Microwave heated reaction-bonded silicon nitride using an inverse temperature gradient

Abstract

The nitridation behavior of Si under a microwave-heating source was studied. Si preforms were produced via an aqueous gel-casting route with 45 vol.% solids loading. Preforms up to 10 mm thick could be produced without cracking. Microwave nitridation of the Si preforms was carried out using a fiberboard insulation box without packing powders in order to cause an inverse temperature gradient. Nitridation began at the unusually low temperature of 950°C. Up to 74% nitridation was achieved by nitriding at 1120°C for 5 hr. Preforms displayed an inverse temperature gradient, with sintering and melting occurring in the center of the preforms.