Whiskerisation of polycrystalline SiC fibres during synthesis

Whiskers of β-SiC have been produced on the surfaces of polycrystalline SiC fibres by carbothermal synthesis. The growth of whiskers occurred simultaneously with siliconisation of the carbon fibres. The chemical composition, structure and morphology of the whiskers were studied using X-ray diffraction (XRD), Raman microspectroscopy, electron energy loss spectroscopy (EELS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that the presence of silica on the surface of initially carbonised fibres was essential for whiskerisation. Nucleation and growth of the whiskers followed the vapour–liquid–solid (VLS) mechanism. The diameter of the whiskers produced ranged from 100 to 300 nm and the average aspect ratio was about 300. Owing to the small size of the whiskers, they are expected to provide more efficient reinforcement in composites than conventional whiskers of larger diameter.