The effects of surface silanol and nano-scale structure on the surface interaction force between solid surfaces in water were studied using silica gels prepared from alkoxide via acid-catalyzed hydrolysis under various conditions. The factors considered in the present study were catalyst type and H₂O/TEOS mole ratios. The surface silanol structure, the interaction between solid surfaces and the inner structure of dried-gels were determined, respectively, by a FT-NIR, FT-IR, Atomic Force Microscope (AFM) and a mercury porosimeter. As a result, when H₂O/TEOS mole ratio (from 4 to 40) was relatively low during acid-catalyzed hydrolysis, almost all of the surface silanols were hydrogen-bonded without free silanols. Since the hydrogen-bonded silanols formed a hydrogen-bonded water layer on silica surface, additional short-range hydration force (shorter than 2nm) appeared between the solid surface and the tip of AFM. Gel structure and force between surfaces markedly varied depending on the type of catalysts. When HCl was used as an acid catalyst, the surface structure of silica gel was very smooth and the force curve between the AFM tip and gel surface was described approximately by DLVO theory for the silica gels prepared at any H₂O/TEOS mole ratios. On the contrary, in the case of nitric acid catalyst, the roughness and pore diameter of silica gels were larger than those of silica gel prepared with HCl, and the force curve between gel surfaces and the AFM tip could not be explained by DLVO theory.

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A new type of pneumatic transport system, which is called “shot type plug flow transporter”, was developed for the transport of ultrahigh bulk density granules. The shot type transporter was characterized by the transport of single plug, and the transport characteristics of tungsten carbide granules of high bulk density were investigated by observing the plug movement in a pipeline. The following results were obtained: (1) the plug length was controlled by the pressure in a feed tank and feed time, (2) the plug was stably transported with small fluctuations in plug length, plug velocity and bulk density in the pipeline except the initial stage of transport, (3) the shot type transport reduced the attrition of granules compared to the conventional plug flow transport, (4) the limiting (i. e. choke) conditions, such as the maximum plug length, the lowest air velocity and the maximum fraction of fine powder under 150μm were determined.

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