LOW-DENSITY SILICON-NITRIDE BEADS AS HIGH-TEMPERATURE MICROWAVE FURNACE INSULATION

Low-density Si3N4 spheroidal beads 3-4 mm in diameter have been made b y an alginate route starting from Si3N4 powder. The beads have been ch aracterized by chemical, X-ray diffraction and compression test techni ques. The ability of the beads to couple with microwave power has been investigated in nitrogen atmosphere at fixed frequency of 2.45 GHz at power levels to 5 kW, and at variable frequency from 4-6.5 GHz at pow er levels to 1.4 kW. The beads showed no signs of deterioration in nit rogen at temperatures up to 1800 degrees C, and seem promising as high -temperature microwave furnace insulation. (C) 1997 Elsevier Science L td.