Ti-metal was processed by arc-plasma irradiation in (CH₄-N₂(H₂)) atmosphere to prepare Ti-C-N ultrafine powders with different carbon ratios C/(C+N). The prepared powders were sintered under hot-pressing to produce non-oxide ceramics. The arc-plasma method enables us to prepare fine TiN and Ti (C, N) powders which have the specific surface area of 32-53m²/g, giving much finer powder for TiC. The sinterability of powders is higher than the commercially-available powders because of fineness of the prepared powders. However, a higher temperature is needed to make dense phase body from the powders with a higher carbon ratio, and hardness and fracture toughness of the sintered bodies increase with the carbon ratio.

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In order to investigate the effects of particle properties including particle shapes on the packing characteristics during tapping, the changes of void fraction, ε, in a tapping bed were measured by using particles with various shapes, sizes and densities. The particle shapes were characterized by a pair of shape indices, i. e., circularity, φ, and smoothness, ζ, through the image analysis of randomly-oriented particles. As a result, it was found that the changes of void fraction with tapping number, n, is expressed by the following simple equation; (ε-ε_f)/(ε_o-ε_f)=exp(-kn^q), where ε_o and ε_f are the initial and the final void fractions in the packed bed.
Furthermore, the effects of particle properties, φ, ζ, as well as particle diameter, d_p, and density ρ on ε_o and ε_f and on the parameters _k and _q were quantified by the multiple regression analysis of experimental results.

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Reactivities of siloxane bridge formed by thermal treatment of fine silica powder surfaces for water and several aicohols were studied quantitatively. Aerosil 200 as a fine silica powder was thermally treated in vacuum, in the temperature range from 25 to 500°C for 4hrs. The heats of immersion in water of heated silica have a broad maximum at about 300°C. The results of immersional heat suggested that rehydroxylation of siloxane on surface of thermally treated silica dose not completely restore the surface to its original condition. The interesting result obtained by Grignard's reagent test was that the siloxanes, in the all of heat-treated silica, were rehydroxylated by exposure to saturated water vapor for 12hrs. This result was also substantiated by change in the spectra of FT-IR and ²⁹Si CP/MAS NMR. In conclusion, rehydroxylation of siloxane was observed by the heat-treatment ranging from 200 to 500°C. However, for the surfaces treated above 300°C, the reaction rate of rehydroxylation decreased. On the other hand, significant reactions were not observed on a few alcohols.

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