Mechanical alloying or mechanical milling is one of popular technique to produce attractive materials including non-crystalline, nano-crystalline, fine structure, metastable materials. In this article, firstly, the history of mechanical alloying is introduced. After that some researches on this topic conducted by one of leading research groups in Japan, where the author participates, will be shown. Also, the brief history of mechanochemistry is presented. Finally, the fusion of these two disciplines will be introduced.

The magnetic properties and microstructures of the HDDR powders fabricated from the NdFeB sintered magnets were investigated in order to improve their orientation. In case of fabricating from the strip cast alloys, the hydrogen-pulverized powders showed the dependence of the orientation on their powder sizes. On the other hand, the pulverized powders from the sintered magnets showed high orientation regardless of their powder sizes. This is due to inheritance of the high crystal orientations of the sintered magnets as starting materials. And the formation of the fine Nd₂Fe₁₄B crystals just at the surface area of the pulverized powders could be processed by the additional annealing under Ar atmosphere in advance of the HDDR treatment. As a result, the residual magnetization of the “capsule-structured” HDDR powders was improved from 100 to 125 emu/g due to remaining the unreacted Nd₂Fe₁₄B phases with high orientation at the inner core of the HDDR powders. This technique would provide the anisotropic NdFeB bonded magnets with high (BH)_max, and the new environment-friendly recycling process of the NdFeB magnets with low cost.

Photocatalytic reduction of CO₂ is attracting attention as one of the CCUS (Carbon dioxide Capture, Utilization and Storage) technologies which are necessary for preventing global warming. Silver (Ag)-loaded Ga₂O₃ photocatalyst is a promising material used for the reduction of CO₂ to CO. In this research, the ultrasonic reduction method was investigated as a method of loading Ag nanoparticles on Ga₂O₃. With this method, Ag nanoparticles were synthesized only by ultrasonic irradiation of silver oxide (Ag₂O) in ethanol solvent. Silver nanoparticles with the particle sizes of 20 ± 2 nm were homogeneously loaded on Ga₂O₃ particles when the loading amount of Ag was in the range of 0.4 wt% to 3.8 wt%. The particle sizes of the loaded Ag particles were ca. 250 nm when using the conventional impregnation and photoreduction methods. Regarding photocatalytic activities for CO₂ reduction, the selectivity toward CO evolution of Ag-loaded Ga₂O₃ prepared by the ultrasonic reduction method was higher than that by the conventional methods. It was shown that Ag loading by the ultrasonic reduction method was not only advantageous for industrial production, but also superior in the photocatalytic performance.