SCIENTIFIC RESEARCH AND DEVELOPMENT
RESEARCH IN THE AREA OF PREPARING MATERIALS
BASED ON FUZED QUARTZ HCBS. PART 6. EFFECT OF FIRING
TEMPERATURE ON MATERIAL SINTERING AND CRISTOBALITIZATION
Yu. E. Pivinskii
and P. V. Dyakin
Translated from Novye Ogneupory, No. 7, pp. 22 – 31, July 2015.
Original article submitted January 30, 2015.
The effect of firing temperature in the range 1000 – 1350°C on indices for shrinkage, porosity, density, and
strength of specimens based both fuzed quartz HCBS with different fineness, and cast system with a granular
filler based upon them, is studied. Maximum indices for ultimate strength in bending are achieved after firing
in the range 1200 – 1250°C. Strength values for different materials are within the limits of 6 – 9%. With a fur-
ther increase in firing temperature in spite of an increase in density material strength is reduced as a result of
cristobalite formation. It is shown that a fundamental factor governing sintering kinetics is starting fuzed
quartz viscosity in the corresponding temperature range.
Keywords: HCBS, fuzed quartz, cristobalite, shrinkage during firing, ultimate strength in bending and com-
pression, LTEC, ductile flow, sintering theory, Pivinskii equation.
The two preceding articles of the current series [1, 2]
have been devoted to studying kinetics of isothermal and
nonisothermal sintering of materials based on fuzed quartz
and a study of the effect of this process on specimens proper
ties. The basis adopted was a firing temperature of 1250°C
with a different isothermal soaking duration. In the present
work a task was set of studying sintering over quite a wide
temperature range, i.e., from 1000 to 1350°C. The isothermal
soaking duration was predominantly 1 h, but in a number of
cases 30 min. Taking account of firing regimes, including in
creased temperatures (1250°C), the associated process of
material cristobalitization was also studied [3 – 5]. As in the
preceding work, the objects studied were cast specimens
both based on the original fuzed quartz suspension with dif
ferent starting properties (Table 1), and also with a granular
filler (Table 2). Specimens were fired in an electric furnace
with a heating rate of 300°C/sec to a prescribed temperature
followed by soaking (60 or 30 min) and arbitrary cooling.
EFFECT OF FIRING TEMPERATURE
ON MATERIAL PROPERTIES
By analogy with the preceding work [1, 2] in this study,
depending on isothermal sintering temperature with soaking
for 1 h, the main properties were compared for a different
pair of materials prepared both from the original suspension
(in all subsequent diagrams curves 1 ), and also based on the
same suspension with granular filler (curves 2 ). The effect of
firing temperature on linear shrinkage YL indices is shown in
Fig. 1, apparent density r
and open porosity P
specimens based on the basic fuzed quartz HCBS (curves 1 )
and with granular filler (see Tables 1 and 2, composition 1).
It has been established that after firing at 1000°C specimen
shrinkage is almost absent and only becomes marked with an
increase in temperature to 1100°C.
It follows from Fig. 1a that even at 1100°C for speci
mens of the two types there is insignificant YL (up to
0.05%). A significant increase is noted for firing tempera
tures exceeding 1200°C. YL for specimens based on HCBS
Refractories and Industrial Ceramics Vol. 56, No. 4, November, 2015
1083-4877/15/05604-0366 © 2015 Springer Science+Business Media New York
Part 1 of the article was published in Novye Ogneupory No. 7
(2014), and parts2–5inNos. 1, 3, 4, and 6 (2015).
OOO NVF Kerambet-Ogneupor, St. Petersburg, Russia.
FGBOU VPO St. Petersburg State Technological University
(Technical University), St. Petersburg, Russia.