Synthesis and characterization of monolithic CVD-SiC tubes

Abstract

International audience† The authors dedicate this article to the memory of our colleague P. Weisbecker who has recently passed away Abstract : The high open porosity of SiC/SiC composites is problematic for uses in advanced thermal or confinement systems. A strong and gas-tight SiC sheath would helpfully complete the composite structure. The aim of this work was to prepare and characterize long, free standing and high strength SiC tubes prepared through a rapid near net shape manufacturing process. The tubes were produced by continuous chemical vapor deposition (CVD) at atmospheric pressure using CH 3 SiHCl 2 /C 3 H 6 /H 2 mixtures. The composition, morphology and microstructure of the CVD-SiC tubes were analyzed in details. The Si/C ratio and crystalline state through wall thickness are related to the progress of gas phase reactions during continuous deposition. The silicon excess in the CVD-SiC coating can be reduced by preheating gases and adding C 3 H 6. C-ring specimens cut from the obtained tubes were submitted to compressive tests at room and high temperature to assess the failure properties and thermomechanical behavior

Fabrication of an ultra‐thick‐oriented 3C‐SiC coating on the inner surface of a graphite tube by high‐frequency induction‐heated halide chemical vapor deposition

“…Figure shows the temperature distribution and thickness distribution of the coating along the tube axis. At a position approximately 230‐240 mm along the graphite tube, the coating obtained a maximum thickness of approximately 615 μm, which was three times higher than in previous reports . There was a significant shift between the highest temperature domain and the thickest area of the coating.…”

“…CVD SiC tubes have been the subject of considerable research. SiC tubes several hundreds of microns thick and several tenths of centimeters long were obtained via high‐frequency induction‐heated atmospheric pressure chemical vapor deposition (APCVD) . Dichloromethylsilane (DCMS, CH 3 SiHCl 2 ), which has a fixed molar ratio of silicon to carbon ( R C/Si ) diluted in hydrogen, is used as a precursor.…”

“…Therefore, good crystallinity and orientation have a significant impact on the application of CVD SiC tubes in nuclear fuel rods. CVD SiC tubes for nuclear fuel rods also require a thickness >100 μm . Using chloride as a precursor can greatly increase the deposition rate to produce a thicker SiC tube.…”