Enhancement of oxidation resistance of CVD SiC coated Cf/C-SiC hybrid composite tubes processed through Si-infiltration

Carbon fiber reinforced SiC based composites show an excellent combination of physical, mechanical and thermal properties. The combination of these properties makes C-f/SiC composites a material of choice for high-temperature load-bearing applications. However, the high-temperature oxidation has been an issue for structural ceramic composites. The combined effect of passive and active oxidation at a different temperature, influencing the overall oxidation behavior of C-f/SiC composites, which is mainly influenced by the partial pressure of oxygen. Although constant research is ongoing to improve the oxidation resistance of C-f/SiC composites, the literature on the in-depth oxidation mechanism of SiC based composites is scant. In the present study, three different types of C-f/C-SiC hybrid composite tubes were fabricated by the liquid silicon infiltration process (LSI) to study the high temperatures oxidation behavior. The dense carbon nanofibers (CNF) containing silicon carbide composite tubes (SiC(CNF)) braided with long carbon fabric (C-f) of different braiding patterns were used as a base matrix material for LSI. Further, a dense and uniform cubic beta-SiC coating was applied on the surface of the above-mentioned hybrid composite tubes by using the chemical vapour deposition (CVD) technique to improve its oxidation resistance property. The oxidation behavior of bare C-f, C-f/C-SiC (LSI) composite and CVD- SiC coated C-f/C-SiC hybrid composite samples were examined separately from room temperature to 1450 degrees C in the air using thermogravimetric analysis (TGA). The exhibited residual mass of LSI composite and SiC coated hybrid composite samples was found to be 24% and 0.7% respectively. It is evident from the TG analysis that SiC coated hybrid composite samples exhibited the highest oxidation resistance amongst all the composites due to the formation of highly dense uniform coating. (C) 2020 Elsevier B.V. All rights reserved.