- 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)
Graphene, as a rising star in materials science, is intensively studied in Li-ion batteries and supercapacitors, owing to its unique structure and excellent properties. The research status of the application of graphene in energy storage field was disscussed and the future development trend was predicted, and therefore to enhance the understanding of the structure-performance relationship of graphene and also the application of graphene in this field. Firstly, the application of graphene in cathode and anode of Li-ion battery, and the application of graphene in electrical double-layer capacitor and pseudo-capacitor were introduced. Secondly, the challenges of graphene in electrical double-layer capacitor were discussed and the ideal structure of graphene applied to electrical double-layer capacitor was proposed. Finally, the "three steps" to realize the commercial application of graphene-based electrical double-layer capacitor were put forward.
Bismuth ferrite is considered to be the largest prospect in the field of device, owing to its both ferroelectricity and antiferromagnetic property at room temperature.It is considered to be the most promising multiferroic compound.The history of the development of multiferroic materials, the crystal structure of bismuth ferrite, and related work and progress on ion substitution modification of ferroelectric properties of bismuth ferrite film in recent years were reviewed in this paper.The focus was on the replacement of the A site by the lanthanide and the low cost alkali metal element, the substitution of the B-site by the transition metal element, and the common substitution of the A and B sites for the leakage current and ferroelectricity of the bismuth ferrite film.The effect of different elements and different doping amounts on residual polarization and coercive electric field value of bismuth ferrate film substituted by A and B sites were systematically summarized.Accordingly, the effect of various elemental ion substitution modification on bismuth ferrite film can be more intuitively understood.At the end of this paper, the urgent work on the influence of fabrication process, electrode material, film thickness and operating voltage of bismuth ferrite thin films was put forward.
Iron-based shape memory alloys have recently attracted widespread attention due to their low cost, excellent workability, machinability and good weldability, and has been identified as a new shape memory material with promising development. Mechanical alloying (MA) and powder metallurgy (PM) are new methods for the preparation of materials, which can be used to prepare shape memory alloy with superior properties. The effect of MA and PM on the phase transformation, microstructure and properties of Fe-Mn-Si-based shape memory alloys, and the application of such alloys in new fields were discussed in details. At last, the problems in the study of MA/PM process for preparing Fe-Mn-Si based SMA, such as process parameters, phase transformation mechanism, recovery stress and low temperature stress relaxation are pointed aod.
The research progress of superhydrophobic surface on metal substrates was reviewed. The main preparation methods of metal-based superhydrophobic surface were discussed, and the advantages and disadvantages of different preparation method were compared. At the same time, the functional properties of metal-based superhydrophobic surface were discussed, and the main problems in preparation and application of metal-based superhydrophobic surfaces were analyzed. It was pointed out that the future development direction of metal-based superhydrophobic surface is to simplify the preparation process, reduce costs, improve the durability and stability of superhydrophobic surface, and prepare metal superhydrophobic surface with self-healing properties.
Polylactic acid (PLA), a new type of bio-based renewable biodegradable material, has attracted more and more attention because of its advantages with high mechanical strength, ease of processing, high melting point, biodegradability and biocompatibility. However, its inherent brittl-eness, low elongation at break and breaking strength severely limit its practical application and has also led to more extensive and comprehensive research. This review summarizes the research progress of toughening polylactic acid with biodegradable macromolecules, especially focusing on the updated development on bio-based polyesters, bio-based elastomers, plant-based biopolymers, natural rubber and vegetable oils, and biomacromolecules, and meanwhile, the problem of weak impact toughness and low crystallization rate and low thermal transition temperature of polylactic acid after improving toughness was proposed, and the future direction of development and the subjects needed to focused on was finally predicted.
NiCrAl/YSZ/NiCrAl-B. e composite coating on TC11 titanium alloy was combusted by friction in oxygen-enriched atmosphere. The combustion products were studied by XRD, SEM, EDS and EPMA. The effect of the composite coating on the combustion behavior of TC11 titanium alloy was discussed. The results show that there is regional microstructural evolution along radial direction in the substrate of the combusted specimen. The substrate near the central hole is the ignition source. When the combustion degree is low, the effect of the YSZ intermediate layer on the combustion behavior of titanium alloys can be ignored. However, when the combustion degree is high, the YSZ intermediate layer dissolves greatly in the titanium alloy melt through decomposition reaction, which provides O and Zr for the titanium alloy melt and accelerates the interaction between Ti and O. Furthermore, the ZrTiO4 combustion product has a worse ability to block oxygen diffusion than TiO2. As a result, NiCrAl/YSZ/NiCrAl-B. e composite coating, especially the YSZ layer, promotes the ext-ended combustion of TC11 titanium alloy.
The supercritical nickel-graphene composite coating was prepared by supercritical carbon dioxide fluid(SCF-CO2) assisted pulsed composite electrodeposition technique with graphene oxide (GO) as the second phase additive. The effect of pulse duty cycle on the microstructure and mecha-nical properties of the coatings was investigated. The results show that the microstructure of composite coating can be refined significantly by the combination of supercritical carbon dioxide fluid and graphene oxide. The change of the (111) and (200) peaks in the XRD patterns of the composite coating shows that change occurs in preferred orientation during the crystallization process. The change of duty cycle has great influence on the mechanical properties of the coatings. The micro-hardness of the supercritical nickel-graphene composite coating is as high as 756.8HV0.2 and the cross-sectional area of wear scar is 4385μm2 at 50% duty cycle. Compared with the nickel-graphene comp-osite coating prepared under conventional conditions, the microhardness and wear resistance of super-critical nickel-graphene composite coating are increased by 1.6 and 11 times.
In order to improve the wear resistance of 1Cr18Ni9Ti stainless steel in NaCl and acid solution environment, the WC-10Co-4Cr coatings with two grain sizes were prepared by plasma spraying, and the corrosion resistance in 3.5%(mass fraction, the same below)NaCl and acid solution(pH = 5.0) were investigated. The results show that the WC, W2C, W and η (CoxWxC) exist in these coatings. The corrosion potential of these coatings is higher than that of 1Cr18Ni9Ti substrate in 3.5% NaCl solution. In the acid solution (pH = 5.0) at different temperatures, the potential difference for the nanometer WC-10Co-4Cr coatings has little change with the temperature. The corrosion mechanism of the coatings in NaCl and acid solution is shown as follows:the oxygen atoms adsorbed on the surface of WC-10Co-4Cr coating, can impel the Co and WC to form the galvanic couple in 3.5% NaCl solution. In the acid solution (pH = 5.0), Co phase in the WC-10Co-4Cr coatings is dissolved to Co2+, and formed the galvanic corrosion with WC phase, so the isolated WC particles are formed on the coating surface.
The NiCrBSi-Ti3SiC2-CaF2-WC self-lubricating anti-wear composite coating was fabricated on TC11 alloy substrate by laser cladding. The phase compositions and microstructure were invest-igated by X-ray diffractometer (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Microhardness was measured with a microhardness tester. Tribological proper-ties of the fabricated composite coatings were evaluated under dry sliding condition at room-temper-ature (25℃), 300℃ and 600℃, and the wear mechanism was analyzed. The results show that the mi-crostructure of the composite coatings consists of γ-Ni eutectic phase, M23C6, TiC, (Ti, W)C, Ti5Si3 hard phase and some Ti3SiC2, CaF2, TiF3 lubricating phase. The microhardness of laser cladding layer is improved greatly. The average microhardness of the laser cladding coating is 863.63HV0.2, which is 2.46 times of the matrix. The friction coefficient and wear rate are lower than that of the substrate. The lowest friction coefficient and wear rate are 0.275 and 4.8×10-5mm3·N-1·m-1 at 300℃, respectively.
The surface of EA4T steel was repaired by ultrasonic vibration assisted laser cladding.The influence of ultrasonic vibration on the forming quality, microstructure and phase composition of laser cladding of EA4T steel were compared and analyzed by optical microscopy (OM), scanning electron microscopy(SEM), X ray diffraction(XRD), and the microhardness of the cladding layer and matrix was tested by microhardness tester.The results show that the cladding forming quality is improved, and the dendritic structure with strong original orientation is broken under the effect of ultrasonic vibration, which reduces the segregation of dendrites within the cladding layer.At the same time, ultrasonic vibration refined grain, promotes the precipitation of Cr23C6 carbide on the dendrites, but it does not change the phase composition of cladding layer.Compared with that without ultrasonic vibration applied, the microhardness distribution of cladding layer is more uniform under the ultrasonic vibration, the average microhardness of cladding layer is increased by 126.2HV0.2, and the average microhardness of heat-affected zone is decreased by 31.2HV0.2.
Compact and uniform coatings were fabricated on LY12 aluminum alloy surface by adjusting process parameters and oxygen flow after micro-arc oxidation (MAO) treatment. The thickness, morphology, phase compositions and corrosion resistance were examined by SEM, XRD and electrochemical test system. The mechanism of MAO with oxygen was discussed, and the effect of oxygen flow on the coating compactness was analyzed. The results indicate that with the increase of time, voltage and concentration of electrolyte, the coating thickness changes regularly. The effect of oxygen on sintering can promote the growth of compact coatings, and the thickness of compact coatings first increases and then decreases with O2 rising. Under the conditions of 105g/L KF, 85g/L KOH, 12g/L NaAlO2, 110V for the voltage, 15min for treatment time and 0.010L/s for oxygen flow, a 30μm-thick compact coating can be formed on LY12 aluminum alloy. The corrosion potential of the coating increases to -0.11V, and the current density reduces to 2.1×10-6A/cm2, which is reduced by two orders of magnitude compared with the matrix and the corrosion resistance of the LY12 aluminum alloy significantly improves.
Homogenization heat treatment on the as-cast Mg-13Gd-3.5Y-2Zn-0.5Zr magnesium alloy was carried out with the temperature range of 505-525℃ and the time range of 4-24h. Optical microscope(OM), scanning electron microscope(SEM), X-ray diffractometer(XRD) and universal material experiment machine were used to analysize the changes of microstructure evolution and mechanical property before and after homogenization. The results show that the reticular eutectic compounds in initial grain structure are transformed into discontinuous bulk-shaped LPSO (long-period stacking ordered) phases at the grain boundary and the discrete distribution of the square-shaped rich rare-earth phases dissolved. The mechanical properties test results show that the ultimate tensile strength and the elongation of the cast magnesium alloy are 172.9MPa and 1.8%, respectively. The mechanical properties of the alloy are improved after homogenization, the ultimate tensile strength of room temperature is 212.3MPa and the elongation is 3.1% under the homogenization of 515℃/16h. At the same time, the ultimate tensile strength of high temperature at 200℃ reaches the highest 237.2MPa and the elongation is 9.7%. The fracture microstructure of as-cast alloy indicates that the fracture is cleavage brittle fracture dominated by tearing edges and cleavage steps, small and shallow dimples occur in the alloy after homogenization treatment, but is still quasi-cleavage fracture dominated by cleavege steps, and limited plasticity is improved. Meanwhile, LPSO phase can be the crack initiation source.
The technology of selective laser melting was used to fabricate Hastelloy X samples. The effect of hot isostatic pressing (HIP) and solution treatment on microstructures and tensile properties of Hastelloy X samples was investigated. The results show the as-deposited samples exhibit clear melt pool morphologies, columnar grain with embedded cellular structures and no obvious precipitates are detected. The corresponding tensile properties are characterized by high strength and low ductility. High temperature tensile fracture surface reveals that the as-deposited samples crack along laser scan tracks. After HIP, the microstructures evolved into equiaxed grains, and large amount of precipitates are found to distribute within grain boundaries and grain interiors. Besides, solidification cracks are effectively healed by HIP. In this circumstance, the tensile strength is decreased by about 48% combined with improved ductility up to 59% after high temperature tensile tests. After HIP+solution treatment, the grain size and morphology keep similar with that in HIP processed state, while the amount of precipitates inside grain areas is significantly reduced and an overall sound tensile property is achieved.
The specimens of the fourth generation single crystal superalloy after heat treatment and at as-cast state were indented and annealed in vacuum at 1100, 1150, 1200, 1250, 1300℃ and 1340℃, respectively. The recrystallized microstructures of the alloy were examined by optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattering diffraction (EBSD). The results show that cellular recrystallization (CRX) occurs in the standard heat treatment samples and as-cast samples after annealing treatment at 1100, 1150℃ and 1200℃. Mixed recrystallization occurs in standard heat treatment samples and as-cast samples after annealing treatment at 1250℃. Equiaxed recrystallization (ERX) develops when the standard heat treatment samples are annealed treatment at 1300℃, while mixed recrystallization occurs in as-cast samples at same condition. ERX develops when these two samples are annealed at 1340℃. The recrystallized layer depth of these two samples increases with the increase of annealing treatment temperature and the depth of standard heat treatment samples is obviously larger than that of as-cast samples.The recrystallized grain of standard heat treatment samples easily grows up at same condition. The interface between the recrystallization grain and original grain is low angle boundary and high angle boundary, while the interface between adjacent recrystallization grains is low angle boundary, high angle boundary, and twinning boundary. It can be inferred that the formation of twins can play an important role in the process of recrystallization.
Friction stir welding(FSW) was performed for 4mm thick T4003 ferritic stainless steel(FSS) with different welding parameters. The effect of welding parameters on microstructure, hardness distribution, and impact toughness of FS-welded joints at room temperature and low temperature was investigated. The results show that the stir zone(SZ) and the thermo-mechanically affected zone (TMAZ) consist of duplex structure of ferrite and martensite. The SZ is heterogeneous along the thickness of the joint and this trend gets more obvious with the decrease of rotational speed and increase of welding speed. In the heat affected zone(HAZ) of the advancing side, the microstructure transits smoothly and no obvious characteristics of deformation and elongation as the rotational speed increases to 250r/min from 150r/min. The hardness distribution of the weld is relatively uniform and the maximum hardness is 290HV, approximately 1.87 times than that of the base material(BM). The welding parameters and temperature exert great effect on the impact absorbing energy of the welded joint. The impact absorbing energy of HAZ and SZ are up to 90%-92%, and 85%-103% of BM, respectively, at room temperature(20℃). While at low temperature(-20℃), the impact absorbing energy of HAZ and SZ reaches 87%-97%, and 82%-95% of BM, respectively. It shows that the weld zone still has better matching between strength and toughness.
Using the bamboo charcoal(BC) material as the template, the metallic chemical compound MoSi2 as the absorption catalyst, the MoSi2/BC porous composite materials were fabricated by the embedded solid reaction sintering method. The components, microstructure and dielectric constant of the MoSi2/BC composite material were detected by XRD, SEM and vector network analyzer respectively. The results show that in the argon protective atmosphere(Ar), at the sintering temperature of 1450℃, the phase composition of MoSi2/BC composite material primarily consists of MoSi2, SiC and amorphous carbon. In the pores of the bamboo charcoal, the SiC whiskers(SiCW) are distributed in an irregular way with different size and length, furthermore to form an intersecting network except MoSi2 particles. The existence of SiCW can significantly improve the wave absorption ability. At the range of 8.2-12.4GHz, after mixed with epoxy resin, the reflection losses of the composites of MoSi2/BC are gradually decreased with the increase of MoSi2/BC content. With the increase of sample thickness at the MoSi2/BC 50%(mass fraction) content, the minimum absorption peak of reflection loss is moving to the low frequency. The composites' lowest reflection loss is -13dB at 11.87GHz, and the reflection bandwidth value below -10dB is around 1.0GHz.This ind-icates that the MoSi2/BC composites possess perfect microwave absorbing performance.
Basalt fiber(BF) was modified with chitosan to investigate the influence of the surface modification on biofilm attachment properties. The surface functional groups, composition and morphology were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photo-electron spectroscopy (XPS) and scanning electron microscopy (SEM). Furthermore, the hydrophi-licity of BF was analyzed by contact angle measurement and the biofilm attachment properties were discussed via the microorganism immobilization tests. The results show that the surface-modified basalt fiber (MBF) can be successfully prepared by physical coating method. The surface roughness of MBF is 209.04nm, and the contact angle of MBF is 66.62°. Moreover, the biomass attached on MBF surface is significantly increased and the biofilm is relatively dense and homogeneous. The micro-organism immobilization rate is increased from (129.27±1.23)% to (179.92±2.63)%, thus illustr-ating that surface modification of basalt fiber can significantly improve biofilm attachment properties.
Carbon microspheres were synthesized by the hydrothermal treatment of saccharides (fructose and starch) in the presence of additives (HCl and KCl) and the subsequent pyrolysis, and the role of the additives in the hydrothermal reaction was also investigated. The results show that carbon microspheres with well-developed nanoporous structures and surface oxygen functional groups are obtained. Both of the additives in the saccharide solutions induce the enlargement of the size of the microspheres. The mean diameter of the microspheres can be tailored in a range from 0.53μm to 6.67μm. The morphology of the microspheres depends on the reaction kinetics during hydrothermal treatment. During pyrolysis, the microstructure of the microspheres is transformed from polymer to glassy carbon, which is accompanied by a mass loss of about 50% and a contraction of over 20% in scale. Both of the additives display distinct effects on the stages of the hydrothermal reaction of the saccharide solutions. The HCl mainly accelerates the hydrolysis kinetic of polysaccharide and the dehydration and fragmentation of monosaccharide, while the KCl chiefly enhances the growth kinetic of the microspheres. The growth of the microspheres is performed through two main ways:the reactive oxygen functionalities present in both the surfaces of the microspheres and the building units and the merged fine microspheres.
Pre-lithiated multiwalled carbon nanotube anode was prepared by internal short approach(IS) for 5min, 30min and 60min. Lithium ion capacitors (LICs) were assembled using pre-lithiated multiwalled carbon nanotubes as cathode and activated carbon(AC) as anode. The structure characterization of multiwalled carbon nanotubes and electrodes were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical performance of pre-lithiated multiwalled carbon nanotube electrodes and pure multiwalled carbon nanotubes electrodes were tested by galvanostatic charge/discharge and electrochemical impedance spectrum. The electrochemical tests indicate that the charge-discharge performance of LIC is greatly improved by pre-lithiation of multiwalled carbon nanotubes. The energy density reaches about 4 times over conventional electric double-layer capacitors (EDLCs) at the current density of 100mA/g. The LICs achived a specific capacitance of 57F/g at the current density of 100mA/g with 60min pre-lithiatiation process. The maximum energy density and power density reach 90Wh/kg and 4130W/kg respectively in the current range of 100-3200mA/g. The capacity retention rate remains more than 85% after 1000 cycles. The LIC shows excellent supercapacitor performance.
Five transparent polyimide thin films with different proportions of 1, 2, 4, 5-, pyromellitic dianhydride (PMDA) were made by copolymerization of 4, 4'-(six fluoro isopropenyl) two phthalic anhydride (6FDA), 4, 4'-two amino -2, 2'-double three trifluoromethyl biphenyl (TFMB) and PMDA, and their properties were characterized. The results show that thermal stability and heat resistance are increased after the introduction of rigid monomers; the dielectric constant of the films is increased with the increase of PMDA content; homopolymer film has higher light transmission rate than copolymer films in visible light; tensile test shows that adding a small amount of PMDA, the tensile strength and elastic modulus of the film are increased, but when the content of PMDA is higher than 40%, the mechanical properties are decreased; the coefficient of thermal expansion of the films are decreased obviously while PMDA content is increased.
Honeycomb sandwich plates are used widely in the aerospace industry. Building accurate finite element models of honeycomb sandwich plates is necessary for analyzing and optimizing the microvibration that occurs in spacecraft. A finite element dynamic model of a honeycomb plate was built, and then by using orthogonal design of experimental computation, the most important material parameters of honeycomb core equivalent model were identified. Through the global optimization based on adaptive sampling guided by response surface model, the parameters of honeycomb core were updated efficiently. The average error of first six modal frequencies of the updated finite element model against experimental result is reduced to less than 1%.
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