A high Li-ion diffusion kinetics in multidimensional and compact-structured electrodes via vacuum filtration casting

Manufacturing process,diffusion co-efficient and areal capacity are the three main criteria for regulating thick electrodes for lithium-ion batteries(LIBs).However,simultaneously regulating these criteria for LIBs is desirable but remains a significant challenge.In this work,niobium pentoxide(Nb_(2)O_(5))anode and lithium iron phosphate(LiFePO_(4))cathode materials were chosen as the model materials and demonstrate that these three parameters can be simultaneously modulated by incorporation of micro-carbon fibers(MCF)and carbon nanotubes(CNT)with both Nb_(2)O_(5) and LFP via vacuum filtration approach.Both as-prepared MNC-20 anode and MLC-20 cathode achieves high reversible areal capacity of≈5.4 m A h cm^(-2)@0.1 C and outstanding Li-ion diffusion coefficients of≈10~(-8)cm~2 s~(-1)in the half-cell configuration.The assembled MNC-20‖MLC-20 full cell LIB delivers maximum energy and power densities of244.04 W h kg^(-1)and 108.86 W kg^(-1),respectively.The excellent electrochemical properties of the asprepared thick electrodes can be attributed to the highly conductive,mechanical compactness and multidimensional mutual effects of the MCF,CNT and active materials that facilitates rapid Li-ion diffusion kinetics.Furthermore,electrochemical impedance spectroscopy(EIS),symmetric cells analysis,and insitu Raman techniques clearly validates the enhanced Li-ion diffusion kinetics in the present architecture.

MD Simulation of Diffusion Behaviors in Collision Welding Processes of Al-Cu, Al-Al, Cu-Cu

To investigate the effects of material combinations and velocity conditions on atomic diffusion behavior near collision interfaces,this study simulates the atomic diffusion behavior near collision interfaces in Cu-Al,Al-Al and Cu-Cu combinations fabricated through collision welding using molecular dynamic(MD)simulation.The atomic diffusion behaviors are compared between similar metal combinations(Al-Al,Cu-Cu)and dissimilar metal combinations(Al-Cu).By combining the simulation results and classical diffusion theory,the diffusion coefficients for similar and dissimilar metal material combinations under different velocity conditions are obtained.The effects of material combinations and collision velocity on diffusion behaviors are also discussed.The diffusion behaviors of dissimilar material combinations strongly depend on the transverse velocity,whereas those of the similar material combinations are more dependent on the longitudinal velocity.These findings can provide guidance for optimizing welding parameters.

3-D FINITE ELEMENT ANALYSIS OF THE EFFECT OF WELDING RESIDUAL STRESS ON HYDROGEN DIFFUSION IN HYDROGEN CONTAINED ENVIRONMENT

The hydrogen distribution of 16MnR steel weldment in hydrogen contained environment was calculated using the finite element method （ FEM）. The effect of welding residual stress on hydrogen diffusion has been discussed using a 3-D sequential coupling finite element analysis procedure complied by Abaqus code. The hydrogen diffusion coefficient in weld metal, the heat affected zone （HAZ）, and the base metal of the 16MnR steel weldment were measured using the electrochemical permeation technique. The hydrogen diffusion without the effect of stress was also calculated and compared. Owing to the existence of welding residual stress, the hydrogen concentration was obviously increased and the hydrogen wouM diffuse and accumulate in the higher stress region.

Influence of Interfacial Diffusion on Mechanical Property of Vacuum Fusion Sinter (VFS) WC-Co Composite Coating

The WC-Co composite coatings bonded tightly to steel substrate have been made by vacuum fusion sinter （VFS）. The concentration distribution of some components were measured by the electron probe, and the microstructure and morphology of VFS coatings were observed and analyzed by SEM, X-ray diffractometer and microhardness tester. Diffusion coefficient of every element was calculated by using the experimental results. The influence of the interracial diffusion on the microstructure, Vickers hardness and interracial bond strength of the VFS coatings was studied in detail. The experimental results show that there is a metallurgical bond area between the VFS WC-Co coatings and the steel substrate. The VFS coatings are characterized by the gradient hardness of the interface and the high bond strength to the steel substate, both of which are beneficial to the improvement of the wear resistance and corrosion resistance.

STUDY ON DIFFUSION WELDING OF ALUMINIUN MATRIX COMPOSITE

Effects of diffusion welding parameters on strength of welded joint based on particle reinforced alumini- um matrix composite Al2O3p/6061Al were studied by comparing with aluminium matrix alloy,Mecha- nism for the loss of joint strength was analyzed.It was pointed out that the key processing parameters affecting the strength of joint was the welding temperature.The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

Predicting effects of diffusion welding parameters on welded joint properties by artificial neural network

The static model for metal matrix composites in diffusion welding was established by means of artificial neural network method. The model presents the relationship between weld joint properties and welding parameters such as welding temperature, welding pressure and welding time. Through simulating the diffusion welding process of SiC w/6061Al composite, the effects of welding parameters on the strength of welded joint was studied and optimal technical parameters was obtained. It is proved that this method has good fault tolerant ability and versatility and can overcome the shortage of the general experiment. The established static model is in good agreement with the actual welding process, so it becomes a new path for studying the weldability of new material.

Si diffusion behavior during laser welding-brazing of Al alloy and Ti alloy with Al-12Si filler wire

In laser welding-brazing of Al alloy (5A06) and Ti alloy (Ti-6Al-4V) with rectangular CO2 laser spot and with Al-12Si filler wire, element Si enriches at the interface between Ti substrate and the filler metal. It is found that the Si diffusion behavior has a significant effect on the formation of interfacial intermetallic compounds. To analyze the Si diffusion behavior, a model for the prediction of the chemical potential for ternary alloy was established. According to the calculated results of the influence of the element content and temperature in Ti-Al-Si system on Si chemical potential, the diffusion behavior of Si element was analyzed for Ti dissolution and melting mode, which presents a good agreement with the experimental data. Further, formation mechanism of the interfacial intermetllic compound was clarified.

Effect of Welding Paramenter on Joint Property of Aluminum Matrix Composite in Liquid-Phase-Impacting Diffusion Welding

In this paper, a new method for welding SiCp/101A was put forward. It is LPI (liquid-phase-impacting) diffusionwelding. Through LPI diffusion welding SiCp/101A aluminum, the effect of welding parameters on the weldedjoint property was investigated, and the optimal welding parameters were brought forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope in order to studythe relationship between the macro-properties of joint and the microstructure. The results show that LPI diffusionwelding could be used for welding aluminum matrix composites SiCp/101A successfully.

Atomic diffusion across Ni_(50)Ti_(50)Cu explosive welding interface:Diffusion layer thickness and atomic concentration distribution

Molecular dynamics simulations are carried out to study atomic diffusion in the explosive welding process of NisoTis0-Cu （at.%）. By using a hybrid method which combines molecular dynamics simulation and classical diffusion the- ory, the thickness of the diffusion layer and the atomic concentration distribution across the welding interface are obtained. The results indicate that the concentration distribution curves at different times have a geometric similarity. According to the geometric similarity, the atomic concentration distribution at any time in explosive welding can be calculated. NisoTis0- Cu explosive welding and scanning electron microscope experiments are done to verify the results. The simulation results and the experimental results are in good agreement.

Liquid-Phase-Impacting Diffusion Welding Mechanism and Microstructure of Welded Joint of Al Matrix Composite SiCp/101A

The liquid-phase-impacting (LPI) diffusion welding mechanism and microstructure of welded joint of aluminum matrixcomposite SiCp/101A have been studied. It shows that by LPl diffusion welding, the interface state between SiCparticle and matrix is prominent, the harmful microstructure or brittle phase can be restrained from the welded joint.Moreover, the density of dislocation in the matrix near the interface and in the matrix are all so higher than that ofparent composite, the dislocation entwists each other intensively resulted in welding the composite successfully.

EFFECTS OF DIFFUSION WELDING PARAMETERS ON JOINT STRENGTH OF SiCw/6061AI COMPOSITE

Diffusion welding was used to join SiCw/6061AI composites. The effects of welding pammeters on strength Of welded joint were investigated. JOint Of high quality for SiCw/6061Al composites can be obtained with aPPropriate diffesion welding parameters.

Study on diffusion welding SiCp/ZL101 with Cu interlayer

Through the vacuum diffusion welding SiCp/ZL 101 aluminum with Cu interlayer,the effect of welding parameter and the thickness of Cu on the welded joint property wasinvestigated, and the optimal welding parameters were put forward at the same time. Themicrostructure of joint was analyzed by means of optical-microscope, scanning electron microscope inorder to study the relationship between the macro-properties of joint and the microstructure. Theresults show that diffusion welding with Cu interlayer could be used for welding aluminum matrixcomposites SiCp/ZL 101 successfully.

MECHANICAL PROPERTIES OF Si_3N_4/METAL DIFFUSION WELDING TIP

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Study on Diffusion Welding Parameters of Particle reinforced Aluminium Matrix Composite Al_2O_(3p) /6061Al

Effects of diffusion welding process parameters on strength of welded joint based on particle reinforced aluminium matrix composite Al 2O 3p /6061Al have been studied through comparing with aluminium matrix alloy. The mechanism for loss of joint strength has been analyzed. It should be pointed out that key processing parameters affecting the strength of joint was welding temperature. The high quality joint can be successfully obtained with appropriate diffusion welding parameters.

Study on process and mechanism of superplastic diffusion bonding of dissimilar steels

The probability, main effect factors and diffusion theory of structural superplastic diffusion bonding of W6Mo5Cr4V2/45 steel have been observed and analyzed by means of tensile test at the room temperature, scanning electron microscope and microhardness test. Results show that after fine graining treatment and short time superplastic pressing formation under the conditions of superplastic temperature and strain rate, W6Mo5Cr4V2/45 specimens can achieve solid state diffusion bonding and the property of welded area is the same as the other parts in the specimen. The diffusion path of carbon element is intergranular and of dislocation.

Microstructure in the Weld Metal of Austenitic-Pearlitic Dissimilar Steels and Diffusion of Element in the Fusion Zone

Microstructure and alloy element distribution in the welded joint between austenitic stainless steel (1Cr18Ni9Ti) and pearlitic heat-resistant steel (1Cr5Mo) were researched by means of light microscopy, scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Microstructure, divisions of the fusion zone and elemental diffusion distributions in the welded joints were investigated. Furthermore, solidification microstructure and S-ferrite distribution in the weld metal of these steels are also discussed.

Interfacial Microstructure and Properties of Ti(C, N)/Ni Bonded by Transient Liquid-phase Diffusion

Effects of the main process parameters（temperature and time） on microstructure and properties of Ti（C, N）/Ni interface bonded by （Cu＋Nb） interlayer in a vacuum diffusion bonding device were investigated. The interfacial microstructures consisted initially of Ni3Nb metallic compound and eutectic of Ni3Nb ＋ CuNiss, and finally transformed to （Ti, Nb） （C, N）＋Ni3Nb near Ti （C, N） and NiCuss ＋ Ni3Nb near Ni when diffusion bonding temperature was 1 523-1 573 K. It was clear that Cu was a constituent in the transient liquid phase （TLP） into which Ni was dissolved by forming Cu-Ni transition liquid. Nb was dissolved in Cu-Ni transition liquid rapidly. Ti （C, N） conld be wetted by resultant Ni-Nb-Cu transient liquid phase which was followed by a little （Ti, Nb） （C, N） solid solution formed at interface. This increased the interface combining capability. Ultimately the interface shear strength was able to reach 140 MPa. The theoretle analysis and experimental results show that the growth of interfacial reaction layer Ni3Nb accords with parabola law, and the activation energy of diffusion reaction is 115.0±0.5 kJ/mol, while the diffusion reaction speed constant is 12.53 mm/s^1/2.

Thermal Diffusion in Masson Pine Wood

In order to analyze the effects of the temperature gradient on moisture movement during the highly intensive microwave-vacuum drying, thermal diffusion of Masson pine wood was studied. Internal distribution of temperature and moisture in Masson pine samples sealed by epoxy resin and aluminum foil was measured, the magnitude of thermal diffusion was calculated and the influencing factors of thermal diffusion were discussed. Results showed that with the transfer of moisture toward the low temperature in wood, opposite temperature and moisture gradient occurred. The initial moisture content （MC）, temperature and time are important factors affecting this process; the thermal diffusion is in proportion to wood temperature, its initial moisture and time. The temperature and distance from hot surface is strongly linearly correlated, and the relationship between MCs at different locations and distance from the hot end surface changes from logarithmically form to exponentially form with the increase in experimental time.

Changing Rule of Carbon-Enriched Zone and Diffusion Behavior of Carbon in Aging 0Cr6Mn13Ni10MoTi/1Cr5Mo Dissimilar Welded Joints

The microstructures, the changing rule of carbon-enriched zone, the diffusion behaviors of elements C and Cr, and thecarbide type of 0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints after aging at 500℃ for various times and afterlong-term service in technical practice were investigated by using the optical microscopy electron probe microanalysis,scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results show that in aging0Cr6Mn13Ni10MoTi/1Cr5Mo dissimilar welded joints, the main carbides are M_3C and a few carbides are M_7C_3 andM_(23)C_6. The M_3C carbide decomposition and dissolution with increasing aging time or aging temperature and theanti-diffusion of C and Cr cause the decrease and disappearance of the carbon-enriched zone. The results are differentfrom those of the A302/1Cr5Mo dissimilar welded joints in previous studies.

AGE STRENGTHENING OF DIFFUSION WELDED JOINT OF Al_2O_(3p)/6061Al COMPOSITE

Tensile strength of diffusion welded joint of aluminum matrix composite is very low due to its poor weld- ability.In this paper, solution and age treatments were conducted on the welded joint of Al2O3p/ 6061Al composite subjected to diffusion welding using Gleeble 1500 machine, and ensile strength and microstructure of welded joint aged at175℃ were measured and analyzed respectively, Results showed that aging precipitation of welded joint is promoted effectively because of redistribution of reinforcement and a few number of dislocations in the matrix of weld zone resulting from welding pressure,and hence tensile strength of welded joint is increased significantly after aging treatment.