Effect of mechanical activation of Al(OH)3 on its reaction with Li2CO3

Article abstract of DOI:10.1134/S0020168512080055

The effect of preliminary mechanical activation of Al(OH)₃ on its solid-state reaction with Li₂CO₃ at temperatures above 800°C has been studied by thermogravimetry, X-ray diffraction, in situ X-ray diffraction, electron mi

Full text of DOI:10.1134/S0020168512080055

ISSN 0020ꢀ1685, Inorganic Materials, 2012, Vol. 48, No. 9, pp. 918–924. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © V.P. Isupov, N.V. Eremina, 2012, published in Neorganicheskie Materialy, 2012, Vol. 48, No. 9, pp. 1039–1045.
Effect of Mechanical Activation of Al(OH)3
on Its Reaction with Li2CO3
V. P. Isupov and N. V. Eremina
Institute of Solid State Chemistry and Mechanochemistry, Siberian Branch, Russian Academy of Sciences,
ul. Kutateladze 18, Novosibirsk, 630128 Russia
eꢀmail: isupov@solid.nsc.ru
Received January 20, 2012
Abstract—The effect of preliminary mechanical activation of Al(OH)3 on its solidꢀstate reaction with
Li2CO3 at temperatures above 800 C has been studied by thermogravimetry, Xꢀray diffraction, in situ Xꢀray
°
diffraction, electron microscopy, and specific surface area and particle size measurements. The results demꢀ
onstrate that preliminary mechanical activation of Al(OH)3 in an AGOꢀ2 planetary mill at 40 for 1 min
allows phaseꢀpure ꢀLiAlO2 to be obtained. The composition of the lithium aluminates resulting from
mechanical activation and heat treatment depends on the phase composition of the aluminum oxides resultꢀ
ing from the thermal decomposition of Al(OH)3. The particle size and specific surface area of the forming
ꢀLiAlO2 have been determined.
g
γ
γ
DOI: 10.1134/S0020168512080055
INTRODUCTION
800 to 850
°
C allows one to produce finely dispersed
γ
ꢀLiAlO2, which can be used in molten carbonate fuel
γ
ꢀLiAlO2 with a large specific surface area is used in
cell electrolyte matrix supports and lithium thermal
batteries [13]. As pointed out earlier [12], the heat
treatment of a mixture containing lithium carbonate
and mechanically activated aluminum hydroxide leads
tritium production in nuclear power engineering [1],
in molten carbonate fuel cell electrolyte matrix supꢀ
port materials [2], as a separator material for lithium
thermal batteries, and to modify the conductivity of
lithium polymer electrolytes [3]. The most widespread
approaches to the synthesis of fineꢀparticle ꢀLiAlO2
are ceramic processing route [4, 5] and sol–gel proꢀ
cesses [6–9].
to the formation of phaseꢀpure ꢀLiAlO2 at a lower
γ
temperature in comparison with unactivated alumiꢀ
num hydroxide. This suggests that the initial state of
aluminum hydroxide has a strong effect on its reaction
with lithium carbonate.
The purpose of this work was to investigate the
effect of the MA of Al(OH)3 on its reaction with
γ
The conventional ceramic processing route is easy
to implement, but the forming ꢀLiAlO2 typically has a
γ
small specific surface area, insufficient for application
in electrolyte matrix supports. Because of this, the
lithium aluminate thus prepared has to be subseꢀ
quently ground into fineꢀparticle material, which
leads to contamination of the product.
Li2CO3
.
EXPERIMENTAL
The starting materials used were crystalline
Al(OH)3 (analytical grade, RF State Standard GOST
11841ꢀ76) and Li2CO3 (pure grade, Purity Standard
TU 6ꢀ09ꢀ3728ꢀ83).
The aluminum hydroxide was first mechanically
activated in an AGOꢀ2 centrifugal planetary mill
Sol–gel processing enables the preparation of
γ
ꢀLiAlO2 with a sufficiently large specific surface area,
S
= 5–10 m2/g, but this approach requires expensive
organic precursors of aluminum and lithium. Moreꢀ
over, sol–gel processes are rather difficult to impleꢀ
ment and present an environmental threat. In this
context, there is currently great interest in novel, enviꢀ
ronmentally safe processes for the synthesis of fineꢀ
(200ꢀml steel vials) at 40g in air for 1, 5, and 10 min.
At milling times of 5 and 10 min, the process was run
discretely, with breaks after every 2.5 min of milling.
We used 5ꢀmmꢀdiameter steel balls. The powderꢀtoꢀ
particle
γꢀLiAlO2 from relatively inexpensive, readily
available chemicals.
Among new synthetic approaches, mechanical ball weight ratio was 1 : 20. Mechanically activated or
activation (MA), widely used to synthesize mixed unactivated Al(OH)3 was mixed with Li2CO3 in an
oxides [10], is of considerable interest. In particular, as agate mortar to give a stoichiometric mixture of
shown by Kharlamova et al. [11, 12] the MA of a mixꢀ LiAlO2. The starting mixtures thus prepared were
ture of aluminum hydroxide and lithium carbonate in reacted in an SNOL 7.2/1100 laboratory muffle furꢀ
an AGOꢀ2 planetary mill, followed by heat treatment nace at a heating rate of 10
°
C/min and then at 800 C
°
of the activation products in air at temperatures from for 4 h.
918

EFFECT OF MECHANICAL ACTIVATION OF Al(OH)3
919
m, %
100
95
90
85
80
75
70
65
2
4
3
5
1
0
100
200
300
400
500
600
700
800
Temperature, C
°
Fig. 1. Weight loss curves of (
1
) gibbsite, (
2
) a mixture of gibbsite and lithium carbonate, and (
3–5) mixtures of lithium carbonate
and mechanically activated aluminum hydroxide. Milling time of (
3
) 1, ( ) 5, and ( ) 10 min; sample weight, 200 mg; heating at
4
5
a rate of 10°C/min in air.
demonstrate that, when crystalline aluminum hydroxꢀ
ide is reacted with lithium carbonate, weight losses
The unactivated and mechanically activated aluꢀ
minum hydroxides and the products of their reaction
with lithium carbonate were characterized by thermoꢀ
gravimetry (TG), Xꢀray diffraction (XRD), in situ
XRD, and specific surface area and particle size meaꢀ
surements.
begin at 220
perature range studied, up to 700
°
C
and are observed throughout the temꢀ
(Fig. 1). Since the
°C
TG curve of individual aluminum hydroxide is similar
in shape to that of the mixture at temperatures of up to
500–550 C, it is reasonable to assume that, below
°
XRD patterns were collected on a D8 Advance difꢀ
these temperatures, the weight loss is predominantly
due to Al(OH)3 dehydration. This assumption is qualꢀ
itatively supported by in situ XRD data (Fig. 2), which
demonstrate that, when the mixture is heated to
fractometer (Bruker, Germany) (Cu
K radiation, air,
α
2
θ
= 10
°
–50
°
, heating rate of
2 C/min). In situ XRD
°
measurements were performed on the D8 Advance
diffractometer (Bruker, Germany), equipped with an
NTK 1200 N highꢀtemperature camera (Al2O3 holders,
200 C, the reflections from Al(OH)3 almost comꢀ
°
pletely disappear and reflections from boehmite
emerge. Their intensity decreases with increasing temꢀ
perature, and they almost completely disappear at
Cu
K
radiation, air,
2
θ
= 10
C/min, temperatures from 25 to 900
scan took 8 min.
°
–50
°
, heating rate of
α
10°
°
С). One XRD
500
carbonate remains essentially unchanged throughout
the temperature range 25–400 . At 500 , there is a
slight decrease in intensity. The XRD pattern taken at
600 shows rather strong reflections from the
ꢀphase of lithium aluminate. After heating to 700
ꢀphase and
ꢀLiAlO2. At higher temperatures, the percentage of
°C. The intensity of the reflections from lithium
TG scans were performed with a Paulik–Paulik–
Erdey thermoanalytical system in air at temperatures
°C
°C
from 20 to 700
°C
and a heating rate of 10 C/min,
°
using alphaꢀalumina crucibles.
°C
The specific surface area of our samples was evaluꢀ
ated from argon adsorption/desorption isotherms.
The particle size of the aluminum hydroxides and the
products of their reaction with lithium carbonate was
determined using a Microsizerꢀ201A particle size laser
analyzer, with ethanol as a dispersion medium. The
morphology of the powders was examined by scanning
electron microscopy (SEM) on a Hitachi TMꢀ100.
α
°C,
there are reflections from both the
γ
α
the
γ
ꢀphase increases, while that of
the
ꢀLiAlO2 as an impurity phase.
α
ꢀLiAlO2
decreases. Nevertheless, even at 900
coexists with
°C
γꢀphase
α
Reaction of mechanically activated aluminum
hydroxide with lithium carbonate studied by TG and
XRD. TG data demonstrate that, during heating of a
mixture of Li2CO3 and mechanically activated
EXPERIMENTAL RESULTS
Reaction of crystalline aluminum hydroxide with Al(OH)3, a weight loss begins at a lower temperature in
lithium carbonate studied by TG and XRD. TG data comparison with the mixture containing unactivated
INORGANIC MATERIALS Vol. 48
No. 9 2012

920
ISUPOV, EREMINA
G*
G
G
G
G
G
G
G
А
А
G
900
800
C
C
700
C
C
C
600
500
G*
C
C
B
G*
400
300
200
25
G*
G*
G*
*
G*
G
10
20
30
, deg
40
50
2θ
Fig. 2. In situ XRD patterns of a mixture of lithium carbonate and unactivated aluminum hydroxide. A =
ꢀLiAlO , B = boehmite, G* = Al(OH) , C = Li CO .
α
ꢀLiAlO , G =
2
γ
2
3
2
3
gibbsite (Fig. 1). Nevertheless, in this case as well aluꢀ
minum hydroxide dehydration prevails in the initial
stages of the reaction. This assumption is supported by
in situ XRD results (Fig. 3). In particular, in the case of
a mixture containing Al(OH)3 mechanically activated
(
800
°
C, 4 h), preliminary milling of Al(OH)3 for just
1 min allows phaseꢀpure
γ
ꢀLiAlO2 to be obtained.
Effect of the MA of Al(OH)3 on the morphology,
specific surface area, and particle size of the solid
phase. The unactivated Al(OH)3 had
(Fig. 5) and consisted predominantly of spheruliteꢀ
like intergrowths of prismatic crystals (Fig. 6). Most of
the intergrowths were 40 to 120
The MA of the Al(OH)3 increased the
by two orders of magnitude. Moreover, MA increased
the percentage of the Xꢀray amorphous phase (Fig. 5).
S
= 0.15 m2/g
for 5 min, heating to 200 C causes its reflections to disꢀ
°
appear, without boehmite formation. The intensity of
the reflections from Li2CO3 remains essentially
µ
m in size (Fig. 7).
S
of the powder
unchanged up to 400
emerge at a temperature as low as 600
800 leads to the formation of almost phaseꢀpure
ꢀLiAlO2
°C. The reflections from
γꢀLiAlO2
°C. Heating to
°C
The average particle size (
= 6/(
is the density of aluminum hydroxide
D) evaluated from
S as
γ
.
D
ρS),
Thus, when a mixture containing lithium carbonꢀ
ate and unactivated or mechanically activated alumiꢀ
num hydroxide is heated to 400 or lower temperaꢀ
where
ρ
(2.4 g/cm3
)
and S is the specific surface area of the
°
C
powder (cm2/g), is on the order of 0.15
time of 5 min).
µ
m (milling
tures, the predominant process is the decomposition
of the aluminum hydroxide.
Milling for 1 min substantially decreased the perꢀ
centage of large particles (40–120 m) and increased
the percentage of smaller particles (less than 40 m in
size). Increasing the milling time to 5 min gave rise to
aggregation processes, which showed up as a reduction
Preliminary milling of Al(OH)3 considerably
µ
increases the percentage of ꢀLiAlO2 in the reaction
γ
µ
products in comparison with unactivated aluminum
hydroxide under comparable heatꢀtreatment condiꢀ
tions. This conclusion is supported by the phase comꢀ
position of the products obtained under identical
heatꢀtreatment conditions after the milling of Al(OH)3
for different lengths of time (Fig. 4). It can be seen
in the percentage of small particles (less than 6
size) and an increase in the percentage of particles
greater than 40 m in size. Finally, milling for 10 min
had little effect on the particle size composition of the
µ
m in
µ
that, under identical heatꢀtreatment conditions solid phase.
INORGANIC MATERIALS Vol. 48
No. 9
2012

EFFECT OF MECHANICAL ACTIVATION OF Al(OH)3
921
G
G
G
G
G
G
G
900
800
А
700
600
500
C
C
C
А
C
C
C
400
300
200
25
G*
G*
10
20
30
, deg
40
50
2θ
Fig. 3. In situ XRD patterns of a mixture of aluminum hydroxide mechanically activated for 5 min and lithium carbonate.
A =
α
ꢀLiAlO , G =
γ
ꢀLiAlO , B = boehmite, G* = Al(OH) , C = Li CO
.
2
2
3
2
3
G
G
G
G
G
G
G
G
А
4
А
3
2
1
10
20
30
, deg
40
50
2θ
Fig. 4. XRD patterns taken after heat treatment (800
) 10 min and Li CO ; ( ) without MA. A = ꢀLiAlO , G = ꢀLiAlO .
2
°
C, 4 h) of a mixture of Al(OH) mechanically activated for (2) 1, (3) 5, and
3
γ
2
(4
1
α
2
3
INORGANIC MATERIALS Vol. 48
No. 9 2012

922
ISUPOV, EREMINA
S
, m2/g
Thus, the milling of gibbsite produces aggregates of
A
, %
90
submicronꢀsized particles, with the aggregate size rangꢀ
ing widely: from a few to hundreds of microns. It is
worth pointing out that a considerable increase in the
specific surface area of aluminum hydroxide upon actiꢀ
vation in planetary mills was reported by Zolotovskii
[14] and Menzheres et al. [15]. Isupov et al. [16]
observed aggregation of submicronꢀsized particles.
20
15
10
5
3
80
70
60
50
40
30
20
10
0
1
Effect of MA on the particle size and morphology of
the products of the reaction between aluminum hydroxꢀ
ide and lithium carbonate. The reaction between crysꢀ
talline Al(OH)3 and Li2CO3 under the experimental
2
conditions of this study (800 C, 4 h) leads to an
°
0
2
4
6
8
10
increase in the specific surface area of the solid phase
by a factor of ~30 (Fig. 5). The reaction product, a
Time, min
mixture of
αꢀ
and
γꢀLiAlO2, is similar in morphology
and particle size to the parent gibbsite (Figs. 6, 7).
Fig. 5.
(
1
) Specific surface of aluminum hydroxide,
(2
) specific surface of lithium aluminate, and (3
) amorꢀ
Milling for 1 min increases the
S of the aluminum
S
phous phase content of mechanically activated aluminum
hydroxide as functions of milling time (the percentage of
the Xꢀray amorphous phase was evaluated from the inteꢀ
hydroxide and sharply reduces the of the reaction
product: phaseꢀpure ꢀLiAlO2. The subsequent variaꢀ
tion in the specific surface area of the ꢀLiAlO2 is simꢀ
γ
grated intensity of the reflection at
d/
n
= 4.82 Å).
γ
100
μ
m
100 μm
(а)
(b)
100 μm
100 μm
(c)
(d)
Fig. 6. Electron microscopic micrographs of the (a) unactivated aluminum hydroxide, (b) the product of its reaction with lithium
carbonate, (c) aluminum hydroxide mechanically activated for 10 min, and (d) the product of the reaction of the mechanically
activated aluminum hydroxide with lithium carbonate.
INORGANIC MATERIALS Vol. 48
No. 9
2012

EFFECT OF MECHANICAL ACTIVATION OF Al(OH)3
923
(а)
12
10
8
0 min
1 min
5 min
10 min
6
4
2
0
4.2
16.5
65.8
262
Particle size, μm
(b)
0 min
1 min
5 min
10 min
12
10
8
6
4
2
0
4.2
16.5
65.8
262
Particle size, μm
Fig. 7. Particle size distributions of the (a) unactivated and mechanically activated aluminum hydroxide and (b) lithium aluminate
synthesized from the aluminum hydroxide.
ilar to the variation in the specific surface area of the
mechanically activated Al(OH)3 used in the synthesis
of the lithium aluminate. The average particle size of
determined from laser light scattering and electron
microscopy data.
Comparison of the particle sizes of the mechaniꢀ
cally activated aluminum hydroxide and the products
of its reaction with lithium carbonate (Fig. 7) demonꢀ
the
m after milling for 5 min to 6–7
10 min. The particles form aggregates which range
γꢀLiAlO2 (D)
evaluated from the
S
data ranges from
1
µ
µ
m after milling for
widely in size, from a few to hundreds of microns, as strates that the peak in the particle size distributions of
INORGANIC MATERIALS Vol. 48
No. 9 2012

924
ISUPOV, EREMINA
3. Morita, M., Fujisaki, T., Yoshimoto, N., and Ishiꢀ
kawa, M., Ionic Conductance Behavior of Polymeric
Composite Solid Electrolytes Containing Lithium Aluꢀ
minate, Electrochim. Acta, 2001, vol. 46, nos. 10–11,
pp. 1565–1569.
the aluminates is shifted to smaller particle sizes in
comparison with the parent hydroxide.
DISCUSSION
4. Hummel, F.A., Thermal Expansion Properties of Some
Synthetic Lithia Minerals, J. Am. Ceram. Soc., 1951,
vol. 34, pp. 235–240.
The present results demonstrate that the initial
stages of the reaction between crystalline Al(OH)3 and
Li2CO3 are dominated by aluminum hydroxide dehyꢀ
dration, which follows a scheme described in suffiꢀ
cient detail in Ref. [17]. According to that scheme, in
the first step of the dehydration process some of the
aluminum hydroxide decomposes to form boehmite,
AlOOH, which was detected by in situ XRD. Next, the
residual aluminum hydroxide decomposes to form
5. Kinoshita, K., Sim, J.W., and Ackerman, J.P., Preparaꢀ
tion and Characterization of Lithium Aluminate, Mater.
Res. Bull., 1978, no. 13, pp. 445–455.
6. Hirano, S., Hayahi, T., and Kageyama, T., Synthesis of
LiAlO2 Powder by Hydrolysis of Metal Alkoxides, J. Am.
Ceram. Soc., 1987, vol. 70, no. 3, pp. 171–174.
χ
ꢀAl2O3. Heating to higher temperatures (above
7. Kwon, S.W. and Park, S.B., Effect of Precursors on the
Preparation of Lithium Aluminates, J. Nucl. Mater.,
1997, vol. 246, nos. 2–3, pp. 131–138.
450 ) leads to boehmite dehydration and ꢀAl2O3
°
C
γ
formation. The oxide phases in question are difficult
to detect by in situ XRD because the strongest reflecꢀ
tions from these phases coincide with reflections from
8. Valenzuela, M.A., JimenezꢀBeccerril, J., Bosch, P.,
et al., Sol–Gel Synthesis of Lithium Aluminates, J. Am.
Ceram. Soc., 1996, vol. 79, no. 2, pp. 455–460.
lithium carbonate and the forming
tions of these aluminum oxides with lithium carbonate
lead to predominant formation of the ꢀphase of lithꢀ
αꢀLiAlO2. Reacꢀ
9. Ribeiro, R.A., Silva, G.G., and Mohallem, N.D.S., The
Influences of Heat Treatment on the Structural Properꢀ
ties of Lithium Aluminates, J. Phys. Chem. Solids, 2001,
vol. 62, no. 5, pp. 857–864.
α
ium aluminate in the initial stage of the process.
Preliminary milling of Al(OH)3 leads to amorꢀ
phization of the material, and the amorphous phase
content increases with increasing milling time (Fig. 5).
The thermal decomposition of the Xꢀray amorphous
10. Avvakumov, E.G., Senna, M., and Kosova, N.V., Soft
Mechanochemical Synthesis: A Basis for New Chemical
Technologies, Dordrecht: Kluwer Academic, 2001.
phase in a wide temperature range, from 250 to 770
leads to the formation of Xꢀray amorphous ꢀalumiꢀ
°
C,
11. Kharlamova, O.A., Mitrofanova, R.P., and Isupov, V.P.,
π
RF Patent 2 347 749, Byull. Izobret., 2009, no. 6.
num oxide, which contains aluminum in fourꢀ, fiveꢀ,
and sixfold coordination [14].
12. Kharlamova, O.A., Mitrofanova, R.P., and
Isupov, V.P., Mechanochemical Synthesis of Fineꢀ
Particle ꢀLiAlO2, Inorg. Mater., 2007, vol. 43, no. 6,
γ
pp. 645–650.
CONCLUSIONS
13. Isupov, V.P., Chupakhina, L.E., and Eremina, N.V.,
Mechanochemical Synthesis of Highly Dispersed
Gamma Lithium Aluminate, Khim. Interesakh Ustoich.
Razvit., 2012, vol. 20, pp. 73–77.
The present results lead us to assume that the difꢀ
ference in phase composition between aluminum
oxides resulting from the thermal decomposition of
unactivated and mechanically activated Al(OH)3 is
one of the major causes why MA influences the phase
composition of the products of the reaction between
14. Zolotovskii, B.P., Scientific Principles behind the Mechꢀ
anochemical and Thermochemical Activation of Crysꢀ
talline Hydroxides in the Fabrication of Supports and
Catalysts, Doctoral (Chem.) Dissertation, Novosibirsk:
Inst. of Catalysis, Sib. Branch, Russ. Acad. Sci., 1992.
Al(OH)3 and Li2CO3
.
Despite the rather large difference in specific surꢀ
face area between the parent aluminum hydroxide and
the forming lithium aluminate, their particle size disꢀ
tributions differ rather little. This suggests that the
lithium aluminate has the same aggregate size as the
parent aluminum hydroxide.
15. Menzheres, L.T., Isupov, V.P., and Kotsupalo, N.P.,
Mechanical Activation of Hydrargillite in a Centrifugal
Planetary Mill: 1. Comparative Characterization of the
Hydrargillite Activation Process in Various Planetary
Mills, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim. Nauk,
1988, no. 3, issue 5, pp. 53–57.
16. Isupov, V.P., Menzheres, L.T., Tatarintseva, M.I., et al.,
Mechanical Activation of Hydrargillite in a Centrifugal
Planetary Mill: 2. Effect of Mechanical Activation on the
Particle Size Composition and Morphology of
Hydrargillite, Izv. Sib. Otd. Akad. Nauk SSSR, Ser. Khim.
Nauk, 1988, no. 19, issue 6, pp. 99–104.
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INORGANIC MATERIALS Vol. 48
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2012