- 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)
In order to improve the mechanical property of traditional electrospinning fibrous membranes, PPESK-fiber/PVDF-bead composite membranes were prepared via simultaneously electrospinning of PPESK concentrated solution and electrospraying of PVDF dilute solution, and then hot pressed at 160℃. The membrane structure, tensile strength, ionic conductivity and cycling performance of lithium-ion batteries were measured by scanning electron microscope, universal tensile test machine, electrochemical work station and battery cycle system. The results show that the hot-pressed PPESK/PVDF composite membrane separator exhibits excellent liquid electrolyte wettability, ionic conductivity reaches 1.92mS·cm-1 at room temperature, PVDF beads are uniformly dispersed in PPESK fibers. The interfacial strength of PPESK fibers is effectively enhanced due to the melt of PVDF beads during the hot press process, hence the mechanical strength of composite membrane is leached 13.2MPa. In addition, cells assembled with PPESK/PVDF composite membrane show high discharge capacity and stable cycling performances.
EVOH-SO3 Li/PET Li-ion battery composite membranes were prepared by means of alternated electrostatic spinning, then the morphology of the membranes was observed by scanning electron microscope, and the electrochemical properties of the membranes were tested by using an electrochemistry work station. The results show that the average diameter of EVOH-SO3 Li/PET fibre is 387nm, both two kinds of fibres exhibit uniform net-like structure. Compared with pure EVOH-SO3 Li fibre, adhesion phenomenon of modified EVOH-SO3 Li/PET fibre is not obvious anymore, and the surface of EVOH-SO3 Li/PET fibre becomes more smooth with enlarged pores between adjacent fibres; the electrochemical window of EVOH-SO3 Li/PET separator is 5.3V, bulk resistance of EVOH-SO3 Li/PET is decreased to 212.31Ω, and the ion conductivity of EVOH-SO3 Li/PET separator is 2.347×10-3 S/cm, the properties of EVOH-SO3 Li/PET membranes are improved compared with EVOH-SO3 Li.
A novel method to fabricate flexible free-standing electrodes with textile structure for lithium-ion batteries was provided by applying extrusion-based three-dimensional (3D) printing technology. Meanwhile, highly concentrated poly(vinylidene fluoride) (PVDF) is used as viscosity modifier, carbon nanotube (CNT) as conducting additive, and lithium iron phosphate (LFP) or lithium titanium oxide (LTO) as cathode or anode active materials respectively to develop printable inks with obvious shear-thinning behavior, and with the apparent viscosity and storage modulus platform value of over 105Pa·s, which is beneficial to the printability and enable complex 3D structures solidification. The electrochemical test shows that both printed electrodes have similar charge and discharge specific capacities under current density of 50mA·g-1. To explore the feasibility of the printed electrodes, a pouch cell with as-printed LFP and LTO electrode as cathode and anode respectively is assembled. The pouch cell without deformation delivers discharge specific capacities of approximately 108mAh·g-1, and there is a tiny increase in discharge specific capacities of around 111mAh·g-1 for bended pouch cell.
The equal molar AlCoCrFeNi high entropy alloys with 5% (volume fraction) TiB2 particles reinforcement were fabricated by spark plasma sintering (SPS). Effect of SPS temperature and pressure on microstructure evolution and mechanical properties of TiB2/AlCoCrFeNi composites was studied using X-raydiffraction (XRD), density testing, scanning electron microscopy (SEM) and mechanical properites testing. The results show that increasing SPS temperature and pressure can improve hardness and compressive strength of TiB2/AlCoCrFeNi composites. The relative density, compressive strength, yield strength and hardness of the TiB2/AlCoCrFeNi composite after sintering at 1200℃ and 30MPa are 99.6%, 2416MPa, 1474MPa and 470HB, respectively. During spark plasma sintering, phase transformation occurs in the high entropy alloy matrix of the composite. The composite after sintering at 1200℃ and 30-45MPa is composed of phases BCC, B2, FCC, TiB2 and σ.
The thermal insulating properties of polymer greatly restrict the application of polymer as the thermal conductivity materials in industry. Multilayer graphene was chosen as a filler due to its unique thermal transfer property. The effect of alumina oxide (Al2O3) and silicon carbide (SiC) with graphene as hybrid fillers on thermal conductivity of polymers was also explored. The thermal conductivity of the composites enhances 161% with 3%(mass fraction) graphene content compared to pure nylon-6(PA6). The thermal conductivity of PA6 composites is within 0.653-4.307W·m-1·K-1 by adjusting hybrid fillers content and the ratio of graphene with Al2O3 and SiC. The best thermal conductivity is 20 times higher than the pure PA6. It is no doubt that the exploration can provide valuable experimental basis for extending the utilization of graphene as thermal conductivity filler and the application of PA6 thermal conductivity materials in industry.
The calcium sulfate/strontium-doped β-tricalcium phosphate composite spherical pellets was fabricated, using the calcium sulfate/strontium-doped β-TCP as raw material, and through the stirring spray drying method, and then composite spherical pellets were combined with silica gel, porous silica gel/calcium sulfate/strontium-doped β-tricalcium phosphate scaffold was obtained by stacking aggregation method in the mould. The XRD, SEM and FT-IR, etc are employed to examine the chemical composition, composite morphology and structure characteristics, and the degradability, porosity, mechanical properties and cytotoxicity of the scaffolds materials were studied. The results reveal that the composite porous scaffolds have irregular pore structure with pore size between 0.2-1.0mm, and they have a large number of micropores on each of the composite spherical pellets, with the aperture between 50-200μm. Moreover, the porosity of the composite scaffolds is about 62%, which can meet the requirements of scaffolds for bone tissue engineering in porosity; the cytotoxicity tests show the composite scaffolds have no cytotoxic effect and it has good degradation. Therefore, it has good application prospect in bone tissue engineering of the bone defect repair of non-bearing site.
A series of Fe NPs/CFs/ER nanocomposite plates were prepared by using Fe nanoparticles as microwave absorbent, the surface modification of as-prepared Fe nanoparticles was carried out by using silane coupling agents (KH-550), carbon fibers were used to enhance the reflection of electromagnetic waves inside and mechanical properties. The results show that microwave absorption of nanocomposite plates increases with increasing of mass percentage of Fe nanoparticles and carbon fibers, their gradient concentration results in resonance phenomena in specific frequency region.The microwave absorption property is anisotropic, the properties of at the vertical direction of carbon fibers towards incident wave are better than the parallel case, the minimum reflectivity peak value of the nanocomposites with 30%(mass fraction, the same as below) of Fe NPs and 5.52% of CFs reaches -26.8dB at 4.9GHz with the matching thickness of 4.56mm.CFs can maintain the bending properties of nanocomposites effectively, the bending strength of the nanocomposite with 30% Fe NPs is just lower than that with 0% Fe NPs by 5.81%.
B4CP/PI polyimide composite films with different powder contents and thicknesses were prepared by particle surface modification and wet mixing machinery-thermal imidization method, using high temperature polyimide as matrix and micro-sized boron carbide (B4C) as thermal neutron absorption material. The thermal neutron radiation shielding property, thermal stability and mechanical property of B4CP/PI polyimide composite films were mainly discussed in this paper. It is shown that the micro-sized B4C functional particles can be well dispersed in PMDA-ODA polyimide matrix, and the thermal stability of B4CP/PI polyimide composite films are significantly improved with the increase of B4C content. However, the mechanical properties of the composite films present the opposite trend; meanwhile, the B4CP/PI polyimide composite films exhibit excellent thermal neutron radiation shielding properties, and the neutron permeability I/I0 presents exponential relationship with the increasing thickness of composite and B4C filler particle content. Therefore, through structural design of the materials, the applications requirements in different fields for materials with high temperature resistant and thermal neutron radiation shielding properties can be met.
Dissimilar materials welding between 2mm-thick AZ31B Mg alloy and 6061 Al alloy plates in overlap form was performed using the friction stir-induced diffusion bond with zinc foil as the interlayer. The microstructure and mechanical properties of the Al/Zn/Mg lap joints were analyzed by means of SEM, EPMA, XRD, tensile experiment and Vickers hardness test. The results show that diffusion layer consists of Al enrichment zone, Al5Mg11Zn4 layer and Mg-Zn eutectic zone at proper rotation speed; however, when rotation speed is low, the residual zinc interlayer remains in the diffusion layer; when rotation speed is high, the Al-Mg intermetallic compounds are present again. Due to the existence of intermetallic compounds in diffusion layer, its microhardness is significantly higher than that of base metal. The addition of zinc foil can improve the mechanical properties of Al/Mg lap joints. According to analysis on the fracture, joint failure occurs in the diffusion layer near to Al side.
The distribution of deformation and residual stress in copper/Al2O3 ceramic/stainless steel brazed joint was investigated by means of finite element numerical simulation. Brazing experiments were conducted to verify the accuracy of simulation results. The results show that residual stress is mainly distributed in the joint area where the deformation is not obvious. Residual stress at the ceramic side has a significant effect on properties of the joints. The fracture tends to occur in the ceramic near stainless steel due to the mismatch of their linear expansion coefficients. The brazed joints may also crack in the ceramic at copper side when TiO reaction layer is formed, and the mechanical properties of the joint are reduced. The contribution of stress component to final residual stress was also analyzed. The tension stress generated by hoop stress and axial stress is the principle factor which decreases the properties of brazed joint. The brazing specimens mainly fracture in the ceramic side near stainless steel, and the accuracy of simulation has been proved by brazing experiments.
Micro-nano structure on zinc substrate was fabricated through the combination of chemical etching with hydrochloric acid aqueous solution and hydrothermal reaction. After modification with perfluorooctanoic solution, the lyophobic surface was prepared. The phase composition, microstructure, chemical composition, and wettability of the as-obtained surface were investigated by X-ray diffractometer, scanning electron microscope, Fourier transform infrared spectrometer, and contact angle tester. The results show that a layer of ZnO nano-rods grows on the surface of the submicrometer structure, and exhibits good resistance to water impact and stability under the combined action of low surface energy material. When hydrochloric acid concentration is 1.0mol/L and hydrothermal reaction temperature is 95℃, the lyophobic surface possesses the best morphology of ZnO nano-rods. The maximum contact angles of distilled water and peanut oil are 154.65° and 144.65°, respectively, and the sliding angle is less than 10°.
High-density coating with FeSiB amorphous ribbons as cladding materials on the surface of mild steel was fabricated by laser cladding. The effect of different pulse widths on formability, microstructure and microhardness of the coatings was analyzed by optical microscope(OM), X-ray diffractometer (XRD), scanning electron microscope (SEM) and microhardness tester. The results show that with the increase of the pulse width, the coating dilute rate rises; the tendency of crack increases and the crack originates from surface to the interface; the degree of crystallization increases and crystallization phases are α-Fe, Fe2B and Fe3Si, fusion zone width increases and the trend of columnar crystals along the epitaxial growth becomes bigger and bigger; the microhardness firstly increases and then decreases. When pulse width is 3.2ms, the structure of the coating is compact, no hole defects, the interface exhibits a good metallurgical combination and the dilute rate is low about 23.2%. Average microhardness of the coating reaches 1192HV, which is about 10 times as much as the substrate.
The amorphous Ni-P/Al2O3 composite coatings with high P content were deposited using the bi-directional pulse electrodeposition. The micrographic morphology and chemical composition of the coatings were examined using the scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) analysis. Also, the phase structure of the coating was characterized using the X-ray diffraction (XRD). By analyzing the electrochemical test results of the coatings, the corrosion resistances of different types of deposits were evaluated. The results show that compared to the direct current (DC) plating, the P content in the Ni-P alloy coatings increases to 12.06%(mass fraction) by bi-directional pulse electrodeposition, which facilitates the formation of the amorphous Ni-P alloy coatings. The PC plating can produce a finer and denser Ni-P/Al2O3 composite coatings with more compact crystallization than that deposited by DC. The Ni-P alloy coatings deposited by the pulse electrodeposition has a better corrosion resistance, and adding composite particles of Al2O3 can further contribute to improving the corrosion resistance of the amorphous Ni-P alloy coatings.
The corrosion behavior of Zn-Al-Mg-RE sealed and unsealed coatings fabricated by high-velocity arc spraying on Q235 steel was studied in seawater with sulfate-reducing bacteria (SRB) using electrochemical impedance spectroscopy(EIS), polarization curve(PC), scanning electron microscopy (SEM) and energy dispersive spectroscopy(EDS). The results show that the corrosion rate of unsealed and sealed Zn-Al-Mg-RE coatings first increases and then decreases; the corrosion resistance of Zn-Al-Mg-RE coating apparently improves by the sealing treatment. After immersion, the two coatings surface is covered by a passivation film layer of microorganism and corrosion products, which avoids the coating from being further damaged.
The effect of rare earth element Ce, Sc and Er on TiB2 particles and matrix alloy micros-tructure of TiB2/Al composites was studied with in situ synthesis method. It shows that the addition of rare earth element improves the microstructure and properties of TiB2/Al composites notably. The particles of TiB2 are relatively homogenously distributed as adding 0.3% (mass fraction) rare earth element Sc and Er, moreover, it is Er that refines the microstructure of matrix alloy most significantly, then is Sc. Similarly, it is demonstrated that the addition of Sc and Er results in better tensile strength, which is enhanced by 32% and 31%, respectively; the addition of Er also leads to the best ductility by 85% with optimal tensile property. Meanwhile, fracture morphology analysis reveals that the fracture of the composites is microporous gathered ductile fracture when adding Sc and Er. Finally, it is verified that the mechanism of rare earth element on composites lies in two aspects:one is that the addition of rare earth element improves the wettability of the composites and suppresses the agglomeration of TiB2 particles; the other is that the addition of rare earth element refines the microstructure of matrix alloy and then improves the tensile strength of the composites.
Through using DSC, XRD, SEM, EDS, static tensile test and other analysis methods of materials, the effect of trace Ce on microstructure and properties of near-rapidly solidified Al-Zn-Mg-Cu alloy was studied in order to find out rational homogenizing heat treatment process. The results show that Ce plays a role of refining grain and purifying molten alloy. The addition of Ce reduces dendritic spacing, refines the grain structures, eliminates dispersed shrinkage. The addition of Ce reduces the initial melting point of low melting eutectic phases by 3℃, under the same homogenization conditions. Trace Ce promotes the dissolution of low melting eutectic phases into the matrix, which improves the effect of homogenization. Homogenization temperatures of alloy A should be lower than 480℃and alloy B should be lower than 470℃; the addition of Ce decreases the homogenization temperature and improves the homogenization effect. The addition of Ce also greatly increases the tensile strength of the alloys.
Through the study on high temperature creep data of HP heat resistant alloy, a prediction method of high temperature creep deformation based on Zc parameter was proposed. The creep resistance of HP heat resistant alloy was predicted by this method. The results indicate that the predicted data are in good agreement with the HP heat resistant alloy creep experimental data at 1000, 980℃ and 930℃. At the same time, the creep rupture life of heat resistant alloy was evaluated by this method, the results show that the predicted principal curves agree well with the experimental data.
Effect of heating rate on creep aging behavior and mechanical properties in the process of creep aging forming of 2219 aluminum alloy was studied. In order to simulate the temperature conditions of the component in autoclave, heating rate was reduced to 0.75℃/min and heating time was prolonged to 4h(real creep aging heating time for a typical component). Creep aging experiments were carried out under three kinds of stress conditions of 0, 150, 210MPa and different aging time, tensile mechanical properties and microstructures (TEM) of materials were analyzed. The results show that lowering heating rate improves mechanical properties of material and prolongs the arrival time of material strength peak compared to heating time of 0.5h(5.5℃/min) in material standard; shape factor of precipitate phase of aluminum alloy increases with the aging time, and then decreases after reaching the peak; when lowering heating rate, significant creep deformation occurs in materials heating stage, creep strain of heating stage are accounted for 29.28% and 21.56% of total creep strain in two kinds of stress conditions of 150MPa and 210MPa, creep strain and steady-state creep rate increase with the rise of stress; therefore, it is necessary to further consider the effect of heating rate on the forming and mechanical property evolution in the study on the characterization of creep aging behavior of component based on the creep aging research of material standard(standard creep specimen).
The tensile and compressive tests on woven carbon fiber epoxy resin composite specimens in different hygrothermal environments were carried out. The moisture absorption, tensile and compressive properties, fracture morphology and dynamic mechanical properties were analyzed. The influence of hygrothermal environments on tensile and compressive properties was investigated. The results show that the absorption process of carbon fiber epoxy composites satisfies Fick's law, and its saturated moisture absorption rate is about 0.86%. After moisture absorption, the surface of specimens becomes smooth, the phenomenon of few fibers pull-out and resin damage occurs, but no chemical reaction and no new substances is generated. After moisture absorption at 130℃, the retention rate of tensile properties is 96%, but the retention rate of compression properties is only 69%. The glass transition temperature of composite laminates after moisture absorption decreases by 33℃ compared with that in dry state.
The special functions of surface morphology in nature have attracted many scholars' interest, and the control of soft-rigid composites has become a hotspot in recent years. The common soft material surface morphological formation methods, including pre-stretched method, heat treating method and swelling method, were introduced in this paper and a way for the generation of surface morphology was provided. The application of surface morphology in engineering including fluid dynamics, optics, and other fields were introduced, and some ideas for reference in wide engineering application were provided. On the basis of this, the development trend of the active control and generation method of the surface morphology was prospected.
Perovskite solar cells(PSCs) have been developed rapidly as one of the most remarkably growing photovoltaic technologies in the last five years. The power conversion efficiency(PCE) of the solar cells has been unprecedentedly increased over the relatively short period. It is of great significance to study the perovskite materials in this kind of solar cells for improving the efficiency. The most focused issues as well as the main progress in varied fabrication techniques and synthesis of new materials in recent years were reviewed in this paper. The characteristics and improvements of varied fabrication techniques are introduced in detail, the necessity and the problems facing for new materials synthesis were analyzed. Finally, a perspective view on reducing the toxicity of perovskite, preparing large-scale perovskite solar cells, and the cost reduction was given to provide the direction for the future research of high-efficiency and stable perovskite solar cells.
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