Using carbon nanotubes (CNTs) as a reinforcement in metal matrix composites (MMCs) is a concentrated topic for materials and processing design in the area of composites science. In this paper, we review our recent development on CNT reinforced powder metallurgy aluminum (Al) MMCs, including the significant issues of processing, microstructures and properties. Main findings on CNT dispersion, composite consolidation, interface microstructures and strengthening mechanisms are introduced.

Although the injection molded Ti alloys show sufficient tensile strength, their fatigue strength was significantly lower than that of wrought material. In this study, the effect of both additions of molybdenum and boron in the Ti-6Al-4V compacts on the microstructural refinement and strength was evaluated. The 4Mo-0.4B added compacts showed fine microstructure and resulted in high tensile strength. However, their fatigue strength was not improved. The degree of influence of oxygen content, relative density and grain size on the tensile strength was estimated, and the main factor of improving tensile strength was the grain refinement. Also, the cause that fatigue strength was not improved was the ratio of the maximum pore diameter to the grain diameter increased due to the microstructural refinement, so that the crack initiated from large pore.

Mg₂Si is a promising n-type thermoelectric (TE) material for TE power generation using waste heat with temperature range of 300 to 600°C. Construction of multilayer composites with Mg₂Si and metallic material brings anisotropy in TE properties and enhancement in mechanical properties. The transverse TE force is created by giving vertical temperature difference in the tilted anisotropic TE material (transverse TE effect). In this study, the tilted Mg₂Si/Ni multilayer composites were focused on, and the influences of the structural conditions on the TE performance were investigated using a finite element simulation (FES). The simulations were carried out using two types of element models of the multilayer composites with different thickness ratio and tilt angle of Mg₂Si layer under the same temperature conditions of 500°C (hot side) and 100°C (cold side). The output power of the multilayer composites as a TE performance was calculated from the open-circuit voltage and the internal resistance estimated using FES. The values changed with the thickness ratio and the tilt angle. The optimum structural conditions of thickness ratio and the tilt angle which maximized the output power of the tilted multilayer composites were found out.

Perlite is a white powder of expanded aluminum silicate manufactured by heat treatment after grinding the perlite ore. Amorphous (glassy) perlite with physical properties such as lightweight, excellent in heat resistance, fire resistance, chemical resistance and heat insulating properties is used in lightweight aggregate and insulation. In particular, it is used as a heat insulating material for LNG tank. These tanks are double-shell-structured, in which perlite is filled as heat insulation material between the outer layer and the inner layer. Perlite is generally withdrawn from the storage tank at the time of the update and the disposal of the tank and is used as landfill materials of industrial waste. Therefore, in this study, we investigated the possibility of synthesizing tobermorite (5CaO·6SiO₂·5H₂O) by hydrothermal treatment using waste perlite as a starting material in order to investigate effective reuse method of natural resources perlite .

Eu-doped ZrO₂ and Zr_1−xCe_xO₂ (x = 0–0.2) nanoparticles were prepared by a hydrothermal method. The photoemission spectra of Zr_1−xCe_xO₂:Eu³⁺ nanocrystalline samples showed the typical emission of Eu³⁺ ions assigned to ⁵D₀→⁷F₁ (590 nm) and ⁵D₀→⁷F₂ (610 nm) transitions and additional emissions of ⁵D₀→⁷F_J with higher J. The spectra were measured at two excitation wavelength of 340 nm (indirect) and 467 nm (direct), and the direct excitation emission was less sensitive compared with 340 nm-induced emission. Asymmetry ratio which was measured by indirect excitation was more effective for monitoring a local lattice distortion in CeO₂-ZrO₂. This is a fundamental knowledge about luminescent spectra for evaluating the nature of catalytic properties.