Mitsunori Yada’s research while affiliated with Saga University and other places

This study presents a novel self-healing mechanism for porcelain ceramics using UV-curable resin to address the inherent brittleness of ceramic materials. A biomimetic double-layered structure was designed, consisting of a high-density outer layer for mechanical strength and a highly porous inner layer for resin storage. The porous layer, achieved through nylon microparticle addition and subsequent volatilization during sintering, reached a porosity of 67%. As confirmed by FT-IR spectroscopy and EDS analysis, UV-curable acrylic resin was successfully incorporated into the porous structure. Three-point bending tests demonstrated efficient healing with a recovery rate of 56% after 5 min of UV irradiation. Both cured resin weight and post-healing bending strength increased logarithmically with UV irradiation time. The bending strength after healing was strongly dependent on the cured resin weight and polymerization depth within the specimen, as evidenced by the correlation between increased polymerization area and higher bending strength. This approach offers a promising solution for developing more reliable and durable ceramic materials, which will be particularly beneficial for aerospace and medical applications where maintenance cost reduction and extended product life are crucial.

A standard chrysotile sample was combined with erythrosine in an aqueous solution. Digital microscopy and energy-dispersive X-ray spectroscopy-scanning transmission electron microscopy (EDS-STEM) observations revealed that erythrosine was thinly and uniformly bonded to the surface of the fibrous chrysotile, forming a reddish-purple chrysotile/erythrosine composite. The amount of erythrosine adsorbed on the chrysotile was evaluated using EDS-STEM, thermogravimetry-differential thermal analysis (TG–DTA), N2 adsorption–desorption isotherms, and erythrosine-adsorption isotherm. Zeta-potential measurements showed that chrysotile had a positive surface potential; however, the chrysotile/erythrosine composite had a negative surface potential. In the aqueous solution, chrysotile and erythrosine were bonded through electrostatic interactions to form a composite. This study improves the reliability of the proposed simple and inexpensive asbestos-detection method to enable its practical application.

Photodegradation and accompanying oxidizing action of peroxotitanium complex (PTC) film were investigated, which made from PTC aqueous solution containing 61.3 mol % peroxo groups (O-O) to total Ti. The apparent activation energy (Ea) of the PTC degradation was revealed to be 132 kJ·mol⁻¹ (λ = 905 nm), according to Arrhenius plot of the degradation rate constant of PTC aqueous solution with microwave hydrothermal treatment at 100–180 °C. The PTC films were slowly decomposed by light irradiation of UV lamp, visible light LED or light bulb, and simultaneously oxidatively decomposed methylene blue dissolved in water. The oxidation reaction occurred even under the light of long wavelength around 900 nm closed to the Ea. Furthermore, the utilization efficiency of active oxygen generated by the photodegradation to the oxidation reaction of acetaldehyde gas was estimated to be 66 and 80 % under UV light (2.00 mW·cm⁻²) and LED visible light (1.50 mW·cm⁻²), respectively.

We have developed a method to detect asbestos by staining the surface of building materials in order to quickly detect asbestos-containing building materials at disaster sites. After staining, asbestos was easily detected by the color and characteristic shape of the images observed under a stereomicroscope. The type of asbestos was confirmed to be chrysotile by polarized light microscopy, X-ray diffraction patterns, and Raman spectra. The percentage of the area of asbestos at the surface of building materials was also determined by an image analyzer after the dye staining, and the distribution percentage of asbestos increased with its total concentration in the building material. Three-dimensional X-ray computed tomography images showed that asbestos was mainly distributed at the surface of building materials. This result suggests that the asbestos at the surface of debris of building materials is more easily and sensitively detected than total asbestos analysis by pulverization. The present method was applied to detect and determine asbestos in debris of building materials wasted at temporary storage sites after disaster and on the wall of a building in use. Therefore, this method can contribute to the classification of asbestos-containing and non-asbestos-containing building materials at disaster sites and demolition sites, as well as to preliminary inspections for the detection of asbestos-containing building materials before demolition of houses and buildings.

Titanium oxide films were prepared from peroxotitanium complex aqueous solution containing a peroxo complex of vanadium, molybdenum or tungsten of 2, 5, 10 mol % by heating at 200 °C for the purpose of suppressing the photocatalytic activities that may be developed by crystallization during long-term use as a prevention film against potential-induced degradation (PID) of crystalline silicon (c-Si) photovoltaic (PV) module. The films containing those dopants crystallized to anatase by hydrothermal treatment at 100 °C for 15 h as an acceleration test, but hardly showed any photocatalytic activity. According to the lattice constants, X-ray photoelectron spectroscopy analyses and UV–visible light reflection spectra, it was estimated that vanadium (V), molybdenum (VI) and tungsten (VI) were substituted with titanium (IV) in titanium oxide heated at low temperature of 200 °C. The titanium oxide films containing the dopants of 2 mol % were coated at 200 °C onto the rear side of front cover glass with 200 nm thickness. No significant PID was observed in the c-Si PV modules based on the film-coated glass by a PID test by applying −1000 V at 85 °C for 2 h.

The surface of α-Fe2O3 nanoparticles was successfully coated with mesostructured silica templated by surfactant assemblies using cetyltrimethylammonium ions. By repeating the coating operation, it was possible to control the thickness of the mesostructured silica phase. In the sample obtained with ten coatings, in particular, the aggregation and sintering of the α-Fe2O3 nanoparticles was suppressed, and the bright red before the heat treatment was maintained even after a heat treatment at 1300 °C.