Influence of Gas Content in Quartz and Corundum Raw Materials Upon the Quality of Silica Glass and Alumina Ceramics

Proc. Int. Conf. on Fundamentals of Glass Science and Technology (Vaxjo, Sweden, June 9-12, 1997), (in press)

ABSTRACT. Gas release of different forms of gas-liquid impurities and diffusion processes in quartz and corundum used as raw materials for producing silica and alumina glasses and ceramics have been studied by the method of kinetic thermodesorption mass spectrometry. Quality of glass products produced from different raw materials under identical conditions depends on the gas (especially water) content in the raw materials. In this respect the greatest attention should be focused on "high-temperature" form of gas-liquid impurities, i.e. those ones released at temperature higher than 600 C due to diffusion out of solid. Incorporation of carbon-containing impurities into quartz results in appearance of dark dots and regions in glass through the reaction of these substances with silica. The effect of water and gases in corundum raw materials on technological parameters is more complicated. On the one hand the increase of water and some other volatile impurities content in corundum makes for good corundum sintering and allows decreasing the sintering temperature. On the other hand this increase reduces ceramics transparency. Diffusion coefficients and activation energies of water diffusion in crystalline corundum and quartz have been determined for the first time.

Laboratory of Catalysis and Gas Electrochemistry