Reaction Sintering of Submicrometer Silicon Powder

Submicrometer silicon powder synthesized by thermally induced, vapor-phase reaction in an aerosol reactor was densified by reaction sintering to form Si₃N₄. The densification behavior of these spherical, nonagglomerated particles in the 0.1 to 0.2 μm size range is described. Competition between densification by silicon sintering and reaction product infilling was observed at typical reaction sintering temperatures. In addition, pore growth during the early stages of silicon presintering adversely affected nitrogen permeability and nitriding rates. The factors influencing the nitridation of ultrafine silicon powders are discussed.