In the machine parts industry, manufacturing with 3D printers that use resin materials is attracting attention because of the demand for complex-shaped products and small-lot production. Although this method does not require a mold, many of the resin materials are petroleum-based resins, and environmental problems are a concern. Therefore, in this study, PLA, which has carbon-neutral properties, was used as the main material. In order to suppress heat generation when used as a mechanical part, a compound containing MoS₂, known as a solid lubricant, is used. PLA pellets and MoS₂ powder were kneaded in a desktop kneader, formed into wire-like filaments, and shaped into tensile test pieces with a 3D printer using a Fused Deposition Modeling (FDM). In the tensile test, as the amount of MoS₂ added increases, the contact area of PLA, which is thought to be due to strength, decreases. Therefore, the tensile strength decreased. On the other hand, the shorter the heat-kneading time of the composite material, the more suppressed the thermal deterioration of PLA and the higher the tensile strength. It is presumed that PLA composite materials with high thermal conductivity combined with MoS₂ are greatly affected by thermal deterioration due to heating during kneading.

The authors have fabricated spark plasma sintering (SPS) compacts with hardness (>200 HV) exceeding those of practical Mg alloys from 20 vol% Al₂O₃/Mg (20 vol%) powder with uniform dispersion of Al₂O₃ particles in Mg using a mechanical milling (MM) method. In this study, for the purpose of surface modification of practical Mg alloy M1A, the properties of M1A laminated compacts with thin 20 vol% layers on the surface of M1A discs fabricated by MM/SPS method were investigated. The surface hardness, lubricity, and wear resistance of the M1A disc were improved by coating the surface of the M1A disc with a highly adherent 20 vol% layer. Based on the results of X-ray diffraction and elemental analysis by SEM-EDS, it is considered that Al diffuses to the M1A disc and Mn diffuses to the 20 vol% layer, resulting in the precipitation of MnAl, an Mn-Al intermetallic compound at the 20 vol% layer/M1A interface. The relationship between the sintering time and the adhesion of the interface was investigated. The results suggest that the amount of Al diffusion from the 20 vol% layer to the M1A disc affects the adhesion of the interface rather than the precipitation of the Mn-Al intermetallic compounds at the interface.

We analyzed the distribution of Co and Mn in the microstructure of ZnO varistor and discussed the effects of Co and Mn addition on electrical properties from the viewpoint that the influences of Co and Mn on the grain boundary layer, not on ZnO grains, are important. ZnO varistor showed excellent non-ohmic properties even when Mn was not incorporated into the ZnO grains. It was also found that the grain boundary layers consisted of thin intergranular layers between ZnO grains and grain boundary multiple points. The spinel particles remain at the grain boundary multiple points, and then react with the liquid phase, which is mainly composed of Bi₂O₃, to form ZnO with conductive properties during the cooling process. In ZnO varistor, the grain boundary multiple points are connected in a mesh-like structure, and if leakage currents occur at these points, the non-ohmic characteristics are degraded. Co and Mn are soluble in the spinel phase and act to increase chemical stability, and they suppress the reaction with the liquid phase, thereby maintaining the insulating properties of the grain boundary multiple points and contributing to the improvement of non-ohmic properties.

We prepared a catalyst-coated wire-mesh filter by thermal plasma spray method in order to develop a new type of carbon soot particulate matter (PM) removal component. The halftone plate of a SUS316 mesh was newly used as a substrate for a PM oxidation catalyst. A thermal plasma-spray method was applied to form a Ni-Pd alloy catalytic layer on the filter. As for the performace of Ni-Pd supported filter, the PM oxidation started from approximately 420°C, and the combustion at the catalytic surface took place at around 500-540°C, and finally a noncatalytic oxidation proceeded at around 650°C. The catalyst lowered a peak temperature around 110-220°C than that of only PM. Furthermore, the catalytic performance was maintained after a 5 times-repeated PM oxidation test. By the characterization of the catalyst layer, it was found that Pd particles were dispersed in a matrix of Ni and segregated on the surface and upper part of the plasma-sprayed film on the wire. The surface morphology did not change after the repeated cycle test. In this study, we found the availability of the plasma-spray catalyzed mesh filter was fabricated and as an environmental material with PM removal catalytic function.