Investigation of thermal oxidation of Al2O3-coated SiC powder

• Oxidation of Al2O3 coated 0.6 μm SiC powder was studied by thermal analysis method.
• Oxidation of coated powder involves crystallization of mullite at ∼1300 °C.
• Process of mullite crystallization has an activation energy of 369 kJ mol−1.
• Oxidation bonding of porous SiC is possible using coated powder at low temperature.
• Oxidation bonded SiC ceramics have interconnected porosity and fine pore structure.

SiC powder (β-form) of sub-micrometre size (d50 of 0.65 μm) was coated with a thin layer (∼12 nm) of boehmite by sol–gel technique. The final powder having ∼24 wt% boehmite was characterized by particle size and surface area determination, chemical analysis, surface potential measurement and Fourier transform infrared (FTIR) spectroscopic analysis. The thermal oxidation behaviour of the coated powder was examined using the simultaneous TG/DTA technique in dry air. The results indicated crystallization of mullite phase and the activation energy of crystallization was determined to be 368.9 ± 15.1 kJ mol−1. Synthesis of porous SiC ceramics of fine pore structure (with average porosity and pore size ranging from 47% to 54% and 170–260 nm, respectively) using thermal oxidation of coated powder was also demonstrated.

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