Microstructure and deposition mechanism of C/SiCN composites prepared by rapid electro-thermal pyrolysis CVD

Abstract

Carbon fiber-reinforced silicon carbonitride ceramic matrix composites (C/SiCN) were prepared by rapid electro-thermal pyrolysis CVD using liquid polymer hexamethyldisilazane (HMDS, (CH₃)₃SiNHSi(CH₃)₃) as precursor. Microstructure morphology and production technique of C/SiCN composites were investigated. Scanning electron microscopy and transmission electron microscopy were respectively employed to characterize microstructures of the as-received C/SiCN composites samples. The high temperature pyrolysis of HMDS results in destruction of molecular chain, fracture of bonds, as well as liquid-gas-solid conversion from polymer to ceramic. Microstructures observation indicates that there is a high degree of coalescence between SiCN matrix and C fiber. The deposition model of liquid precursor electro-thermal pyrolysis CVD is different from that of gas precursor isothermal chemical vapor infiltration. Rapid liquid flow and slow gas diffusion are key factors for the difference of two methods. Preparation of rapid electro-thermal pyrolysis CVD consists of four steps including liquid polymer infiltration, polymer pyrolysis, rapid deposition of pyrolyzed substances and rapid densification, respectively.

Keywords

C/SiCN composite / electro-thermal CVD / microstructure / deposition model

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