In this paper, we have tried to observe a particle assembling state in a suspension conveniently and not expensively by using an optical microscope. Sample suspensions were sandwiched by two cover glasses for microscope keeping a certain gap space with 10 μm beads. Distilled water suspensions of 0.48 μm alumina powders were prepared to three types of assembling states, which are network coagulated, dispersed and blocky coagulated, by adding poly-carbonic ammonium, by changing suspension concentration up to 5 vol%. The observed images were changed to the gray images, and then they were numerically analyzed after classified to two and 256 levels based on whiteness. The analyzed results by the 256 levels can distinguish the differences of the three types of assembling states.

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Experimental studies have been carried out about improvement of hydro-cyclone performance by use of local electrostatic field and fluid flow control method in the upper plate. By use of the local electrostatic field applied in the under-flow section, with the center lod as a negative electrode and the outer wall as a positive electrode, the particle separation performance was improved.
By use of pre-treatment of feed slurry mixing in electrostatic potential field, particle separation performance increased with the increase of absolute value of negative zeta potential.
The partial separation efficiency increased in case of the special ring attached on the upper plate in order to improve particle separation performance. The optimum angle of the special ring was found from the experimental data. By use of the proposed methods, the separation efficiency of particle is increased and the proposed new methods may be effective in practical separation process.

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In this study, the uniformity of particle concentration in a cavity die containing the unstable dispersed particles is predicted by using one-dimensional flow model for non-Newtonian fluid in a cavity and the Stokesian sedimentation model. In order to depict the movement of particles, the equation combining the one-dimensional flow equation in a cavity with the particle concentration equation predicting the sedimentation is derived. We investigated the resolution to avoid the sedimentation from the operational and material point of views. As a result, we found the appropriate conditions to prevent from the problems.

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The combination of thermodynamics of colloidal suspensions and the DLVO theory succeeded in constructing a colloidal phase diagram in a map of surface potential and solid content of particles of 10-1000 nm diameters. The experimentally-determined packing density agreed with the prediction from the phase diagram. A phase transition from a dispersed suspension to a flocculated suspension during pressure filtration occurred when an applied pressure exceeded a critical value. Based on the colloidal phase transition, new filtration theories were developed for a flocculated suspension. Multi component colloidal suspensions of the 800 nm SiC-30 nm SiC-150 nm Al₂O₃-Y ions system were heterocoagulated to distribute uniformly the sintering additives （Al₂O₃ plus Y₂O₃） around SiC particles. The green compacts were highly densified above 99％ theoretical density by hot-pressing at 1950℃ and the sintered SiC provided flexural strengths above 1000 MPa.

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The increase in the environmental concerns highlight the need to build up a sustainable society based on recirculation of our limited natural resources. Our research group has been studying hydrothermal solidification for the recirculation of inorganic waste materials. The wastes generally contain higher amount of aluminum components, yielding the formation of large crystals as the prevention factor of the strength. It was found that the formation of nano-size crystals by the controlling of reaction condition enables the strength development. It was expected that these solidified waste materials show the self-humidity controlling property and the fixation of heavy metals through ion exchange. In this paper, the results of the hydrothermal solidification using inorganic wastes will be discussed.

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