0
Li CO3
2
pure, fine-particle α-LiAlO , with negligible amounts
Al(OH)3
AlO(OH)
2
of lithium carbonate impurities. Increasing the MA
time of the mixture to 3 and 5 min leads to a further
reduction in the particle size of the gibbsite and the
formation of X-ray amorphous aluminum hydroxide
impurities.
γ-LiAlO2
0
200
400
600
800
Temperature, °C
Heat treatment of the activated mixture leads to not
only a further increase in the rate of the reaction
between the crystalline oxides and lithium carbonate
but also the decomposition of the X-ray amorphous
Fig. 5. Effect of heat treatment temperature on the inte-
grated intensity of reflections from the phases formed
during heat treatment of a mechanically activated mixture
of lithium carbonate and gibbsite (τ
= 1 min).
MA
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SYNTHESIS OF FINE-PARTICLE
261
(а)
(b)
α
α
α
C
C
C
α
α
α
α
C
C
7
00°С
α
α
α
α
α
α
700°С
650°С
C
C
C
α
C
α
650°С
C
α α
α
C
C
C
600°С
C
C
600°С
1
0 20 30 40 50 60 70 10 20 30 40 50 60 70
2θ, deg
2θ, deg
(c)
(d)
α
α
α
γ
α
α
α
γ
γ
α
γ
α
γ
γ
700°С
α
γ
α
γ
γ α
γ
γ
γ
700°С
γ
γ
650°С
00°С
6
50°С
α
α
α
α
α
C
C α
α
γ
α
6
00°С
α
6
1
0 20 30 40 50 60 70 10 20 30 40 50 60 70
2θ, deg
2θ, deg
Fig. 6. X-ray diffraction patterns of the products obtained by heat-treating the starting mixture of aluminum hydroxide and lith-
ium carbonate (a) and the mixtures mechanically activated for 1 (b), 3 (c), and 5 min (d) (heat treatment time, 4 h).
CONCLUSIONS
lowed by heat treatment of the mechanically activated
mixture in the range 650–700°C for several hours,
The mechanical activation of a mixture of gibbsite
and lithium carbonate in an AGO-2 planetary activa-
tor for 1–3 min at a centrifugal acceleration of 10g, fol-
allows one to obtain fine-particle α-LiAlO with char-
2
acteristics acceptable for the use of the material in a
matrix electrolyte for molten carbonate fuel cells. The
present results demonstrate that, to obtain α-LiAlO
2
Table 1. Effect of MA time on the phase composition of the with a small percentage of γ-LiAlO impurities, the
2
reaction products obtained by heat-treating mixtures of alu-
MA of the reaction mixture should cause no signifi-
minum hydroxide and lithium carbonate in air at 700°C for
cant aluminum hydroxide amorphization (no more
than 1–2%).
4
h
Weight percent
τMA, min
А, %
Li CO3 α-LiAlO2 γ-LiAlO2
2
ACKNOWLEDGMENTS
0
1
3
5
0
1.5
11
1.7
–
–
98.3
99.0
94.0
88.3
–
1.0
6.0
11.7
We are grateful to N.V. Bulin for performing the
X-ray diffraction work. This study was supported by
the Russian Federation Ministry of Education and
Science (state research target for the Institute of Solid
State Chemistry and Mechanochemistry, Siberian
16
–
A is the degree of gibbsite amorphization.
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Vol. 55
No. 3
2019