The effects of transition metals on carbothermal reduction synthesis ofβ-SiC

• Main Authors: Chih-Ming Chuang, 莊誌銘
• Other Authors: Yung-Jen Llin
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/59958600947990128356

碩士 === 大同大學 === 材料工程學系(所) === 92 === This research is divided into two parts. In the first part, I will use phenolic-resin and Ludox were as the starting materials and add transition metals and use carbothermal reduction to synthsize β-SiC powder. I will discuss the effect of the kinds and the amount of additive on reaction temperature of β-SiC and powder properties. The other part of this research is that I will use activated carbon fabric and TEOS to prepare SiC fabric by shape memory synthesis. I hope that the morphology of SiC preserved the morphology of carbon. Adding Fe, Co, Ni, Cu enhance β-SiC formation at lower temperature. Adding Fe and Cu caused product to sinter. The product remained as powder when reactants contained Co and Ni. Although reactant with Cu can form β-SiC at 1300℃, the melting point of Cu is lower than reaction temperature, which leads reactants stick together as a cake the reaction surface decreases. Consequently, the reactant can not effectively convert into β-SiC. Adding Mn into reactants can not produce β-SiC at lower temperature. The reason is similar to that of adding Cu. The existence of Mn promoted SiO(g) formation but can not enhance reactants to convert to β-SiC. The yields of adding 1wt% Fe, Co, Ni after reaction at 1400℃ are higher than that of reactants without additives after reaction at 1400℃. The yields of adding 1wt% Fe, Co are even higher than reactants without additives after reaction at 1500℃. It can be seen that adding 1wt% Fe, Co, Ni can promote β-SiC formation at low temperature. The highest yield is by adding 1wt% Fe which is 76.87%. Adding Co has the second highest yield (73.14%) and adding Ni has 30.40% of yield, but it near to reactants without additives after reaction at 1500℃ (32.07%). The product of adding 1wt% Fe was sintered so that it needed to crush and mill. The yield of samples adding 1wt% Co was near to that of sample adding 1wt% Fe. The powder contained few whisker. Its particle size is about 100~200nm. The product of samples adding 1wt% Ni contains a lot of whisker. After reaction at 1500℃ for 8hr, activated carbon fabric can convert to β-SiC fabric. The product remains the shape of carbon and is flexible. Activated carbon fabric has many micro-pore on surface after activated process. The micro-pore provides many reaction area and promote reaction.