Interfacial coordination bonds accelerate charge separation for unprecedented hydrogen evolution over S-scheme heterojunction

Inspired by natural photosynthesis,fabricating high-performance S-scheme heterojunction is regarded as a successful tactic to address energy and environmental issues.Herein,NH_(2)-MIL-125(Ti)/Zn_(0.5)Cd_(0.5)S/NiS(NMT/ZCS/NiS)S-scheme heterojunction with interfacial coordination bonds is successfully synthesized through in-situ solvothermal strategy.Notably,the optimal NMT/ZCS/NiS S-scheme heterojunction exhibits comparable photocatalytic H_(2)evolution(PHE)rate of about 14876.7μmol h^(−1)g^(−1)with apparent quantum yield of 24.2%at 420 nm,which is significantly higher than that of recently reported MOFs-based photocatalysts.The interfacial coordination bonds(Zn–N,Cd–N,and Ni–N bonds)accelerate the separation and transfer of photogenerated charges,and the NiS as cocatalyst can provide more catalytically active sites,which synergistically improve the photocatalytic performance.Moreover,theoretical calculation results display that the construction of NMT/ZCS/NiS S-scheme heterojunction also optimize the binding energy of active site-adsorbed hydrogen atoms to enable fast adsorption and desorption.Photoassisted Kelvin probe force microscopy,in-situ irradiation X-ray photoelectron spectroscopy,femtosecond transient absorption spectroscopy,and theoretical calculations provide sufficient evidence of the S-scheme charge migration mechanism.This work offers unique viewpoints for simultaneously accelerating the charge dynamics and optimizing the binding strength between the active sites and hydrogen adsorbates over S-scheme heterojunction.

Rational design of interfacial bonds within dual carbon-protected manganese oxide towards durable aqueous zinc ion battery

Manganese-based cathode materials are promising candidates for aqueous zinc ion batteries(AZIBs)by reason of their low cost and high energy density.However,their practical applicability is hampered by the intrinsic defects of poor electrical conductivity,sluggish reaction kinetics,and severe structural deterioration.Herein,we constructed a hierarchically porous structure composed of carbon-encapsulated Mn O nanoparticles(MOC)and three-dimensional(3D)nitrogen-doped graphene aerogel(NGA)(denoted as MOC@NGA).The hybrid was synthesized by a facile in-situ coprecipitation and annealing of manganesebased metal-organic framework(Mn-MOF74)and NGA composite(Mn-MOF74@NGA).Specifically,the carbon shells inherited from organic ligand of Mn-MOF74 could restrain the volume changes of Mn O,and the porous NGA prevented the agglomeration of MOC nanoparticles and enriched the types of interfacial chemical bonds.Profiting from the synergistic effect of rich interface chemical bonds and dual-carbon protection,the MOC@NGA hybrids exhibit fast interfacial electron/charge transfer and transport,and outstanding structural stability.Therefore,MOC@NGA cathode delivers an excellent rate performance(270 and 99.8 m Ah g^(-1)at 0.1 and 2.0 A g^(-1))and maintains an excellent specific capacity of 151.6 m Ah g^(-1)after 2,000cycles at 1.0 A g^(-1).Moreover,the fabricated MOC@NGA-based quasi-solid-state battery not only achieves outstanding flexibility but also displays impressive cycling stability,demonstrating a promising potential for portable and flexible equipment.This work provides a feasible strategy for the fabrication of the bridging structure of manganese-based oxides and porous carbon matrix for high-specific capacity and durable AZIBs cathodes.

Metal-free two-dimensional phosphorene-based electrocatalyst with covalent P-N heterointerfacial reconstruction for electrolyte-lean lithium-sulfur batteries

The use of lithium-sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes.Two-dimensional(2D)few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium-sulfur battery electrocatalysts,which,however,have limitations of restricted catalytic activity and poor electrochemical/chemical stability.To resolve these issues,we developed a multifunctional metal-free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen-doped carbon-coated multiwalled carbon nanotubes(denoted c-FBP-NC).The experimental characterizations and theoretical calculations show that the formed polarized P-N covalent bonds in c-FBP-NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides,thus alleviating the shuttle effect.Meanwhile,the robust 1D-2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer.Impressively,with c-FBP-NC as the sulfur host,the battery shows a high areal capacity of 7.69 mAh cm^(−2) under high sulfur loading of 8.74 mg cm^(−2) and a low electrolyte/sulfur ratio of 5.7μL mg^(−1).Moreover,the assembled pouch cell with sulfur loading of 4 mg cm^(−2) and an electrolyte/sulfur ratio of 3.5μL mg^(−1) shows good rate capability and outstanding cyclability.This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry,demonstrating great potential in lithium-sulfur batteries.

Effects of Fe-Al intermetallic compounds on interfacial bonding of clad materials

The growth of intermetallic compounds at the interface between solid Al and Fe and the effects of intermetallic compound layers on the interfacial bonding of clad materials were investigated. The results showed that the interface between the solid Fe and Al formed by heat-treatment consisted of Fe2Al5 and FeAl3 intermetallic compound layers, which deteriorated the interfacial bonding strength. Fractures occurred in the intermetallic compound layer during the shear testing. The location of the fracture depended on the defects of microcracks or voids in the intermetallic compound layers. The microcracks in the intermetallic compound layer were caused by the mismatch of thermal expansion coefficients of materials during cooling, and the voids were consistent with the Kirkendall effect. The work will lay an important foundation for welding and joining of aluminum and steel, especially for fabrication of Al-Fe clad materials.

Recent Advances in Interface Modification of Cu/graphite Composites and Layered Ternary Carbides of Modified Layer Candidate

We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.

INTERFACIAL BONDING IN AS DEPOSITED AND ANNEALED Co/C SOFT X RAY MULTILAYER MIRRORS

Interfacial bonding in as deposited and annealed Co/C soft X ray multilayer structures is investigated by X ray photo electron spectroscopy (XPS).It is found that there is interdiffusion between cobalt and carbon in the as deposited Co/C multilayers,and this is confirmed by structure characterization using low angle X ray diffraction (LAXD).The calculation of the chemical shifts in Co C system based on Miedemas macroscopic atom model suggests that it is impossible to detect the chemical shift experimentally in the Co C compound,which is consistent with the XPS results.The presence of metallic carbide bonding is evidenced through the nature of the carbon bonding in survey taken at Co C and C Co interfaces of annealed samples.Our results also indicate that XPS is a direct method to probe the chemical bonding at the interfaces.

Selective interfacial bonding and thermal conductivity of diamond/Cu-alloy composites prepared by HPHT technique

Cu-based and Cu-alloy-based diamond composites were made by high-pressure-high-temperature （HPHT） sintering with the aim of maximizing the thermal conductivity of the composites. Improvements in interfacial bonding strength and thermo-physical properties of the composites were achieved using an atomized copper alloy with minor additions of Co, Cr, 13, and Ti. The thermal conductivity （TC） oh- mined exhibited as high as 688 W.m-1.K-1, but also as low as 325 W.m-1.K-l. A large variation in TC can be rationalized by the discrepancy of diamond-matrix interfacial bonding. It was found from fractography that preferential bonding between diamond and the Cu-alloy matrix occurred only on the diamond {100} faces. EDS analysis and Raman spectra suggested that selective interfacial bonding may be attributed to amorphous carbon increasing the wettability between diamond and the Cu-alloy matrix. Amorphous carbon was found to significantly affect the TC of the composite by interface modification.

Interfacial microstructure and mechanical behavior of Mg/Cu bimetal composites fabricated by compound casting process

Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated.It is found that a good metallurgical bonding can be achieved at the interface of Mg and Cu,which consists of two sub-layers,i.e.,layer I with 30μm on the copper side composed of Mg2Cu matrix phase, on which a small amount of dendritic MgCu2 phase was randomly distributed;layerⅡ with 140μm on the magnesium side made up of the lamellar nano-eutectic network Mg2Cu+(Mg) and a small amount of detached Mg2Cu phase. The average interfacial shear strength of the bimetal composite is measured to be 13 MPa.This study provides a new fabrication process for the application of Mg/Cu bimetal composites as the hydrogen storage materials.

A novel method to improve interfacial bonding of compound squeeze cast Al/Al-Cu macrocomposite bimetals:Simulation and experimental studies

A facile and innovative method to improve bonding between the two parts of compound squeeze cast Al/Al-4.5 wt.%Cu macrocomposite bimetals was developed and its effects on microstructure and mechanical properties of the bimetal were investigated.A special concentric groove pattern was machined on the top surface of the insert(squeeze cast Al-4.5 wt.%Cu) and its effects on heat transfer,solidification and distribution of generated stresses along the interface region of the bimetal components were simulated using ProCAST and ANSYS softwares and experimentally verified. Simulation results indicated complete melting of the tips of the surface grooves and local generation of large stress gradient fields along the interface. These are believed to result in rupture of the insert interfacial aluminum oxide layer facilitating diffusion bonding of the bimetal components. Microstructural evaluations confirmed formation of an evident transition zone along the interface region of the bimetal. Average thickness of the transition zone and tensile strength of the bimetal were significantly increased to about 375 μm and 54 MPa, respectively, by applying the surface pattern.The proposed method is an affordable and promising approach for compound squeeze casting of Al-Al macrocomposite bimetals without resort to any prior cost and time intensive chemical or coating treatments of the solid insert.

Predicting and controlling interfacial microstructure of magnesium/aluminum bimetallic structures for improved interfacial bonding

In this study,an overcasting process followed by a low-temperature(200°C)annealing schedule has been developed to bond magnesium to aluminum alloys.ProCAST software was used to optimize the process parameters during the overcasting process which lead to Mg/Al bimetallic structures to be successfully produced without formation of Mg-Al intermetallic phases.Detailed microstructure evolution during annealing,including the formation and growth of Al-Mg interdiffusion layer and intermetallic phases(Al12Mg17 and Al3Mg2),was experimentally observed for the first time with direct evidence,and predicted using Calculation of Phase Diagrams(CALPHAD)modeling.Maximum interfacial strength was achieved when the interdiffusion layer formed at the Mg/Al interface reached a maximum thickness the without formation of brittle intermetallic compounds.The precise diffusion modeling of the Mg/Al interface provides an efficient way to optimize and control the interfacial microstructure of Mg/Al bimetallic structures for improved interfacial bonding.

Abnormal interfacial bonding mechanisms of multi-material additive-manufactured tungsten-stainless steel sandwich structure

Tungsten(W)and stainless steel(SS)are well known for the high melting point and good corrosion resistance respectively.Bimetallic W-SS structures would offer potential applications in extreme environments.In this study,a SS→W→SS sandwich structure is fabricated via a special laser powder bed fusion(LPBF)method based on an ultrasonic-assisted powder deposition mechanism.Material characterization of the SS→W interface and W→SS interface was conducted,including microstructure,element distribution,phase distribution,and nano-hardness.A coupled modelling method,combining computational fluid dynamics modelling with discrete element method,simulated the melt pool dynamics and solidification at the material interfaces.The study shows that the interface bonding of SS→W(SS printed on W)is the combined effect of solid-state diffusion with different elemental diffusion rates and grain boundary diffusion.The keyhole mode of the melt pool at the W→SS(W printed on SS)interface makes the pre-printed SS layers repeatedly remelted,causing the liquid W to flow into the sub-surface of the pre-printed SS through the keyhole cavities realizing the bonding of the W→SS interface.The above interfacial bonding behaviours are significantly different from the previously reported bonding mechanism based on the melt pool convection during multiple material LPBF.The abnormal material interfacial bonding behaviours are reported for the first time.

Interfacial bonding characteristics and mechanical properties of H68/AZ31B clad plate

Interfacial bonding,microstructures,and mechanical properties of an explosively-welded H68/AZ31B clad plate were systematically studied.According to the results,the bonding interface demonstrated a“wavy-like”structure containing three typical zones/layers:(1)diffusion layer adjacent to the H68 brass plate;(2)solidification layer of melted metals at the interface;(3)a layer at the side of AZ31B alloy that experienced severe deformation.Mixed copper,CuZn_(2),andα-Mg phases were observed in the melted-solidification layer.Regular polygonal grains with twins were found at the H68 alloy side,while fine equiaxed grains were found at the AZ31B alloy side near the interface due to recrystallization.Nanoindentation results revealed the formation of brittle intermetallic CuZn_(2) phases at the bonding interface.The interface was bonded well through metallurgical reactions due to diffusion of Cu,Zn,and Mg atoms across the interface and metallurgic reaction of partially melted H68 and AZ31B alloys.

Effect of Interfacial Bonding on the Toughening of Al_2O_3/Ni Ceramic Matrix Composites

The main Iimitation to the toughening of the α-Al2O3/Ni composite is the poor bonding atthe interface. which causes the nickel particles to be pulled-out during crack propagation with-out obvious plastic deformation. A proper control of oxygen content at the Al2O3-Ni interfacecan promote wetting at the intedece, and produce a mechanically interlocked and chemically strengthened intedece, causing most of the nickel particles to be stretched to failure and to expe-rience severe plastic deformation during crack propagation in the composite. Fracture toughnesstesting using a modified double cantilever beam method with in situ observation of crack prop-agation in a scanning electron microscope shows that the composite with the strengthenedinterface has a more desirable R-curve behaviour and a higher fracture toughness value than thenormal composite.

超高性能混凝土钢纤维-基体界面黏结性能研究综述

超高性能混凝土(UHPC)是一种相对较新的水泥混凝土复合材料,由于其优异的机械强度和耐久性,在基础设施建设中具有巨大的应用潜力。钢纤维与基体的界面黏结性能是决定UHPC其他力学性能的主要因素,包括抗拉、抗折、抗压强度和破坏模式(断裂行为)。本文通过讨论并比较多种纤维拉拔测试方法和分析模型,全面综述了UHPC的纤维-基体黏结行为的研究进展;详细确定并讨论了影响纤维-基体黏结的参数,包括纤维的几何形状和方向、表面处理、基体的组成和强度。最后,基于现有研究,对未来UHPC增强方法和测试细节提出了建议。

Nanofiber Composite Reinforced Organohydrogels for Multifunctional and Wearable Electronics

Composite organohydrogels have been widely used in wearable electronics.However,it remains a great challenge to develop mechanically robust and multifunctional composite organohydrogels with good dispersion of nanofillers and strong interfacial interactions.Here,multifunctional nanofiber composite reinforced organohydrogels(NCROs)are prepared.The NCRO with a sandwich-like structure possesses excellent multi-level interfacial bonding.Simultaneously,the synergistic strengthening and toughening mechanism at three different length scales endow the NCRO with outstanding mechanical properties with a tensile strength(up to 7.38±0.24 MPa),fracture strain(up to 941±17%),toughness(up to 31.59±1.53 MJ m~(-3))and fracture energy(up to 5.41±0.63 kJ m~(-2)).Moreover,the NCRO can be used for high performance electromagnetic interference shielding and strain sensing due to its high conductivity and excellent environmental tolerance such as anti-freezing performance.Remarkably,owing to the organohydrogel stabilized conductive network,the NCRO exhibits superior long-term sensing stability and durability compared to the nanofiber composite itself.This work provides new ideas for the design of high-strength,tough,stretchable,anti-freezing and conductive organohydrogels with potential applications in multifunctional and wearable electronics.

Construction of interfacial dynamic bonds for high performance lignin/polymer biocomposites

Lignin is the largest natural aromatic biopolymer,but usually treated as industrial biomass waste.The development of lignin/polymer biocomposites can promote the high value utilization of lignin and the greening of polymers.However,the weak interfacial interaction between industrial lignin and polymer induces poor compatibility and serious agglomeration in polymer owing to the strong intermolecular force of lignin.As such,it is extremely difficult to prepare high performance lignin/polymer biocomposites.Recently,we proposed the strategy of in situ construction of interfacial dynamic bonds in lignin/polymer composites.By taking advantage of the abundant oxygen-containing polar groups of lignin,we inserted dynamic bonding connection such as hydrogen bonds and coordination bonds into the interphase between lignin and the polymer matrix to improve the interfacial interactions.Meanwhile,the natural amphiphilic structure characteristics of lignin were utilized to construct the hierarchical nanophase separation structure in lignin/polymer composites.The persistent problems of poor dispersity and interfacial compatibility of lignin in the polymer matrix were effectively solved.The lignin-modified polymer composites achieved simultaneously enhanced strength and toughness.This concise review systematically summarized the recent research progress of our group toward building high-performance lignin/polymer biocomposites through the design of interfacial dynamic bonds(hydrogen bonds,coordination bonds,and dynamic covalent bonds)between lignin and different polymer systems(polar plastics,rubber,polyurethane,hydrogels,and other polymers).Finally,the future development direction,main challenges,and potential solutions of lignin application in polymers were presented.

Simultaneously improving fabrication accuracy and interfacial bonding strength of multi-material projection stereolithographybymulti-step exposure

Multi-material additive manufacturing(MMAM)takes full advantage of the ability to arbitrarily place materials of addi-tive manufacturing technology,enabling immense design free-dom and functional print capabilities.Among MMAM technologies,projection stereolithography(PSL)exhibits a great balance of high resolution and fast printing speed.However,fabrication accuracy of multi-material PSL is hin-dered by large overcure used to strengthen interfacial bond-ing weakened by chemical affinity and material-exchange process.We present a novel multi-step exposure method for multi-material PSL process to overcome this shortcoming.Firstly,the whole layer is moderately exposed producing over-cure of single-material PSL level to generate geometries.Then weakened interfaces are strengthened individually with addi-tional steps of exposure.The multi-step exposure is integrated into the already efficient materials printing order of multi-material PSL process.Curing depth and overcure of photocur-able resins are modeled and characterized.Exposure required to achieve sufficient interfacial bonding of single-material interfaces built through material-exchange process and multi-material interfaces with altering materials printing order is determined with tensile tests.Microfluidic channels are used to compare fabrication accuracy of traditional single-step exposure and our multi-step exposure method.This method can be widely applied in multi-material PSL to improve fabri-cation accuracy in a variety of applications including micro-fluidic devices.

Static and dynamic mechanical behaviour of ECO-RPC

Ecological reactive powder concrete (ECO-RPC) with small sized and differentvolume fraction steel fibers was prepared by substitution of ultra-fine industrial waste powder for50% to 60% cement by weight and replacement of ground fine quartz sand with natural fine aggregate.The effect of steel fiber volume fraction and curing ages on the static mechanical behaviour ofECO-RPC was studied. Using the split Hopkinson pressure bar technique, the dynamic mechanicalbehaviour of ECO-RPC was investigated under different strain rates. The results show that the staticmechanical behaviour of ECO-RPC increases with the increase of steel fiber volume fraction andcuring ages. The type of ECO-RPC with the substitution of 25% ultra-fine slag, 25% ultra-fine flyash and 10% silica fume is better than the others with compressive strength, flexural strength, andfracture energy more than 200 MPa, 60 MPa and 30 kJ/m^2, respectively. ECO-RPC has excellent strainrate stiffening effects under dynamic load. Its peak stress, peak strain and the area understrain-stress curve increase with the increase of strain rate. Its fracture pattern changes frombrittleness to toughness under high strain rates.

Preparation and characterization of different surface modified SiCp reinforced Al-matrix composites

The effects of SiCp surface modifications(Cu coating,Ni coating and Ni/Cu coating)on the microstructures and mechanical properties of Al matrix composites were investigated.Surface modification of SiC particles with Cu,Ni and Cu/Ni,respectively,was carried out by electroless plating method.SiCp/Al composites were prepared by hot pressed sintering followed by hot extrusion.The results show that the surface modification of SiC particles plays an effective role,which is relative to the type of surface coating,and the interfacial bonding become stronger in the following order:untreated SiCp<Ni(Cu)-coated SiCp<Ni/Cu-coated SiCp.The Ni/Cu-coated SiCp/Al composites exhibit the best comprehensive mechanical properties,with ultimate tensile strength(σUTS)and fracture strain(εf)of 389 MPa and 6.3%,respectively.Compared with that of untreated-SiCp/Al composites,theσUTS andεf are enhanced by 19.3%and 57.5%.

First-principles investigation on stability and electronic structure of Sc-dopedθ′/Al interface in Al−Cu alloys

The properties of Sc-dopedθ′(Al_(2)Cu)/Al interface in Al−Cu alloys were investigated by first-principles calculations.Sc-doped semi-coherent and coherentθ′(Al_(2)Cu)/Al interfaces(Sc doped in Al slab(S1 site),Sc doped inθ′slab(S2 site))were modeled based on calculated results and reported experiments.Through the analysis of interfacial bonding strength,it is revealed that the doping of Sc at S1 site can significantly decrease the interface energy and increase the work of adhesion.In particular,the doped coherent interface with Sc at S1 site which is occupied by interstitial Cu atoms has very good bonding strength.The electronic structure shows the strong Al—Cu bonds at the interfaces with Sc at S1 site,and the Al—Al bonds at the interfaces with Sc at S2 site are formed.The formation of strong Al—Cu and Al—Al bonds plays an important role in the enhancement of doped interface strength.