Interaction of x-ray amorphous aluminum oxide with lithium carbonate: Effect of the chemical history of aluminum oxide

Article abstract of DOI:10.1023/A:1022685826889

The high-temperature (950-1050°C) crystallization behavior of x-ray amorphous Al₂O₃ and its reaction with lithium carbonate in the range 500-700°C were studied using Al₂O₃ samples prepared by five different procedures: thermal decomposition of Al(NO ₃)₃·9H₂O, Al₂(C ₂O₄)₃·nH₂O, aluminum hydroxides synthesized via Al³⁺ precipitation from aluminum nitrate and aluminum chloride solutions by a 20% excess of a concentrated NH ₄OH solution, and sol-gel-prepared aluminum hydroxide. The results demonstrate that the preparation procedure has a significant effect on the crystallization behavior and solid-state reactivity of x-ray amorphous aluminum oxide.

Full text of DOI:10.1023/A:1022685826889

Inorganic Materials, Vol. 39, No. 3, 2003, pp. 280–284. Translated from Neorganicheskie Materialy, Vol. 39, No. 3, 2003, pp. 346–351.
Original Russian Text Copyright © 2003 by Sinitskii, Oleinikov, Murav’eva, Tret’yakov.
Interaction of X-ray Amorphous Aluminum Oxide
with Lithium Carbonate: Effect of the Chemical History
of Aluminum Oxide
A. S. Sinitskii, N. N. Oleinikov, N. N. Murav’eva, and Yu. D. Tret’yakov
Moscow State University, Moscow, 119899 Russia
e-mail: van@igic.ras.ru
Received June 4, 2002
Abstract—The high-temperature (950–1050°C) crystallization behavior of x-ray amorphous Al O and its
2
3
reaction with lithium carbonate in the range 500–700°C were studied using Al O samples prepared by five dif-
2
3
ferent procedures: thermal decomposition of Al(NO ) · 9H O, Al (C O ) · nH O, aluminum hydroxides syn-
3
3
2
2
2
4 3
2
3
+
thesized via Al precipitation from aluminum nitrate and aluminum chloride solutions by a 20% excess of a
concentrated NH OH solution, and sol–gel-prepared aluminum hydroxide. The results demonstrate that the
4
preparation procedure has a significant effect on the crystallization behavior and solid-state reactivity of x-ray
amorphous aluminum oxide.
INTRODUCTION
EXPERIMENTAL
In recent years, there has been increasing interest in
X-ray amorphous aluminum oxide samples were
nanocrystalline and amorphous materials because they prepared by five different procedures.
often possess unusual properties, rarely encountered in
Samples 1 and 2 were obtained by thermal decom-
bulk materials. For example, x-ray amorphous materi-
als are highly reactive [1–3]. However, analysis of
available data [1–6] indicates that solid-state reactions
involving x-ray amorphous materials have not been
studied in detail.
position of hydrated oxy salts: Al(NO ) · 9H O and
3
3
2
Al (C O ) · nH O, respectively.
2
2
4 3
2
Samples 3 and 4 were obtained via thermal decom-
position of hydroxides, which were synthesized by
slowly adding an aluminum nitrate (sample 3) or alumi-
num chloride (sample 4) solution to a 20% excess of a
In this context, it is of interest to examine the effect
of the chemical history of x-ray amorphous reagents on
their behavior in solid-state reactions.
concentrated NH OH solution. Preliminary experi-
4
ments showed that, to obtain pure materials, free of
–
3
–
To this end, we investigated solid-state reactions of NO and Cl impurities, the hydroxides must be
variously prepared x-ray amorphous aluminum with
lithium carbonate, Li CO . This approach (the use of
washed repeatedly with distilled water.
2
3
Sample 5 was also prepared by thermal decomposi-
tion of aluminum hydroxide. In this case, aluminum
hydroxide was synthesized with the use of a colloidal
solution which was prepared from a 0.1 M Al(NO3)3
solution via ion exchange and then freeze-dried using
liquid nitrogen and a Usifroid SMH-15 sublimator.
x-ray amorphous aluminum oxides prepared by differ-
ent procedures) is of great interest because it is
expected to shed some light on whether the structure of
an x-ray amorphous phase depends on the preparation
procedure, which can be ascertained by examining
changes in its reactivity. In other words, the reaction
between x-ray amorphous aluminum oxide and lithium
In all preparations, thermal decomposition was run
carbonate is used as a kinetic probe to characterize the at 400°C for 1 h.
state of the x-ray amorphous phase.
After synthesis, the samples were examined by
scanning electron microscopy (SEM) (Fig. 1) on a
JEOL JEM-2000FXII transmission electron micro-
scope equipped with a scan-mode accessory (accelerat-
ing voltage of 200 kV).
Amorphous aluminum oxide was chosen as one of
the reagents because it is a convenient system for study-
ing the noncrystalline state [4]. Typically, Al O pre-
pared via thermal decomposition of aluminum hydrox-
ide or oxy salts (oxalates, nitrates, and others) at rela-
2
3
Next, the samples were annealed in the temperature
tively low temperatures is amorphous [4] and remains range 500–900°C and then air-quenched. X-ray diffrac-
in this state over a wide temperature range.
tion (XRD) analysis showed that the annealed samples
0
020-1685/03/3903-0280$25.00 © 2003 MAIK “Nauka/Interperiodica”

INTERACTION OF X-RAY AMORPHOUS ALUMINUM OXIDE WITH LITHIUM CARBONATE
281
3
µm
3 µm
(
a)
(b)
3
µm
3 µm
(
c)
(d)
3
µm
(
e)
Fig. 1. SEM micrographs of samples (a) 1, (b) 2, (c) 3, (d) 4 and (e) 5, prepared by hydroxide decomposition at 400°C.
remained amorphous. Trace amounts of crystalline using the Scherrer formula
γ-Al O were only present after 900°C annealing.
2
3
0
.94λ
D = ------------- -- ,
β cosθ
Subsequent annealing at higher temperatures (950,
1
000, and 1050°C) for 1 h led to quantitative crystalli-
where λ the x-ray wavelength and β is the full width at
half maximum of the intrinsic diffraction profile (rad).
The estimated error in D was 8–10%.
zation, yielding significant amounts of γ-Al O at
2
3
9
50°C and α-Al O at 1050°C, as determined by XRD
2 3
analysis (table).
It can be seen from the table that the particle size of
After annealing at 950°C (γ-Al O ), we determined γ-Al O has a significant effect on the γ
α phase
2
3
2
3
the size of coherently scattering domains in the samples transition. At a smaller particle size (samples 1 and 5,
INORGANIC MATERIALS Vol. 39 No. 3 2003

2
82
SINITSKII et al.
D = 80 and 95 Å, respectively), the formation of
The former mixtures were fired at 500, 600, and
α-Al O at 1000 and 1050°C proceeded more rapidly. 700°C for 15 min to 3 h, and the latter were fired at
2
3
After annealing at 1050°C, samples 1 and 5 consisted 600°C for 3 h. After heat treatment, all of the samples
almost entirely of α-Al O . At a larger particle size were characterized by XRD.
2
3
(
samples 3 and 4), the amount of α-Al O was smaller.
2 3
Note that the relative amounts of α- and γ-Al O after
annealing at 1000 and 1050°C were estimated from
integrated XRD intensities.
2
3
RESULTS AND DISCUSSION
The reaction mixtures were first fired at 500°C for
Thus, the above results demonstrate that the prepa- 15 min and 1 h. XRD examination showed however that
ration procedure has a significant effect on the crystal- quantitative reaction took place only at 600 and 700°C.
lization behavior of aluminum oxide.
Surprisingly, even at these moderate firing tempera-
tures, we obtained the high-temperature form of lithium
To study the reaction between aluminum oxide and
lithium carbonate, we prepared two sets of equimolar
mixtures using x-ray amorphousAl O samples synthe-
aluminate, γ-LiAlO , which is thermodynamically sta-
2
ble only above 900°C [6]. This seems to be due to the
high excess surface energy of x-ray amorphous Al O .
2
3
2
3
sized at 400°C: appropriate amounts of aluminum
oxide and lithium carbonate were either mixed and then
thoroughly ground in acetone or ground with a small tion rates in mixtures of lithium carbonate and x-ray
amount of distilled water and then air-dried for 3 days. amorphous Al O during firing at 600°C for 15 min.
The XRD patterns in Fig. 2 illustrate different reac-
2
3
(
a)
(a)
(b)
(c)
Li CO
2
3
Li CO
2
3
Li CO
2
3
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
(b)
Li CO
2
3
Li CO
2
3
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
(
c)
Li CO
2
3
γ-Al O
γ-LiAlO2
2
3
γ-LiAlO2
γ-Al O
2
3
2
0
25
30
35
40
45
50
θ, deg
20
25
30
35
40
45
50
2θ, deg
2
Fig. 2. XRD patterns from 1 : 1 reaction mixtures of Li CO
Fig. 3. XRD patterns from 1 : 1 reaction mixtures of Li CO
2 3
2
3
and Al O after firing at 600°C for 15 min; mixtures pre-
and Al O after firing at 600°C for 180 min; (a–c) same as
2
3
2
3
pared using samples (a) 2, 5, (b) 1, 3, and (c) 4.
in Fig. 2.
INORGANIC MATERIALS Vol. 39 No. 3 2003

INTERACTION OF X-RAY AMORPHOUS ALUMINUM OXIDE WITH LITHIUM CARBONATE
283
(a)
(b)
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
(c)
(d)
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
γ-LiAlO2
2
0
25
30
35
40
45
50
θ, deg
20
25
30
35
40
45
50
2θ, deg
2
Fig. 4. XRD patterns from 1 : 1 reaction mixtures of Li CO and Al O after firing at 600°C for 180 min; mixtures prepared using
2
3
2 3
samples (a, c) 2 and (b, d) 3 by grinding with (a, b) acetone and (c, d) water.
The reaction between Li CO and samples 2 (ther- high-temperature annealing of aluminum oxide sam-
2
3
mal decomposition of aluminum oxalate) and 5 ples (table): γ-Al O in sample 4 exhibits the highest
2 3
(
decomposition of sol–gel-prepared aluminum hydrox- thermal stability, which seems to be raised further by
ide) is illustrated in Fig. 2a. All of the diffraction peaks the incorporation of lithium ions in the course of solid-
present are from Li CO , except for the weak reflection state reaction.
2
3
with d = 2.68 Å, which points to the beginning of
It is of interest to follow the reaction between Li CO
2
3
γ-LiAlO formation.
2
and Al O as the firing time increases to 3 h (Fig. 3).
2
3
The extremely low reactivity of Li CO with sam-
The reaction of Li CO with samples 2 and 5
2 3
2
3
ples 2 and 5 correlates with SEM data (Fig. 1), which (Fig. 3a) remains slow: only weak reflections (d = 3.96,
demonstrate that these samples have a far denser micro- 3.16, and 2.68 Å) from γ-LiAlO appear.
2
structure compared to samples 1, 3, and 4. Thus, the
very slow reaction rate in the mixtures in question can
be explained by the small contact (reaction) area.
Phase composition of Al O samples annealed at 900–
2 3
050°C
1
In contrast, samples 1, 3, and 4 offer a large reaction
area because of the large specific surface of the powder.
Nevertheless, the corresponding mixtures also differ in
reaction rate.
Phase composition
50°C
XRD D, A
80 α/γ = 0.48 α-Al O
Sample
no.
9
9
00°C
1000°C
1050°C
Samples 1 (decomposition of aluminum nitrate) and
3
(decomposition of aluminum hydroxide prepared via
1
2
3
4
5
XAP* γ-Al O
2
3
3
3
3
3
2
3
a nitrate route) rapidly react with lithium carbonate to
XAP γ-Al O
115 α/γ = 0.12 α/γ = 1.04
130 α/γ = 0.09 α/γ = 0.17
form γ-LiAlO (Fig. 2b), whereas the reaction between
2
2
sample 4 (decomposition of aluminum hydroxide pre-
XAP γ-Al O
2
pared from AlCl ) and lithium carbonate yields γ-Al O
3
2
3
XAP γ-Al O
140 γ-Al O
α/γ = 0.12
95 α/γ = 0.67 α-Al O
2
2
3
(
Fig. 2c), which seems to be stabilized by lithium ions
residing in tetrahedral sites.
XAP γ-Al O
2
2
3
Note: The preparation procedures of samples 1–5 are described in
text.
The formation of γ-Al O upon firing this mixture at
2
3
6
00°C for 15 min correlates well with the results of the
* XAP = x-ray amorphous phase.
INORGANIC MATERIALS Vol. 39 No. 3 2003

2
84
SINITSKII et al.
instance of more homogeneous starting mixtures, the
effect of the chemical history of aluminum oxide on its
reactivity with lithium carbonate will be weaker.
(a)
Li CO
2
3
This assumption is strongly supported by the results
obtained for the mixtures of lithium carbonate and alu-
minum oxide prepared by grinding with water and then
reacted at 600°C for 3 h (Fig. 4). The XRD patterns dis-
played in Fig. 4 (comparison of sample 2, prepared by
decomposing aluminum oxalate, and sample 3, pre-
pared by decomposing aluminum hydroxide obtained
via a nitrate route) indicate that, for the mixtures
ground with water (Figs. 4c, 4d), the differences in the
solid-state reactivity of lithium carbonate with alumi-
num oxide are much smaller compared to those ground
in acetone (Figs. 4a, 4b).
γ-LiAlO2
γ-LiAlO2
(b)
Li CO
2
3
γ-LiAlO2
Figure 5 illustrates the reaction between Li CO and
γ-LiAlO2
2
3
Al O at 700°C over a period of 1 h.
2
3
Whereas Li CO is almost nonreactive with sam-
2
3
ples 2 and 5 at 600°C (Figs. 2a, 3a), the rate of
γ-LiAlO formation at 700°C is rather high (Fig. 5a).
2
The reaction of Li CO with samples 1 and 3 proceeds
2
3
(c)
in almost the same way as at 600°C (Fig. 5b). Finally,
in the case of sample 4, γ-LiAlO begins to transform
2
into α-LiAlO , as evidenced by the splitting of the dif-
fraction peaks with d = 3.98, 3.15, and 2.72 Å into two
components (Fig. 5c).
2
γ-LiAlO2
γ-LiAlO2
γ-Al O
2
3
Thus, our results demonstrate that the chemical his-
tory of x-ray amorphous aluminum oxide has a signifi-
cant effect on its solid-state reactivity with Li CO .
2
3
2
0
25
30
35
40
45
50
θ, deg
ACKNOWLEDGMENTS
2
We are grateful to A.V. Knot’ko for carrying out the
electron-microscopic studies.
This work was supported by the Leading Scientific
Schools Program, grant no. 00-15-97435.
Fig. 5. XRD patterns from 1 : 1 reaction mixtures of Li CO
2
3
and Al O after firing at 700°C for 60 min; (a–c) same as in
2
3
Fig. 2.
In the case of samples 1 and 3, the intensity of the
reflections from γ-LiAlO2 remains unchanged
Figs. 2b, 3b), indicating that increasing the firing time
REFERENCES
(
1
2
. Tret’yakov, Yu.D., Tverdofaznye reaktsii (Solid-State
Reactions), Moscow: Khimiya, 1978.
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1991, vol. 36, no. 2, pp. 5–9.
does not change the extent of reaction. This finding sug-
gests that, during the first 15 min of firing, the reaction
of Li CO with samples 1 and 3 takes place on the sur-
2
3
face of the reactants and that the diffusional flux at
6
00°C is insufficient for volume reaction.
3
. Schmalzried, H., Chemical Kinetics of Solids, Wein-
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An important point is that, even though diffusion is
impeded at 600°C, phase transitions proceed rather rap-
4. Osipov, K.A., Amorfnye i ul’tradispersnye kristalli-
cheskie materialy (Amorphous and Ultrafine Crystalline
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vol. 36, no. 2, pp. 3–4.
idly. In the case of sample 4, the γ-Al O formed in the
2
3
first 15 min of firing rapidly converts into γ-LiAlO in
2
5
the course of subsequent firing for 3 h, as evidenced by
the small number and low intensity of reflections from
γ-Al O (Fig. 3c).
2
3
Thus, the homogeneity of the starting mixture has a
profound effect on the reaction rate and path because,
at 600°C, diffusion is impeded, and a higher homoge-
neity of the reaction system ensures a larger reaction
area. It is, therefore, reasonable to expect that, in the
6
. Toropov, N.A., Barzakovskii, V.P., Lapin, V.V., and Kurt-
seva, N.N., Diagrammy sostoyaniya silikatnykh sistem:
Spravochnik (Phase Diagrams of Silicate Systems: A
Handbook), issue 1: Dvoinye sistemy (Binary Systems),
Moscow: Nauka, 1965.
INORGANIC MATERIALS Vol. 39 No. 3 2003