Synthesis and Characterization of Ceramic Precursor Aluminum-Containing Polycarbosilane and its Pyrolysis

The aluminum-containing polycarbosilane (Al-PCS) was synthesized by reaction of an aluminum alkoxide with polycarbosilane (PCS). The Al-PCS product was characterized by element analysis, gel permeation chromatography (GPC), as well as Fourier transform (FT-IR) and nuclear magnetic resonance (¹H, ²⁹Si, ¹³C, and ²⁷Al NMR) spectroscopy. The results show that Al-PCS is very similar to PCS in structure. This preceramic precursor is described as a dispersion of Al(AcAc)₃-based particles in the PCS chain matrix. The pyrolysis process of Al-PCS was investigated by thermogravimetry (TG), FT-IR, and X-ray diffraction (XRD). The pyrolysis of Al-PCS includes three sequential stages: First, the condensation and thermal decomposition into the inorganic state; second, the transition toward the third stage involving the thermal decomposition of the side chains into an amorphous state; third, the crystallization of β-SiC.