• Nanoporous metals have drawn considerable attention due to their highly functional properties. They are generally produced by selective dissolution of elements from a multicomponent alloy (known as the dealloying method). As this method is based on differences in the electrode potential of each element present in the alloy, and this potential is high for noble metals, porous structure can be obtained only for noble metals. Recently we have found a new, simple and easy dealloying method without using aqueous solution, which enable us to develop an open nanoporous non-oxidized metallic material even with base metals (such as Ti, Ni, Cr, Fe, Mo, etc), metalloids and their alloys.

This technique is very powerful for developing new functional electrodes, catalysts, filters as well for removing toxic metallic element from the surface of biomaterials containing the toxic element.

• It is well known that nano-scale impurity/solute clusters, defects, defect clusters and their complexes affect the mechanical and electrical properties in materials. However, it is very difficult to observe these objects even by state-of-the-art electron microscopes. We overcome the difficulty by employing noble two techniques: laser three-dimensional atom probe (3D-AP) technique and positron annihilation spectroscopy (PAS). Laser 3D-AP can map out each atom in various materials (metals, semiconductors, insulators) in three-dimensional real space with nearly atomic scale resolution. PAS can detect vacancy-type defects and defect-impurity complexes very sensitively.

By combining these methods, we are going to reveal the functions of the fine impurity clusters and defects to the materials: developments of new nano-structured materials, the mechanism of degradation of aged structural materials, the fall in the yield of semiconductor device production, and developments of quantum devices etc.

We have developed a technique for quantitative analysis of microstructures (e.g., dislocations and irradiation defect aggregates) of activated and nuclear-burned specimens in the context of the Week Beam Scanning Transmission Electron Microscope (WB-STEM) method, which boasts extremely high measurement accuracy as a quantitative analysis method for lattice defects.
In combination with a dedicated heated sample holder with fully automated temperature measurement and current control in a cartridge-type heating furnace, changes in dislocation microstructure can be dynamically measured in-situ along with a highly reliable temperature history.

Conventional TEM methods require expertise in reciprocal space and dislocation theory, but our WB-STEM method is equipped with automatic analysis software for film thickness measurement and dislocation loop feature extraction, making it possible to analyze irradiation defects easily and precisely.

• Since its design, the WB-STEM method has been developed for implementation and on-site repair in radiation controlled areas where nuclear materials are handled, with special aperture and diffraction disc selection equipment, control and analysis software.
• WB-STEM accepts irradiation defect analysis of activated specimens from all over the world, including RPV monitoring specimens from European reactors and neutron-irradiated materials from US research reactors.
• It is also used to analyze the properties of iron-containing nuclear fuel simulated debris in decommissioning projects.

We support research organizations that currently use transmission electron microscopy to observe microstructures to introduce the WB-STEM method by special modification. We will instruct researchers who have no experience using transmission electron microscopy in the procedure for dislocation analysis.

• The cold spray (CS) technique is known as a new technique not only for coating but also for thick depositions. It has many advantages, i.e. dense coating, high deposition rate, low oxidation, and no phase transformation. We have been carrying out establishment of innovative preparing and coating techniques using the CS, and maintenance of reliability and safety of the cold sprayed repairing parts and coatings. Moreover, in order to evaluate the compatibility between a substrate material and particles based on an adhesion mechanism and scientific basis, various adhesion conditions are examined a micro / nano-structure observation and a molecular simulation.

Our targets were mainly hot section parts of thermal power plants and reactor piping and tubes etc. Recently, it is possible to make a ceramic coating. Therefore, we accelerate the evolution of the other fields including the creation of the functionality materials in near future.

• We are studying hydrogen embrittlement property of high strength steels from the aspects of both the effect of hydrogen on mechanical properties of high strength steels and hydrogen uptake behavior in corrosive environments. The topics of our study includes clarification of mechanism of hydrogen embrittlement of various steels, investigation of hydrogen entry caused by corrosion using electrochemical techniques, hydrogen visualization, proposing evaluation methods for hydrogen embrittlement property and so forth.

Collaborative research in the field of hydrogen embrittlement, for example, hydrogen embrittlement properties of high strength steels and the effects of metallographic structure and hydrogen traps, proposal of evaluation methods for hydrogen embrittlement property for some specific steel and for parts with specific shape, development of novel hydrogen visualization techniques.