Masahisa Sobue

Reaction Sintering Mechanism of Submicrometer Silicon Powder in Nitrogen

Knowing the nitridation mechanism of Si is important to obtain near-net-shape high strength reaction bonded ceramics. In this report, comparison of nitridation mechanism of small spherical Si powder produced by plasma arc method and large faceted Si powder, is discussed on the basis of microstructural analyses by SEM and TEM. From the analyses, nitrogen diffuses through the oxide film of Si powder and forms Si 3 N 4 under the oxide films during the initial stage of sintering. At higher temperature, the oxide film transform into fine Si 3 N 4 grains when heated to the 1350°C. The Si 3 N 4 has morphology of hollow shell and a size, which corresponds to that of the original Si particles.