• Our research aims at developing methods, including instrumentation, for characterizing surface (or interface) at the nano-meter level. Most of our research subjects are related to the surface forces measurement, which can directly monitor the interaction between two surfaces. We study phenomena occurring at the solid-liquid interface such as adsorption and structuring of liquids. We have developed the resonance shear measurement which is a sensitive method for evaluating properties of confined liquid for nano-rheology and tribology. Twin-path surface forces apparatus we developed enabled us to study wide variety of samples such as metals, ceramics and plastics.

These methods are applicable for characterizing lubricants, nano-materials, paints, sealants, and cosmetics. We hope to conduct collaborative research with a willing company for a practical application of this technology in industry.

• Our lab develops accurate nanometer scale characterization methods of crystal structures by convergent-beam electron diffraction (<strong>CBED</strong>) and electronic structures by electron energy-loss spectroscopy (EELS) and soft-X-ray emission spectroscopy (<strong>SXES</strong>) for evaluating new functional materials. For performing crystal structure studies, we developed a new Ω-filter electron microscope and a refinement soft-ware, which can perform not only atom positions but also electrostatic potential and charge distributions. For electronic structure studies, a high-resolution EELS microscope and SXES instruments were developed.

Collaborated research of Local structures (symmetry, polarity, lattice defects) by CBED and electronic structures (bandgap, dielectric property and chemical state) by EELS and SXES on semiconductors, metals and dielectric materials are acceptable. Instructions of those analysis methods are also acceptable.

• 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.

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

• We developed both pH and Cl- imaging plates, which can visualize the pH and Cl- concentration on metal surfaces in acidic environments. The pH range is from 3.0 to 0.5, and Cl- concentration up to 4 M can be measured. Fluorescent dyes are successively used for pH and Cl- imaging in the field of biology, but their sensitivity tends to be insufficient in acidic and/or highly concentrated chloride solutions. A glass plate with a sol-gel sensing layer, which contains a pH indicator or a Cl- sensitive florescent dye was fabricated and validated using the solutions with various pH values and Cl- concentrations. Changes in the pH and Cl- distribution on stainless surface in an acidic environment were measured quantitatively.

The newly developed imaging plates can be used to investigate the mechanism of various chemical reactions, such as corrosion, which occurs in an acidic environment. Micro-flow imaging using our sensing technique will be a promising approach to understand the catalytic chemistry of metal surfaces.
強調

• 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.

• General metallic biomaterials, such as stainless steels and conventional CoCr alloys, show a high Young's modulus ten times higher than that of human bones. This is an unfavored feature because it causes the so-called "stress shielding effect" when they are used as implants. β-type Ti alloys have a relatively lower Young's modulus, but they come with a compromise of low wear resistance. The current novel CoCr-based alloys are a breakthrough; they exhibit both a low Young's modulus similar to human bones and a high wear and corrosion resistance. Moreover, they exhibit superelasticity with a huge recoverable strain over 17%, also showing promise as shape memory alloys.

It is the first time that a low Young's modulus, a high corrosion and wear resistance, and a superior superelastic behavior are simultaneously obtained in a single material. The current novel CoCr-based alloys are promising for biomedical applications such as total hip or knee joint replacements, bone plates, spinal fixation devices, and vascular stents.

Colorful TiO2 Particle
https://www.t-technoarch.co.jp/data/anken_en/T19-849.pdf

Transition metal compounds are known to exhibit a wide variety of colors. Until now, it has been possible to color white titanium oxide by doping with transition metal ions, but it is difficult to avoid biotoxicity derived from transition metals.

• In the present invention, titanium oxide inorganic pigments that do not contain transition metals and have various colors such as white, yellow, red, gray, green, purple, black, and skin color have been realized.

New applications of titanium oxide pigments are expected in the cosmetics field, where biotoxicity is an issue.

• 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.

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