STUDY OF THE SINTERING MECHANISM OF A MATERIAL
OBTAINED FROM CRYSTALLIZED CASTINGS PREPARED FROM
DISCHARGES OF LITHIUM-ALUMINOSILICATE GLASS AFTER CASTING
E. I. Suzdal’tsev
and A. S. Ermolaev
Translated from Novye Ogneupory, No. 12, pp. 48 – 50, December, 2015.
Original article submitted July 15, 2015.
Studies are made of the sintering mechanism of a material produced from castings crystallized at 850°C for
2 h. The cast products are obtained from discharges of lithium-aluminosilicate glass after its casting. The ap
parent activation energies for sintering materials OTM-357, 357-C, and OTM-357-O were calculated and
were determined to be 65 ± 15, 155 ± 15, and 245 ± 15 kcal/mole, respectively.
Keywords: glass-ceramic, lithium-aluminosilicate glass, linear shrinkage, activation energy, density, poros
ity, water absorption.
The “Tekhnologiya” Scientific-Industrial Association is
currently using ceramics technologies to obtain products
made of glass-ceramics OTM-357 and OTM-357-O (the
main phase is b-spodumene) [1 – 4]. In accordance with
these technologies, the products are obtained by slip casting
in gypsum molds. The slips are prepared from grains of
amorphous lithium-aluminosilicate (LAS) glass (material
OTM-357) and from pre-crystallized grains or cullet from
products that were rejected after firing (material OTM-
357-O). The preliminary crystallization of grains of LAS
glass is carried out at1170 – 1250°C for4–8h.
It was shown in [5, 6] that a material can be obtained
from castings which are made from discharges of LAS glass
after its casting and are crystallized at 850°C for 2 h. The
material obtained in this manner is used to make semifin
ished products that are subsequently sintered at 1250°C with
a hold from 2 to 5 h long (the name of this material is
357-C). Material 357-C has a stable phase composition in the
form of a solid solution of b-spodumene and rutile, and both
its porosity and its water absorption are close to zero.
Materials OTM-357, OTM-357-O, and 357-C have simi
lar properties despite the fact that they are obtained from dif
ferent raw materials: amorphous LAS glass, crystallized
product rejects (1250°C over 4 – 6 h), and castings that are
obtained from discharges of LAS glass after casting and are
crystallized at 850°C for 2 h. The similarity of these materi-
als’ properties may be related to certain aspects of the mecha-
nisms by which they undergo sintering and to the fact that the
final maximum temperature in the heat treatment is the same:
1250°C. Thus, it is important to study the sintering mecha
nisms of the given materials.
The sintering mechanism of material OTM-357-O was
studied in detail in  and the apparent activation energy for
sintering was calculated from the formula
t = Kexp(E/RT )
where t is the time needed to achieve a certain degree of con
solidation; K is a constant that depends on the properties of
the material being sintered and the value chosen for porosity;
E is the apparent activation energy of the sintering process; R
is the universal gas constant; T is temperature. The apparent
activation energy for the sintering of material OTM-357-O
was determined to be 128 kcal/mole.
In accordance with ,
we made the following conclusion: the similar values of ap
parent activation energy for the sintering of material
OTM-357-O (128 kcal/mole) and amorphous quartz powder
Refractories and Industrial Ceramics Vol. 56, No. 6, March, 2016
1083-4877/16/05606-0670 © 2016 Springer Science+Business Media New York
Obninsk Scientific-Industrial Association “Tekhnologiya”, Ob
ninsk, Kaluga Oblast, Russia.
1 kcal = 4.2 kJ.