Highly crystalline SiCf/SiC composites produced by particle enhanced polymer impregnation and pyrolysis (PE-PIP)

Abstract

• SiO 2 layer of SiC particles can be used to reduce the carbon in PIP-SiC matrix. • SiO 2 -C reactions take place during the heat treatment at 1400 °C for 8 h. • Carbon reduction enhances the density and crystallinity of PIP-SiC matrix. • Open porosity arising from carbon loss should be sealed to finalize processing. Silicon carbide fiber (SiC f ) reinforced/silicon carbide (SiC) matrix composites (SiC f /SiC) produced by polymer impregnation and pyrolysis (PIP) typically exhibit low density and crystallinity due to the formation of a SiC x O y amorphous matrix. This compromises the mechanical and thermal properties of the composites. Here, a particle enhanced PIP (PE-PIP) method is proposed whereby fine silicon carbide particles (SiC p ) containing amorphous silica (SiO 2 ) layer are incorporated into the liquid poly (carbosilane) (PCS)-based precursor. The addition of SiC p improved the bulk density and decreased the open porosity of the composites compared to conventional PIP processing. After heat treatment at 1400 °C for 8 h, the true density of the composites was enhanced further with a reduced carbon content via the carbothermal reactions between SiO 2 and the excess carbon present in the PIP matrix. However, the bulk density reduced due to increased open porosity which could be sealed by subsequent processing. This novel processing approach has the potential to deliver high density, high crystallinity SiC f /SiC with low carbon content by PIP at low temperature (1400 °C).

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