查看更多>>摘要：The growth of base-metal-based heterostructures on metal-free carriers is considered an effective strategy for designing low-cost high-efficiency hybrid electrocatalysts with electronic modulation for bifunctional hydrogen evolution reaction(HER)and oxygen evolution reaction(OER),as well as further overall water splitting(OWS).Herein,Ni/Ni3N heterostructures with regulable composition are grown in-situ on N-defective graphitic carbon nitride(g-C3N4)through a novel ammonia-free topochemical self-nitridation route.Benefitting from the synergetic effect between Ni/Ni3N heterointerface and the strong support of g-C3N4 carrier,the as-fabricated Ni/Ni3N/g-C3N4 composite performs superior capacity toward both HER and OER in alkaline conditions.The optimal Ni/Ni3N/g-C3N4 sample requires low overpotentials for HER(55 mV)and OER(253 mV)to drive a current density of 10 mA cm-2,along with long-term durability.Furthermore,the constructed Ni/Ni3N/g-C3N4(+||-)electrolytic cell for alkaline OWS can afford a current density of 10 mA cm-2 under a voltage of 1.556 V with outstanding stability.
查看更多>>摘要：We developed a novel low-activation,ultrafine-grained W-Cr-V multicomponent alloy(MCA)with excel-lent thermal stability and desirable high-temperature strength.The as-sintered W70Cr15V15(at.％)alloy was mainly composed of a body-centered cubic(BCC)solid solution matrix with an average grain size of～0.45 μm,minor hexagonal close-packed(HCP)phase,and ultrafine oxides at grain boundary(GB)regions.The average grain size of the MCA was＜2 μm after heating at 1500 ℃ for 1 h,showing a high thermal stability of the microstructure.Accordingly,the estimated grain growth exponent n(～7)and the corresponding activation energy(～433 kJ mol-1)of the MCA indicate that diffusion during the grain growth in the present W-Cr-V alloy is dominated by the GB diffusion.Such high thermal stability can be mainly attributed to the significant pinning effects from the in-situ formed oxides at GBs.Besides,the nonequilibrium segregation of Cr and V at GBs also contributes to the thermal stability of the alloy at temperatures of 1200 ℃ and below.Furthermore,the average high-temperature compressive strength of the alloy was over 1376 MPa at 1100 ℃,mainly due to the prominent solid solution and GB strengthening which were still effective at the high temperature.The results indicate that the present low-activation W-Cr-V alloy system with exceptional thermal stability and high-temperature mechanical properties could be a promising candidate for structural materials in future fusion reactors.
查看更多>>摘要：In austenitic Mn-steels with low stacking fault energy,the deformation twin is known to play an im-portant role in plastic deformation.Usually,the position grain boundary is preferred to observe and in-vestigate the formation process of the deformation twin,while other suitable formation positions may be neglected.Here,high-resolution transmission electron microscopy is used to observe and characterize the formation of intracrystalline twins in 120Mn13 steel at the early stage of tensile plastic deformation at the atomic scale.The result shows that intracrystalline twins nucleate through overlapping stacking faults generated by three different perfect dislocations dissociating on consecutive {111}-type planes,which is different from twin nucleation mechanisms that have been proposed.Subsequently,they become large-sized intracrystalline twins or twin bands throughout the whole grain by twin nuclei growing themselves and connecting to adjacent twin nuclei or existing twins in the same growth direction.Intracrystalline twins are mainly formed in three positions,namely near the grain boundary,at the end or side of existing twins.The stacking fault sources of intracrystalline twins at different positions are different.
查看更多>>摘要：The application of aramid fiber(AF)/polyetheretherketone(PEEK)composites is currently hindered by the inert surface and poor wettability of AF,resulting in weak interfacial adhesion and poor mechani-cal properties.Surface coating and the introduction of nanostructures have been proven to be effective approaches to address this problem.Herein,a simple hybrid sizing agent has been developed to modify the AF surface,consisting of soluble polyimide(PI)as a compatibilizer,carboxyl-functionalized carbon nanotubes(CNT-COOH)as a rigid unit,and aramid nanofibers(ANF)as a flexible component.The syner-getic effects of Pl and the multiscale flexible-rigid structure(CNT-COOH/ANF)contribute to the formation of chemical and physical bonds between AF and PEEK matrix,further improving the interfacial adhesion and stress transfer efficiency.Attributed to the enhanced wettability and roughness of AF,compared with unsized AF,the flexural strength(220.97 MPa),modulus(13.26 GPa),ILSS(13.36 MPa),and storage modu-lus(12.93 GPa)of the AF/PEEK composite increase by 132.60％,99.00％,18.97％,and 82.70％respectively.Additionally,the flexible-rigid nanonetwork facilitates the penetration of the PEEK resin into pore spaces.This simple and effective approach exhibits promising potential in enhancing the interfacial bonding of AF/PEEK composites.
查看更多>>摘要：Recrystallization annealing is widely used to tailor the microstructure and enhance the performance of cold-deformed metallic materials.However,the underlying recrystallization mechanisms are debated,even with the use of cutting-edge characterization techniques.Here,we develop a Track-Rex toolbox to analyze quasi-in-situ electron backscatter diffraction(EBSD)datasets of two magnesium(Mg)alloys dur-ing static recrystallization via grain correlation.The results show that the recrystallized grains do not always grow;instead,they can shrink or even be consumed.This is attributed to the presence of newly formed recrystallized grains that possess a growth advantage over the old recrystallized grains.The rare earth containing Mg-2.4Zn-0.2Ce wt.％(ZE20)alloy exhibits a higher nucleation activity in the shear bands compared to the commercial Mg-3Al-1 Zn(AZ31)alloy.Regardless of the nucleation timing and sites,re-crystallized grains in the ZE20 alloy show consistent off-basal orientations,serving as the origin of the rare earth texture.Moreover,the off-basal texture of these recrystallized grains is further strengthened through preferential growth during subsequent annealing.On the contrary,the recrystallized grains in the AZ31 exhibit scattered basal orientations that grow uniformly,resulting in a weak basal texture.
Muhammad AbbasKashif HussainNavid Hussain ShahMubashar Ilyas...
160-170页
查看更多>>摘要：Memory catalysis and conventional Fenton reactions are intended to counteract prevailing energy and environmental crises;however,poor performance and the need for UV irradiation question their sustain-ability.Herein,we demonstrate defect-engineered,dual Z-scheme MoS2/WO3-x/Ag2S exhibiting enhanced photo-Fenton(PFR),night-Fenton(NFR),and photocatalytic activities(PR)against tetracycline(TC)and Rhodamine B(RhB).Defects enable the catalyst to store ample electrons just like metals,which play a vi-tal role by exciting H2O2 during Fenton reactions.It removed 91.54％,76.43％,and 83.39％TC(40 mg L-1)in 100 min and registered degradation rate constants of 0.05379,0.02858,and 0.04133 min-1 against RhB(20 mg L-1)during PFR,NFR,and PR respectively.The total organic carbon(TOC)removal rates reached 58.56％and 60.88％during TC and RhB degradations in PFR,respectively.Solid and Liquid EPR analy-sis shows it can excite H2O2 to carry Fenton reactions with and without light.It demonstrates wide pH adaptability and tremendous potential to simultaneously counter energy and environmental crises.
查看更多>>摘要：The endeavor to attain prolonged stability and heightened electromagnetic interference shielding effec-tiveness(EMI SE)in polymer-matrix composites remains an arduous pursuit,particularly when subjected to external mechanical trauma or adverse environmental conditions.In this context,a self-healing and efficient EMI shielding polycaprolactone(PCL)composite with a unique electromagnetic gradient and interface-metalized segregated structure is assembled through layer-by-layer casting and a hot-pressing process.The combined effect of the induction of the electromagnetic gradient layer and the massive mul-tiple interface reflection and scattering from the segregated-like structure results in an exceptional EMI SE of 57.0 dB and a low reflection(R)value of only 0.28.Additionally,the composite boasts impressive photothermal and electrothermal properties,allowing for self-healing under solar irradiation or electri-cal stimulation.Remarkably,this self-healing capability has been demonstrated through five cutting and healing cycles,exhibiting an impressive EMI SE retention rate of 88％.Consequently,the composite with rapid photo/electro-driven self-healing properties will be able to maintain EMI shielding performance.
查看更多>>摘要：Photocatalytic water splitting is a popular pathway for H2 evolution,but the slow water oxidation greatly hampers the overall activity.To harness photogenerated holes in an efficient and lucrative way,the wa-ter oxidation reaction is replaced by selective oxidation of organic compounds to achieve simultaneous production of H2 and value-added chemicals.Herein,an alternative tactic is reported where an organic compound(benzylamine,BA)not only serves as the precursor for N-benzylidene-benzylamine(NBBA)production but also provides hydrogen sources for H2 evolution,achieving the goal under anhydrous conditions.This process is realized using an S-scheme photocatalyst composed of ZnIn2S4 and the UiO-66-NH2(U6N)metal-organic framework(MOF).The S-scheme carrier transfer mechanism was validated by in-situ irradiated X-ray photoelectron spectroscopy(ISI-XPS)and femtosecond transient absorption(fs-TA)spectroscopy.With increased carrier efficiency and reinforced redox power endowed by the S-scheme heterojunction,the composite performed better than ZnIn2S4 and MOF.The performance was further ameliorated by Pt-cocatalyst modification,achieving an H2 production rate of 5275 μmol h-1 g-1 as well as BA conversion of 94.3％with 99.3％NBBA selectivity.Mechanistic studies reveal that BA is ini-tially oxidized to carbon-centered radicals and further to imines along with the release of protons.The imine reacts with another BA molecule to form NBBA,while the protons are reduced to H2.This work provides new insights into concurrent photocatalytic H2 production and selective organic oxidation from organic amines using S-scheme photocatalysts.
查看更多>>摘要：Compared to a cast AlSi10Mg alloy,a laser powder bed fused(LPBF)AlSi10Mg alloy shows superior yield strength and strain hardening capability.However,the underlying microstructure origin has not been comprehensively understood.In this work,the microstructural evolution of an LPBF AlSi10Mg alloy dur-ing tensile deformation was investigated.Synchrotron X-ray diffraction characterization shows that both stress and strain exhibit significant partition between an Al phase and a Si phase upon tensile deforma-tion.This leads to a significant strain gradient between those two phases,which is evident by the high density of dislocations in the cell boundaries of the deformed alloy.The strain gradient results in long-range internal stress,also known as back stress,in the cell boundaries,and in turn leads to enhanced strength and strain hardening in the LPBF AlSi10Mg alloy.Quantitatively analyses via loading-unloading-reloading tests show that during the tensile deformation,the back stress contributes 135 MPa to the yield strength of the alloy,which continuously increases with increasing the strain beyond the yielding point.This work illuminates the microstructural origin of the back stress in the LPBF AlSi10Mg alloy,i.e.the back stress arises from the stress/strain partition between the Al and Si phases in the cellular structures,and the back stress leads to significant strengthening of the alloy upon tensile deformation.This work may also provide guidance for manipulating the mechanical properties of additively manufactured Al-Si alloys for specific application needs.
查看更多>>摘要：Renewable energy-driven water electrolysis is considered as an environmentally friendly hydrogen(H2)production technology.Replacing the oxygen evolution reaction(OER)with the urea oxidation reaction(UOR)is a more effective way to improve the energy efficiency of H2 generation.Herein,a highly effi-cient 2D NiFeMo-based UOR catalyst and 1D NiFeMo-based HER catalyst are prepared by adjusting the concentration of MoO4-.The MoO4-can serve as the key regulator to adjust the balance between the electrolytic dissociation(α)of the reactants and the supersaturation(S)to modulate the morphological and electronic structure.The prepared 2D NiFeMo nanosheet UOR catalyst and 1D NiFeMo nanorod HER catalyst can achieve a current density of 100 mA cm-2 at a potential of 1.36 and 0.062 V,respectively.In a HER/UOR system,a cell voltage of 1.58 V is needed to achieve a current density of 100 mA cm-2.The HER/UOR system operated stably for over 60 h with 3 times the direct water electrolysis current den-sity.Moreover,the in situ Raman characterization coupled with XPS analysis clarifies that the addition of high-valence Mo can lower the transition energy barrier between the low and high oxidation state of Ni,which in turn lowers the overpotential of UOR.This work provides a novel strategy for synthesizing morphology-dependent electrocatalysts for different catalytic systems.
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