Mullite Coating on Recrytallized Silicon Carbide and Its Cycling Oxidation Behavior

Mullite coating on recrystallized silicon carbide was successfully prepared by the sol-gel route. The cycling oxidation of coated recrystallized silicon carbide was performed at 1500℃. For comparison, the oxidation of uncoated recrystallized silicon carbide was also carried out at the same condition. The results indicated that a layer of compact, adhesive and crack free mullite coating was found on the recrystallized silicon carbide. After oxidation, the new coatings exhibit adherence and crack resistance under thermal cycling between room temperature and 1500℃, therefore the oxidation resistance capability of silicon carbide was enhanced. With the increase of the dipping frequencies, namely, the increase of the thickness of mullite coating, the oxidation resistance of silicon carbide would be further improved. The formation mechanism of mullite coating was analyzed and discussed and the oxidation dynamics model of coated-mullite silicon carbide has been also proposed.