In the present study, we have examined the wear properties of the sintered pure iron subjected to two distinct heat treatments such as nitriding-quenching (NQ) and carburizing-quenching (CQ). Based on our current observations, the martensite layer was formed on the surface layer following each treatment, whereas the hardness of the NQ martensite was much higher than that of the CQ one. The wear of the CQ specimen was slightly smaller than that of the NQ martensite, despite the lower value of the initial hardness. Meanwhile, the hardness of the CQ surface after the sliding tests significantly elevated relative to the NQ surface resulting in the better wear resistance. EBSD analysis demonstrated that the plastic deformation on the CQ surface along the sliding direction. Furthermore, the micro area X-ray diffraction along the surface layer of the CQ surface showed that a small amount of the retained austeite which reduced locally during the test. Therefore, the CQ-treated surface showed the excellent wear resistivity due to the surface hardening by the stress-induced transformation of the retained austenite dispersed in the martensite, in addition to the strain hardening of the martensite itself. In contrast, the worn surface of the NQ specimen showed slight plastic deformations of the ferrite grains beneath the martensite layer, but not in the surface martensite layer. This deformation under the martensite layer was due to the hardness gap between inward and the heat-treated surface, and might contribute to form the concave profile on the sliding surface. Consequently, this study could demonstrate such the difference in the wear mechanisms between the CQ and the NQ specimens.

We studied the magnetic entropy change (ΔS_m) of the double perovskites Sr₂RRuO₆ (R = Dy and Tb). The magnetic entropy change shows a peak near the second-order phase transition temperature (~40 K). The values of maximum −ΔS_m and relative cooling power for a magnetic-field change of 5 T are 2.41 J/(kg K) and 48 J/kg for the DyRu compound and 1.72 J/(kg K) and 36 J/kg for the TbRu compound, respectively. Strong interactions between the rare-earth and transition-metal magnetic moments shift −ΔS_m of the rare-earth moments to high temperatures. We compared the results of Sr₂RRuO₆ (R = Dy and Tb) with those of oxides possessing a giant magnetocaloric effect.

High-purity mullite (3Al₂O₃·2SiO₂) has excellent mechanical properties at high temperature, such as high flexural strength and excellent creep resistance, and are thus promising as high-temperature structural ceramics. The mechanical properties at high temperature are influenced by factors such as the Al₂O₃/SiO₂ ratio, impurities, and the microstructure; therefore, the relationships among these factors and their effect on the mechanical properties at high temperature have been investigated with respect to improving the properties of high-purity mullite. High-thermal-stability mullite has thus been developed by the control of the Al₂O₃/SiO₂ ratio, the amount of impurities, and the microstructure with high precision. The mechanical properties of this newly developed mullite are superior to those of high - purity mullite with a composition of 3Al₂O₃·2SiO₂. We have successfully applied this mullite for the components of high-performance furnaces such as the roller hearth kiln (RHK) because this mullite has high thermal stability and exhibits better long-term stability at temperatures as high as 1600°C in an oxidizing atmosphere. The RHK with high-thermal-stability mullite components has been widely accepted by the ceramic device industry, which produces advanced materials such as electronic components. High-thermal-stability mullite has thus contributed to the development and stabilization of product properties and efficiency, and offers faster sintering times, all of which contribute significantly to the development of a wide variety of ceramics.

Oxide-based all-solid-state batteries (OX-SSBs) have been expected as next generation rechargeable batteries. In the OX-SSBs, charge transfer reaction occurs at electrode-solid electrolyte interface and then both of them must adhere well with smaller interfacial ion transfer resistance. Although various kinds of electrodes and solid electrolytes have been proposed, most of them are composed of different elements and concentrations, and, in addition, they have different thermal stability. Thus, sintering process frequently provide mutual diffusion layer around the interface, which often induce highly resistive interface and then degrade the performance of the OX-SSBs. To overcome this problem, we have focused on aerosol deposition (AD), a room temperature ceramics densification technology, to develop electrode-solid electrolyte interface at lower temperature. By applying the AD process, we have developed 4 V- and 5 V-class electrode-solid electrolyte composite electrodes and investigated their electrochemical properties as OX-SSBs at 100°C. Moreover, the AD can realize inverted-stack Li-free thin-film OX-SSBs, where crystalline LiCoO₂ electrode is formed on amorphous LiPON film. Our recent works on OX-SSBs using the AD will be introduced in this review.

The Li_1+x-y(Nb,Ta)_1-x-3yTi_x+4yO₃ (0.06 ≤ x ≤ 0.33, 0 ≤ y ≤ 0.09) forms a unique and periodical structure as a superstructure. In this work, toward application of the unique qualities of an electro-ceramic, we fabricated oriented bulk ceramics by slip casting in a strong magnetic field of 12 T. The c-axis of the powders was aligned parallel to the magnetic field. As a result, we found anisotropic- electric properties which were caused by a superstructure with intergrowth layers of corundum-type [Ti₂O₃]²⁺. In the Li-Nb-Ti-O system, the Qf value parallel to the c-axis was about five times greater than that of perpendicular to the c-axis. We concluded from our analytical and simulation results that the large Qf value parallel to the c-axis was caused from a combination of two factors; one being the anisotropic electron conductivity and the other the anisotropic bonding strength in the superstructure by insertion of the intergrowth layer.

Bi-axial grain alignment by modulated rotating magnetic field (MRF) is a candidate of material production process which can be applicable at room temperature. However, to raise MRF into a practical process, one should quantitatively understand requirements for achieving alignment of hard magnetization axis by rotating field. In this review article, rotation speed of MRF and time-dependent viscosity of slurry as two of the requirements are focused on. Orientation degrees of high-critical temperature superconductors’ green compacts aligned in MRF were found to be improved with the increase in concentration of butanol added in ethanol-based slurry. This is because time derivative of viscosity of slurry is lowered by the addition of butanol. The author’s group has recently developed an equipment that can generate a linear-drive type MRF and, in this review article, attempted to improve an effective rotation speed component in MRF by ingenuity of arrangement of the permanent magnet unit. At the current stage, the effective rotation speed has been successfully increased to be more than 500 rpm. Due to this, the orientation degrees of magnetically aligned powder samples of a high-critical temperature superconductor were also improved. Design of the arranged permanent magnet unit applicable to each substance is important.

The aerosol gas deposition (AGD) is a low temperature method for film formation. No heating procedure exists in the AGD process during the formation of the AGD films, where even ceramic films can be fabricated. We have demonstrated the advanced AGD with the practical application of a room temperature film-forming device for ceramics that can form a thin insulating film with excellent electrical insulation at a high deposition rate. For example, an alumina film having a withstand voltage of 5 kV with a film formation of about 300 mm round area is required. In order to obtain such a high dielectric breakdown electric field strength, it is necessary to form a homogeneous film in which alumina particles are densely bonded. In this report the conventional AGD system has been improved and a new target AGD has been developed. The deposition has been performed by the arrival of active species (atoms, molecules and fine nanoparticles) along the target surface. In order to handle homogeneous large areas and high-speed film formation, a new mask plate was added for cutting flying particles in specular direction. Good alumina film quality was obtained by the new target AGD added the mask plate using 30 mm wide nozzle.