Advanced Control of Microstructure and Property of Structural Metallic Materials

Features

Microstructure represents various kinds of heterogeneities in the metallic materials, i.e., grains, component phase, lattice defects and chemical inhomogeneity such as impurity/alloying elements. It can be modified through control of phase transformation/precipitation and deformation/recrystallization by adjusting compositions of materials and/or through processing routes (heat treatment, deformation). Such expertise in micro/nanostructure control is very important in production of current materials from viewpoints of energy saving and recycling in structural materials such as steels and titanium alloys.
We attempt to apply more advanced control of micro/nanostructures, such as atomic structures of crystalline interfaces, chemistory in an atomic scale (e.g., segregation) and so on. Fundamentals of microstructure formation (thermodynamics, kinetics, crystallography) are examined both theoretically and experimentally to clarify key factors for microstructure control. Another important aspect in our research is the improvement of mechanical property by microstructure manipulation.

Targeted Application(s)/Industry

Possibilities to establish new functions (e.g., superplasticity, shape memory/superelasticity) as well as superior mechanical properties (e.g., ultrahigh strength with high toughness/ductility) is also explored.

Suppression of Intergranular Degradation of Polycrystalline Materials by Grain Boundary Engineering

Features

Intergranular degradation often results in decreased lifetime, reliability and economical efficiency of polycrystalline materials. In spite of persistent efforts to prevent such degradation, its complete suppression has not yet been achieved. Grain boundary studies have revealed that coincidence-site-lattice (CSL) boundaries have stronger resistance to intergranular degradations than random boundaries. The concept of ‘grain boundary design and control' has been refined as grain boundary engineering (GBE). GBEed materials which are characterized by high frequencies of CSL boundaries are resistant to intergranular degradations. Our group has achieved very high frequencies of CSL boundaries in commercial stainless steels by GBE. GBEed stainless steels showed significantly stronger resistance to intergranular corrosion (see Figs. 1 and 2), weld-decay, knife-line attack, stress corrosion cracking, liquid-metal embrittlement, radiation damage, etc. and much longer creep life (see Fig. 3) than the unGBEed ones.

Targeted Application(s)/Industry

By using this GBE processing, we expect to conduct effective collaborative research in related fields.

Precipitation Hardened Co-based Alloy

Features

The high-temperature strength in Co-based alloys is inferior to that in Ni-based superalloys due to no available ’ phase for strengthening Co-based alloys. We have found a new intermetallic compound Co3(Al,W) ’ phase, and /’ Co-Al-W-based wrought and cast alloys show excellent high-temperature strength. The /’ Ir-Al-W-based alloys are also available for high-temperature uses at over 1100 °C. The Co-based alloys also have good wear resistance. For example, friction stir welding (FSW) of high-softening-temperature materials such as steels and titanium alloys is possible using a Co-based alloy tool. We hope to conduct collaborative research with willing company for a practical application of the Co- or Ir-based alloys for high-temperature uses including FSW applications.

Advanced Nanotechnology for Critical metal free secondary battery

Features

Monoatomic layered materials of Graphene, Transition metal sulfide nanosheet, nanocrystalline active materials, nanoparticles and nanoporous materials are investigated for realizing high capacity, high power, high safety and low cost energy storage devices as a post- Lithium ion battery. Advanced chemistry of functional materials and device processes for All solid state battery, Magnesium battery, fuel cells, supercapacitor and wearable batteries are investigated.

Targeted Application(s)/Industry

Academia – Industry collaboration with manufacturing companies of functional materials, batteries, and also smart grid, renewable energy, electrical power companies are encouraged for developments of advanced energy materials and post-Lithium ion battery.

Emergence in collective electrons in organic molecular materials

Features

The main research subjects in this group are the experimental investigations of the organic molecular conductors. The characteristic properties of the organic materials are multiple flexibilities owing to the assemble structure of nanometer-size molecules. This flexbility comes up recently for developing the organic electronic devices. We explore the fundamental electronic properties of the organic molecular materials which have wide range of the ground states from superconductivity to insulating states resulting from the strongly correlated electrons in the molecular pi-orbital. Such features are closely connected to flexible and multiple degrees of freedom in charge, spin, molecular latticeand molecules themselves. We are actively studying on the interesting and important issues in the condensed matter physics from the viewpoints of the characteristic flexbility of the organic molecular materials. We are prepared to provide academic consultations to companies interested in our research.

Neutron scattering study on macroscopic quantum phenomena

Features

In contrast to other scattering techniques, such as x-ray and electron diffractions, neutron scattering has the following advantages: 1) light atoms, such as H and Li, can be detected; 2) electron spins can be detected; 3) low energy excitations can be investigated. Using the neutron scattering technique, we search for macroscopic quantum phenomena in many-body electron systems, such as macroscopic singlet ground states in the quantum frustrated magnets and spin-fluctuation-mediated unconventional superconductors.

Targeted Application(s)/Industry

As noted above, neutron scattering can be used for investigating magnetic structure, spin dynamics, light atom positions in crystalline materials and their dynamics. Hence, this technique is very useful when those pieces of information are to be known.

Oxide Electronics

Features

Our research group investigates creation of functional oxides and their functionalities. We synthesize thin films by pulsed laser deposition and sputtering methods and bulk specimens, and develop their novel synthetic routes. Recently, we are studying electrically conducting rare earth oxides, transparent room temperature ferromagnetic semiconductors, and layered superconductors with monatomic Bi layer. We will develop our materials design by extending materials range and performing oxide heteroepitaxy.

Targeted Application(s)/Industry

Collaborative research in fields of oxide electronics with novel electric conducting oxides and oxide spintronics with ferromagnetic semiconductors and novel ferromagnetic oxides.

Low temperature reforming of hydrocarbons using metal oxide nanoparticles synthesized by supercritical method

Features

Our research group has succeeded in synthesizing various metal oxide nanoparticles with controlled size and exposure crystal planes by using organic modifiers under supercritical water conditions. The oxygen storage/release capacity of those materials in the low-temperature region is very high, and the reforming reaction of oxidative hydrocarbon proceeds at a significant rate. Besides, by combining the supercritical CO2 drying method, we have succeeded in forming a complex in which oxide nanoparticles are dispersed at a high concentration on the surface of the porous material, realizing both high oxygen storage/release capability and stability.

Targeted Application(s)/Industry

Low-temperature reforming reaction of biomass wastes, heavy oils, and methane. In the future, it is expected to be a technology that will lead to the construction of a low-carbon society, including CO2-free complete recycling of waste plastics.