The effects of Al addition to Ni-Cr-Mo-B alloy with corrosion and wear resistance on age hardening behavior were investigated. Examined compositions were Ni-22 mass% Cr-23 mass% Mo-1 mass% B without Al and with 2, 3 and 4 mass% Al. The powders with these compositions were produced by gas atomization, followed by sieving under 150 μm in particle size. Then, solution treatment was carried out at 1473 K for 7.2 ks in vacuum. Also, aging treatment at 1073 K for 14.4 ks in vacuum was carried out after the solution treatment. Both of cooling conditions after these heat treatments were air cooling. As a result, two kinds of hardening phenomena were observed. One was the hardness increase with increase of Al addition of more than 3 mass% after solution treatment by formation of Mo rich intermetallic compound. The other was age hardenability by precipitation of fine aging precipitate by Al addition of more than 2 mass%.

To improve the properties of powder magnetic core for motors, such as iron loss, resistivity and strength, pure iron powder was deformed into flaky-shaped and then annealed to decrease strain by deformation. It was confirmed that the strength of iron core increased with increasing the aspect ratio of powder. However, the resistivity extremely decreased. The iron core showed properties as follows; density = 7.66 × 10⁶ g/m³, resistivity = 2.5 × 10⁴ μΩ·m, iron loss (B_max = 1 T, f = 400 Hz) = 30 W/kg, iron loss (B_max = 1 T, f = 800 Hz) = 63 W/kg, B_5k = 1.49 T, radial crushing strength = 95 MPa. Especially, eddy current loss coefficient was 0.008 mWs²/kg, extremely lower than electromagnetic steel sheet and powder magnetic core reported ever.

Eu- and Pr-doped and codoped ceria Ce_1−x−yEu_xPr_yO_2−δ (x = 0, 0.01; y = 0, 0.0005) powder samples were synthesized by a coprecipitation method. The samples were characterized by XRD, color measurement, and UV-Vis diffuse reflectance spectroscopy. X-ray diffraction data indicated the formation of solid solution with fluorite-type structure. Pr doping to CeO₂ resulted in the brown color, although Eu-doped CeO₂ showed the same yellow as CeO₂. Eu- and Pr-codoped ceria of Ce_0.9895Eu_0.01Pr_0.0005O_2−δ showed brown color and the color change under light irradiation. The UV-vis spectra suggested photochromic properties.

Two kinds of raw material powders for high-performance copper base PM parts were developed, one of which was an aluminum bronze powder and the other one was a nickel bronze power. Regarding the aluminum bronze powder, aluminum-calcium fluoride and phosphorus were added as the sintering acceleration additives, and it was made certain that the aluminum bronze powder with these sintering acceleration additives was successfully sinterable in the conventional sintering atmosphere, such as with [H₂+N₂] mixed gas. This powder is very suitable as the raw material powder for copper base PM parts having high corrosion and wear resistance. On the other hand, with respect to the nickel bronze powder, the powder of the Cu-Ni-Sn system was investigated, and it was revealed that the sintered specimen which was made by sintering the alloyed powder of this ternary system, followed by air-cooling and an aging treatment, had a very fine modulated structure and showed a much higher radial crushing strength of more than 1200 MPa. This powder is very suitable as the raw material powder for copper base PM parts having high strength and high corrosion resistance.

Cu-Zn-based brasses possess excellent strength and corrosion resistance. However, producing bulk brass parts/bodies via conventional powder metallurgy has been difficult due to the high vapor pressure of Zn. This problem is circumvented in Cold Spray, in which solid powder particles, accelerated in a supersonic gas stream, are deposited on a substrate to form dense coatings without long exposure of powder particles to high temperature. In this study, a water-atomized Cu-Zn-Mn-Al-Fe brass powder about 30 μm in average diameter was cold sprayed with and without powder pre-annealing on an aluminum substrate in a nitrogen gas stream heated to 873 K. The as-atomized brass powder consisted predominantly of β solid solution, while the powder pre-annealed at 1023 K had both α and β solutions. Coatings with more than 3 mm in thickness and of nearly full density were produced with or without powder pre-annealing. An increase in deposition efficiency was noted with the coatings sprayed with the pre-annealed powder. Cold Spray provides a viable means for the fabrication of high-strength brass coatings.

Conductive inks that are composed mainly of metal nanoparticles are used as core materials for printed electronics. We developed a production method of new copper complex solutions, which by reductive heating yielded copper nanoparticles dispersion liquids of less than 100 nm in particle diameter. The copper complex solutions are grouped into three classes according to the ratio of two absorbance maxima in their extinction spectra, which determines the average particle diameter of the product copper nanoparticles. We found that Class II copper complex solution contains ultrafine copper nanoparticles of only ~1 nm in diameter as secondary species. They serve as effective nuclei allowing a size-controlled copper nanoparticle growth from the copper complex solution, thereby limiting the average size of the product copper nanoparticles to ~20 nm.

Silver powder was produced through water atomization at the high pressure of 80 MPa. Before the water atomization, silver was melted at 1330°C under nitrogen atmosphere. Scanning electron microscope observation showed that the as-prepared silver powder had various particles with morphologies such as spherical, irregular and coarse. The volume average particle size (D₅₀) of as-prepared silver powder determined by laser photo-scattering method was 7.7 μm. D₅₀ was influenced by the condition of atomization angle and drain rate. D₅₀ decreased with decreasing to atomization angle and drain rate. Electron probe micro analysis revealed that the oxygen content in as-prepared silver powder was 50 ppm. The specific resistivity of silver paste decreased to 1.75 × 10⁻⁸ Ω·m with increasing the sintering temperature. When silver paste was sintered at 900°C for 10 min, the microstructure of silver paste was densified with the large grain growth.

Carbon layer and carbon nanotube encapsuled Ni nanoparticles were prepared on α-Al₂O₃ support powder by rotary CVD using nickelocene as a precursor. The effect of deposition temperature (T_dep) on microstructure and compositions was investigated. The Ni content increased with increasing T_dep at 413–813 K. The highest Ni content was 2.1 mass% at 813 K. The carbon layer encapsuled Ni nanoparticlues was obtained at 613 K. Carbon nanotube encapsuled Ni nanoparticles was obtained at 893 K.