Study on the characteristics of high temperature alloy surface profile grinding process

High-temperature alloy profile grinding is mainly used in the machining of aero-engine turbine structural parts, which require high surface quality and high machining efficiency. However, the process ability of machining high-temperature alloys is poor. For this reason, this paper conducts experimental research on the surface profile grinding process of high-temperature alloys to meet the surface quality and machining efficiency requirements of high-temperature alloy structural parts. Using a precision profile grinding machine, WA and SG grinding wheels are selected for profile grinding tests on three types of workpieces with curved surfaces: flat, convex, and concave. Each shape of the workpiece was shaped-ground using WA and SG grinding wheels separately. The orthogonal experimental method was used to perform profile grinding by changing three factors: grinding wheel speed, feed, and backlash. The surface roughness after grinding was measured and compared, and the most suitable process parameters for grinding three curved workpieces with WA and SG grinding wheels were obtained by comparing the surface quality and machining efficiency. The grinding strategy is also given for surface roughness and machining efficiency. It provides a basis for the improvement of the quality and efficiency of high-temperature alloy forming and grinding

Pulsed Light Synthesis of High Entropy Nanocatalysts with Enhanced Catalytic Activity and Prolonged Stability for Oxygen Evolution Reaction

Abstract The ability to synthesize compositionally complex nanostructures rapidly is a key to high‐throughput functional materials discovery. In addition to being time‐consuming, a majority of conventional materials synthesis processes closely follow thermodynamics equilibria, which limit the discovery of new classes of metastable phases such as high entropy oxides (HEO). Herein, a photonic flash synthesis of HEO nanoparticles at timescales of milliseconds is demonstrated. By leveraging the abrupt heating and cooling cycles induced by a high‐power‐density xenon pulsed light, mixed transition metal salt precursors undergo rapid chemical transformations. Hence, nanoparticles form within milliseconds with a strong affinity to bind to the carbon substrate. Oxygen evolution reaction (OER) activity measurements of the synthesized nanoparticles demonstrate two orders of magnitude prolonged stability at high current densities, without noticeable decay in performance, compared to commercial IrO2 catalyst. This superior catalytic activity originates from the synergistic effect of different alloying elements mixed at a high entropic state. It is found that Cr addition influences surface activity the most by promoting higher oxidation states, favoring optimal interaction with OER intermediates. The proposed high‐throughput method opens new pathways toward developing next‐generation functional materials for various electronics, sensing, and environmental applications, in addition to renewable energy conversion

Mechanical Metamaterials Foams with Tunable Negative Poisson’s Ratio for Enhanced Energy Absorption and Damage Resistance

Systematic and deep understanding of mechanical properties of the negative Poisson’s ratio convex-concave foams plays a very important role for their practical engineering applications. However, in the open literature, only a negative Poisson’s ratio effect of the metamaterials convex-concave foams is simply mentioned. In this paper, through the experimental and finite element methods, effects of geometrical morphology on elastic moduli, energy absorption, and damage properties of the convex-concave foams are systematically studied. Results show that negative Poisson’s ratio, energy absorption, and damage properties of the convex-concave foams could be tuned simultaneously through adjusting the chord height to span ratio of the sine-shaped cell edges. By the rational design of the negative Poisson’s ratio, when compared to the conventional open-cell foams of equal mass, convex-concave foams could have the combined advantages of relative high stiffness and strength, enhanced energy absorption and damage resistance. The research of this paper provides theoretical foundations for optimization design of the mechanical properties of the convex-concave foams and thus could facilitate their practical applications in the engineering fields

Asymmetric Modulation on Exchange Field in a Graphene/BiFeO₃ Heterostructure by External Magnetic Field

Graphene, having all atoms on its surface, is favorable to extend the functions by introducing the spin–orbit coupling and magnetism through proximity effect. Here, we report the tunable interfacial exchange field produced by proximity coupling in graphene/BiFeO₃ heterostructures. The exchange field has a notable dependence with external magnetic field, and it is much larger under negative magnetic field than that under positive magnetic field. For negative external magnetic field, interfacial exchange coupling gives rise to evident spin splitting for <i>N</i> ≠ 0 Landau levels and a quantum Hall metal state for <i>N</i> = 0 Landau level. Our findings suggest graphene/BiFeO₃ heterostructures are promising for spintronics

Chromosome-level genome assembly of Paralithodes platypus provides insights into evolution and adaptation of king crabs

10.1111/1755-0998.13266Molecular Ecology Resources212511-52