Chemical Vapor Deposition and Characterization of Thick Silicon Carbide Tubes for Nuclear Applications

SiC/SiC composites have an outstanding mechanical behavior under irradiation, but their high porosity excludes their use as nuclear fuel claddings in the future nuclear power plants. A complementary thick and tight SiC sheath could be a solution to ensure the first barrier towards fissile materials. The aim of this work is to make long, free standing and high strength SiC tubes. A few hundred micrometers thick tubular coatings were produced by chemical vapor deposition at atmospheric pressure, from CH3SiHCl2/Ar/H2 mixtures. Their chemical compositions and microstructures were studied by electron probe microanalysis, Raman spectroscopy and scanning electron microscopy. The deposition rate, composition and microstructure were investigated as a function of the substrate temperature and the gas flow rates. A Fourier transformed infrared spectroscopy analysis of the gas phase was carried out at the reactor outlet. The Si/C ratio, the SiC degree of crystallization and the surface morphology are strongly related to the maturation of the gas phase and the deposition regime.