For large scale use of renewable energy, hydrogen society is necessary to overcome supply and demand mismatch in time and space. Polymer-electrolyte fuel cells (PEFCs) represent a superior system that exhibits high-efficiency, offering better power generation, meeting the desired levels of demand. However, in order to facilitate widespread use of fuel cells, cost and lifetime problems must be resolved. We are systematically designing and developing new materials from the molecular level to the device level. In the fuel cell systems, different components such as membrane, catalysts, and catalyst layer share significant functions and work in a well-coordinated manner, and hence, the total cell system must be optimized for the best performance. The systematic design and developing approaches concerning electrocatalysts for PEFCs are proposing.

Research on nanostructuralization of fine particle for advanced functional materials has progressed rapidly in the last few decades because of the synergistic advantages of both high characteristic performance and resource and energy saving issue. Currently, research interest on nanostructured particles is focused on controlling their inner structure and morphology toward the practical application. Nanostructuralization of fine-particles into porous, hollow, core-shell, and composite, has attracted significant attention. The obtained nanostructured fine-particles will have superior properties, such as high specific surface area, low density, hybrid functionalities, and weather-resistance, compared to that of the bulk and/or single component spherical particle. For example, the high specific surface area of nanostructured fine particles plays a crucial role on the material saving issue, and it is significantly worth especially when having a deal with expensive and rare raw materials. In this review, recent approaches and issues on nanostructuralization of fine particles are introduced.

LiFePO₄ has attracted attention as a promising cathode material for lithium ion battery, because it consists of abundant elements. However, the battery performance of this material is limited by its low electron conductivity and low lithium ion diffusion rate. Coating its surface with an electronically conductive material, such as carbon, is one of the major methods to overcome this issue. In this study, we tried to synthesize Au nanoparticles (NPs) on the surface of carbon-coated LiFePO₄ (LiFePO₄/C) using sonochemical reaction to further enhance the electron conductivity. The size of Au NPs deposited on the surface of LiFePO₄/C changed in relation to the concentration of Au ions. The battery performance of the Au NPs-deposited LiFePO₄/C, as evaluated at a high constant current rate of 20 C, showed an improvement in the polarization and discharge capacity of LiFePO₄/C.

It is required to obtain quickly thermal conductivities of small specimens by simple measurement techniques to promote material development. Thermal conductivity measurement for thermal insulators usually needs long time, for example, a few days by the guarded hot plate method using a large specimen. It is useful for material development if more quick measurement of thermal conductivity is done with small specimens. The flash method is one of the promising methods to get thermal diffusivity in short time without contacts. However, only thermal diffusivity of dense solid has been measured by the flash method. In this study, laser flash method was applied to measure the thermal diffusivity of thermal insulators which consist of silica nanoparticles and glass fiber. As a result, it was made clear that the laser flash method was reliable for the measurement of thermal insulators. Besides, it was found that the thermal diffusivity of the thermal insulators was influenced by the content ratio of hydrophilic and hydrophobic silica nanoparticles.

A separation and recovery process of precious metals from E-waste was developed using chlorination. Release behaviors of metal elements from incinerated ash of spent printed circuit board were followed during the heat treatment under a chlorine gas stream. Capturing behaviors of volatilized chlorides were also followed when the chloride gases were supplied to the bed of carbon particles. Rate analysis was conducted for the release and capturing behavior of precious metals obtained by changing the treatment temperature and residence time. Gold and silver in the ash was completely released when heated for 1 hour at 1000°C. The total amounts of released gold and silver from incinerated ash were successfully recovered by adjusting the thickness of the bed of carbon particles at 800°C. The rate analysis for the release and capturing indicated that gold showed lower activation energies for both release and capturing reactions than those of silver.

The purpose of this study is to clarify the zinc removal mechanism by a natural component of organic soils, namely leaf mold and construct quantitative model. We performed batch removal experiments at different concentrations of zinc in the range 10–50 mg/dm³. The dosage of leaf mold was also changed up to 20 g/dm³. The obtained results highlighted that sorption isotherm showed a Langmuir type for each initial concentration of zinc. X-ray absorption fine structure analysis revealed that atomic arrangement of leaf mold was not changed between before and after zinc removal experiments. From above results, it was confirmed that the zinc removal mechanism by leaf mold was surface complexation formation. Based on the experimental results, we constructed a quantitative model incorporating surface complexation by leaf mold. The pH edge for Zn(II) removal by leaf mold was successfully represented by the quantitative model.

In this study, the properties of Ce³⁺-doped Y₃Al₅O₁₂ (YAG:Ce³⁺) phosphors for white light emitting diodes by mechanical method was evaluated. The YAG:Ce³⁺ phosphors were synthesized by the mechanical method using an attrition-type mill without any extra-heat assistance. BaF₂, YF₃ and Al(OH)₃ was used as an additive for its lower temperature reaction, respectively. The synthesis of YAG:Ce³⁺ phosphor was favorably achieved after 10–30 min by mechanical processing with the addition of each additive. As a result, it was made clear that the quantum yield of phosphor was well related to the crystallite size of the sample regardless of the kind of additives. The absorption rate of YAG phosphors were also well related to its median diameter. Both relationships almost agreed to those obtained for the YAG:Ce³⁺ phosphors synthesized by solid reaction method. It was suggested that the increase of crystallite size and median size of the sample synthesized by mechanical method is key issue to achieving higher quality of YAG:Ce³⁺ phosphor.

Ball motions in wet ball milling with a tumbling ball mill were simulated using the discrete element method (DEM). Results of DEM simulation were compared with the results of ball motions and real grinding tests in wet ball milling. In observation of wet ball milling phenomena, ball media slipped in pure water remarkably, but ball motions were clearly activated by the addition of low content of fine particles. In DEM simulation, calculated ball motions were adjusted to observed motions with change of friction coefficient. Then, impact energy of ball media was calculated as a key factor of grinding. Results of grinding tests of wet ball milling were well related to the impact energy. At the grinding tests with various rotation speed, all plots of particle size (d₅₀) of ground product vs cumulative impact energy agreed to just one curve.