PROCESSING OF A SILICON-CARBIDE-WHISKER-REINFORCED GLASS-CERAMIC COMPOSITE BY MICROWAVE-HEATING

A calcium magnesium aluminosilicate-based glass that contained 10 wt% of silicon carbide whiskers (SiCw) as reinforcement was prepared by ta pe casting, followed by sintering either in a conventional furnace or in a microwave oven. The results were consistent with retardation of g lass sintering through whisker bridging. The glass, by itself, was sin tered to almost-full density at 750 degrees C for 4 h by conventional furnace sintering; the best sintered composite, with an estimated dens ity of similar to 90%, was obtained at 800 degrees C with a dwell time of 4 h. Sintering at a temperature of >800 degrees C did not improve the densification but rather resulted in severe whisker oxidation. A r educed densification rate was observed for the samples that were sinte red in nitrogen. By contrast, in the microwave oven, almost-full densi ty for the glass and similar to 95% of the theoretical density for the composite were obtainable at 850 degrees C for 15 min, which represen ted a reduction of similar to 10 h of the total processing time and a reduced SiCw oxidation.