We report atomic resolution in scanning tunneling microscopy studies of porous silicon surfaces, after vacuum heat treatment at 850 °C and above. The (100) sample surfaces show some 2 × 1 reconstruction as for single-crystal (100) surfaces, but the (111) samples do not show any clear reconstructions, probably because the column tops are too small for large structures such as 7 × 7 to form. The atomic planes on the column tops are parallel to the substrate for both (100) and (111) samples, in agreement with low-energy electron diffraction studies.

In order to study the effect of C/C preform on the oxidation properties of C/C-SiC composites, four kinds CVD-SiC coated C/C-SiC composites with different initial densities of C/C preform were prepared. The thermogravimetric oxidation behavior from 25 to 1450°C of prepared C/C-SiC composites and the isothermal oxidation of CVD-SiC coated C/C-SiC composites under static air at 1500 °C were studied. And the bending properties of SiC coated C/C-SiC composites before and after oxidation were investigated. The results show that the initial oxidation temperature of C/C-SiC composites increases first and then decreases with the increase of initial C/C density, which is determined by the porosity and SiC content of the composites. When the C/C density is 1.0 g/cm3, the initial oxidation temperature is 633 °C. The CVD coated C/C-SiC composites with initial C/C density of 1.0 g/cm3 exhibited the best static oxidation resistance at 1500 °C. The weight loss is 4.23% after oxidation for 10 h at 1500 °C, and the bending strength retention rate is 71.2%.