Synthesis and Pyrolysis Behaviors of Polysilazanes for Spray Pyrolysis

Abstract

Polysilazanes, high potential precursors for Si₃N₄ materials, were synthesized from trichlorosilane and methyldichlorosilane. The molecular weight of these polysilazanes increased as the mixing ratio of trichlorosilane to methyldichlorosilane increased. Their pyrolysis behavior were studied by TG, DTGA (Differential Thermal Gas Analysis) and Mass spectrometer. The major chemical species of gas evolved from samples in He atmosphere was ammonia at 350°C, and methane at 570°C. Moreover, on heating the samples in N₂, the DTGA curve showed that the reaction occurred from 400° to 950°C, and especially two DTGA peaks appeared at 570° and 750°C. When these polysilazanes were heated at 1300°C in N₂, α-Si₃N₄ formed, but a mixture of α-Si₃N₄ and β-SiC was obtained by heating them at 1400°C in Ar.