Synthesis and Ceramization of Polymethylsilane Precursors Modified with Metal Chlorides

Abstract

Polymethylsilane (PMS) modified with titanium chloride (TiCl₄) or molybdenum chloride (MoCl₅) was pyrolyzed at various temperatures to enable a detailed investigation of stable phases formed during pyrolysis. The existence of TiSi₂ in PMS-TiCl₄ precursor and β-MoSi₂ in the PMS-MoCl₅ precursor below 1273 K suggested a strong interaction between Si-H and the metal chlorides during mixing. During pyrolysis of the PMS-10 mass% TiCl₄ precursor, a silicon rich Si-Ti-C state was obtained below 973 K, which simultaneously formed crystalline Si, TiSi₂, and SiC phases at relatively low temperatures below 1273 K. During pyrolysis of the PMS-MoCl₅ precursors, however, formation of crystalline Si and SiC phases were not accelerated, while the crystalline β-MoSi₂ or α-MoSi₂ phase was formed rapidly.