Cu–Mo harmonic-structured composite was produced via mechanical milling (MM) followed by spark plasma sintering (SPS), and its thermal and mechanical properties were investigated in detail. Microstructural observation of the MM powders and SPS compacts was achieved using scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDS). The mechanical properties of the SPS compacts were evaluated using results of the Vickers hardness test. The thermal properties of them were evaluated using results of thermo-mechanical analysis and laser flash method. SEM/EDS micrographs profile indicated that the Cu–Mo harmonic-structured composite has the network region composed of molybdenum and the dispersed region of copper. The Cu–Mo harmonic-structured composites demonstrate low coefficient of linear expansion and enough thermal conductivity compared to the conventional Cu–Mo particle dispersed composite. The hardness of Cu–Mo harmonic-structured composite corresponds to the Voigt model of the rule of mixture of Cu and Mo. The harmonic structure control is effective for an improvement of the thermal and mechanical properties.

We focused on the development of paints with low infrared emissivity and low thermal conductivity. To achieve the goal, glass flakes coated with copper or silver were selected as additives. These were mixed in commercially available phthalic acid resin paint, and ordinary painting was carried out. The spectral infrared emissivity of metal-coated glass flakes added paints decreased to 0.75 or less. Particularly, for the 20 wt% Ag-coated glass flakes added paint, it was very effective as 0.37 in the middle infrared ray (4.5 μm) and 0.55 in the far infrared ray (11.5 μm). And the thermal conductivity also fell very well. The values of the 20 wt% Ag-coated glass flakes added paint and 20 wt% Cu-coated glass flakes added paint were 0.11, 0.08 [Wm⁻¹K⁻¹] respectively. That is, by adding metal-coated glass flakes to the paint, we succeeded in reducing both infrared emissivity and thermal conductivity. Further, the specular reflectance (5° incidence) of infrared rays was very low at around 0.03 to 0.04, which was almost the same value as the base paint. From the microscope observation, the glass flakes were stacked and clogged. This would have resulted in the above performance.

Rice husk was converted to SiC or SiO₂ and used for making porous ceramics or foamed glass. The rice husk derived SiC was aggregated, but by adding a peptizer it was possible to disperse to the same extent as commercially available SiC. Such dispersed SiC derived from rice husk was able to be used as a foaming agent to fabricate ceramic foams. We also succeeded in making foamed glass using rice husk derived SiC as a foaming agent and in fabricating foamed glass using rice husk derived silica matrix added with glass modifiers.

The compression Young’s modulus and strength of lattice structures with porosity between 47.8% and 82.6% produced by Selective Laser Melting (SLM) of a Ti6Al4V powder were investigated. The Young’s modulus and yield strength range from 1 GPa to 20 GPa and from 10 MPa to 250 MPa, respectively. On increasing porosity, both stiffness and strength decrease. When porosity increases above 60-65%, the strength shows an accentuated decrease compared to the stiffness decrease. The absence of struts parallel to the loading direction in the lattice structure allows to achieve higher yield strength than other structures having the same Young’s modulus.

Since the oral cavity is open to the external environment, a tremendous number of microorganisms adhere to its surface and form a biofilm on it. The microorganisms in the oral biofilm cohabit with the host as the indigenous microbiota and utilize nutrients, such as carbohydrates, proteins, and amino acids, which are supplied from bodily fluid (saliva, etc.) and dietary foods. However, when the balance between the host and the bacteria is disrupted by changes in the host’s eating habits, prophylactic behavior, immunological activity, etc., oral diseases can occur. The excessive and frequent intake of carbohydrates might increase bacterial acid production from carbohydrates, initiating dental caries, while poor oral hygiene might cause bacteria to accumulate and promote the bacterial production of cytotoxic metabolites from proteins and amino acids, initiating periodontal diseases. When dental biomaterials are placed in the oral cavity, their surfaces also become covered by the oral biofilm and are influenced by bacterial metabolism. Our recent studies suggested that bacteria can invade polymethyl methacrylate and reduce its hardness and alter its components, and bacterial oxygen consumption can create oxygen concentration cells on titanium surfaces and cause then to corrode. Possible mechanisms that might underpin these microbiological deteriorations were discussed.

Raw silk can be doped with metal element such as Ca and Zn due to high affinity of sericin, outer layer of the raw silk. Thus, raw silk doped with metal element is expected to show various functions favorable as biomaterials. In this study, we investigated to apatite-forming ability in simulated body fluid (SBF) and antibacterial activity against Escherichia coli of metal-doped raw silk fabric. The samples were prepared by soaking in the aqueous solution containing Ca, Cu or Zn ion. Cu-doped and Zn-doped raw silk fabric showed antibacterial activity, suggesting antibacterial agents of Cu and Zn released from the samples killed the bacteria. On the other hand, Ca-doped raw silk fabric showed both apatite-forming ability and antibacterial activity. The apatite formation on fabric is might be because Ca ion released from the sample increased a degree of supersaturation of SBF to respect with apatite and accelerate the apatite formation. Also, it is considered that release of Ca ion causes pH increase locally and the bacteria hardly survive at the sample surface. Therefore, Ca-doped, Cu-doped and Zn-doped raw silk fabric are useful as antibacterial biomaterials. Further, Ca-doped raw silk fabric has potential to bond to living bone.

Fe₃O₄ catalysts were prepared on α- and γ-Al₂O₃ support powders by rotary chemical vapor deposition using ferrocene as an Fe precursor. The Fe content, microstructure and CO oxidation property of the Fe₃O₄/Al₂O₃ catalysts were investigated. Fe₃O₄ particles, less than 30 nm in diameter, surrounded by layers of carbon were precipitated on the α-Al₂O₃ support powder 10–20 μm in diameter. Faceted Fe₃O₄ particles several nm in diameter were precipitated on an α-Al₂O₃ support powder 40–50 nm in diameter, while minute Fe₃O₄ was deposited on a γ-Al₂O₃ support powder. The Fe content in the Fe₃O₄/Al₂O₃ catalysts ranged from 0.39–1.78 mass%. The Fe₃O₄/Al₂O₃ catalysts exhibited CO oxidation activities; the light-off temperature of the Fe₃O₄/γ-Al₂O₃ catalyst was 333 K and the oxidation of CO reached 100% at 553 K.

In this study, the effect of nitrogen (N) doping and microstructural changes on the electrical and thermal properties of silicon carbide (SiC) were investigated. SiC powder was treated in a N₂ atmosphere at 1673, 1973 and 2273 K for 3 h and subsequently sintered by spark plasma sintering (SPS) at 2373 K for 300 s in a vacuum or in a N₂ atmosphere. The a-axis of the N₂-treated SiC powders was almost constant, while the c-axis slightly decreased with an increase in the temperature of N₂ treatment. The relative density of the SiC powder sintered body decreased from 72% to 60% with an increase in the temperature of N₂ treatment. The increase in temperature of N₂ treatment caused a decrease in the thermal and electrical conductivities of the SiC. Upon N₂ treatment at 1673 K and sintering in a N₂ atmosphere, SiC exhibited a high electrical conductivity of 1.5 × 10³ S m⁻¹ at 1123 K. SiC exhibited n-type conduction, and the highest Seebeck coefficient was −310 μV K⁻¹ at 1073 K.

In this work, criteria for optimization of the Spark Plasma Sintering (SPS) regimes to manufacture transparent MgAl₂O₄ ceramics have been suggested. These criteria are not derived from the microstructural characteristics of the sintered samples – density or grain/pore size. In our approach, the criteria for optimization are the coefficients in the equation describing the normalized optical density. After the choice of the criteria was justified, they were used for obtaining transparent MgAl₂O₄ ceramics with improved optical properties by SPS at optimal temperatures, pressures and heating rates. The suggested criteria were determined for representative sets of MgAl₂O₄ ceramic specimens obtained by SPS using different processing parameters.

Since titanium has a different elastic modulus from the human bone, stress shielding occurs and it causes the difficulty of direct bonding. However, making the porous titanium enables to approximate the elastic coefficient of the human bone. In vivo experiments are indispensable for practical use of porous titanium implants, but it has been considered difficult to process porous titanium into implant shapes. In this study, we aimed for in vivo experiments to embed a sample in rabbit bone, and fabricated a miniaturized implant type sample compared to the actual one used in dental care. Porous titanium was fabricated by spark plasma sintering (SPS). As a result, it was found that it was possible to prevent destruction of the specimen during fabricating by maintaining the compressive force at 30 MPa and the sintering temperature at 570°C for 15 minutes. The compressive strength of the specimen was 150 MPa.