Home – Home – Jornals – Geography and natural resources 2016 number 6S

The paper presents the results of a comprehensive study of silica glass produced from quartzite of the Bural-Sardyk deposit on its resistance to crystallization during thermal tests. A method for producing silica glass at a specially modified industrial plants for growing «REDMED10-M» and «REDMED 8» single-crystals is described. Melting of glass samples was performed in a vacuum and vacuum-compression method (with a pressure of up to 6 atm, argon). In order to evaluate the optical quality of the glass obtained from the absorption spectrum of the sample it was checked against the absorption of KI and KU-1 brand of glass. In the course of study, the glass obtained from chemically enriched quartz concentrates subjected to procedure a high-temperature exposure (cristobalite formation) was compared with that produced from quartz and concentrates not subjected to such a procedure. Thus, the objects of studies were glasses obtained from quartz concentrates of the four types: fine quartzite, cristobalite of fine quartzite, «superquartzite» and cristobalite of «superquartzite». A test procedure for resistance to crystallization of various types of silica glass samples is provided. The results of a comprehensive study based on X-ray phase analysis, and electronic and optical microscopy have shown that glass samples obtained from cristobalite grits of «superquartzite» are optically better and more resistant to crystallization than the samples obtained from «superquartzite» grits, fine quartzite and cristobalite of fine quartzite. Phase of cristobalite in glass samples occur at a temperature of 1150 °C in the spectra of X-ray diffraction. It is found that the crystallization of the quartz plates after annealing at 1200 °C during 2 hours is only on the surface.