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Single-crystal copper (Cu), whose atom arrangement is in the same direction and has no grain boundary, is widely used in defense technology, civil electronics and network communication. As a diamond machinable material, fan-shaped patterns are commonly generated on the machined surface in single-point diamond turning (SPDT), which affects the machined surface quality and the optical function it carries. Previous studies on the surface generation mechanism in SPDT of single-crystal copper were limited to experimental analyses, while there is a lack of fundamental understanding in the generation mechanism and suppression method of fan-shaped pattern. In the present study, the fan-shaped patterns, surface quality, cutting force and chip morphology generates during SPDT of typical crystal planes (100), (110) and (111) of single-crystal copper were studied both from theoretical and experimental analyses. A molecular dynamics (MD) simulation was conducted to present the fundamental generation mechanism of the fan-shaped patterns from atom arrangement directions and its angle changing with the primary cutting direction in micro scope, while a cutting dynamics model was established to simulate the generation of fan-shaped patterns on the machined surface in macro scope. Based on theoretical and experimental analysis, it was found that the different atom density arrangement directions of single-crystal copper and main cutting direction of SPDT caused fluctuations in the friction coefficient, which further caused the vibration of the cutting system and generated the fan-shaped patterns. The SPDT of crystal planes (100) can achieve the best surface quality. The present research provides a fundamental understanding of fan-shaped pattern formation on the machined surface, and provides a reference to obtain better surface quality in machining of single-crystal copper.

Ultra-precision fly cutting (UPFC) is a typical discontinuous cutting process where a cutting tool flies simultaneously with the rotation of a spindle and cuts the surfaces of a workpiece intermittently. To obtain good surface roughness with an acceptable productivity, it is crucial to investigate the influence of cutting chips and tooling movement during the cutting process. In UPFC, it is found that the surface rough patterns (SRPs), which are affected by submillimetre-size cutting chips, are generally formed at the tool-out area of each tool feed imprint on the machined surface. The formation of SRPs in UPFC is assumed to be affected by the size effect that is critical in new surface generation in the micromachining process. In this process, the tooling cuts through both the surface layer and inner layer grains of the workpiece during chip formation, thus resulting in the formation of an SRP. In this research, the influence of cutting parameters on the SRP is investigated; a hybrid constitutive Johnson Cook model is established and a finite element simulation using the established constitutive model is conducted to analyse the generation of the SRP. Experimental and simulation results indicate that when surface grain ratio is larger than 35 %, the inconsistent fracture strain between the surface and inner layers is the primary reason of the fracture inside the uncut chip in UPFC. SRPs are thus formed owing to the void formation and tooling movement marks on the machined surfaces. Increasing the spindle speed and reducing the feed rate minimise the occurrence probability of the SRP. Upon addressing the issues described above and with informative findings, this research provides an in-depth understanding of SRP generation affected by size effect in UPFC, and further presents a basis for improving the quality of machined surfaces.

Recently, there has been an increase in accidents due to thermal runaway issues with the mass adoption of electric vehicles in China. Avoiding thermal runaway incidents has become an essential need for electric vehicle development. Controlling abnormal temperatures is a key scientific study in battery thermal safety research. Therefore, this study provides a comprehensive analysis of module temperature distribution in the high Ni content commercial lithium-ion battery module for electric vehicles by three experimental groups. The results of the tests show that the wrap-full insulation keeps heat and mitigates the temperature non-uniformity better, but the bottom-only insulation reduces temperature faster. Active cooling can reduce the non-working module temperature from 45 °C to 27 °C in 2160 s, but natural convection keeps the temperature at about 45 °C. Under complex operating, the maximum temperature difference of the module reaches 9–10 °C. After adding active cooling, the maximum temperature difference on the module is reduced by 1 °C, and the cooling speed is accelerated by 35 %. In short, a thermal gap exists between the total positive and negative and other, which is one of the primary causes of the large temperature difference within the module. The heat transfer direction inside the module is from the middle to the sides, but it is the opposite under natural cooling. We hope to provide a useful analysis of module temperature distribution that guides the cooling layout design/application.

The spin state of antibonding orbital (eg) occupancy in LaCoO3is recognized as a descriptor for its oxygen electrocatalysis. However, the Co(III) cation in typical LaCoO3(LCO) favors low spin state, which is mediocre for absorbing oxygen-containing groups involved in oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), thus hindering its further development in electrocatalysis. Herein, both experimental and theoretical results reveal the enhancement of bifunctional electrocatalytic activity in LaCoO3by N doping. More specifically, electron energy loss spectroscopy and superconducting quantum interference devices magnetic analysis demonstrate that the Co(III) cation in N-doped LaCoO3(LCON) achieves a moderate egoccupancy (≈1) compared with its low spin state in LaCO3. First-principle calculation results reveal that N dopants play a bifunctional role of tuning the spin-state transition of Co(III) cations and increasing the electrical conductivity of LCO. Thus, the optimized LCON exhibits an OER overpotential of 1.69 V at the current density of 50 mA/cm2(1.94 V for pristine LCO) and yields an ORR limiting current density of 5.78 mA/cm2(4.01 mA/cm2for pristine LCO), which offers a new strategy to simultaneously modulate the magnetic and electronic structures of LCO to further enhance its electrocatalytic activity.

An oxygen electrocatalyst consisting of Ni nanoparticles interpenetrated in porous NiO nanosheets was successfully synthesized.The liquid Zn–air battery reveals a large open-circuit potential of 1.47 V, the maximum power density at 225 mW cm-2, and excellent device stability of over 120 h.The flexible solid-like rechargeable Zn–air battery shows excellent stability (no evident weakening after 240 cycles) and bendability.