Effect of polycarbosilane addition to a mixture of rice husk and coconut shell on SiC whisker growth

In this paper, we report the synthesis of SiC whiskers by the carbothermal reduction of a mixture of rice husk (RH) and coconut shell (CS). Addition of polycarbosilane (PCS) to the mixture of RH and CS led to extensive growth of the whiskers. The phase and microstructural analysis of the synthesized whiskers were carried out by X-ray diffraction and electron microscopic techniques, respectively. The synthesized whiskers were single crystals of β-SiC, grown on a (111) plane along the 〈111〉 direction. The vapor–solid and vapor phase mechanisms played a more dominant role in massive whisker growth than the vapor–liquid–solid mechanism. The increased SiO gas concentration, due to the evolved SiO and CO gases from the highly reactive SiOC ceramics formed from the PCS, facilitated the extensive growth of SiC whiskers. The whisker growth was more on the CS surface than on the RH surface, and attributed to the higher surface area and the carbon reactivity of the CS. The Raman spectroscopy showed the presence of 4H-SiC, 6H-SiC and 15R-SiC type stacking faults in 3C β-SiC.