THERMAL-ANALYSIS OF NEW GLASS-CERAMIC COMPOSITE TAPES AND THEIR COMPONENTS

Glass ceramic tapes prepared from various AlN, glass and organic binders were studied by simultaneous TG-DTA. Thermooxidative decomposition of polymeric binder, dehydration, oxidation of residual carbon, glass crystallization and oxidation of AIN were detected and evaluated. Results are compared with those obtained with the pure components AlN and glass. The rate of oxidation of various AlN charges at >800 degrees C in an air flow depends on their specific surface and eventual special (antihydrolytic) coating. In the ceramic composite the oxidation of AlN is much slower than in free AlN powder because of the embedding in the glass matrix. The glass exhibits crystallization to cordierite, the crystallization rate and final crystallinity depending on the P2O5 and B2O3 contents and the particle size of the glass. In the composite the crystallization of the glass component is accelerated and proceeds to a higher degree owing to the smaller particle size and to interactions between glass and filler. Grinding of the ceramic raw mix results in additional adsorption of moisture.