Catalyst–Support Interaction in Polyaniline‑Supported Ni_(3)Fe Oxide to Boost Oxygen Evolution Activities for Rechargeable Zn‑Air Batteries

Catalyst–support interaction plays a crucial role in improving the catalytic activity of oxygen evolution reaction(OER).Here we modulate the catalyst–support interaction in polyaniline-supported Ni_(3)Fe oxide(Ni_(3)Fe oxide/PANI)with a robust hetero-interface,which significantly improves oxygen evolution activities with an overpotential of 270 mV at 10 mA cm^(-2)and specific activity of 2.08 mA cm_(ECSA)^(-2)at overpotential of 300 mV,3.84-fold that of Ni_(3)Fe oxide.It is revealed that the catalyst–support interaction between Ni_(3)Fe oxide and PANI support enhances the Ni–O covalency via the interfacial Ni–N bond,thus promoting the charge and mass transfer on Ni_(3)Fe oxide.Considering the excellent activity and stability,rechargeable Zn-air batteries with optimum Ni_(3)Fe oxide/PANI are assembled,delivering a low charge voltage of 1.95 V to cycle for 400 h at 10 mA cm^(-2).The regulation of the effect of catalyst–support interaction on catalytic activity provides new possibilities for the future design of highly efficient OER catalysts.

Tree‑Inspired Structurally Graded Aerogel with Synergistic Water,Salt,and Thermal Transport for High‑Salinity Solar‑Powered Evaporation

Solar-powered interfacial evaporation is an energy-efficient solution for water scarcity.It requires solar absorbers to facilitate upward water transport and limit the heat to the surface for efficient evaporation.Furthermore,downward salt ion transport is also desired to prevent salt accumulation.However,achieving simultaneously fast water uptake,downward salt transport,and heat localization is challenging due to highly coupled water,mass,and thermal transport.Here,we develop a structurally graded aerogel inspired by tree transport systems to collectively optimize water,salt,and thermal transport.The arched aerogel features root-like,fan-shaped microchannels for rapid water uptake and downward salt diffusion,and horizontally aligned pores near the surface for heat localization through maximizing solar absorption and minimizing conductive heat loss.These structural characteristics gave rise to consistent evaporation rates of 2.09 kg m^(-2) h^(-1) under one-sun illumination in a 3.5 wt%NaCl solution for 7 days without degradation.Even in a high-salinity solution of 20 wt%NaCl,the evaporation rates maintained stable at 1.94 kg m^(-2) h^(-1) for 8 h without salt crystal formation.This work offers a novel microstructural design to address the complex interplay of water,salt,and thermal transport.

Interplay of laser power and pore characteristics in selective laser melting of ZK60 magnesium alloys:A study based on in-situ monitoring and image analysis

This study offers significant insights into the multi-physics phenomena of the SLM process and the subsequent porosity characteristics of ZK60 Magnesium(Mg)alloys.High-speed in-situ monitoring was employed to visualise process signals in real-time,elucidating the dynamics of melt pools and vapour plumes under varying laser power conditions specifically between 40 W and 60 W.Detailed morphological analysis was performed using Scanning-Electron Microscopy(SEM),demonstrating a critical correlation between laser power and pore formation.Lower laser power led to increased pore coverage,whereas a denser structure was observed at higher laser power.This laser power influence on porosity was further confirmed via Optical Microscopy(OM)conducted on both top and cross-sectional surfaces of the samples.An increase in laser power resulted in a decrease in pore coverage and pore size,potentially leading to a denser printed part of Mg alloy.X-ray Computed Tomography(XCT)augmented these findings by providing a 3D volumetric representation of the sample internal structure,revealing an inverse relationship between laser power and overall pore volume.Lower laser power appeared to favour the formation of interconnected pores,while a reduction in interconnected pores and an increase in isolated pores were observed at higher power.The interplay between melt pool size,vapour plume effects,and laser power was found to significantly influence the resulting porosity,indicating a need for effective management of these factors to optimise the SLM process of Mg alloys.

Insights into the Origins of Solar-Assisted Electrochemical Water Oxidation in Allotropic Co_(5.47)N/CON Heterojunctions

Solar irradiation can efficiently promote the kinetics of the oxygen evolution reaction(OER)during water splitting,where heterojunction catalysts exhibit excellent photoresponsive properties.However,insights into the origins of photoassisted OER catalysis remain unclear,especially the interfaced promotion under convergent solar irradiation(CSI).Herein,novel allotropic Co_(5.47)N/CoN heterojunctions were synthesized,and corresponding OER mechanisms under CSI were comprehensively uncovered from physical and chemical aspects using the in situ Raman technique and electrochemical cyclic voltammetry method.Our results provide a unique mechanism where high-energy UV light promotes the Co^(3+/4+)conversion process in addition to the ordinary photoelectric effect excitation of the Co^(2+)material.Importantly,visible light under CSI can produce a photothermal effect for Co^(2+)excitation and Co^(3+/4+)conversion,which promotes the OER significantly more than the usual photoelectric effect.As a result,Co_(5.47)N/CoN(containing 28%CoN)obtained 317.9%OER enhancement,which provides a pathway for constructing excellent OER catalysts.

Microwave heating as a universal method to transform confined molecules into armchair graphene nanoribbons

Armchair graphene nanoribbons(AGNRs)with sub-nanometer width are potential materials for the fabrication of novel nanodevices thanks to their moderate direct band gaps.AGNRs are usually synthesized by polymerizing precursor molecules on substrate surface.However,it is time-consuming and not suitable for large-scale production.AGNRs can also be grown by transforming precursor molecules inside single-walled carbon nanotubes(SWCNTs)via furnace annealing,but the obtained AGNRs are normally twisted.In this work,microwave heating is applied for transforming precursor molecules into AGNRs.The fast heating process allows synthesizing the AGNRs in seconds.Several different molecules were successfully transformed into AGNRs,suggesting that it is a universal method.More importantly,as demonstrated by Raman spectroscopy,aberrationcorrected high-resolution transmission electron microscopy and theoretical calculations,less twisted AGNRs are synthesized by the microwave heating than the furnace annealing.Our results reveal a route for rapid production of AGNRs in large scale,which would benefit future applications in novel AGNRs-based semiconductor devices.

Size effects on process performance and product quality in progressive microforming of shafted gears revealed by experiment and numerical modeling

As one of the indispensable actuating components in micro-systems,the shafted microgear is in great production demand.Microforming is a manufacturing process to produce microgears to meet the needs.Due to the small geometrical size,there are uncertain process performance and product quality issues in this production process.In this study,the shafted microgears were fabricated in two different scaling factors with four grain sizes using a progressively extrusion-blanking method.To explore the unknown of the process,grain-based modeling was proposed and employed to simulate the entire forming process.The results show that when the grains are large,the anisotropy of single grains has an obvious size effect on the forming behavior and process performance;and the produced geometries and surface quality are worsened;and the deformation load is decreased.Five deformation zones were identified in the microstructures with different hardness and distributions of stress and strain.The simulation by using the proposed model successfully predicted the formation of zones and revealed the inhomogeneous deformation in the forming process.The undesirable geometries of microgears including material unfilling,burr and inclination were observed on the shaft and teeth of gear,and the inclination size is increased obviously with grain size.To avoid the formation of inclination and material unfilling,the punch was redesigned,and a die insert was added to constraint the bottom surface of the gear teeth.The new products had then the better forming quality.

An extraordinary-performance gradient nanostructured Hadfield manganese steel containing multi-phase nanocrystalline-amorphous core-shell surface layer by laser surface processing

Reducing grain size(i.e.increasing the fraction of grain boundaries)could effectively strengthen nanograined metals but inevitably sacrifices the ductility and possibly causes a strengthening-softening transition below a critical grain size.In this work,a facile laser surface remelting-based technique was employed and optimized to fabricate a∼600μm-thick heterogeneous gradient nanostructured layer on an austenitic Hadfield manganese steel,in which the average grain size is gradually decreased from∼200μm in the matrix to only∼8 nm in the nanocrystalline-amorphous core-shell topmost surface.Atomic-scale microstructural characterizations dissected the gradient refinement processes along the gradient direction,i.e.transiting from the dislocations activities and twinning in sub-region to three kinds of martensitic transformations,and finally a multi-phase nanocrystalline-amorphous core-shell structural surface.Mechanical tests(e.g.nanoindentation,bulk-specimen tensile,and micro-pillar compression)were conducted along the gradient direction.It confirms a tensile strength of∼1055 MPa and ductility of∼10.5%in the laser-processed specimen.Particularly,the core-shell structural surface maintains ultra-strong(tensile strength of∼1.6 GPa,micro-pillar compressive strength of∼4 GPa at a strain of∼8%,and nanoindentation hardness of∼7.7 GPa)to overcome the potential strengthening-softening transition.Such significant strengthening effects are ascribed to the strength-ductility synergetic effects-induced extra work hardening ability in gradient nanostructure and the well-maintained dislocation activities inside extremely refined nanograins in the multi-phase nanocrystalline-amorphous core-shell structural surface,which are evidenced by atomic-scale observations and theoretical analysis.This study provides a unique hetero-nanostructure through a facile laser-related technique for extraordinary mechanical performance.

Nitrogen-doping assisted local chemical heterogeneity and mechanical properties in CoCrMoW alloys manufactured via laser powder bed fusion

CoCrMoW alloys with different nitrogen(N)additions(0,0.05,0.1,and 0.2 wt%)were prepared via laser powder bed fusion(LPBF).The effects of N content on the microstructure and mechanical properties were investigated.The results indicate that the LPBFed CoCrMoW alloy with 0.1 wt%N addition(0.1 N alloy)shows the best combination of mechanical properties with a yield strength of~983 MPa and an elongation of~19%.Both the LPBF process and the N addition impose great effects on suppressing theγtoεmartensitic transformation,resulting in a decrease in the width and amount ofεlaths/stacking faults.Besides,the N addition promotes the segregation of elements Mo,W,and Si along the cellular sub-grain boundaries(CBs),forming fine and discontinuous precipitates rich in Mo,W and Si along the CBs in the 0.1 N alloy,but dense and continuous(Mo,W)5Si_(3)precipitates along the CBs in the 0.2 N alloy.The(Mo,W)5Si_(3)precipitates with a tetragonal structure were observed and characterized for the first time in the Co-Cr based alloys.The negative mixing enthalpy between the non-metallic elements N,Si and the metallic elements Mo,W,Cr,and the rapid solidification induced segregation of high melting point elements such as Mo and W along CBs during LPBF process,synergistically contribute to the chemical heterogeneity in the alloys.The pure FCC matrix,the slightly increased segregation of Mo,W,Si elements and fine precipitates along the CBs contribute to the good combination of strength and elongation of the 0.1 N alloy.However,though pure FCC phase was present in the 0.2 N alloy,the dense and continuous(Mo,W)5Si_(3)precipitates along CBs acted as nucleation sites for cracks,deteriorating the elongation of the alloy.Overall,it is possible to tune the mechanical properties of the LPBFed CoCrMoW alloy by adjusting the local chemical heterogeneity.

Achieving ultrahigh strength and ductility in high-entropy alloys via dual precipitation

The strength-ductility trade-offhas been a longstanding dilemma in metallic materials.Here we report an innovative approach to achieve a high strength-ductility synergy via dual precipitation of sheared and bypassed precipitates.(Ni_(2) Co_(2) FeCr)_(96-x) Al_(4) Nb_(x)(at.%)alloys strengthened by nanoscale L12 particles and Laves precipitates were selected as a model for this study,and their precipitate microstructures and mechanical properties were thoroughly investigated.The dual-precipitation-strengthened alloys exhibit a yield strength of more than 1400 MPa,an ultimate tensile strength of over 1800 MPa,and a uniform elon-gation of 18%,thus achieving a high strength-ductility synergy.Our analysis reveals that the nanoscale L1_(2) precipitates contribute to the strength via the particle shearing mechanism,whereas the Laves phase provides the strengthening through the Orowan bypass mechanism.The study of deformation microstruc-tures shows that the L1_(2) precipitates are sheared by stacking faults,which facilitates long-range disloca-tion gliding through the matrix.As a result,deformation induces the formation of hierarchical stacking fault networks and immobile Lomer-Cottrell locks,which effectively enhance the work hardening ca-pability and plastic stability,thereby resulting in a high ductility at high strength levels.Dislocations are piled-up against the interface between the Laves precipitates and matrix,which increases the work hardening capability at the early stages of plastic deformation but causes stress concentrations.The dual precipitation strategy may be useful for many other alloys for achieving superior mechanical properties for technological applications.

Frontiers in high entropy alloys and high entropy functional materials

Owing to their exceptional properties,high-entropy alloys(HEAs)and high-entropy materials have emerged as promising research areas and shown diverse applications.Here,the recent advances in the field are comprehensively reviewed,organized into five sections.The first section introduces the background of HEAs,covering their definition,significance,application prospects,basic properties,design principles,and microstructure.The subsequent section focuses on cutting-edge high-entropy structural materials,highlighting developments such as nanostructured alloys,grain boundary engineering,eutectic systems,cryogenic alloys,thin films,micro-nano-lattice structures,additive manufacturing,high entropy metallic glasses,nano-precipitate strengthened alloys,composition modulation,alloy fibers,and refractory systems.In the following section,the emphasis shifts to functional materials,exploring HEAs as catalysts,magneto-caloric materials,corrosion-resistant alloys,radiation-resistant alloys,hydrogen storage systems,and materials for biomedicine.Additionally,the review encompasses functional high-entropy materials outside the realm of alloys,including thermoelectric,quantum dots,nanooxide catalysts,energy storage materials,negative thermal expansion ceramics,and high-entropy wave absorption materials.The paper concludes with an outlook,discussing future directions and potential growth areas in the field.Through this comprehensive review,researchers,engineers,and scientists may gain valuable insights into the recent progress and opportunities for further exploration in the exciting domains of high-entropy alloys and functional materials.