Growth of SiC whiskers in the system SiO2-C-H2nucleated by iron

摘要: Abstract A study has been made of the nucleation, growth and morphology α- β-SiC whiskers obtained from silica carbon in hydrogen between 1200 1300°C by a VLS process with iron as agent. On polycrystalline substrates - solid starting materials or an inert third material β-whiskers are mainly grown [111] direction; on basal {0001} prismatic {10 1 0} faces α-SiC single crystals addition α-[0001] α-[1 0] respectively grow epitaxially. The rate is order mm/hr, irrespective polytype direction. depends relative position C, SiO2 substrate; given arrangement increases increasing temperature activation energy about 85 kcal/mole. As to be expected for which supply vapour rate-limiting, higher relatively larger droplets. β-[111] often show fluctuation diameter, whereas α-whiskers always smooth. For smooth ratio diameter Fe-Si-C alloy droplet at tip 2, knotted generally larger. These ratios associated minima Gibbs free surface vapour-liquid-solid interface. It discussed how instabilities liquid can give rise knottiness system where SiC grows gas phase Si/C ⪡ via ⪢ 1.