The characterisation of SiC_f/SiC composites made by conventional and particle enhanced polymer infiltration pyrolysis

The inclusion of silicon carbide particles (SiC_P) into the precursor during polymer infiltration pyrolysis (PIP) has been shown to enhance the density and crystallinity of (SiC_f/SiC) composites in an approach termed particle enhanced polymer infiltration pyrolysis (PEPIP). In this work, the microstructure and properties of composites fabricated via PEPIP and conventional PIP were compared. In both cases, the matrix contained two distinct microstructural regions: Type-A is an interconnected, stiff matrix phase comprising sub-micron grain 3C-SiC and is predominant in the PEPIP samples (88 vol%); while Type-B predominates in PIP samples (76 vol%) and is a compliant phase forming nanocrystalline 3C-SiC mixed with amorphous SiC_xO_y. The SiC_P appear to break up the precursor aggregates during pyrolysis, creating finer pore channels between the fibres. This refines the microstructure, accelerating the decomposition of SiC_xO_y phase and thereby increasing the amount of Type-A phase, which increases the crystallinity and density of the SiC matrix.