The welding arc,as a carrier for the conversion of electrical energy to thermal energy,has a direct impact on the quality of welding by its properties and *** the tungsten inert gas(TIG)welding process under the condi...
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The welding arc,as a carrier for the conversion of electrical energy to thermal energy,has a direct impact on the quality of welding by its properties and *** the tungsten inert gas(TIG)welding process under the condition of Ar-He alternating gas supply,the arc is alternately converted between Ar arc and He arc with an alternating gas supply cycle,which has obvious arc change *** FLUENT software was used to numerically simulate the characteristics of the TIG arc under the condition of alternating gas supply,and the arc temperature field,arc pressure,electric potential and current density distribution under the condition of alternating gas supply were *** with the real-time data of arc pressure measured by the water-cooled copper plate with holes,it is proved that the TIG arc has obvious dynamic characteristics under the condition of Ar-He alternating gas *** unique dynamic TIG arc acts on the 5A06 aluminum alloy weld,causing the molten pool to stir,resulting in uniform microstructure and grain refinement at the weld,and thereby improving the mechanical properties of the welded joint.
Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional *** of the current methods,however,...
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Multi-component transition group metal borides(MMB_(2))have become a research hotspot due to their new composition design concepts and superior properties compared with conventional *** of the current methods,however,are complicated and time-consuming,the mass production remains a ***,we proposed a new high-efficiency strategy for synthesis of MMB_(2)using molten aluminum as the medium for the first *** prepared Al-containing multi-component borides(TiZrHfNbTa)B_(2)microcrystals had a homogeneous composition with a hexagonal AlB_(2)structure and ultra-high hardness value of∼35.3 GPa,which was much higher than data reported in the literature and the rule of mix-ture ***,combined with the First-principles calculation results,we found that the Poisson’s ratio(v)values exhibit a clearly ascending trend from 0.17 at VEC=3.5 to 0.18 at VEC=3.4,then to 0.201 at VEC=3.2 with the increasing of Al *** indicates that the intrinsic toughness of multi-component boride microcrystals is obviously enhanced by the trace-doped Al ***,the fabricated Al-containing multi-component boride microcrystals have superior oxidation activation en-ergy and structural *** enhanced oxidation resistance is mainly attributed to the formation of a protective Al2 O3 oxide layer and the lattice distortion,both of which lead to sluggish diffusion of O_(2).These findings propose a new unexplored avenue for the fabrication of MMB_(2)materials with supe-rior comprehensive performance including ultra-hardness and intrinsically improved thermo-mechanical properties.
Ceramic capacitors designed for energy storage demand both high energy density and ***-ing a high breakdown strength based on linear dielectrics is of utmost *** this study,we present the remarkable performance of den...
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Ceramic capacitors designed for energy storage demand both high energy density and ***-ing a high breakdown strength based on linear dielectrics is of utmost *** this study,we present the remarkable performance of densely sintered(1-x)(Ca_(0.5)Sr_(0.5)TiO_(3))-xBa_(4)Sm_(28)/3Ti_(18)O_(54) ceramics as energy storage materials,with a measured energy density(Wrec)of 4.9 J/cm^(3)and an ultra-high ef-ficiency(η)of 95%which is almost optimal in linear dielectric that has been *** unravel the underlying mechanisms,we conducted a systematic investigation on the influence of adding paraelec-tric Ba_(4)Sm_(28/3)Ti_(18)O_(54)(BST)on both microstructure and macroscopic electrical properties of Ca_(0.5)Sr_(0.5)TiO_(3)(CST).Notably,the addition of BST effectively reduces the grain size of *** conduction mechanism is primarily governed by grain boundaries,where high-density grain boundaries act as barriers to charge carrier transport due to their elevated ***,the activation energy associated with grain boundaries increases with rising resistivity,implying a lower concentration of free vacancies within these *** increased barrier height for oxygen vacancy migration at grain boundaries compensates for the grain boundary defects,thereby resulting in enhanced breakdown *** characteristic offers a substantial advantage in terms of thermal and frequency stability(25-175℃,1-100 Hz).This work introduces a candidate material with outstanding comprehensive energy storage properties.
Amorphous alloys, i.e., metallic glasses, combine high strength, hardness, excellent wear and corrosion resistance, and unique thermoplasticity due to their short-range ordered but long-range disordered glassy structu...
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Amorphous alloys, i.e., metallic glasses, combine high strength, hardness, excellent wear and corrosion resistance, and unique thermoplasticity due to their short-range ordered but long-range disordered glassy structures. However, critical size constraints limit their applications in advanced fields such as electrocatalysis, sensing, and complex devices. Here we report a novel lattice metamaterial fabricated by conformally depositing NiNbSn amorphous alloy coatings onto three-dimensional(3D)-printed polymer scaffolds with a cubic micro-nano lattice template. The cubic lattice design enables efficient stress transfer and uniform strain energy distribution,minimizing stress concentration. Meanwhile, the NiNbSn coating, featuring amorphous and nanocrystalline components, further enhances the structure through size hardening. The resulting hybrid polymer/alloy lattice shows excellent mechanical properties and an exceptional energy absorption capacity. Furthermore, coating the hybrid lattice with a NiMoPB glassy film results in a 3D nano-micro electrode for glucose detection, achieving a sensitivity of 13 times higher than that of the castcounterpart. Our strategy opens a new path to fabricating hybrid polymer/MGs micro-nano lattice structures with excellent mechanical and electrochemical performance, broadening the potential applications of metamaterials.
Surface engineering,which modulates the electronic structure and adsorption/desorption properties of electrocatalysts,is one of the key strategies for improving the catalytic ***,we demonstrate a facile solid-phase re...
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Surface engineering,which modulates the electronic structure and adsorption/desorption properties of electrocatalysts,is one of the key strategies for improving the catalytic ***,we demonstrate a facile solid-phase reaction for surface engineering of MnO_(2)to boost the oxygen reduction *** reaction with surface hydroxy groups,La single atoms with loading amount up to 2.7 wt%are anchored onto a-MnO_(2)*** surface engineering,the oxygen reduction reaction(ORR)kinetics is significantly improved with the half-wave potential from 0.70 to 0.84 V,the number of transferred electrons from 2.5 to 3.9 and the limiting current density from 4.8 to 6.0 mA·cm^(-2).In addition,the catalyst delivers superior discharge performance in both alkaline and neutral metal–air *** functional theory(DFT)calculations reveal that atomic La modulates the surface electronic configuration of MnO_(2),reduces its d-band center and thus lowers the OOH*and O*reaction energy *** work provides a new route for rational design of highly active electrocatalyst and holds great potential for application in various catalytic reactions.
The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM) imaging and first-p...
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The interfacial structure of the α-Mg/14H-LPSO phase in rare earth-including magnesium alloy was investigated via high-angle annular dark-field scanning transmission electron microscopy(HAADFSTEM) imaging and first-principles calculations of density-functional *** possible interfacial models were constructed according to the different terminations of the LPSO phase,and the corresponding interfacial energies were calculated,from which the four most stable structures(Terl-MgY-hollow,Ter2-Zn-hollow,Ter3-MgYII-hollow and Ter4-Mg-bridge) were *** interfacial phase diagrams related to the Y chemical potentials were obtained from the calculations,and the most stable interfacial structure was ***-MgY-hollow and Ter2-Zn-hollow have the lowest interfacial energies in the range of-0.7 eV <Δμγ<-0.6 eV,where fluctuating change of state is the minimized and the interface is the most *** separation work of the two models was calculated to predict the bonding strength of the structures at both ends of the *** calculation results show that the maximum interfacial separation work is 1.45 J/m^(2) for the interface model of α-Mg and 14H-LPSO phase structure with Ter2-Zn-hollow termination.
Bacterial adhesion is a critical process in many fields,such as implant infections,microbiologically influenced corrosion and bioelectricity generation in microbial fuel *** bacterial adhesion,the contact area between...
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Bacterial adhesion is a critical process in many fields,such as implant infections,microbiologically influenced corrosion and bioelectricity generation in microbial fuel *** bacterial adhesion,the contact area between the attached bacteria and the patterned surface plays an important *** this study,different surface topographies and treatments were employed to simulate three circumstances with different contact areas.A nanostripe structure with a period of 576.9 nm and a height of 203.5 nm was fabricated on pure titanium by femtosecond laser *** in liquid attached to the peaks of the nanostripe structure and were stretched on the two adjacent *** with the polished surface,the contact area between bacteria and the nanostripe surface was reduced to 50%,resulting in a reduction(about 50%)in the coverage rate of attached *** addition,the nanostripe surface was a hydrophobic surface with a water contact angle(WCA)of 112.1°,and the surface potential of the nanostripe surface was higher than that of the polished ***,the surface potential and wettability of the nanostripe surface played a minor role in the bacterial adhesion due to the reduced contact *** drying,the attached bacteria on the nanostripe surface sank into the valley region and the contact area was about 40%larger than that on the polished *** lateral strength of bacterial adhesion on nanostripe surfaces was higher than that on polished surfaces,due to the larger contact *** applying a lateral force of 10.0 nN,the percentage of bacteria remaining on the nanostripe surface(31.1%)was higher than that on the polished surface(11.9%).Hence,the bacterial adhesion on the nanopatterned surface was mainly determined by the contact *** in-depth exploration of the relation between bacterial adhesion on the nanopatterned surface and the contact area enables the rational surface designs of biomaterials to regulate bacterial adhesion.
To further enhance the properties of high-entropy alloy (HEAs) and enable its potential applications,we employed a combination approach involving ball milling and induction melting to fabricate in-situ TiC reinforced ...
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To further enhance the properties of high-entropy alloy (HEAs) and enable its potential applications,we employed a combination approach involving ball milling and induction melting to fabricate in-situ TiC reinforced composites within the FeMnNiCo high entropy alloy *** effect of TiC content on the microstructure and mechanical properties of the composites were *** was observed that in-situ formed TiC did not induce any phase transition,maintaining the FCC structure of the high-entropy alloy *** the volume fraction of TiC increased,both the number and size of TiC particles increased,leading to agglomeration in *** introducing 5 vol% of TiC in the composites,a significant enhancement in ultimate tensile strength (609.2 MPa) and yield strength (349.1 MPa),corresponding to a respective increase by 32% and 46% compared to the matrix,was achieved;meanwhile,an elongation value as high as 45% was *** combination of exceptional tensile strength and good plasticity is attributed to synergistic effects from orowan mechanism and solid solution strengthening.
Efficient interfacial charge transfer and robust interfacial interactions are crucial for achieving the superior spatial separation of carriers and developing efficient heterojunction photocatalysts. Herein, BiOBr/AgB...
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The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present ***,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 allo...
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The Al_(2)O_(3)laminated preforms with different layers thickness were prepared by freezing casting in present ***,the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al_(2)O_(3)laminated preform based on pressure infiltration ***,the influence of freezing temperature on the microstructure,mechanical properties and fracture behavior of magnesium-based laminates was *** results indicated that with the decrease of freezing temperature,the thickness of Al_(2)O_(3)layers decreases gradually,the number of layers increases obviously,and the interlayers spacing *** with the decrease of interlayers spacing,the size of Mg17Al12 phase precipitated in the AZ91 alloy layers was refined,and the compression strength and strain were both improved *** micro-cracks initiated in Al_(2)O_(3)layers during loading process,while the AZ91 layers could effectively suppress the initiation and propagation of ***,the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks,which endowed the Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials with better strength and ***,the best compression properties of Al_(2)O_(3p)/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of−50℃,the compression strength and elastic modulus of which were the 160%and 250%of monolithic AZ91 alloy,respectively.
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