STABILITY OF SIC SIC COMPOSITES IN ENVIRONMENTS CONTAINING O-2 AND H-2/

Silicon carbide composites with carbon interfaces have been analyzed b y thermal gravimetric analysis (TGA) in O-2 and H-2 environments to pr edict their performance as structural materials in fusion applications . Conditions for testing included temperatures between 800 and 1200 de grees C, O-2 concentrations ranging from 100 to 1500 ppm, and H-2 conc entrations of 0.1 and 1%. Weight losses observed by TGA were determine d to be primarily due to the oxidation of the carbon interface. Linear -parabolic kinetics governed the interfacial oxidation for all of the conditions in O-2. By focusing on the linear region, a simple model es timated the linear rate dependency on O-2 partial pressure to be on th e order of 0.911. Weight loss data in H-2 environments yielded activat ion energies of 18 and 34 kcal/mol for 0.1 and 1%, respectively. The w eight loss rates in H-2 were 6 to 26 times slower than rates in O-2, w hen approximations were made assuming linear kinetics.