MODIFYING A QUARTZ CERAMIC AND INCREASING ITS EMISSIVITY
BY USING AN ORGANOSILICON BINDER
E. I. Suzdal’tsev
and E. V. Gorelova
Translated from Novye Ogneupory, No. 2, pp. 130 – 133, March, 2014.
Original article submitted October 24, 2013.
The article presents research results and describes a new method of obtaining a nonporous quartz ceramic with
higher emissivity. The method entails bulk modification with an organosilicon binder.
Keywords: emissivity, quartz ceramic, bulk modification, organosilicon binder.
Quartz ceramics possess a unique combination of physico-
technical and service properties. Although they satisfy a
wide range of demanding requirements established for mod-
ern materials used in high-speed aircraft, quartz ceramics
also have a low emissivity. Their emissivity needs to be in-
creased to increase their resistance to the effect of hot gas
flows. It is known that the properties of the ceramics can be
altered significantly by modifying the raw materials with dif-
ferent types of dopants. This approach is also not exclusive
to quartz ceramics.
The best doping material to use to improve the ablation
resistance of ceramics is chromium oxide. The addition of
to a quartz ceramic increases heat loss due to an in
crease in the emissivity of the material at temperatures above
1300°C and the absorption of roughly 2000 kcal of heat per
kilogram, this heat being consumed in the formation of for
mation of Cr
O and CrO .
The system SiO
was studied in fairly extensive
detail by Banting and Kite. Their findings indicated that at
high temperatures the system does not include any binary
compounds and two immiscible liquids are formed (Fig. 1)
. These circumstances, together with the “darkening” of
the ceramic (the increase its emissivity) that takes place due
to the “suspension effect,” increase the viscosity of the melt
and thus lower the rate of ablation of the material in an in
coming heat flow.
Additions of Cr
in amounts no greater than 5 wt.% do
not have a significant effect on the sintering of quartz ceram
ics (Fig. 2). An increase in the size of the addition leads to
abrupt activation of the crystallization process. After a ce
ramic with additions of Cr
is fired in the range
1100 – 1300°C, the main phases in it are SiO
cristobalite. The limiting temperature for sintering a quartz
Refractories and Industrial Ceramics Vol. 55, No. 2, July, 2014
1083-4877/14/05502-0117 © 2014 Springer Science+Business Media New York
OAO ONPP “Tekhnologiya,” Obninsk, Kaluga Oblast, Russia.
Fig. 1. Phase diagram of the system Cr
plotted by Kite).