The transport of a fine powder under an extremely dense phase condition was tried using a progressive cavity pump that is a type of constant-volume pump.
When the void fraction of the powder in the transport pipe is larger than that of loose packing, the pressure drop in the powder transport can be estimated by previous theoretical equations using the dynamic internal and wall-friction coefficient. However, if the void fraction of a powder in the pipe is lower than that of the loose packing condition, the pressure drop increases suddenly and can't be estimated by the previous theory. The reason the experimental result is different from the value calculated by the previous theory is that the pressure drop depends on the particle-wall friction loss by the powder pressure. Therefore, we try to estimate the pressure drop in the pipe using the powder pressure acting on the pipe wall the same way as the estimation of that in a bin. The calculated value based on our method shows good agreement with the experimental data.

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To carry out the shape separation of irregular-shaped fine particles, a rotating vibrating conical disk separator was developed, and its separation characteristics were investigated by using fine particle mixtures differing in shape and size under various operating conditions. It was confirmed that relatively good performance was obtained for particles about 30 to 50μm in diameter under the optimal conditions. The conical disk adopted in this paper was effective for the shape separation of fine particles because the disk was able to diminish the adhesion of particles to the disk, and to promote the rolling motion of useful spherical particles in the radial direction of the disk.

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In this paper, the effect of slurry preparation conditions on the characteristics of silicon nitride granules prepared by a spray drying process was investigated. The slurry flocculation structure was changed by adjusting the pH value and adding a dispersant, respectively. A single granule was characterized by its porosity, measured with a mercury porosimeter, as well as by its tensile strength measured by a microcompressive testing machine.
As a result, a new method to characterize the relationship between slurry preparation conditions and the characteristics of the granules was proposed. From the analysis by this method, it was found that the tensile strength of the granules changed becoming larger with the adhesive force between primary particles than with the contact number of primary particles.
Furthermore, the characteristics of the granules were correlated with the microstructure of green compacts.

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Spherical calcium phosphate fine particles, the ratio of Ca/P of which was 5:3 and 3:2, were prepared by ultrasonic spray pyrolysis. ICP analysis showed that as-prepared powders were stoichiometric composition. Hydroxylapatite was obtained from the solution with a Ca/P ratio of 5:3 and tricalcium phosphate was obtained from that of 3:2. The effects of concentration, pyrolysis temperature, and flow rate on particle size, size distribution, and crystal phase were investigated. The relative densities of tricalcium phosphate and hydroxylapatite sintered at 1100°C were about 99% and 97%, respectively.

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The adsorption conformation of the magnetic powder and binder resins in the dispersion process was investigated to clarify the mechanism of kneading dispersion. A planetary Mixer was used for the kneading dispersion. The adsorption conformation was investigated by the dispersibility of magnetic paint, the quantitative ratio of the removed binder resin from the magnetic powder, the number of the no-absorbed sites on the magnetic powder, and the number of adsorption sites in the binder resin. These results lead the following conclusions. Although the amount of the adsorbed resin is almost determined at the beginning of the kneading because there are few adsorption sites in the resin adsorbed on the magnetic powder, the bonding power between the magnetic powder and the binder resin in weak. As the kneading dispersion progresses, the number of the adsorbed sites in one resin molecule increases and the bonding power between the magnetic powder and the binder resin becomes strong.

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Precursors with hexaferrite composition were prepared from Ba(OH)₂ 8H₂O and α-Fe₂O₃ or amorphous Fe₂O₃ powders by a planetary mill-treatment in acetone. Extracted water from Ba(OH)₂·8H₂O brought about hydration and resulted in amorphization of α-Fe₂O₃. The mill-treatment promoted agglomeration between hydrated amorphous Fe₂O₃ and Ba(OH)₂ in acetone which had poor polarity. The precursors derived from α-Fe₂O₃ and Ba(OH)₂·8H₂O formed BaFe₁₂O₁₉ at 800°C through the intermediate formation of BaFe₂O₄ at 600-700°C. This hexaferrite powder showed poor sinterablity. In contrast, using the amorphous Fe₂O₃ as a constituent, BaFe₁₂O₁₉ formed directly at 700°C. From this powder, dense sintered materials consisting of fine plate-like particles of about 1μm can be obtained at temperatures lower than 1250°C. Above 1250°C, the size of plate-like particles increased to 10μm without intragranular pore defects.

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Amorphization of two kinds of titanium oxide powders, anatase and rutile, during a planetary mill treatment was investigated. The amorphization of anatase markedly progresses despite its average particle size which is much smaller than that of the ground product. The powders are mechanochemically hydrated to form agglomerates in acetone with low polarity. The shear stress generated during mill treatment induces plastic deformation in the defloccuration process of the agglomerates, resulting in the promotion of amorphization. The addition of water to acetone accelerates the amorphization by promoting hydration. This amorphization process through the agglomeration-defloccuration process suggests a high possibility of synthesizing composite particles composing of hydrated oxide and inorganic salts with high polarity.

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A wet classification process for a high-grade powder and for the use of low-grade resources has been investigated. The boundary size at which the particles are precipitated or not in a centrifugal separator was analyzed. As a result, classificating of the particles below 325 mesh could be performed. Thus, the separation size D(μm) expressed by Stokes diameter could be reprensented by;
D²=338²·Q·r^-3·n^-2
using the flow rate Q(m³/h), the radius r(m), and the rotation speed n(rpm) of the rotary vessel.

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The wettabilities of fine silica powder surfaces loaded with trimethylsilyl groups (TMS) were studied microscopically and macroscopically. Modification was carried out by the chemical reaction of hexamethyldisilazane (HMDS) molecules with surface silanols, and the TMS coverage was determined by the elemental analysis of carbon. The microscopic wettability was investigated by water vapor adsorption and the IR spectroscopic method. The macroscopic wettability was examined by various preferential dispersion tests. The results are summarized as follows: (1) HMDS molecules preferentially reacted with free type surface silanols. (2) The macroscopic wettability drastically changed at a TMS coverage of about 40%. (3) The effect of steric hindrance appeared clearly at a TMS coverage above 40%. Hence, a portion of residual surface silanols is shielded by TMS, and water molecules cannot access these sites. (4) In the case of TMS coverage below about 40%, cooperative adsorption takes place durring the first stage of adsorption. Then, by the occurrence of multilayer adsorption, a continuous two dimensional water layer is formed during the latter stage of adsorption. On the other hand, for the samples whose coverages are above about 40%, the adsorbed amount was about 65% of theoretical monolayer capacity in spite of high relative pressure at about P/P₀=1. Therefore, such a continuous two-dimensional water layer is not formed due to the steric hindrance of the TMS, and multilayer adsorption cannot occur in this case. The surface property is estimated to be hydrophobic. (5) The results of preferential dispersion tests on macroscopic wettability were in agreement with the results of the water vapor affinity of microscopic wettability.

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A rheological property of a condensed ceramic slurry used in the commercial production of high tension electrical insulators was discussed under the condition of lower pH. Two types of slurry were used, one was mainly composed of Kaolinitic clay, and the other was Sericitic clay. Discussions were based on the experimental results, i. e. the difference in the amount of adsorbed and desorbed ions on the particles surface, on the difference in the potential value, and on the microstructural difference observed through the SEM observation of those freeze-dried slurries. It was found that the difference in the rheological behavior between the two types of condensed ceramic slurry was brought about mainly by the difference in the aggreagation state of the clay particles due to the exposed mineral species, such as SiO₂ or Al₂O₃, which preferentially appeared in the cleavage depending on the type of clay minerals used.

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A new Y-Fe-O compound was synthesized by the RF thermal plasma evaporation method using a co-precipitated powder or nitrate solutions of Y and Fe as raw materials.
The XRD pattern showed that its crystal structure was a face-centered cubic of Y and Fe with a₀=0.485nm. In an experiment using a nitrate solution of Y:Fe=1:3 and an Ar-O₂ plasma, the unknown ultrafine particles of almost single phase were synthesized as a dendrite. The diameters of the primary particles were about 10nm.
From the results of the experiments, using Ar-O₂ plasma and controlling the Y:Fe ratio, the radiation heat of plasma tail flame was shown to be necessary for synthesizing the unknown in a perfect single phase.
Heating the unknown powders of almost a single phase at various temperatures for 8hr made it clear that the unkown powders were attracted to a magnet if the half widths of XRD peaks were below certain widths.

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Computer simulation of the sintering process was tried to understand the effect of sintering conditions on sintering behavior. The proposed simulation method involves major transport mechanism in the initial-stage sintering process: surface diffusion, volume diffusion, evaporation-condensation, and grain-boundary diffusion.
Moreover, this method can be applied to the simulation of sintering behavior for different size particles. The sintering experiment was performed with spherical copper particles in contact. The sintering particles were observed by SEM, and the neck growths were measured by SEM pictures. The simulated neck growth agreed well with the experimental ones.
It is possible to analyze the material transfer of the sintering process by this simulation and to determine the best condition for sintering.

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In order to analyze the size distribution of sub-micron particles by the sedimentation field-flow fractionation, a new apparatus which includes a rotary joint consisting of a flat surface seal and a rotary column with changeable wall material and channel thickness was coustructed.
At a low ionic strength in the aqueous carrier solution, the elution time of particles in sedimentation field-flow fractionation deviates from that by Giddings' theory, resulting in underestimation of the particle size. In this case, the elution time of particles can better be estimated by considering the particle-wall interaction and the fluid force effect. In the methanol carrier solution, the behavior of particles is apparently the same as that in the aqueous carrier solution. The particle size could be estimated by Giddings' theory when the aqueous or methanol solution with a certain concentration of di-2-ethylhexyl sodium sulfosuccinate (Aerosol OT) surfactant was used as a carrier solution.

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