Periodical ridge microtextures are formed on material surfaces by fine particle peening (FPP) with a shallow peening angle. However, the influences of various FPP conditions on the formation of ridge microstructures have not been clarified. This study was performed to investigate the relationship between FPP conditions and the shape and size of the ridge texture, and then to explore methods for fabricating periodical microstructured surfaces. The results indicated that increasing peening time and particle supply rate under certain conditions can increase the ridge size. The ridge size was also shown to be dependent on the hardness of the substrate and the particle diameter. On the other hand, the possibility of forming uniform ridges over a large area should be possible by overlapping the processing area of FPP.

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A mist system for laser-induced wet treatment without a solution bath was developed. Disk-shaped SUS316L specimens were sprayed with aluminum nitrate while irradiated with a laser, generating a treated layer containing aluminum and oxygen. This layer was equivalent to the treated layer generated by conventional laser-induced wet treatment, in which the specimens are soaked in a solution and irradiated with a laser. A treated layer including cavities was generated on the specimens irradiated with a laser focused on the specimen surface. A homogeneous treated layer was generated with the laser at a defocus distance of 0.25 mm. Friction test results indicated that the generated fiction track of the specimen treated using the mist system was thinner than that of untreated specimens. This suggested that wear resistance of SUS316L steel would be improved by laser-induced wet treatment with the mist system.

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A novel electric field activation technology was developed that improved the polishing rate of colloidal silica slurry. In general, colloidal silica slurry is used in final polishing of semiconductor substrates, such as a sapphire wafer and silicon wafer. It is a colloidal solution consisting of a stable dispersion of nanometer-size silica particles. In this study, we have developed a new nozzle that can to apply an electric field to enhance activation of colloidal silica slurry. Using this nozzle, the absolute value of the zeta potential of the silica particles became large, and the polishing rate of silicon wafer was improved by 11%.

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