Protective coatings and characterization of coal tar pitch matrix based carbon carbon composites

Carbon carbon composites have been known widely for their superior ceramic-like performance, and for that reason, they are also considered as ceramic matrix composites. Even though this class of material is robust like engineering ceramics in a harsh working environment, it holds a significant drawback of oxidation. Since carbon materials are prone to oxidation, they need to be protected externally via coatings of thermally stable materials. The paper focuses on coatings and comparison of c/c composites by SiO2 and Al2O3 via the sol-gel process with coatings carried out by dipping method by using TEOS and Al(NO3)3.9H2O. PVA as a binding agent, has been used to avoid cracks upon sintering of coatings. Coated specimens were subjected to flame ablation test and prime characterizations such as SEM, Optical microscopy, weight loss under flame test, and Raman spectroscopy have been carried out. C/C composites were treated with silane before coatings in order to attain the highest compatibility among the substrate and coatings. Results suggest the high performance of the c/c composites coated with Al2O3 while samples coated with SiO2 offered modest performance and poor compatibility.