New LTCC (Low Temperature Co-fired Ceramics) material that consists of Mg₂SiO₄, SrTiO₃ and highly crystallized Li-Mg-B-Si-O glass was developed. The dielectric constant was 8.8 and Q value was 1620 at 25 GHz (Qf = 40500 GHz). And also, its temperature coefficient of dielectric constant τ_εr was +16 ppm/°C, which was much smaller than that of the existing LTCC material having high Q value. It is a promising LTCC material applying to the high frequency electric component.

We investigated the crystal structure and ferroelectric domains of Bi₄Ti₃O₁₂ by the single-crystal X-ray diffraction and transmission electron microscopy (TEM) techniques. The space group in the ferroelectric phase was found to be P1a1. We successfully refined the crystal structure based on this space group. The calculated spontaneous polarization by the point charge model is good agreement with the reported experimental value. The 180° and 90° ferroelectric domain structures were observed by the [001]-zone dark-field TEM imaging. In the 180° domain structure, we determined that one component of the polarization vector is along the a-axis. The annular bright-field scanning transmission electron microscopy images displayed every atomic position in spite of the highly distorted structure of Bi₄Ti₃O₁₂. The tilting and distortion of the TiO₆ octahedra were also clearly observed. Therefore, we directly evaluated the ferroelectric displacements of Bi and Ti ions.

Miniaturization of parts is proceeding in various industrial applications such as medical, automotive electrical equipment and nanotechnology. Furthermore, lots of these parts have complex shapes which are difficult to fabricate by normal machining or forming. Selective Laser Melting (SLM) process is one of the techniques to improve this drawback, because SLM process can produce the complex shaped parts. However, commercial SLM machine tends to fabricate the large size products in recent years. Therefore, accuracy of its dimension is insufficient for the precision parts making. Precision SLM machine is expected to become an effective method for manufacturing small parts. In this research, we developed a precision SLM machine equipped with customized Computer Aided Manufacturing (CAM) software and single mode Yb fiber laser which can focus into 50 μm. Eventually, the precision parts fabricated by developed SLM machine have the wall with thickness of 100 μm. Various types of precision and complexed shape parts were fabricated by developed SLM machine.

The previous study indicated powder metallurgy (PM) Ti-64 alloys with oxygen showed the increment of not only their tensile strength but elongation. This study investigated the elongation improvement mechanism of Ti-64 alloys with oxygen atoms. The elemental mixture of Ti-64 alloy powder and TiO₂ particles (0~0.4 mass%) was used as starting materials, and consolidated by spark plasma sintering (SPS). The following heat treatment in vacuum was applied to sintered materials. β transus temperature increased by oxygen addition because it was one of α-phase stabilizer elements. Prior-β grains size and aspect ratio of α-Ti grains were changed by heat treatment conditions. For example, Ti-64 + O alloys after heat-treated at β-phase temperature range showed needle-like α-Ti grains with a large aspect ratio (6.1~7.0) although those with heat treatment at α + β-phase temperature had α-grains with a small aspect ratio of 3.3~4.0. These grain morphology changes strongly depended on the heat temperature, not oxygen contents. In addition, the latter materials indicated high elongation (16~17%) compared to the former with 9~10%. When Ti-64 + O alloy specimens after tensile test were analyzed by SEM-EBSD, Kernel average misorientation (KAM) maps showed many plastic strains induced in small aspect ratio α-Ti grains.

The present study deals with the simultaneous sintering of multiple pieces in the electric-current sintering apparatus to examine the mass production of sintered materials. Titanium was selected as the starting powder and the electric-current sintering apparatus equipped with the hot wall (HW) composed of carbon heat insulator and heater was used for the sintering. Sintering was performed at 900°C for 10 min and 45 samples were simultaneously prepared by using maximum 15 graphite dies (30 mmϕ). The high dense sintered materials (>95% T.D.) could be obtained and the deviation of thickness was improved drastically by adopting the prepressing to powder before sintering. However, the large deviation of the density of sintered materials was confirmed in the sintering without HW due to the variety of the sintering temperature of the dies. These results indicate that the simultaneous sintering of multiple pieces in the electric-current sintering apparatus is possible if the uniformization of the sintering temperature by the equipment of HW and prepressing process are properly performed.

The rod-Ni/Mg₂Si composites with anisotropy in the thermoelectric properties were focused on, and the influence of the structural conditions (volume fraction and tilt angle of Ni rod) in the composites on the thermoelectric properties was investigated using a finite element simulation. The mixture laws in the thermoelectric properties were verified from the simulation results. The relations between the thermoelectric properties of the tilted rod-Ni/Mg₂Si composites and the structural conditions were quantitatively clarified. Furthermore, the thermoelectric performance of the tilted composites was calculated using the clarified quantitative relations, and the optimum structural conditions bringing the maximum thermoelectric performance were predicted.

Titanium dioxide (TiO₂) is considered a main material in energy and environment fields. This work focused on the production of synthetic rutile-TiO₂ (LA) material from natural ore by milling-ultra sonic assisted in acid treatment. Modified-TiO₂ nanocomposite of synthetic rutile and anatase nanopowder was synthesized by high energy milling process. After milling process, the average sizes of samples were decreased at 30% as calculated from XRD peaks. The band gap value of samples analyzed by UV-Vis spectrometer showed that the decrease of the band gap in LA composite at 3.34 eV might be associated with the presence of rutile phase in anatase matrix relating to the highest photocatalytic activity under visible light illumination. Polyethylene plastic was supplemented with different LA nanocomposite loading by thermal attachment process. Photocatalyst property of LA nanocomposite was investigated photocatalytic activity under Xe lamp illumination and investigated by FTIR and XRD technique. The optimized content of LA nanocomposite was performed at 2 wt.% in PE film. FTIR patterns did not detect the difference of plastic degradation. However, the significant change in PE crystalline monitored by XRD technique confirmed the decrease of crystallite size by peak shifted position and size decreasing at 10% by photocatalyst effect.

A new type of centrifugal casting process is developed using conventional high-speed centrifuge. Developed process has characteristic of huge centrifugal acceleration of up to several thousand G during the casting. Alumina molds, compacted by high-speed centrifugal compaction and slightly sintered to porous bodies, are used. Alumina molds must be soaked completely into molten metal during casting, since by such configuration the pressure around the molds is balanced as quasi-isotropic hydraulic pressure to prevent mold collapse. Weak molds realize, on the other hand, easier demolding. Impregnation of the molten metal into pores of the molds can be predicted by Washburn’s equation. High-speed centrifugal casting realizes very precise shape transferability of several microns. An ant’s complex eyes and tiny hears on the legs are accurately reprinted onto Sn-Bi eutectic alloy cast.

Diesel nozzle tips with multiple inwardly tapered holes (SCM415) and 3Y-zirconia artificial teeth were made by a high-speed centrifugal compaction process (HCP) combined with 3D printed resin cores or molds. The resin cores and molds featured designed shapes and the green compacts were eliminated by heating in the process. We used an LED laser 3D printer because of its accurate shape transferability. However, UV resins commonly used for this type of 3D printer are of a thermosetting type and difficult to eliminate by heating. Therefore in the present study we introduced a wax-based UV resin into the 3D printer. Changing the resin from acrylic (as used in previous studies) to a wax-based resin improved the quality of the products. Namely, the crack introduction, carbon residue in the products and sintering hindrance were considerably reduced. Low thermal expansion and complete evaporation by thermal decomposition of the wax-based UV resin helped to diminish the above-mentioned issues.