Experimental study of the chemical vapor deposition from CH3SiHCl2/H2: Application to the synthesis of monolithic SiC tubes

International audienceThe aim of the present work is to synthesize high strength monolithic SiC tubes to improve the imperviousness of a SiC/SiC composite structure. A few hundred micrometers-thick tubular coatings were produced by chemical vapor deposition (CVD) at atmospheric pressure, from CH 3 SiHCl 2 /Ar/H 2 mixtures. The CVD-SiC tubes were obtained by deposition on the inner walls of a SiO 2-tube substrate, previously coated with a pyrocarbon interfacial layer to promote delamination. A continuous deposition process was developed to allow the realization of relatively long CVD-SiC tubes, by sliding the heating system along the substrate. The chemical composition and the microstructure of the tubes were studied by electron probe microanalysis, Raman spectroscopy and scanning electron microscopy. The deposition rate, composition and microstructure of the CVD-SiC coatings were investigated as a function of the substrate temperature and the gas flow rates. A Fourier transformed infrared (FTIR) spectroscopy analysis was carried out at the reactor outlet to characterize the gas phase reactions. The FTIR analysis of pure species from the Si-C-Cl-H system as well ab initio calculations at the density functional theory (DFT) level allowed the assignment of the main IR features in the experimental spectra and th