- 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)
Recently, with the development of research techniques, researchers have discovered numerous new phenomena in nanowires with potential applications. Clearly depicting the structure-activity relationship between nanowire structure and mechanical properties has important guiding significance for the design, service and performance optimization of nanodevices. Firstly, several typical in-situ testing methods of mechanical properties of nanowires were summarized. Secondly, the mechanical properties such as elasticity and strength of various nanowires in tensile tests were introduced. The size-dependent plastic deformation of nanowires was described. In addition, the unique mechanical behavior of nanomaterials in the in-situ tests was discussed. In the future, it is necessary to systematically study the effect of electron beam irradiation on the deformation behavior of nanowires during in situ electron microscopy characterization and to investigate the mechanical properties exhibited by nanowires under complex external field environments. Thus, a complete set of theoretical guidance systems can be established, which is an important development direction in the field of in situ characterization of nanomaterial properties.
Nanofluidics is the study on the behavior of fluid flow in a nanoscale-confined channel with at least one characteristic dimension smaller than 100 nm. Nanofluidics can exhibit unique physical phenomena such as ultrafast water transport, surface charges control ion transport that cannot be observed at microscales or in bulk structures. A significant growth of attention in nanofluidics was achieved due to the representative phenomena and effects, which make them potentially useful in osmosis energy generation, nanofluidic diodes or transistors, desalination, biology, and other applications. In the past few years, the fabricating nanofluidic channels is burgeoning throughout the globe and can be widely used for energy conversion due to the rapid advancement of micro- and nanotechnology. This review mainly focused on the research progress of the nanofabrication methods of nanofluidic channels, including nanolithography, microelectromechanical system(MEMS) based techniques, nanofluidic channels based on nanomaterials, and other natural nanofluidic materials. The preparation methods including electron beam lithography, focused ion beam lithography, scanning probe lithography, extreme ultraviolet lithography, interference lithography, and sacrificial layer releasing were discussed in detail. The advantages and disadvantages of each nanofabrication method were pointed out. Following that, the recent application progress of nanofluidics from five aspects was summarized: in salt differenatial energy conversion, responsive ionic gate, sensors of ion detection, sensing of single molecules, and water desalination. Finally, the current challenges were discussed, and the fantastic opportunities and perspectives in the fabrication of nanofluidic channels were prospected, such as high cost, reliability and stability need to beimproved, etc.
Rechargeable aqueous zinc-ion batteries (ZIBs) have been widely studied because of its excellent performance, low price and environment-friendly, and the structure design of ZIBs cathode with high capacity and long cycle life have become the focus. PAN solution containing Mn(NO3)2·xH2O was used as a core layer and PAN solution as skin layer by coaxial electrospinning. Due to the concentration gradient diffusion, Mn(NO3)2·xH2O diffused to the cortex. And MCNFs with sebaceous glandular structure on the surface was obtained by carbonization. MnO2 was electrodeposited on its surface, and MnO2@MCNFs cathode with excellent affinity with electrolytes were prepared. The results show that the sebaceous gland structure not only increases the specific surface area of cathode, but also constructs the riveting effect between MCNFs and α-MnO2, which enhances the interface bonding between the substrate and the active material, reduces the shedding of α-MnO2, reduces the interface resistance, and shortens the electron conduction and ion diffusion path. The test shows that the specific capacity of the first cycle of 3% MnO2@MCNFs can reach about 581.16 mAh/g under the current density of 100 mA/g, and the specific capacity of 120 mAh/g can be maintained after 1000 cycles under the high current density of 1 A/g, and the coulomb efficiency is around 99%.
Fuel cell, which directly enables the generation of electricity from the conversion of the fuel through an electrochemical reaction at the electrode and electrolyte interface, without going through the heat engine process, is an incredibly powerful renewable energy technology. The electrochemical reaction in fuel cell is not restricted by the Carnot cycle, so it has high energy conversion efficiency. Proton exchange membrane fuel cell (PEMFC), in particular, has been regarded as the most promising candidate for transportations, portable equipment and fixed devices.However, there are still some problems in PEMFC, including high cost, insufficient power and poor stability, which limit the large-scale commercial application of PEMFC. The basic reason behind these problems lies in the key materials, such as cathode catalyst, gas diffusion layer, proton exchange membrane and bipolar plate in fuel cell, which can not meet the requirements of PEMFC commercialization owing to their high cost and low performance. Therefore, in order to achieve large-scale application of PEMFC, advanced cathode catalysts, gas diffusion layers, proton exchange membranes and bipolar plates are needed. For the requirement of low-cost and high-performance advanced materials for PEMFC, the research status of these key materials and main challenges in their practical application were summarized in the review, and the future development direction was pointed out: developing the technology of large-scale preparation of platinum alloy and metal-nitrogen-carbon (M-N-C) compound catalysts, preparation of proton exchange membranes with high proton conductivity and excellent mechanical property, studying the influence of modified gas diffusion layer on PEMFC performance under different working conditions, developing coatings or new metal materials with excellent corrosion resistance and electrical conductivity for bipolar plates.
As a new type of energy storage device, aqueous zinc-ion capacitors (AZICs) have excellent performance, such as high power density, high energy density, long cycle life and high safety.AZICs have a high application prospect in the field of civil electronic equipment and military electrified weapons and equipment, and are expected to become a new generation of energy storage scheme instead of lithium-ion batteries.In this paper, the recent advances of carbon-based materials for zinc ion capacitors, such as activated carbon, carbon nanotubes, graphene and biomass derived carbon were summarized. The zinc ion storage performance of MXenes was analyzed in detail, and the energy storage mechanisms of transition metal oxides were revealed. It is pointed out that developing the cathode materials with high capacity, high voltage tolerance and low temperature adaptability is of great importance.
Metal foam composite is a kind of lightweight composite with low density, high strength, high shielding performance, high damping performance and other characteristics. It has a wide range of application prospects in aerospace, drilling trap floats, artificial bone and other fields, which has attracted people's attention. In this paper, based on the research of the existing literature, the fabrication methods of metal foam composites were introduced, the effect of microstructure on the properties of metal foam composites was analyzed, the progress of mechanical properties, damping properties, shielding properties and heat insulation and their mechanisms of metal foam composites and their applications in relevant fields were reviewed, which provides a theoretical basis for the development of metal foam composites in the future, and the new fabrication technology, modeling research, sandwich structure of metal foam composites and the fabrication of high performance foam hollow sphere composite were also prospected.
A novel kind of lattice-distributed ESTM-fabrics was developed by using polyethersulfone(PES) and U3160.The loading amounts of PES on ESTM-fabrics are 15 g/cm2(ES-15), 25 g/cm2(ES-25), 35 g/cm2(ES-35), respectively. ESTM-fabrics reinforced BMI resin (trademarks: 6421) matrix composites(ESTM-fabric/6421) were prepared through RTM process.Dynamic mechanical thermal analyses(DMTA) and impact resistance as well as residual strength of ESTM-fabric/6421 were studied and the toughened mechanism was analyzed by fluorescence microscope.An untoughened 6421 BMI resin matrix composite (ES-0) reinforced by neat U3160 fabrics was studied to compare performance of composites as well.The results of DMTA show that ES-0 has only one glass transition temperature(Tg) representing pure BMI resin.The toughened composites exhibit two Tg: the relaxation peak appearing at 230-250 ℃ represents toughener PES phase and the relaxation peak appearing at 191-195 ℃ represents BMI phase. The results of low velocity impact testing show that the initial damage threshold load(DTL) is decreased significantly. DTL of toughened composites is far greater than ES-0 sample, which is the same as maximum peak load.With the increase of PES loading in toughened composites, DTL are increased and the projected delaminated areas are decreased.Fluorescence microscopic results of the specimens after low velocity impact show that the major impact failure of ES-0 sample is delamination. The toughened composites exhibit a great deal of interlaminar and intralaminar matrix crack under the impactor as well as more serious ply splitting on the back surface of specimens, which conical damage is less than ES-0 sample.The compression strength after impact(CAI) of ES-0 sample was 144.66 MPa while CAIs of the toughened composites ES-15, ES-25 and ES-35 increased to 205.85 MPa, 265.74 MPa along with 275.14 MPa, respectively. Fluorescence microscopic results of the CAI specimens reveal that ES-0 sample has massive delamination damage without ply splitting. A lot of ply splitting and obvious matrix cracks appear in ES-15 sample.The major impact failure of ES-25 and ES-35 samples is ply shear damage.These damage modes can absorb massive energy that lead to the higher CAI of the toughened composites.
In order to solve the problems of delamination failure and fiber destruction in the traditional metal-composite hybrid forming method, a new hybrid structure combining metal additive manufacturing, composite weaving and stitching processes was designed. The metal skeleton and woven composite materials were co-cured and formed after completing normal stitching, which increased the bonding strength among heterogeneous materials. Flexible forming and stable connection between metal and composite materials on macroscopic scale were also realized. The in-plane bending performance of the new hybrid structure was investigated by a three-point bending test. The damage morphology of the sample parts and their failure mechanisms were analyzed by non-contact image measurement. The results show that: hybrid structural failure is a combination of multiple failure modes, including compression fracture on the upper side of the fiber layer and tensile fracture on the lower side of the fiber layer, interlaminar failure of heterogeneous materials and plastic damage of metals; the interlaminar delamination is caused by the presence of matrix cracks and interlaminar shear stresses next to the interface, as well as incompatible stiffnesses between adjacent layers; the structural bending strength and bending modulus of elasticity of the samples increase with the increasing structural thickness in the experimental range; the stitching fibers introduced at the openings can inhibit the expansion of delamination cracks to a certain extent and improve the structural resistance to delamination.
The hygrothermal aging of T800 carbon fiber/epoxy resin composites in seawater environment were studied. The prepared specimens were immersed in artificial seawater 70 ℃, 3.5% NaCl solution for 30, 60 and 90 days for corrosion. The mechanical properties of the materials were analyzed by mass change, surface morphology before and after aging, infrared spectroscopy, dynamic mechanical properties, compression test and interlayer shear test. The results show that the moisture absorption rate of T800 carbon fiber/epoxy resin matrix composites in 3.5% NaCl solution is 0.39%, 0.47%, 0.53%. Good adhesion between unaging sample fiber and matrix, and the damage of the interface between the fiber and the matrix become more serious with the increase of time after aging in 3.5% NaCl solution. The glass transition temperature(Tg) is decreased from 189.16 ℃ to 177.54, 171.88 ℃ and 168.06 ℃ after 30, 60 and 90 days aging. After aging with 3.5%NaCl solution, the maximum compressive failure load of specimens for 30, 60 and 90 days is decreased by 3.2%, 8.4% and 15.3%, respectively, and the compressive strength is decreased by 3.0%, 8.2% and 15.9%, respectively. The maximum interlaminar shear failure load is reduced by 3.0%, 9.2% and 14.9%, and the shear strength is reduced by 3.0%, 9.7% and 16.4%, respectively.
Under the condition of high-speed stirring, the external stress of the molecular assembly process was adjusted to prepare short-channel, rod-shaped ordered mesoporous silica. The effect of different template removal methods on the water vapor adsorption performance of mesoporous silica was studied, and the enhancement method of mesoporous silica adsorption performance was obtained. The method of mesoporous silica adsorption performance. The results show that the short-channel (500-700 nm), rod-shaped mesoporous silica can be prepared, and the temperature at which the templating agent is removed during the preparation process has a greater impact on the surface hydroxyl concentration of the material. The combination of extraction and low-temperature calcination is selected to remove the template, the material obtained by extracting 4 times, calcining 250 ℃ has the best water vapor adsorption performance. Under the experimental conditions, the equilibrium adsorption time is about 7.5 min, which is 78.95% of the commercial SBA-15, and the equilibrium adsorption capacity of 0.73 g·g-1 is 1.49 times of the commercial SBA-15.
Ti-doped WC-Ni3Al cemented carbide was prepared by spark plasma sintering for improving mechanical properties. The effect of different Ti contents on the microstructure and mechanical properties of WC-Ni3Al cemented carbide was investigated. The results show that due to Ti addition, the small amount of Al2O3reactively formed in WC-Ni3Al is smaller and more uniform than the sintered sample without adding Ti. The refinement of Al2O3 and the in-situ (Ti, W) C synergistically enhance the hardness of the WC-Ni3Al cemented carbide. Meanwhile, the fracture toughness is improved because the in-situ (Ti, W)C and WC have a better interface combination, facilitating the bridging and deflection formation of cracks. The WC-Ni3Al cemented carbide with 3% (mass fraction) Ti obtains the optimal mechanical properties, with hardness of (19.29±0.18) GPa and fracture toughness of (13.14±0.24) MPa·m1/2.
The effect law of heat treatment process on the microstructure of GCr15SiMo steel was studied, and the dynamic and high temperature mechanical behavior of GCr15SiMo steel with different microstructure was analyzed by using Hopkinson rod and GNT100-2 high temperature tensile testing machine. The results show that the mass fraction of M3C-type carbide particles of GCr15SiMo steel decreases from 2.319% to 0% when the quenching temperature increases from 800 ℃ to 920 ℃; the failure strains of GCr15SiMo steel all increase with the increase of strain rate during dynamic compression.When the true strain is 0.2 and 0.8, the rheological stress of GCr15SiMo steel decreases by 13.45%, 21.44%, 27.49% and 31.79% respectively with the increase of quenching temperature. The accelerated decrease of rheological stress is mainly related to the structure and adiabatic shear mechanism during dynamic compression deformation; at high strain rate, the macroscopic deformation of GCr15SiMo steel changes from pier coarseness to shear failure along 45°, the adiabatic shear mechanism is one of the main reasons for the change in deformation behavior, and the structure is one of the key factors affecting the sensitivity to adiabatic shear; during dynamic compression deformation of GCr15SiMo steel, the deformation temperature rises between 117 ℃ and 333 ℃, and the M3C carbide particle re-solution is one of the key factors for the increase of tensile strength and decrease of yield strength of high temperature performance. When the quenching temperature is 920 ℃, the microstructure of GCr15SiMo steel is uniform twin martensite. The subgrain boundaries in the twin crystal martensite can effectively impede the dislocation movement, which show obvious strain hardening phenomenon under the tensile stress, and the stress-strain curve shows a more significant rising trend than that at quenching temperature of 800 ℃.
The wear resistance of titanium alloy is poor, the preparation of amorphous alloy coating on the surface of titanium alloy moving parts is a choice to maintain the advantages of titanium alloy and improve its wear resistance. The microstructure and tribological behaviour of Ti-based bulk amorphous alloy before and after cryogenic-thermal cycling treatment were studied by XRD diffractometer, differential scanning calorimeter, SEM, friction and wear tester. The results show that after cryogenic-thermal cycling treatment, the titanium-based bulk amorphous alloy remains completely amorphous, and the relaxation enthalpy increases by 11%. After cryogenic-thermal cycling treatment, the average hardness of Ti-based amorphous alloy decreases from 6.84 GPa to 6.59 GPa and the average elastic modulus decreases from 118.70 GPa to 103.43 GPa, but the ratio of hardness to elastic modulus increases. The wear rate of titanium-based bulk amorphous alloy after cryogenic-thermal cycling treatment is reduced by about 10% under the load of 5 N and 10 N. Compared with TC4 alloy, the wear rate is reduced by 20% under 5 N load and 50% under 10 N load, respectively.TC4 alloy shows serious adhesive wear due to its low hardness. After cryogenic-thermal cycling treatment, the wear mechanism of titanium-based amorphous alloy is changed from abrasive wear of as-cast Ti-based amorphous alloy to the complex mechanism with abrasive, adhesive and oxidation wear. With the increase of load, adhesive wear decreases and abrasive wear is dominant.Generally, cryogenic-thermal cycling treatment is an effective way to improve the tribological properties of Ti-based bulk amorphous alloy.
QPQ (quench-polish-quench) is recognized as an effective surface modification technology which can improve the corrosion and wear resistance of metal materials. However, it is environmentally constrained in real application. In order to explore an environmental friendly and efficient surface modification technology, PNCO (plasma oxynitrocarburising) was developed and compared with QPQ technology for 45 steel. The cross-sectional microstructure, phase composition, microhardness profile, wear and corrosion resistance were tested and analyzed by optical microscopy, SEM, XRD, microhardness tester and wear tester etc. The results show that a compound layer thickness of 20.14 μm and effective hardened layer thickness of 59 μm, surface hardness of 760HV0.05, wear rate of 1.39×10-3 g·N-1·m-1 and corrosion mass loss rate of 0.39% were obtained by PNCO. The XRD results demonstrate that PNCO treated samples mainly contain FexN compound and Fe3O4 oxide. A comparative study between PNCO and QPQ shows that the sectional microhardness, wear and corrosion resistance of the treating layers are the same level. The study provides a feasible research area for environmentally efficient surface modification technology.
Based on selective laser melting (SLM), the high speed steel samples with nearly full density and low defects were prepared by using the printing strategy consisted of preheated printing substrate, low laser power and slow scanning speed. The effect of solid-solution oil-quenching as well as 1-4 times high temperature tempering on the microstructure and mechanical properties of selective laser melted high speed steel was contrasted and analyzed. The results demonstrate that fine austenite grains can be obtained due to the high melting/cooling rate in SLM process, solving the problems of coarse ledeburite organization and carbide network in high speed steel. The structure of steel is martensite and retained austenite after solid-solution oil-quenching. High speed steel sample transformed into tempered martensite during multiple tempering, accompanied with a large number of micro-sized and nano-sized carbides precipitated. The quenched and triple tempered Tempered-Ⅲ sample has a hardness of 60HRC, a flexural strength of 3621 MPa and a bending fracture strain of 10.1%, exhibiting an outstanding combination of hardness, strength and toughness. The bending fracture strain of high speed steel decreases owing to the coarsening of carbides in four times tempering. The integration of SLM, solid-solution oil-quenching and high-temperature tempering, which forms the combined effects of fine-grain strengthening, martensitic hardening and precipitation strengthening, provides a new approach for complex shaped high speed steel parts with high strength and toughness.
The nano-SiC/AlSi7Mg mixed powder was prepared by mechanical mixing method. The specimens of nano-SiC particle reinforced AlSi7Mg composite were fabricated by selective laser melting (SLM). The relative density, phase and microstructure were observed and analyzed, and the microhardness and tensile properties were tested. The results show that the relative densities of SLM nano-SiC/AlSi7Mg composite are increased firstly and then decreased with the increase of scanning speed and scanning space, and the maximum relative density reaches 99.75%. The microstructure of specimens is similar to that of SLM-formed Al-Si alloys, and the network-structured Si phase is uniformly embedded in the α-Al matrix. There are nano-SiC agglomerates and Mg2Si phase in the α-Al matrix, which has a similar distribution to Si. Compared with AlSi7Mg, the microstructure of specimens is changed from columnar to equiaxed grain, and the grains are significantly refined (the average grain size is 1.36 μm). Due to the addition of SiC, grain refinement strengthening and solid solution strengthening are produced, and the hardness and strength of composite are significantly improved. The hardness, tensile strength and yield strength reach 137.3HV, 448.3 MPa and 334.7 MPa, respectively. However, the elongation is reduced to 3.9%, and the fracture mode is mainly brittle fracture.
The 7075-H18 high-strength aluminum alloy sheet with a thickness of 2 mm is selected as a research object. The quench sensitivity, isothermal phase transformation and kinetics of the alloy were systematically studied via a variety of experimental and numerical techniques such as microstructural analysis, micro-hardness testing, and transformation kinetics modeling and calculation, by which the time-temperature-property(TTP) diagram was established. The results show that 7075-H18 aluminum alloy sheet possesses high quench sensitivity. The tip temperature in time-temperature-property diagram is about 350 ℃, an incubation period of only 0.23 s and a quenching sensitive temperature range of 271 ℃ to 404 ℃. In addition, the critical linear quenching cooling rate corresponding to the curve with a transformation rate of 0.5% is 969.7 ℃/s, exceeding the cooling rate achieved by cold-die quenching. During isothermal quenching, the main precipitate is the coarse η equilibrium precipitate. The longer is the isothermal time, the coarser are the η particles within the grains and at the boundaries. As a result, more particles at grain boundaries tend to be continuously distributed and precipitate free zones get wider. The phase transformation process of the 7075-H18 sheet is successfully predicted using isothermal transformation kinetics model established from the experimental data. According to the model, the precipitation rate of η particles is the highest at 350 ℃ and precipitates in way of nucleation and growth mechanisms, manifesting itself by the growth, thickening and mutual merger of lamellar precipitates. The theoretical data are consistent with the characteristics of η particles observed under transmission electron microscope and the time-temperature-property diagram.
In order to investigate the cyclic deformation behavior in radial direction of extruded AZ31B magnesium alloy, the asymmetric compression-compression cyclic deformation test under strain-controlled was carried out at the strain amplitudes of 0.75%, 1.0%, 2.0% and 4.0%. The results indicate that the hysteresis curves of cyclic deformation show good symmetry at the small strain amplitudes of 0.75% and 1.0%. At the large strain amplitudes of 2.0% and 4.0%, the hysteresis curve shows poor symmetry, and the inflection point appears on the hysteresis curve. With the increase of cycles, the plastic strain amplitude decreases, and all materials exhibit cyclic hardening behavior. The hardening rate during tensile process is much higher than that of compression process at small strain amplitude, however the difference is not obvious at large strain amplitude. The analysis reveals that the effect of dislocation slip is greater on the entire life of magnesium alloy with 〈11${\rm{\bar 2}}$0〉 silk texture along the radial orientation at the small strain amplitude. At the wide strain amplitude, the deformation mechanism evolves during the cyclic process with the increase of plastic deformation, the base plane dislocation and tensile twinning of lower critical resolved shear stress(CRSS) can not fully meet the deformation requirements, while the initiation of slip system and residual twinning of higher CRSS cause inflection point of hysteresis curves. The incomplete twinning-detwinning process results in a large number of residual twins in the deformed matrix, which affects the hardening rate during the cyclic deformation process, the fatigue life is reduced in the meantime.
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