The condition to grow the peritectic crystal of copper-germanium alloy by the Czochralski method is discussed based upon the known theories on the distribution of solute near the solid-liquid interface and the onset of constitutional supercooling during crystal growth from the stirred melt. It is proposed that the alloy crystal should be pulled at a controlled rate from a hyperperitectic melt. The pulling rate has to be higher than a minimum rate which is necessary for the steady growth of the peritectic crystal but needs to be lower than a maximum rate given by a critical rate resulting in constitutional supercooling at the same time. Pullings of the coppergermanium alloy rods were carried out under the predicted condition. It is shown that the investigation of the microstructures of the peritectic ζ phase which were formed in the pulled rods supports the above discussion.

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The oxygen reduction is the cathode reaction in fuel cells and metal/air cells. The development of a new catalyst, which can efficiently progress the cathode reaction, is very important. In this study, Co, Co oxide, Pt and Pt oxide thin films prepared by reactive sputtering were characterized by XRD, XPS, EPMA and X-ray fluorescence analysis and their oxygen reduction activities in a KOH solution were investigated using rotating disk electrode method. CoO thin film could be prepared alone by sputtering Co target in Ar-50%O2 and 100%O2 gas, while Co (OH) 2 was found on the surface of the Co thin film obtained in 100%Ar by XPS analysis. On the other hand, Pt, PtO and PtO2 thin films were obtained by sputtering Pt target in 100%Ar, Ar-50%O2 and 100%O2, respectively. The oxygen reduction on the Co and Co oxide thin films was under mixed control of diffusion and charge transfer, and the charge transfer probably progressed by a 4 electron pathway. For both Co-and Pt-component system, the oxide thin films surpassed the metal one in the activity of oxygen reduction. Moreover, there was a similarity that the activity of the oxide thin film increased with increasing the oxygen/metal atomic ratio. However, it was confirmed that the oxygen reduction activity of the CoO thin film was too low to substitute for the noble metal catalyst.

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The processes for obtaining fine Sr-ferrite particles have direct efects upon the crystallite size and distribution of sintered Sr-ferrite specimens. The influence of grinding conditions on the production of fine Sr-ferrite particles during ball mill grinding was investigated. The grinding experiments were carried out under dry and wet conditions, and dry condition with methanol as a grinding aid. Particle size distributions of the ground products were measured by the microscopic method, and could be expressed accurately as described by a modified Gaudin-Schuhmann equation. The fine grindability of Sr-ferrite particles was evaluated by the median particle size in undersize distribution, and the ratio of 10% and 90% cumulative weight passing sizes that showed the broadness of the size distribution. Sr-ferrite particles with a median particle size of 0.8-1.0μm were produced. The broadness of the size distribution increased with decreasing median particle size of the ground products. The broadness of the size distribution by wet grinding and dry grinding with a grinding aid was lowered using larger grinding media.

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Grinding studies using a vertical stirred mill were carried out in order to produce fine Srferrite particles. Laboratory tests were conducted in dry and wet conditions, and dry condition using methanol as a grinding aid. The operational variables in the stirred mill were the grinding ball size, the feed mass of sample, and the volume of water (wet condition). The size distribution of ground products was measured by the microscopic method, and could be expressed by a modified Gaudin-Schuhmann equation. The products were evaluated by the median particle size and the ratio of 10% and 90% cumulative weight passing sizes in the undersize distribution. The results of testing showed that the grinding ball size affected especially the fine grindability of the Sr-ferrite particles at each grinding condition. The product size of the Sr-ferrite particle in the stirred mill was finer than that in the ball mill; particles with a median particle size of 0.2-0.4μm were obtained in wet grinding.

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The rice husk activated carbon (RHAC) was examined to treat the sewage exhausted from a pig house. The RHAC reduced the sewage stain greater than commercial granular coconut-shell activated carbon and activated carbon fiber did. The RHAC was useful to reduce the total organic carbon content and the suspended substance concentration of the sewage, while hardly reduced biological oxygen demand. Mesopores at the diameter of 10-50nm, which were preferentially produced on the RHAC, were suggested to be effective to remove a brown stain in the sewage.

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