Polyaluminocarbosilane as precursor for aluminum-containing SiC fiber from oxygen-free sources

Abstract

Aluminum-containing silicon carbide (SiC) fiber, such as Tyranno SA fiber, is the typical 3rd generation SiC fiber. Polyaluminocarbosilane (PACS) is the precursor of Al-containing SiC fiber. PACS was synthesized via elimination of HCl during the reaction between dimethyaluminium chloride ((CH3)2AlCl) and polycarbosilane (PCS) in this work. Composition and structure of the as-synthesized PACS were characterized by elemental analysis, FT IR, GPC, and TG, respectively. The results showed that, the yield of the reaction was 72.5% and the reaction degree of Si–H bonds was 16.5%. The obtained PACS had melting point of about 218.8°C, experimental formula as SiC2.003Al0.023O0.048H3.713, number average molecular weight Mn of 1859, weight average molecular weight Mw of 4895, polydispersity index (Mw/Mn) of 2.632. The molecular structure of PACS was similar to that of PCS. Four stages could be divided during pyrolysis process of PACS according to TG spectrum. The ceramic yield was found to be around 67.3% at 1000°C in N2 atmosphere. The PACS precursor is melt spinnable into flexible and uniform green fibers with the diameter about 12.6μm.