Studies on formation and siliconization of carbon template of coir fibreboard precursor to SiC ceramics

Formation reaction of carbon template of coir fibreboard samples via pyrolytic decomposition was studied by methods of thermogravimetric, derivative thermogravimetric and differential thermal analysis using different heating rates (5-20 K min(-1)). The major decomposition reaction at 250-500 degrees C had activation energy and frequency parameter of 121.84 +/- 8.78 kJ mol(-1) and 3.2 x 10(9)-2.1 x 10(11) min(-1), respectively, supporting a free radical mechanism. Siliconization reaction of the carbon template was also studied by non-isothermal DTA technique using varying heating rates (5-20 K min(-1)); exothermic C-Si reaction was preceded by endothermic melting of Si and it had activation energy of 2793.09 +/- 187.65 kJ mol(-1); diffusion through solid reaction product was found to control the heterogeneous chemical reaction process. On the basis of these experimental results separate experiments were conducted for preparation of carbon templates and their subsequent siliconization. The correlations between the properties of the coir fibreboard precursor, the carbon template and the siliconized product (SiC) were explained. (C) 2014 Elsevier Ltd. All rights reserved