High Temperature Passive Oxidation Mechanism of CVD SiC
The passive oxidation mechanism of CVD SiC was discussed from experimental results with high-temperature thermogravimetry and thermodynamic analyses. The bubble formation temperature around 1900 K could be too low for an oxygen inward diffusion limited process but conform to a CO outward diffusion limited process. The parabolic rate constant (kp) had weak oxygen partial pressure (PO2) dependence, kp ∝ PO2 n where n = 0.09 to 0.12. These n values may be consistent with the CO outward diffusion limited process. The activation energy of kp obtained in the present study, 210 kJ/mol, could suggest a different mechanism from the well-approved oxygen molecule permeation limited process at lower temperatures below 1600 K. Amorphous phase was significantly contained in SiO2 scales formed in an N2-O2 atmosphere. No effect of the amorphous formation on kp was identified.
Shigeji Taniguchi, Toshio Maruyama, Masayuki Yoshiba, Nobuo Otsuka and Yuuzou Kawahara
T. Goto "High Temperature Passive Oxidation Mechanism of CVD SiC", Materials Science Forum, Vols. 522-523, pp. 27-36, 2006