Silicon carbide coating on UO2 pellet by a combustion reaction

The coating of silicon carbide (SiC) and pyrolytic carbon (PyC) on a UO2 pellet was prepared by using a combustion reaction between carbon and silicon layers. The pyrolytic carbon and silicon were deposited by thermal decomposition of propane at 1250 degrees C in a chemical vapor deposition unit and microwave pulsed electron cyclotron resonance plasma chemical vapor deposition (PECVD) of silane at 500 degrees C was followed by a combustion reaction between the two layers. Microstructural observation of the layer with SEM showed that an inner layer existed following the surface contour of the pellet and an outer layer had a small amount of fine pores inside. Chemical analysis with EDX and AES revealed that the inner and outer layers were pyrolytic carbon and silicon carbide, respectively. From the TEM observation, the silicon carbide formed during the combustion reaction was fine crystalline beta-silicon carbide. Temperature distribution of the specimen during the combustion reaction was estimated by empirical and numerical methods.