The morphology and mechanism of formation of SiC in C/C-SiC composites fabricated by liquid silicon infiltration

Abstract

Carbon fibre reinforced carbon and silicon carbide dual matrix composites (C/C-SiC) are a new type of high performance brake materials. In the present study, C/C-SiC brake composites were fabricated by the combination of chemical vapor infiltration (CVI) with liquid silicon infiltration (LSI). Results show the composite is composed of 55%C, 39% β-SiC, and 6%Si. There exist two different areas of SiC, one zone of coarse micro-β-SiC grains between 5 and 20 μm at the SiC/silicon interface, and this zone usually forms inside the porosity of the carbon fibre reinforced carbon (C/C) preform such as around the fibres and among the C/C bundles. The other zone consists of fine nano-SiC particles with dimensions of 100-800 nm at the pyrocarbon/carbon fibre interface. From these observations, reaction mechanisms governing the siliconization of porous C/C preform are proposed. After an initial reaction of carbon with liquid silicon, an initial continuous SiC layer formed on the silicon/pyrocarbon interface, and the subsequent formation of SiC is controlled by diffusion of carbon atoms and/or silicon atoms through the already formed SiC layer.