Three kinds of inorganic–organic hybrid gel sheets were prepared from the liquid mixtures of ethyl silicate and water–soluble phenol resin. The prepared transparent gel sheets were fired at various temperatures. The density of the fired sheets jumped up at 773–1023 K with disappearance of organic groups. The sheets kept the prepared shape after the 1273 K firing, and their density increased with the silica content. After the firing at 1873 K, the sheets with high carbon content (C/SiO2: 5.60, 3.52) were converted into the sheets composed of silicon carbide aggregate with excess carbon, while the sheet with low carbon content (C/SiO2: 1.43) was converted into the fragile powders.

A study has been made of the relationship between crystal structure and hardness of N-implanted Fe-surface layers. The substrates used were polycrystalline Fe-sheets 1 mm thick with a purity of 99.9 %. The ion implantation of 14N+ was performed with doses ranging from 7.5×1016 to 1×1018 ions/cm2 at an energy of 100 keV. The substrate temperatures during implantation were kept at -40, 20, 100 and 200 °C. The crystal structure of N-implanted layers was identified by X-ray diffraction method (XRD). The near surface hardness was measured by a Knoop hardness tester. The XRD patterns revealed that the iron-nitride peculiar to each implantation condition was formed, and the iron-oxide was embedded in the nitrides in case of higher temperature implantation. N-implantation led to hardness increase, whose degree also depended on implantation conditions. The comparison between the structure and hardness of implanted layers indicated that, among the phases of iron-nitrides produced by 20 °C implantation, ε-phase is the hardest and the γ-Fe203 and γ'-Fe4N formed by 200 °C implantation are harder than the ε-phase nitrides. These results are discussed with respect to the surface composition estimated by Rutherford backscattering spectrometry (RBS) using 1.5 MeV 4He+-ions.