Synthesis of SiC microtubes with radial morphology using biomorphic carbon template

Abstract

Silicon carbide (SiC) microtubes have been successfully synthesized from a wood template with unidirectional pores by a vapor–solid (VS) reaction at 1450 °C in a dynamic argon/hydrogen atmosphere (Ar/H 2 = 80/20). Biomorphic wood cells are transformed into carbon preforms by a two-step carbonization process at 500 and 1000 °C. The gaseous Si precursor (SiO (vapor)) reacts directly with the free surface of the carbon template to form a SiC layer. Further diffusion occurs to permit SiC layer growth into the carbon template. The as-synthesized SiC is mainly β-SiC with a small amount of pseudo α-SiC. The residual free carbon in the as-synthesized SiC volatilizes through a burnout process at 650 °C in air. The synthesized SiC microtubes possess the villus-like and radial grain morphology on the outer surface, and show the fine grains on the inner surface. A model for the formation of SiC microtubes from porous carbon preforms is proposed, and the morphology and mechanism of synthesis of the SiC microtubes in the VS reaction are discussed.