Mullitization Behavior of Al₂O₃-SiO₂ coating deposited by CVD

The aim of the paper is to study the phase composition and the mullitization behavior of the Al₂O₃-SiO₂ coating deposited by CVD at 550°C using AlCl₃-SiCl₄-H₂-CO₂ precursor gaseous. The DTA and XRD were used to examine the mullitization behavior of the coating. The as-deposited coating was composed of γ-Al₂O₃ and amorphous SiO₂. The DTA curve has four peaks. The very weak exothermic peak appeared at about 793°C represented the formation of mullite. The first sharp exothermic peak appeared at about 984°C represented the formation of δ-Al₂O₃. The very weak endothermic peak appeared at about 1240°C represented the formation of α-Al₂O₃. The second sharp exothermic peak appeared at about 13371 also represented the formation of mullite. The results indicate the CVD process was no-oxidation and the Al₂O₃-SiO₂ coating can become into mullite-alumina coating by heat-treating it at 1350°C for 2 h.