Subsurface damage pattern and formation mechanism of monocrystalline β-Ga_(2)O_(3) in grinding process

Monocrystalline beta-phase gallium oxide (β-Ga_(2)O_(3)) is a promising ultrawide bandgap semiconductor material. However, the deformation mechanism in ultraprecision machining has not yet been revealed. The aim of this study is to investigate the damage pattern and formation mechanism of monocrystalline β-Ga_(2)O_(3)in different grinding processes. Transmission electron microscopy was used to observe the subsurface damage in rough, fine, and ultrafine grinding processes. Nanocrystals and stacking faults existed in all three processes, dislocations and twins were observed in the rough and fine grinding processes, cracks were also observed in the rough grinding process, and amorphous phase were only present in the ultrafine grinding process. The subsurface damage thickness of the samples decreased with the reduction in the grit radius and the grit depth of cut. Subsurface damage models for grinding process were established on the basis of the grinding principle, revealing the mechanism of the mechanical effect of grits on the damage pattern. The formation of nanocrystals and amorphous phase was related to the grinding conditions and material characteristics. It is important to investigate the ultraprecision grinding process of monocrystalline β-Ga_(2)O_(3). The results in this work are supposed to provide guidance for the damage control of monocrystalline β-Ga_(2)O_(3)grinding process.

High‑Valence Transition Metal Modified FeNiV Oxides Anchored on Carbon Fiber Cloth for Efficient Oxygen Evolution Catalysis

Developing efficient and durable non-noble metal-based oxygen evolution catalysts is of great importance for electrochemical water splitting.Here,we report a new and facile strategy for controllable synthesis of high-valence Mo modified FeNiV oxides as efficient OER catalysts.The Mo-dopant displays a significant influence on the valence state of Fe species in the catalysts,which lead to tunable OER performance.When the feed ratio of Mo-dopant is 5%,the Mo-modified FeNiV oxide shows the best OER performance in terms of low overpotential(237 mV at the current density of 10 mA cm^(−2)),Tafel slope(38 mV per decade),and high mass activity,which exceeds its counterparts and most reported OER catalysts.Furthermore,by assembling the catalyst with a carbon fiber cloth,the fabricated water-splitting device exhibits excellent activity and longterm durability in alkaline electrolyte compared with commercial catalysts equipped device.This work not only provides a series of Mo-modified FeNiV-based oxides as high-performance OER catalysts but also offers a new pathway to tune the charge states of OER active centers.