- Ei，ESCI收录期刊
- 中国科学引文数据库(CSCD)核心期刊
- 中文核心期刊
- 文摘与引文数据库(Scopus)
- 剑桥科学文摘(CSA)
Based on different high-entropy alloys (HEAs) systems, the latest research progress in additive manufactured high-entropy alloys was reviewed. The rapid solidification microstructure, segregation and precipitation behaviors of high-entropy alloys fabricated by additive manufacturing with different compositions were described. Especially, the analysis was focused on the mechanical properties, deformation and strengthening mechanisms. It was pointed out that the appropriate additive manufacturing process should be selected for different high-entropy alloy systems, and the influencing factors of forming quality need to be further studied. Finally, it was proposed that high-entropy alloys with both excellent strength and high plasticity can be developed and prepared by additive manufacturing technology.
With the rapid development of electric vehicles, people have higher requirement for the energy density and lifespan of power batteries. The cycle performance and rate performance of lithium-ion batteries can be effectively improved through the modification of the positive and negative active materials, the application of new conductive agents and binders, and the optimized design of the electrode group distribution ratio. However, the problems caused by the preparation process of the traditional electrode and the characteristics of the single-layer electrode structure put a limit on the further improvement of the performance of the lithium-ion battery. Therefore, solving the problems of the traditional single-layer electrode structure itself is an important direction of lithium-ion battery research. Three solutions to solve the problems of the single-layer electrode structure by analyzing the related research on the multilayer composite electrode structure were summarized in this paper which are increasing the stability of the electrode surface, increasing the conductivity of the electrode surface and adjusting the internal component distribution of the electrode, and they have their own advantages.By analyzing the characteristics and limitations of different schemes and preparation processes, new directions and ideas for electrode design and engineering application of lithium-ion batteries and other battery systems were proposed in this paper. Finally, the current research status of the multilayer composite electrode structure was summarized in this paper.
With the development of electronic information technology and people's pursuit of convenient life, smart flexible wearable devices have attracted the attention of many scholars. In the development of smart wearable devices, flexible conductive materials play a vital role. As the most basic flexible conductive textile material, conductive yarn is widely used in smart wearable products. However, most traditional textile materials are insulating materials and cannot directly form conductive yarns and smart wearable products. The preparation methods and application research progress of metal-based conductive yarns, carbon-based conductive yarns, and conductive polymer-based conductive yarns, as well as the application research progress in wearable strain sensors, wearable supercapacitors, wearable electric heating devices and other aspects were introduced. The problems that need to be solved in the research of conductive yarns in recent years were analyzed, mainly including improving the conductivity, flexibility and environmental stability of conductive yarns. In addition, in view of the convenience, comfort, washing durability, and sensitivity required by smart wearable devices, it was proposed that the sensitivity, durability of flexible conductive yarn and the combination of textile materials and conductive materials have become the main development of wearable flexibles smart product.
The oil/water mixture is sepearated and then treated, it can not only realize the reuse of oil and water resources, but also effectively avoid the environmental pollution caused by directly discharging. Therefore, it is particularly important to do research on the materials, which is used to separate the oil/water mixture for saving resources and protecting the environment. Among them, the special wettable nanofiber membranes with superhydrophobic/superoleophilic or superhydrophilic/superoleophobic have attracted substantial attention in the application research of oil/water separation. In this review, the theoretical basis of special wettability and the applications of electrospinning nanofiber membranes were described. The research progress of special wettable nanofiber membrane materials in oil/water separation field was summarized. Finally, it was pointed out that in the oil-water separation process, the fine microstructure on the special wettability nanofiber membranes is easily damaged by mechanical damage and chemical pollution, which greatly limits its applications in oil-water separation. At the same time, the future of the special wettable nanofiber membrane materials was briefly discussed.
SnO2 nanorods were grown on two kinds of seed layers formed from SnCl2·2H2O and SnO2 nanoparticles precursors, respectively, and used as one-dimensional electron transport materials to fabricate perovskite solar cell (PSCs). Effects of the seed layers on morphology, structure, optical properties of SnO2 nanorods and perovskite films, charge transfer at SnO2/perovskite interfaces as well as device performance were investigated by utilizing field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet-visible-near infrared spectroscopy(UV-vis), steady-state photoluminescence spectroscopy (PL) and volt-ampere characteristic curves (J-V). The results show that more dense seed layers can be formed from SnO2 nanoparticles and SnO2 nanorods films formed from SnO2 nanoparticles are more smooth and uniform relative to those grown from SnCl2·2H2O. The perovskite films deposited on the former show better crystallization quality and higher light absorption. The maximum efficiency of the device based on the SnO2 nanorods is 12.93%. This work demonstrates that SnO2 nanoparticles are a kind of excellent seed layer material for growing SnO2 nanorods films, and lays foundation for the preparation of high-performance perovskite solar cells based on one-dimensional electron transport materials.
The effects of hypereutectic Al-17Si-4Cu-0.5Mg alloy were prepared by semisolid extrusion. The effect of solution time on microstructure and properties of hypereutectic Al-17Si-4Cu-0.5Mg alloy was studied. Results show that spheroidization occurs in the Si phase with the increase of solution time. When the solution time reaches 10 h, the circularity of eutectic Si is 0.72. High concentration of Cu element is enriched around Si phase in as cast state. After solution for 1 h, Cu element is rapidly dissolved into the matrix. As solution time is increased from 1 h to 16 h, the diffraction peak intensity of θ(Al2Cu) and Q(Al5Si6Cu2Mg8) phases on the XRD curve is decreased, and the dislocation density in the alloy matrix is greatly reduced. After aging treatment at 180℃ is performed on the solution treated samples, the θ' and Q' phases precipitate. As the solution time increases, the alloy strength value shows a "double peak" phenomenon. After solution treatment for 1 h, the tensile strength of the alloy reaches 269 MPa and the yield strength is 233 MPa. Compared with the unheated alloy, they are increased by 43.3% and 42.7%, respectively. This is mainly because there is still larger dislocation density in the matrix at the initial stage of solution, and the precipitation has stronger pinning hindrance to the dislocation after aging treatment. When the solution time is 10 h, the tensile strength and yield strength of the alloy reach 311 MPa and 263 MPa, respectively. The roundness of Si phase and the strengthening effect of fine precipitates are the main reasons for the formation of the second strength peak.
Ceramics and metals have large differences in thermal expansion coefficients, which can easily lead to large residual stresses in the joints. The researchers used the method of adding an intermediate layer to successfully reduce the residual stress in the joints. In the present work, using AgCu/Cu foam/AgCu composite filler as interlayer, brazing ZrB2-SiC ceramics and Inconel 600 alloy has been studied. Microstructure, shear strength and residual stress were studied in details for conditions with different thickness of Cu foam. The results show that with or without the addition of Cu foam, the brazed joints consists of Agss, Cuss and (Cr, Fe)7C3 phases without obvious defects. Shear strength of brazed joint is improved after introducing the Cu foam. With the increase of Cu foam thickness, the Cuss is quantitatively increased, and shear strength is increased first and then decreased. When thickness of Cu foam is 1 mm, the maximum shear strength is obtained as 72.5 MPa. The residual stresses of joint were calculated by using ABAQUS. The residual stress on the metals side is reduced by 50.6 MPa, and the ZrB2-SiC side by 110.3 MPa of the brazed joint with Cu foam. The results further prove that the addition of Cu foam can effectively reduce the residual stress and improve the shear strength of joints.
The Sn4.7Ag1.7Cu+Ag composite solder/Cu joint was prepared with Sn4.7Ag1.7Cu+Ag composite solder by transient liquid phase (TLP) bonding process.The microstructure of the joints under constant temperature aging was observed by SEM, combined with EDS, the microstructure and properties of the joints under different processes were compared and analyzed. The results show that the service performance of Sn4.7Ag1.7Cu+Ag/Cu joint at high temperature (300℃) is improved with the increase of Ag particle content. When the content of Ag is 25% (mass fraction), the joint does not break after 15 days of service at 83℃ higher than the melting point (217℃) of the base solder, and the tensile strength is 25.74 MPa, which achieves the purpose of low-temperature welding and high-temperature service. Comparing with Sn4.7Ag1.7Cu/Cu joints under reflow welding, with the aging process, the residual Ag particles in Sn4.7Ag1.7Cu+Ag composite solder/Cu joint are dissolved and a large number of Ag3Sn compounds are produced near the interface of the joint. A large number of bulk Ag3Sn compounds can effectively inhibit the diffusion of Sn into the Cu substrate and achieve the purpose of inhibiting the growth of the Cu3Sn layer.Under the condition of service temperature of 200℃, with the aging process, the mechanical properties of the Sn4.7Ag1.7Cu+Ag composite solder/Cu joint first decrease and then increase, then decrease to a stable state, and its mechanical properties are better than that of the Sn4.7Ag1.7Cu/Cu joint.
Extra-coarse-grained WC-Co cemented carbides are focused by researchers due to the high wear resistance and toughness, whereas the densification and WC grain tailoring are key factors for obtaining excellent performance. Extra-coarse-grained WC-10Co cemented carbides with an average grain size of 8.3-8.8 μm were prepared by a mild-ball-milling and vacuum sintering processes with ultra-fine WC powder obtained by mild-ball-milling method.The effects of sintering time on density, WC grain and mechanical properties were studied. The results show that the relative density first increases and then decreases with sintering time increasing from 30 min to 120 min.Ultra-fine pores also increase by the oxidation and accumulation of Co on the surface, and abnormal grains are formed by the aggregation of some WC grains.Therefore, the elimination of pores is hindered.Furthermore, the average grain size of WC firstly increases and then decreases due to orderly dissolution-precipitation of ultra-fine WC and fragmented fine WC, and finally WC grains are formed with wide distribution.As sintering holding time increases to 60 min, the partial spherical WC grain with curved surface is transformed into performance friendly hexagonal prism grain with rounded edge through faceted steps growth mechanism. Here, the bending strength and impact toughness reach the maximum of 1733 MPa and 28 kJ·m-2, respectively.Furthermore, the primary defects are difficult to be completely eliminated in some grains during sintering.With longer sintering holding time, the increased multiple defects result in the deterioration of properties.
Based on a mature formula of resin based friction material, the influence of copper fiber content (mass fraction) on the physical properties, mechanical properties, friction and wear properties and brake noise of friction material was studied. The results show that the density, hardness and internal shear strength of the friction material are increased with the increase of the content of copper fiber, the porosity and compression amount are decreased gradually, and the pH value has no obvious difference with the change of the content of copper fiber. Through the bench test of SAE J2521 and SAE J2522, it is found that the addition of copper fiber has little effect on the nominal friction coefficient of the friction material. Adding proper amount of copper fiber is beneficial to improve the contact state between the friction material and the surface of the dual part, stabilize the friction coefficient, and improve the anti-fading performance of the friction material; with the increase of the content of copper fiber, the wear rate of the friction material is first decreased and then slightly increased, and when the mass fraction of copper fiber is 9%, the wear rate is the lowest; adding proper amount of copper fiber is beneficial to suppress the generation of noise, when the mass fraction of copper fiber is 7%, the noise performance is the best.
TC4/Ni60/Ni-graphite composite functional coatings with 25% (mass fraction), 35% and 45%Ni-graphite were prepared on TC4 titanium alloy surface by coaxial powder-feeding laser cladding technology. The forming quality, microstructure and mechanical properties of the composite coatings were studied by means of penetrant inspection, X-ray diffractometer, scanning electron microscope, energy spectrum analyzer, electron probe microanalyzer, white light interferometer, microhardness tester and friction and wear tester. The results show that the 35%Ni-graphite coating has the best forming quality, and different content Ni-graphite coatings have the same types of reaction precipitates, mainly Ti2Ni, TiC, TiB2, graphite and matrix α-Ti.The TiC coated graphite semi coherent composite phase and TiC, Ti2Ni cross growth coherent composite phase are formed in all coatings, the semi-coherent TiC coating can alleviate the melting of graphite in the molten pool, and the coherent TiC-Ti2Ni composite phase can make the brittle Ti2Ni structure uniformly refined. With the increase of Ni-graphite content, the average microhardness and wear resistance of the coatings decrease gradually, while the anti-friction performance first increases and then decreases, and the wear mechanism is abrasive wear.
Composite coatings were prepared by using polisilizane as matric resin and h-BN as functional filler.Raw BN was modified by chemical method to improve its distribution in composite coatings.FT-IR and TEM characterizations were applied to analyse the chemical structure of the raw BN and modified BN samples.SEM was used to observe the microstructure of the as-prepared coatings.The optimal resin content was set as 50% (mass fraction) by characterizing the microstructure of composite coatings with varied resin contents. In addition, basic properties of composite coatings were also tested and analysed.The results show that raw BN is successfully modified using chemical method.The modified BN displays better distribution in composite coatings as expected.The as-prepared coatings have good impermeability and thermal-oxidation resistance.
Ordered core (PEO)-shell (PHB) microfibers were prepared by coaxial electrostatic spinning technology and high-speed rotating receiving roller with polyoxyethylene (PEO)/chloroform solvent as core spinning solution and poly (β-hydroxybutyrate) (PHB)/chloroform solvent as shell spinning solution. The surface morphology, core-shell structure, thermal properties, crystallization properties and mechanical properties of core (PEO)-shell (PHB) microfiber film were characterized and analyzed by SEM, TEM, DSC, TGA, XRD and DMA. The results show that PEO/PHB microfiber has remarkable core-shell structure; fiber arranges in the same direction and the average diameter are 0.57-1.27 μm; the crystal structure of core (PEO)-shell (PHB) microfiber includes α-type crystal of PHB and monoclinic crystal of PEO; when the spinning voltage is increased, the diameter of the fiber decreases, and the crystallinity increases first and then decreases; the fiber diameter increases with the increase of injection speed, and the crystallinity first increases and then decreases; with the increase of the collection distance, the fiber diameter first decreases and then increases, and the crystallinity first increases and then decreases. By changing the single spinning condition, the corresponding fiber films with the spinning voltage of 18 kV, the push velocity of 0.07 mm/min and the collection distance of 8 cm all have high mechanical properties. Compared with pure PHB fiber and PEO fiber, the thermal stability of each component in ordered core (PEO)-shell (PHB) microfiber is improved.
The FBG sensors, embedded in triangle region of composite T-stiffened panels, were used to monitor the strain change during curing process and quasi-static compression real-timely. The results show that the compression load of stiffened panels with the FBG sensor embedded along the stiffener is the same as that without the FBG sensor. The FBG sensor embedded in the triangular area of the stiffened panels can effectively monitor during the curing process, and it can also be used to monitor the temperature and strain changes real-timely after curing process. In the quasi-static compression process, the strain curve measured by the FBG sensor is the same as the force-displacement curve. The FBG sensors can monitor accurately the damage such as lamination and cracking in the stiffened panels without affecting the property of the stiffened panels.
The hygrothermal aging test of T800 carbon fiber/epoxy resin composites was carried out. Through mass change, surface morphology before and after aging, dynamic mechanical properties, infrared spectroscopy, interlayer shear and compression tests, the effects of solution immersion in deionized water and 3.5% (mass fraction, the same as below) NaCl solution at 70℃ on the mechanical properties of carbon fiber/epoxy resin composites were studied. The results show that the moisture absorption rate of T800 carbon fiber/epoxy resin matrix composite is relatively low in deionized water and 3.5%NaCl solution, which is 0.82% and 0.67%, respectively; Good adhesion between unaging sample fiber and matrix, after aging in 3.5%NaCl solution, the interface damage between fiber and matrix is more serious than that in deionized water. After immersion in deionized water, the shear strength is decreased by 8.8%, the compressive strength is decreased by 4.3%. After soaking in 3.5% NaCl, the shear strength is decrease by 10.1%, the compressive strength is decreased by 4.7%. The Tg of the samples decreased after aging in the two solutions, but the difference is not significant, at the same time, no new substances are generated or chemical reactions occur. The research results provide a basis for the application of T800 carbon fiber/epoxy resin composites in corrosive environment.
The effects of thermo-oxidative aging on the mechanical properties of three-dimensional orthogonal carbon/glass fiber/bismaleimide composite (3D-CF/GF/BMI composite) and laminated carbon/glass fiber/bismaleimide composite (LM-CF/GF/BMI composite) were studied by means of three-point bending and inter-laminar shear tests. The mass loss behavior, infrared spectra, macroscopic and microscopic morphology, bending properties and inter-laminar shear properties of the composites were analyzed at different aging time. The results show that a large amount of resin decomposition caused by thermal oxygen aging produces a large number of cracks on the surface and inside the composites, and the interface properties continue to decline. Eventually, the overall mechanical properties of the composite material decrease, resulting in the decline of the overall mechanical properties of the composite, but the performance retention rate of the 3D-CF/GF/BMI composite is always higher than that the of LM-CF/GF/BMI composite. This is because Z-binder yarns in the 3D-CF/GF/BMI composite exist, and the obstruction of the cracks propagating along the layers by Z-binder yarns can make all fibers together to resist external forces in the case of severe degradation of resin and interfacial properties. The "modified random process model" is used to predict all the bending strength of 3D-CF/GF/BMI composite aged at 200℃ for 180 days. The prediction error is less than 10%, indicating that the model is reliable.
To improve the dispersibility of the silicon dioxide (SiO2) and investigate the effect of particle size on the properties of matrix, 50, 90 nm and 220 nm nano-SiO2 were prepared by Stöber method, and SiO2 nanofluid (NF) was prepared by grafting the organosilanes and polyether amine on the surface of SiO2nanoparticles. Chemical structure and physical morphology of nanofluid were investigated by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), thermo gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The mechanical properties of SiO2 nanofluid/epoxy resin (NF/EP) composites with different particle sizes and different contents were studied, the results indicate that the mechanical properties of composites are increased first and then decreased with the increase of content. The 50 nm SiO2nanofluid has the best effect on improving impact strength, the impact and bending strength of epoxy resin are enhanced by 54.55% and 11.64% with the 1 phr addition. The 220 nm SiO2nanofluid has the best effect on improving bending properties, the impact and bending strength of epoxy resin are enhanced by 50.00% and 17.51% with the 1 phr addition. The results of the DSC and linear expansion coefficient tests show that the NF/EP composites have higher glass transition temperature and lower linear expansion coefficient than pure epoxy. Thus, with adequate mechanical properties and low coefficient of thermal expansion, NF/EP composites can be considered as promising candidates in the electronic packaging fields.
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