Fabrication and Microstructure Evaluation of Oxide and Carbide Ceramic Coatings onto Heterogeneous Substrates by Solid-Vapor Reaction

Abstract

Silicon carbide (SiC) and alumina (Al2O3) have been synthesized on graphite and silica (SiO2) substrates, respectively, using a solid-vapor reaction (SVR). SiC and Al2O3 layers are synthesized on each substrate by reacting between SiO vapor and substrate (SiO (vapor) + 2 C (from graphite)), and between AlO vapor and substrate (2AlO (vapor) + 1/2O2 (from SiO2)). Both reaction processes were performed at 1400 °C for 9 hour at a heating rate of 5 °C/min under an Ar/H2 (160:40) flow of 200 sccm (ml/min). The pack composition for each case was adjusted with 1:1 mole ratio, which was used as precursors of the AlO and SiO vapors. The synthesized SiC layer consists of α-SiC and β-SiC, and its thickness is affected by the porosity of graphite. The Al2O3 top layer synthesized on SiO2 substrate is coarse and relatively porous, resulting in some defects.