Effect of particle size on oxidation of silicon carbide powders

Oxidation kinetics of micro-sized and nano-sized SiC powders was investigated by using thermogravimetry (TG) analysis. The oxidation kinetics of SiC powders was strongly influenced by particle size; the weight gain and rate constant increased with decreasing particle size of SiC powders. The inceptive oxidation temperatures of micro-sized and nano-sized SiC powders were 843 and 783 °C, respectively. The weight gain of micro-sized and nano-sized SiC powders was in a parabolic relationship with oxidation time over 1100–1200 °C. The values of the parabolic rate constant at 1100, 1150 and 1200 °C were 5.02 × 10−6, 6.58 × 10−6 and 9.65 × 10−6 mg2 mm−4 min−1, respectively, for micro-sized SiC powders, and 8.11 × 10−6, 10.34 × 10−6 and 13.20 × 10−6 mg2 mm−4 min−1, respectively, for nano-sized SiC powders. The oxidation activation energy of micro-sized and nano-sized SiC powders was about 110.74 and 82.64 kJ mol−1, respectively. The oxidation mechanism of SiC powders was controlled by the permeation of molecular oxygen.