- 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)
Introducing coherent precipitates is an important method to strengthen alloys. Recently, it is found that the introduction of coherent B2 phase in multi-principal element alloys with BCC structure can improve the mechanical properties significantly, developing a new class of important series alloys. The up-to-date knowledge of these alloys from the perspectives of composition, microstructure, phase stability, and mechanical properties was summarized. These alloys exhibit high yield strength over a wide temperature regime, but the ductility presents different characterization due to the compositional difference. At present, their engineering application is limited due to their weaker thermal stability at elevated temperature, especially above 500℃, and furthermore, the design of compositional content appears to be more easy method to resolve the problem. This paper aims at providing guidance to further design of multi-principal element alloys with coherent BCC/B2 dual-phases.
Magnesium batteries with the advantages of low cost, high energy density and high safety are expected to be applied in large-scale energy storage and power vehicles in the future. However, magnesium batteries are still in the early development, and cathode is the key reason that limits the battery performance. The high charge density of Mg2+ results in slow diffusion of Mg2+ in cathode materials. Therefore, how to improve the electrochemical performance of cathode materials is the focus and difficulty in the field of magnesium batteries. By analysing the related researches, six strategies for improving the electrochemical performance of cathode materials were summarized in this paper, namely, reducing the particle size, using the shielding effect of the solvent, increasing the interlayer distance, regulating anions, exploring new structures and developing double ion batteries. By clarifying the root cause that makes the strategies effective and pointing out the advantages and limitations of the strategies, this paper provides valuable guidance for the development of high-performance cathode materials for magnesium batteries. Finally, the development status of magnesium battery cathode materials was summarized, and the future development trend of cathode and the whole battery system was prospected.
Electrode binder is an essential part to maintain the integrity of electrode, and it is very important to improve the specific capacity and cycle stability of the battery. Polyacrylic acid (PAA) is widely used as the binder of anode or cathode in the lithium batteries because it contains more polar functional groups and can be dissolved in water. Due to possessing a lot of polar groups, PAA binder has better adhesion. But the hydrogen bond formed between the molecular chains by polar groups makes the PAA molecular chain more rigid, which is not conducive to maintaining the integrity of the electrodes during charging and discharging. It indicates that controlling the number of PAA functional groups and changing the type of functional groups/molecular chain structure of PAA binder have a great influence on the improvement of battery performance. The effect of PAA binder on electrochemical performance of lithium battery in recent years was reviewed in this paper, focusing on the structural characteristics, modification and application methods and their effects on the initial coulombic efficiency, cycling stability and impedance of different lithium batteries. Perspectives on the future of modified PAA binder were reviewed. The effects on the performance of the binder were explored after introducing different structures such as elastic or conductive groups. Improving the interface performance is to be suitable for cathode and anode with different active materials, and to improve the lithium ion diffusion coefficient. Then the performance of lithium battery is also enhanced.
Due to its large specific surface area, excellent penetration resistance and a large number of functional groups distributed on the surface, graphene oxide(GO) has become a research hotspot in the fields of anticorrosion, permeation separation and coating mechanical properties. The research progress of GO application on metal surface in recent years was reviewed. On the basis of domestic and foreign literature, the research progress of GO applied on metal surface for anticorrosion, permeation separation, mechanical properties of coating and other aspects was described, and the mechanism was summarized and analyzed. The anticorrosion mechanism is mainly the physical barrier effect of GO and its chemical inertness to the electroactive medium. The mechanism of osmotic separation is mainly the multi-layer pore structure and functional groups of GO. The main mechanism of mechanical properties of the coating is the good compatibility between GO and coating and the formation of chemical bond between surface functional groups and metal matrix. It was pointed out that there is still a lack of GO composite preparation technology that meets the requirements of environmental protection, low cost and large-scale industrialization, the technological parameters involved, the design of composite phase system and other aspects still need further study. It was also proposed to be applied to metal anticorrosion, oil-water separation and mechanical properties of coating, so as to solve the key problems such as corrosion resistance of metal surface, oil-water permeability and separation performance, bonding force between coating and metal substrate.
Thermoplastic composite materials are widely used in automobile, aerospace and military fields due to their advantages of high impact toughness, recyclability and excellent environmental adaptability. However, the high viscosity of the thermoplastic resin after melting makes it difficult to impregnate the fiber adequately. As the intermediate material of composite materials, the preparation of prepreg has been relatively mature. The fibers in the prepreg have been impregnated with resin, so the composite material prepared by the prepreg has fewer voids. The preparation method of thermoplastic prepreg and analysis of the advantages and disadvantages of various preparation methods were introduced in this paper, including solution impregnation, melt impregnation, powder impregnation, film stacking lamination, commingled yarns and reactive of chain growth impregnation. The impregnation mechanism of melt infiltrated fibers was described and some research results of impregnation mechanism were summarized. The effects of parameters such as immersion temperature, immersion pressure and traction speed on the properties of prepreg were discussed. Finally, the main problems and the development direction in the production of prepreg were summarized. In the future, methods such as multidisciplinary integration, fiber and resin modification and computer simulation of the impregnation process can be used to promote the industrial development of thermoplastic prepreg.
Soda lime/aluminosilicate glass is widely used in commercial and national defense industries due to its excellent physical properties such as high strength and high hardness. Fatigue fracture is one of the main failure modes of glass. Investigating the fatigue behavior is of great importance to its processing, life prediction and failure prevention. In this paper, the fundamental and experimental methods of static fatigue and dynamic fatigue of soda lime/aluminosilicate glass were reviewed.The conclusions obtained by comparing the fatigue behavior of soda lime silicate and aluminosilicate glass demonstrate that the threshold load for radial crack initiation of raw soda lime silicate glass is much lower than raw aluminosilicate glass, the threshold load for radial crack initiation of chemically strengthened soda lime/aluminosilicate glass is increased with the surface compressive stress; the crack growth rate of raw soda lime/aluminosilicate glass increase with fictive temperature and this phenomena is more evident in aluminosilicate glass; the raw soda lime/aluminosilicate glass shows a loading rate-dependent strength while the chemically strengthened aluminosilicate glass does not. Consequently, the effect of different stress state and environment atmosphere on the behavior of static fatigue and dynamic fatigue of static fatigue and dynamic fatigue is an important issue to be studied.
Ferrosilicon alloy is widely used as alloying agent and deoxidizer in the steelmaking process, which containing the metallic impurities of Al, Ca, and Ti would directly affect the cleanliness of the molten steel. Therefore, metallic impurities from the ferrosilicon alloy removed by the top blowing Ar-O2 gas was carried out. The morphology, composition, and area fraction of impurity phases of metallic impurities in the ferrosilicon alloy were compared before and after Ar-O2 gas blowing treatment by automatic scanning electron microscopy, and contents of metallic impurities were measured by inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a large amount of metallic impurity phases precipitate in the ferrosilicon alloy raw material, which mainly contain Al, Ca, and Ti impurities, and their contents are 1.11% (mass fraction, the same below), 0.31% and 0.11%, respectively. After blowing Ar-O2 gas for 5 minutes, contents of Al and Ca are dropped sharply to 0.66% and 0.13%, respectively. After blowing Ar-O2 gas from 45 minutes, the removal rate of impurity elements is slowed down and the refining reaction tends to reach equilibrium. After 120 minutes of blowing Ar-O2 gas, contents of Al, Ca and Ti are 0.42%, 0.014% and 0.094%, respectively; meanwhile the removal efficiency of Al, Ca and Ti are 62.16%, 95.48% and 14.54%, respectively. The refining method of blowing Ar-O2gas can effectively remove impurity elements of Al and Ca in the ferrosilicon alloy, while no significant change in Ti content is found.
The KNO3-based water-soluble salt core was prepared using 70%KNO3-30%KCl (mole fraction) as a matrix material and glass fiber as a reinforcing material by stirring casting method. The effects of different glass fiber contents on the bending strength, impact toughness, water solubility rate and hygroscopic rate of the water-soluble salt core were compared and analyzed. The scanning electron microscopy and energy spectrometer were used to analyze the microstructure characteristics of the water-soluble salt core strengthened by glass fiber. The results show that with the increase of glass fiber content, the bending strength and impact toughness of the salt core are increased, and the water solubility rate and moisture absorption rate are gradually decreased. When the mass fraction of glass fiber is 30%, the salt core has the largest bending strength of (38.85±0.61) MPa and impact toughness with (2.13±0.1) kJ/m2, and the water solubility rate is still as high as (476.5±12.0) g/(min·m2), and the moisture absorption rate is (0.085±0.007)%. The microanalysis shows that the glass fibers are evenly distributed among the matrix of KNO3-based water-soluble salt core, which significantly refines the KCl primary phase. The average grain size of KCl primary phase is reduced from 57.89 μm to 24.13 μm, which is the main strengthening mechanism of the salt core. The crack will deflect when encountering glass fibers during the crack propagation, and the fiber pull-out is also observed, which is the main toughening mechanism of the salt core.
The dynamic deformation behaviors of 2519A aluminum alloy treated by T87, T8, T9 and T9I6 were investigated by the split Hopkinson pressure bar in the strain rate range of 1040-5900 s-1, and the microstructure evolution of the alloys during high velocity impact were analyzed by means of metallography and transmission electron microscopy, the effect of different thermo-mechanical treatments on dynamic responses of aluminum alloy 2519A was revealed. The results show that the dynamic yield strength of 2519A-T8 or T9 aluminum alloy is increased significantly than T87 treated alloy, but the adiabatic shear susceptibility is dramatically improved. Interrupted aging T9I6 can improve θ' (Al2Cu) precipitates density and make them much finer and denser, which reduce the decomposition rate of θ' precipitates and enhance its stability at high strain rate. So 2519A-T9I6 aluminum alloy has much higher dynamic yield strength, and lower adiabatic shear susceptibility, which shows best performance at high strain rate.
The Mg-9Al-3Si-0.375Sr-0.78Y alloy specimens were compressed at constant isothermal strain rate by Gleeble 3500 thermal-simulation machine. The hot deformation behavior in the range of 250-400℃ and strain rate 0.001-10 s-1were studied. The results show that the peak stress decreases with the decreasing of strain rate and the increasing of temperature, meanwhile, the sensitivity of peak stress to strain rate increases with the decreasing of deformation temperature. In addition, the Arrhenius constitutive equation of hot deformation considering strain is established. The calculated flow stresses are compared with the experimental results, in the range of 300, 350℃ and 0.001-10 s-1, the mean absolute errors of the model are 1.57% and 1.76%, respectively. The average deformation activation energy is about 183.58 kJ/mol, and the average strain rate sensitivity index is 0.1616. The α-Mg phases exhibit dynamic recrystallization characteristics obviously. The size of β-Mg17Al12 phases decreases and its distribution becomes uniform, and the morphology of primary Mg2Si phase changes little. At low temperature (250-300℃), dynamic recrystallization occurs only at the grain boundary. Under high temperature (350-400℃) deformation, the primary α-Mg grains show significant dynamic recrystallization. With the increasing temperature and decreasing strain rate, recrystallization degree increases and recrystallization grain grows gradually.
Various contents (0%, 2%, 5% and 8%, mass fraction, the same below) of TiB2/Al-4.5Cu composites were prepared by mixed salt reaction method. After T6 heat treatment, XRD, ICP, OM, SEM, EDS and tensile test at room temperature were adopted to observe microstructure and assess mechanical properties of the composites. XRD and ICP tests confirm that the alloys contained only α-Al, Al2Cu and TiB2, Al3Ti and Al2B phases are not found.OM and SEM observations show that the average grain size of α-Al in the matrix material is 167.5 μm, while is 110.4, 87.2, 75.2 μm in 2%, 5%, and 8% TiB2/Al-4.5Cu, respectively. TEM observation indicates that the TiB2 particles are quadrate and hexagonal structure dispersed in the grain boundary chiefly. Room-temperature tensile experiments show that with the increasing of TiB2 content, the mechanical properties of TiB2/Al-4.5Cu composites are improved gradually. Especially, for the composite with TiB2 mass fraction of 8%, the yield strength(YS), ultimate tensile strength(UTS), elastic modulus and microhardness are 356 MPa, 416 MPa, 92.5 GPa and 96.5HV, separately. However, the elongation(δ) decreases from 10.3% to 4.3%. Analysis suggests the enhancement of load transfer, fine crystal and dislocation proliferation are all the factors that greatly improve the mechanical properties of TiB2/Al-4.5Cu composites, in especial, the dislocation cell and loop distributed around TiB2 particles play a decisive role in enhancing the strength.
In order to reveal the microstructure transformation mechanism of the process of depositing dissimilar material on the surface of mold steel containing Cr, the 316L stainless steel was deposited on two kinds of mold steel. The microstructure and hardness were characterized by SEM, EPMA, XRD etc, moreover, the mechanism of microstructure transformation in the interface and deposition zone was analyzed by the combination of melting-solidification dynamic process and Schaeffler diagram. The results show that the microstructure near the deposition interface shows obviously different characters due to the difference of matrix element composition and phase distribution. The thickness of transition zone of high Cr ledeburite steel is 200 μm, the transition zone is obviously different from other areas of the deposition layer in terms of its morphology and phase; the carbides in the transition zone undergo complex changes, such as local aggregation and growth at first, and then uniform distribution among dendrites. However, the thickness of microstructure transition zone of the deposition layer in P20 steel is less than 20 μm, the microstructure grows in the form of dendrite and is connected with the non transition zone of the deposition layer, meanwhile, dispersed granular carbides are found in the dendrites. Under the action of the dynamic changes of C, Cr, Ni and other elements in the molten pool, the composition phase of the non transition zone in the two kinds of steel deposition layers is also obviously different; the matrix phases of deposition layers in high Cr ledeburite steel and P20 steel are austenite phase and martensite phase respectively, as a result, the range of hardness variation is 295-325HV0.2 and 500-575HV0.2, respectively.
The high-performance reduced graphene oxide/sulfur (rGO/S) composite cathode was obtained by integrating sulfur nanoparticles with graphene oxide (GO) in liquid phase reduction by self-assembly process. The morphology and microstructure of the materials were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The results show that sulfur nanoparticles are uniformly distributed among the graphene sheets and effectively encapsulated by the graphene sheets. The mass fraction of sulfur in 35-rGO/S composite is as high as 83.6%. The initial discharge capacity of the 35-rGO/S composite cathode can reach 1197.3 mAh·g-1 at a current density of 0.2 C, and the capacity remains 730 mAh·g-1 after 200 cycles, manifesting outstanding cycling stability.
Phonon-liquid thermoelectric material β-Cu2-xSe can achieve an excellent thermoelectric performance. Molecular dynamic simulations were performed to study the thermal conductivity of β-Cu2-xSe. The correlation between diffusivity of "liquid-like" ions and the thermal conductivity was analyzed. The effect of doping and vacancies on the material's thermal conductivity was also investigated. The results show that "liquid-like" ion's diffusivity and the thermal conductivity are strongly connected. Enhancement of Cu ions mobility in β-Cu2-x Se increases the non-harmonic vibration of the crystal lattice, which strengthens the phonon scattering and reduces the thermal conductivity. Doping and vacancies have different influences on "phonon-liquid" materials' thermal conductivity. Vacancies are conducive to the movement of "liquid-like" ions, leading to the decrease in the phonon acoustic branch frequency, which effectively reduce the thermal conductivity. Vacancies may significantly improve "phonon-liquid" materials' thermoelectric conversion efficiency, while the effect of doping on thermal conductivity is not significant.
Based on the excellent chelating ability of phytic acid (PA), Ag+, Cu2+, Fe3+, and Zn2+, were used to chelate with PA, and deposited on the surface of layered double hydroxides (LDHs) to form core-shell structure, so as to improve the interfacial compatibility between layered clay and polymer matrix. Surface coated LDHs (LDHs@PA-M) loaded with different metal ions were prepared. The micromorphology of LDHs@PA-M loaded with different metal ions was studied and applied in the strengthening modification of poly(ε-caprolactone) (PCL). The results show that PA can form stable and uniform nano-coatings with Ag+ and Cu2+on the surface of LDHs. With the excellent antibacterial activity of Ag+ and Cu2+, the antibacterial rates of LDHs@PA-Ag+ and LDHs@PA-Cu2+ against Escherichia coli (E.coli) both exceed 99.99%. Compared with pure PCL, the tensile strength and elongation at break of LDHs@PA-Cu2+/PCL nanocomposites (mass fraction of LDHs@PA-Cu2+ is 1%) increase by 30.7% and 33.3%, reaching 40.9 MPa and 816%, respectively. The enhancement of mechanical properties for LDHs@PA-Cu2+/PCL nanocomposites is the most remarkable. The antibacterial rate of LDHs@PA-Cu2+/PCL and LDHs@PA-Ag+/PCL nanocom-posites against E.coli both exceed 99.99%. It shows excellent antibacterial activity, which expands the application of layered clay/bio-based polymer nanocomposites in the field of active packaging.
The precipitation method was employed to synthesize hollow column-like CuS with copper nitrate and sodium thiosulfate as materials. The related morphology and crystalline phase of the sample were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and the fourier transform infrared (FT-IR). Meanwhile, the degradation performance of hollow column-like CuS was investigated with methyl orange (MO) as a contamination. The results show that the as-prepared hollow column-like CuS is assembled from CuS nanosheets. The diameters and the length of hollow column-like CuS are 400 nm and 2.0 μm, respectively. The Fenton-like catalyst consisting of hollow column-like CuS and H2O2 shows excellent degradation ability for dye. After 110 min, the degradation rate of methyl orange reaches 86.6%, which is superior to the degradation ability of CuS with a solid structure.
Graphene loaded ferric oxide (G/Fe3O4) composites were prepared by chemical modification using graphene and nano-Fe3O4 as raw materials. The composites were characterized by transmission electron microscope, X-ray diffractometer and Fourier infrared spectrometer, and G/Fe3O4 composites were added to SN 5W-30 lubricating oil, and the dispersion stability and tribological properties of composites in lubricating oil were studied by plasma spectrometer and four ball friction tester. The results show that G/Fe3O4 composite materials generated by the co-modification of oleic acid and silane coupling KH570 are better dispersed on the graphene surface than with oleic acid modification alone; precipitation stability experiments show 10 days later, iron content in the lubricating oil is decreased by 48.3% without composite added, iron content is decreased by 39% with oleic acid modified composite added, and iron content is decreased by 31.1% with oleic acid and KH570 jointly modified composite; four-ball experiments show that G/Fe3O4 composites acting as lubricating oil additives have good tribological properties, the use of oleic acid and KH570 joint modification effect is better than the use of oleic acid modification, the maximum card-free bite load PB is increased by 6.5%, the diameter of the mocha is decreased by 4.4% and the coefficient of friction is decreased by 4.8%.
Composite materials are prone to delamination defects during the preparation process. For the non-destructive testing and evaluation of carbon fiber reinforced polymer (CFRP) delamination defects, a standard specimen with embedded delamination defects was prepared, and then phased array ultrasonic non-destructive testing technology was used to detect the delamination defects. The qualitative assessment and quantitative evaluation of delamination defects were carried out. First, the delamination defect specimen was prepared with the autoclave forming process, and polyimide films were embedded in the specimen before progress; then, the specimen was inspected using phased array ultrasonic technique, qualitative and quantitative measurement of delamination defects were analyzed with ultrasonic S-scan and C-scan image, uncertainty analysis of test results were also discussed in combination with the sound field simulation. The results show that the shapes of the delamination defects in the sample are regular, the embedment depth and size are consistent with the preset. The index direction size of the delamination defect is more accurate, and the scan direction size is larger than the actual size. Phased array ultrasonic technique can accurately identify the shape, size and position of delamination defects with high detection accuracy and still has good detection effects for small defects.
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