Whiskerisation of polycrystalline SiC fibres during synthesis

Abstract

Whiskers of b-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.BCT/0445

Porous Si/SiC Composite Based on Nonwoven Cellulosic Fabrics: Synthesis and Characterization

“…The formation of SiC whiskers during the synthesis of biomorphic SiC ceramics from mineralized cellulosic preforms was reported by many authors 10,26 . In the present study, impurities from the cellulosic fabrics acted as whisker nucleation sites; at the same time silicon deposited on the carbon surface promotes the growth of SiC whiskers 27 …”

Formation of Porous SiC Ceramics by Pyrolysis of Wood Impregnated with Silica

“…Impurities from wood or sodium silicate might have acted as nucleation sites. Silica deposited on the carbon surface is known to promote the growth of SiC whiskers 21 …”

Effect of defects on graphitization of SiC

“…Vyshnyakova, Institute for Problems of Materials Science, National Academy of Sciences, Ukraine. 16 Raman spectroscopy and x-ray diffraction (XRD) studies of whiskers showed that the whiskers had beta-SiC structure. Sintered SiC disks were obtained from Saint-Gobain (Northborough, MA).…”