Tohoku University · Materials Science
Professor Yamato Hayashi's research lab specializes in the development of advanced functional nanomaterials through innovative sonochemical and sol-gel processes. The lab focuses on synthesizing rare-earth and transition metal-based thin films, noble metal nanoparticles, and doped metal oxides with tailored magnetic, catalytic, and structural properties. Key research directions include the design of eco-friendly nanoparticle synthesis using ultrasound, the fabrication of self-healing ceramic coatings, and the creation of metastable liquid alloy and oxide nanostructures under non-equilibrium sonochemical conditions. The lab emphasizes sustainable materials processing and applications in energy, electronics, and environmental remediation.
Figures are computed from collected data and may differ slightly.
Amorphous Tb-Fe thin films prepared by the sputtering method in the compositional range Tb/sub x/Fe/sub 1-x/ (x=0-0.5) are investigated in view of their potential for use in electromagnetic thin film actuators. The magnetostriction and the coercive force for the Tb-Fe films are examined for different sputtering conditions to obtain both soft magnetic properties and large magnetostriction in this system. As a result, Tb-Fe thin films having large magnetostrictions (180*10/sup -6/ at 1 kOe) and lo
Ecodesigns for nano-sized noble metal particles were investigated by a new liquid-solid (metal oxide-alcohol) system. We have reduced noble metal oxides as low-emission starting materials by ultrasound and tried to fabricate various noble metal nanoparticles (Ag, Au, Pt, Pd) at room temperature, Noble metal oxides were investigated during decomposition. These reductions are ecologically clean, because many noble metal oxides are not toxic, and during decomposition, O/sub 2/ is evolved. By choosi
In this study, gallium oxide (Ga2O3) nanoparticles were synthesized by sonochemical techniques at room temperature. We investigate the ultrasound irradiation conditions and the solvent type to synthesize Ga2O3 nanoparticles. γ-Ga2O3 nanoparticles were synthesized by irradiating gallium metal with ultrasound in hydrazine monohydrate solvent. The irradiation of hydrazine with ultasound suppresses the generation of ·OH, and GaOOH was not formed, and gallium metal directly oxidized. When the synthes
The investigation of self-healing ceramic coatings is of great importance in many critical applications. We have investigated the feasibility of self-healing coatings which automatically repair the damaged part by physical and chemical reaction. In particular, we have focused on swelling clay (hectorite), which expands cubically and blocks the reactants from the substrate. In this study, we have tried to deposit clay and silica multi-layers using the spin coating technique. These coatings are an
In this study, we investigated the fabrication of supersaturated gallium (Ga)-aluminum (Al) liquid alloy and Al<sup>3+</sup>-doped γ-Ga<sub>2</sub>O<sub>3</sub> nanoparticles (NPs) at near room temperature (60 °C) using sonochemical and sonophysical effects. Supersaturated Ga-Al liquid alloy microparticles (D<sub>av</sub> = 1.72 µm) were formed and stabilized at 60 °C by the thermal nonequilibrium field provided by sonochemical hot spots. Compared with liquid Ga, supersaturated Ga-Al liquid allo
Silica xerogels were prepared by the sol-gel method under ultrasonic irradiation, using tetraethylorthosilicate (TEOS) as the starting material. Hexamethyldisiloxane (HMDSO) was used as the hydrophobizing agent. When preparing silica xerogel, it is necessary to perform aging and hydrophobization to suppress shrinkage during ambient pressure drying, however, such treatments are time-consuming. In this study, the semi-solid hydrogel was irradiated with ultrasonic for the first time in order to acc
Recently, environmental problems, such as global warming, have become more severe; thus, there is a requirement to implement sustainable development goals in materials processing. In this study, we investigated a low-cost and environmentally-friendly sonochemical process for the synthesis of metal nanoparticles with large specific surface areas and catalysis effects. Au<sub>2</sub>O<sub>3</sub> hydrate and Ag<sub>2</sub>O were reduced to Au and Ag, respectively, at room temperature in a short ti
The waterglass or St o¨ ber method is commonly used to synthesize spherical colloidal silica; however, these methods have some disadvantages, such as complicated processes for the removal of sodium ions and expensive and energy-consuming raw materials such as tetraethoxysilane (TEOS). In this study, size-controlled spherical colloidal silica was synthesized from silicon metal at room temperature using an ultrasound process with hydrazine monohydrate as the solvent. Silicon metal dissolves easily
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