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The oxidation behavior of high-purity silicon carbide (SiC) prepared by chemical vapor deposition was investigated by thermogravimetry, transmission electron microscopy, and Raman spectroscopy in the temperature range 1534–1902 K in pure O2. The carbon layer formed at the SiC/SiO2 interface upon oxidation above 1784 K. Raman peaks corresponding to D- and G-bands could be identified from the carbon layer. Bubbles were observed in the SiO2 scale after the oxidation at 1873 K. This could be attributed to the accumulation of CO gas at the SiC/SiO2 interface, resulting in the formation of the carbon layer and bubbles. These suggest that the oxidation rate of SiC is limited by the outward diffusion of CO in the SiO2 scale in this temperature range.

Nonlinear ultrasonics plays an important role in the detection of closed cracks in critical structures and machines, such as atomic power plants and airplanes. Although the design and operation of nonlinear measurement require realistic modeling and simulation in two dimensions (2D), only one-dimensional modeling has succeeded in reproducing subharmonic generation. In this study, we propose 2D analysis using a damped double nodes (DDNs) with compression residual stress in the finite-difference time-domain method. We then succeeded in reproducing the essential feature of observed subharmonic generation at closed stress corrosion cracks.