- 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)
Interface is a key factor affecting the comprehensive performance of magnesium matrix composites, and how to carry out interfacial modulation has been a hot research topic in magnesium matrix composites. Focusing on three types of interface structures of magnesium matrix composites (coherent, semi-coherent and incoherent) and two key issues (interfacial wettability and interfacial reaction) affecting the interface properties, the research progress of interface optimization schemes was reviewed in this paper and the guidelines for the design and regulation of interfacial structures to achieve good interfacial bonding were proposed: good wettability and slight interfacial reaction. In view of the improvement of interface properties of magnesium matrix composites, the addition of rare earth elements can be considered in the future to purify the interface and improve wettability. The matrix and reinforcement are selected according to engineering needs to obtain composite materials with excellent performance in certain aspects. New reinforcement surface coatings will be developed to fully enhance the capabilities of interfacial bonding. First-principles and other computational simulation methods will be used to deeply explore the relationship between interface structure and interface performance.
Multilayered AZ91-(SiCP/AZ91) clad plates were fabricated at 300, 350 ℃ and 400 ℃ successfully by extrusion. The microstructure evolution, bonding interface and the mechanical properties of the AZ91-(SiCP/AZ91) clad plates were investigated in detail. The results show that grain of both of the AZ91 layer and SiCP/AZ91 layer are refined due to the dynamic recrystallization (DRX) during the extrusion processes and the SiCP/AZ91 layer processes much finer grain size. The SiCP distribution of SiCP/AZ91 layer is improved with increasing of extrusion temperature. No obvious delamination is observed in the AZ91-(SiCP/AZ91) clad plates fabricated at different temperatures. The metallurgical bonding of the interface between AZ91 and SiCP/AZ91 basically occurs in the extrusion die. The room-temperature strength of the AZ91-(SiCP/AZ91) composite lies between the AZ91 alloy and the SiCP/AZ91, corresponding well with the rule of mixture (ROM). The inadhesion of the SiCP in the SiCP/AZ91 layer is the main reason for the failure of the AZ91-(SiCP/AZ91) clad plates during tensile test.
The effect of carbon nanotubes (CNTs) on the aging behavior of Mg-9Al matrix composites was studied, and the evolution of microstructures, mechanical properties and thermal conductivity of composites during the aging treatment were discussed. Results show that the addition of CNTs increases the solid solubility of Al in Mg matrix and limited the migration of grain boundaries during the aging process, which can promote the formation of continuous precipitated phases β-Mg17Al12 in CNTs/Mg-9Al composites. The rod-shaped continuous precipitates in coherent relationship with Mg matrix can effectively hinder the dislocation movement, which can improve the mechanical properties of the composites. Besides, the reduction of solid solution Al atoms during aging process and the addition of CNTs can improve the thermal conductivity of the composites. The property evaluation indicates that the tensile yield strength, ultimate tensile strength, diffusivity and thermal conductivity of peak-aged 0.4CNTs/Mg-9Al composite are 275 MPa, 369 MPa, 34.5 mm2/s and 68.4 W/(m·K) respectively, showing 17%, 23%, 43% and 45% increasing in comparison with those of Mg-9Al before aging.
As a kind of rechargeable batteries, alkali metal-ion battery is one of the important energy storage devices at present. Due to the advantages of enhanced energy density, high work potential, no "memory effect", small self-discharge, environment-friendly, alkali metal-ion batteries have attracted extensive attention in recent years. Electrode material is one of the most important factors that influence the electrochemical performances of alkali metal-ion batteries. Therefore, the key to the improvement of alkali metal-ion batteries is to seek electrode materials with high specific capacity and stable structures. Quantum dots/carbon composites (QDs/C), integrating the advantages of quantum dot materials and carbon materials have turned out to be outstanding candidates for electrode materials of alkali metal-ion batteries. In this work, a brief introduction of quantum dot materials was given at first, and then the progress of QDs/C, including element QDs/C, compound QDs/C and heterostructure QDs/C in alkali metal-ion batteries, was summarized respectively. The advantages and disadvantages of QDs/C as electrode materials of alkali metal-ion batteries were discussed in the last part.In view of the shortcoming, the future development goal was proposed: (1)Exploring the innovative approach to slove the agglomeration of quantum dots and the relative composites; (2)Researching the structure and property of SEI film to improve the initial coulombic efficiency; (3)Clarifying the reaction mechanism to obtain the better electrochemical performance.
The additive friction stir deposition (AFSD) technology is a new solid-state additive manufacturing technology. The metal bars, powders, and wires are used as feedstock. During the additive process, the friction heat generated by the friction between feedstock and the plate and the plastic deformation heat generated by the severe deformation of feedstock form a viscoplastic deposition layer. The deposition layer is stacked layer by layer to form three-dimensional parts. Because of its solid phase characteristics, it has many advantages over fused-based metal additive technologies and has become a research hotspot in the field of additive manufacturing. In this paper, the latest research progress of AFSD technology at home and abroad was reviewed from four aspects of equipment development, microstructure evolution, material flow characteristics and mechanical properties change. The feasibility of the application of this technology in engineering practice was analyzed and the application prospect in the field of metal coating reinforcement for material repair parts of additive manufacturing was forecasted. Finally, it was pointed out that the heat generation mechanism, material flow characteristics, auxiliary optimization process, and intelligent equipment development are the future research directions.
SiC ceramics has been extensively used in heat exchangers because of their excellent mechanical properties, high thermal conductivity, and superior thermal shock, corrosion, and oxidation resistance. However, there is a wide variation in the thermal conductivity of SiC ceramics, depending on the raw materials, molding process, sintering process, and sintering additives. The thermal conductivity of SiC ceramics (≤ 270 W·m-1·K-1) is much lower than that of 6H-SiC single crystals (490 W·m-1·K-1) because of pores, grain boundaries, impurities, and defects in SiC ceramics. In this work, the important factors affecting the thermal conductivity of SiC ceramics were analyzed, including temperature, pore, crystal structure, and second phase. Further, the preparation processes of high conductivity SiC ceramics were systematically compared based on hot-pressed sintering, spark plasma sintering, pressureless sintering, recrystallization sintering, and reaction sintering. The improvement measures of thermal conductivity of SiC ceramics were summarized, including the optimization of the type and content of sintering aids, high-temperature annealing, and adding a high-thermal-conductivity second phase. Finally, the prospects and research directions of low-cost and high-thermal-conductivity SiC ceramics are proposed.
Stretchable superhydrophobic materials can greatly improve the mechanical properties of hydrophobic materials and have great application potential in future scientific and technological products.The preparation methods of stretchable superhydrophobic materials are divided into: the use of elastic materials, the design of stretchable structures, and the combination of elastic materials and stretchable structures.The principles and advantages and disadvantages of various preparation methods were analyzed. The effective measures to improve the durability of stretchable superhydrophobic materials were summarized, and the application principles and characteristics of stretchable superhydrophobic materials in the fields of flexible sensors, emerging electronic equipment, medical protection, liquid mixture purification, micro-droplet control were described.The existing stretchable superhydrophobic materials still face problems such as insufficient durability, high preparation cost and complex process.The research should focus on further development of material system, improvement of stretching principle and introduction of new technologies and new processes.The future development direction is light, flexible, green environmental protection, intelligent and fine.
The solidification microstructure of the Mg-5Al alloy is controlled by the Gd content (0.00%, 0.25%, 0.50%, 0.75%, 1.00%, mass fraction, the same below) and high pressure (3 GPa), and the correlation between microstructure and compressive properties at room temperature was studied. The results show that the microstructure is single solid solution only when the the content of Gd is 0.75%, for the Mg-5Al-xGd alloys solidified under atmospheric pressure graphit mold casting. In the Mg-5Al-0.75Gd alloy, no eutectic phase form at the grain boundaries, granular Al2Gd phase is dispersed on the matrix, and the average grain size is about 85 μm. Moreover, the compressive strength and the maximum compressive strain of the Mg-5Al-0.75Gd alloy solidified under atmospheric pressure are 379 MPa and 33.46% respectively, which are higher than those of alloys with intergranular second phase. For the Mg-5Al-xGd alloys solidified under 3 GPa pressure, the microstructure is single solid solution when the Gd content is ≤ 0.25%, and there are eutectic phase Al2Gd at the grain boundaries (among dendrites) when the Gd content is ≥ 0.50%. In addition, the grain sizes of the Mg-5Al-0.25Gd and Mg-5Al-0.75 Gd alloys solidified under 3 GPa pressure are 74 μm and 38 μm respectively. However, the compressive strength and the maximum compressive strain of the Mg-5Al-0.25Gd alloy are 402 MPa and 33.61% respectively, which are superior than that of the Mg-5Al-0.75Gd alloy with the compressive strength of 341 MPa and the maximum compressive strain of 25.12%. Therefore, the existence form of Al and Gd at grain boundaries is an important factor affecting the mechanical properties of the Mg-5Al-xGd alloys.
A new type of corrosion-resistant steel (B-NS) for ship hull was developed by adding alloying elements Cu, Cr and Ni according to the corrosion characteristics of marine environment. The corrosion resistance of B-NS was investigated by electrochemical test, full immersion test and dry-wet cyclic test, and the cross-sectional morphology and composition of the rust layer were analyzed by scanning electron microscope and energy dispersive spectroscopy. The results show that the addition of alloying elements effectively reduces the saturated current density and corrosion rate of B-NS steel under full immersion and dry-wet cyclic test. The alloying elements promote the formation of a more stable and dense protective rust layer under dry-wet cyclic test. The alloying elements give B-NS ship plate steel excellent corrosion resistance mainly in improving the thermodynamic stability of B-NS ship plate steel, promoting the formation of rust layer to prevent aggressive media from corroding the substrate, and giving the rust layer cation-selective permeability to prevent Cl- from penetrating into the rust layer.
Inconel 617 nickel-based superalloy with 3 mm wall thickness was welded by laser beam using two different heat input welding parameters. The microstructure of the welded joint was observed by optical microscope and scanning electron microscope, and the mechanical properties of the welded joint at room temperature (25℃) and high temperature (900℃) were tested. The results show that the laser welding heat input has a significant effect on the microstructure and mechanical properties of Inconel 617 welded joints. The front width of the laser weld obtained by high heat input (200 J/mm) process parameters is 3.88 mm. The grain size in the middle of the weld fusion zone is coarse, and the grain orientation is disordered. The secondary dendrite arm spacing in the middle of the weld is large (6.71 μm). The carbide particle size between the dendrites is coarse, and the solidification microsegregation of Mo, Cr alloy elements is serious. The width of heat affected zone is about 0.29 mm. The eutectic structure of γ+carbide is formed in the grain boundary and grain interior. This is because during the heating process of the welding, the spherical carbide particles and the surrounding austenite in the heat-affected zone liquefy and the eutectic structure is formed during the solidification process after welding. The front width of the laser weld obtained by low heat input (90 J/mm) process parameters is 2.28 mm, the grains inside the weld are columnar which is formed by epitaxial growth along the fusion line and directional solidification along the heat flow direction. The secondary dendrite arm spacing in the middle of the weld is small (2.26 μm), the carbide particles between dendrites are small, and the width of heat affected zone is about 0.15 mm. The tensile strength test at room temperature (25℃) shows that the welded joints obtained under high heat input fracture from the middle of the weld, and the tensile strength and elongation decrease, which is caused by the segregation of solid solution elements in the weld. The welded joints obtained under low heat input fracture from the base metal. At high temperature (900℃), all samples fracture from the base metal, which is due to the weakening of the grain boundary of the base metal at high temperatures.
In order to clarify the fatigue crack propagation behavior of pearlitic rail, the three-point bending fatigue crack propagation rate of U75V heavy rail steel in rolling state and heat treatment state was measured. The microstructure, lamella, fracture morphology and fatigue crack propagation trajectory of rail were observed by optical microscope, scanning electron microscope and EBSD. The results show that the average distance between fatigue striation of rolled and heat-treated rails is 252.5 nm and 215.4 nm, the fracture surface of rolled rail presents cleavage steps and river patterns, and the river patterns tend to merge.However, the fatigue fracture surface of the heat-treated rail presents a large number of cleavage steps, more microcracks and tear edges, and the river pattern is dominated by tributaries.The fatigue crack growth rate of heat-treated rail is much lower than that of rolled sample, and it is also slow to reach the stage of crack instability.The fatigue crack propagation mode of rolled and heat-treated rail is the mixed propagation mode of transgranular fracture and intergranular fracture dominated by transgranular fracture, the pearlite lamellae spacing of rolled and heat-treated rails is 272.2 nm and 148.4 nm respectively. The pearlite lamellae of heat-treated rails is fine and has various directions, while there are significant pearlite clusters in the heat-treated rail.There are many branch cracks and crack bridges in the crack growth path, which hinders the crack propagation in the heat-treated U75V heavy rail steel, which is an important reason why the fatigue crack propagation rate of the heat-treated rail is lower than that of the rolled rail.
Flexible energy storage devices are at the forefront of next-generation power supplies, one of the most important components of which is the gel electrolyte. The dual network gel electrolyte for PAM/P123 zinc ion batteries was prepared by free radical polymerization. It was found that the addition of a small amount of triblock copolymer P123 can macroscopically improve the tensile strength, toughness and compressive strength of the gel electrolyte. Microscopically, the gel skeleton forms 0.6 μm mesopores and increases the surface pore distribution density, thereby improving the wettability of the electrolyte. The PAM/P123 series electrolytes not only have a high average swelling rate, but also have a higher conductivity than pure PAM electrolyte in the range of -30℃ to 65℃. Among which, PAM/P123-2 is a series of electrolytes with the best performance, with an average swelling rate of 1920.79%, and the conductivity at 0℃ is 36.2 mS·cm-1.The Zn/MnO2 battery prepared by using PAM/P123-2 gel electrolyte is stable during cycling at 0℃, with the capacity retention rate reaching 82.39% after 1000 cycles.
CFRP composites are widely used in aerospace due to their excellent mechanical properties, however, due to the anisotropy of the individual plies, the electro magnetic interference(EMI) shielding efficiency(SE) for vertically polarized waves of the unidirectional fiber laminates is poor. In order to protect electronics within these equipments from increasingly severe electromagnetic interference, it is particularly important to enhance the electromagnetic shielding efficiency of the CFRP. In this paper, Al particles were introduced and a conductive network was constructed in the CFRP interlaminar region by condensing the Al particles on the prepreg surface. The effects of different Al particle contents on EMI SE and mechanical properties of composites were studied. With the increase of Al particle contents, the electrical conductivity and the EMI SE of CFRP composites increase. When the Al mass fraction in the resin is 33.3%, the in-plane conductivity of the composites increases by 3 orders of magnitude, the EMI SE of the Al particle sandwich CFRP composites is improved by more than 10 dB in the frequency range of 3-17 GHz. With the increase of Al particle contents, the interlaminar shear strength and bending strength of the composites increase first and then decrease. When the Al mass fraction in the resin is 33.3%, the interlaminar shear strength (ILSS) of the composites increases by 5.2% to 80.5 MPa, and when the Al mass fraction in the resin is 50%, the bending strength of the composites increases by 20% to 1441.0 MPa and the bending modulus increases by 10.2% to 101.83 GPa. It can be seen that the mechanical properties and electromagnetic shielding effectiveness of the Al particles sandwich CFRP composite can be improved simutaneously. It is a kind of structure electromagnetic shielding integrated composite with broad application prospects.
Carbon/carbon-polyimide composites were prepared by chemical vapor infiltration and vacuum-pressure impregnation curing process. Firstly, the carbon felt was deposited with pyrolytic carbon by chemical vapor infiltration method to prepare porous carbon/carbon materials with pyrolytic carbon contents of 7.33%(mass fraction, the same below), 14.55% and 22.00%, respectively. Then, through a specific impregnation curing process, the carbon/carbon-polyimide composites P1, P2 and P3 and the control group P0 without pyrolytic carbon were obtained in turn. Through SEM, linear expansion coefficient test and mechanical properties test, the effects of different pyrolytic carbon contents on the microstructure, average linear expansion coefficient and mechanical properties of carbon/carbon-polyimide composites were investigated. The results show that in the temperature range of 20-300℃, the XY-direction average linear expansion coefficients of P0, P1, P2 and P3 are between (0.67-0.79)×10-6℃-1, and the XY-direction average linear expansion coefficients of four groups are basically the same. The Z-direction average linear expansion coefficients of P1, P2 and P3 decrease by 41.6%, 41.8% and 24.1%, respectively compared with P0. Pyrolytic carbon significantly reduces the Z-direction average linear expansion coefficient of materials. The XY-direction compressive strengths of P0, P1, P2 and P3 are 243.91, 244.73, 216.65 MPa and 210.79 MPa, respectively, and the Z-direction compressive strengths are 269.22, 258.80, 246.68 MPa and 219.20 MPa, respectively. The compressive strength of P1 is equivalent to that of P0. The Z-direction bending strengths of P0, P1, P2 and P3 are 92.77, 77.11, 80.71 MPa and 86.06 MPa, respectively. Different pyrolytic carbon contents have different effects on the mechanical properties of materials. The lower pyrolytic carbon content can basically maintain compressive strength of materials, while the higher pyrolytic carbon content can basically maintain bending strength of materials.
Hypercrosslinked polymers(HCPs) were prepared by cashew nut shell liquid(CNSL), an agricultural by-product, as a raw material, using external cross-linker method and solvent cross-linker method, and named F-HCP and C-HCP, respectively. The adsorption properties of volatile organic compounds(VOCs) on F-HCP and C-HCP were investigated. The prepared adsorbent was characterized by infrared spectroscopy(FTIR), thermogravimetric analysis(TGA), N2 adsorption and scanning electron microscopy(SEM). The adsorption properties of six kinds of VOCs on F-HCP and C-HCP were investigated by static adsorption method. The o-xylene was used as a typical VOC for dynamic adsorption, and the influence of inlet concentration on adsorption was investigated. The results show that F-HCP has higher static adsorption performance than C-HCP, and the static adsorption capacities of o-xylene, toluene, cyclohexane, n-hexane, methyl ethyl ketone, and acetone on F-HCP are 930, 801, 300, 214, 203 mg·g-1and 164 mg·g-1, respectively. At the inlet concentration of 2171 mg·m-3 for o-xylene, the dynamic adsorption capacity of F-HCP and C-HCP for o-xylene is 149 mg·g-1 and 146 mg·g-1, respectively. The equilibrium adsorption capacity increases with the increase of the inlet gas concentration. The cyclic regeneration adsorption experiments indicate that the adsorption capacity of C-HCP after five cycles of adsorption is 93.9% of the first adsorption capacity.
Two-dimensional Cr2S3 nanosheets were successfully prepared by using chromium trichloride and sulfur powder as raw materials with atmospheric pressure chemical vapor deposition (CVD), and the surface morphology, crystal structure, and macroscopic magnetic properties of Cr2S3 nanosheets were systematically investigated. The results show that the optical morphology of two-dimensional Cr2S3 nanosheets is mainly triangular, with the maximum size of 156.8 μm and the minimum thickness of 2.59 nm (about 2 unit-cell thickness); the crystal structure is rhombohedral phase structure, similar to monoclinic NiAs-type crystal structure; the magnetic test shows that the two-dimensional Cr2S3 in rhombohedral phase is ferromagnetic material at low temperature, with the magnetic easy axis direction in-plane, and its Néel temperature is about equal to 120 K. The saturation magnetization intensity is maximum at 75 K. The magnetic properties of two-dimensional Cr2S3 nanosheets remain very good after one month in air, and it is an environmentally stable two-dimensional magnetic material.
In order to prepare low expansion, high strength and light weight composites, ZrW2O8-Cf/E51 composites were prepared by compression molding method, and the effects of ultrasonic time on its microstructure, thermal expansion behavior and ultimate tensile strength were studied. The results show that the agglomerated particles will be blocked by the fibers and gather on the surface of fiber bundles during the preparation. Within 20 minutes, the agglomeration of ZrW2O8 particles can be reduced by prolonging the ultrasonic time. With the decrease of particle agglomeration, the fracture surface of the composites will be changed from plane without fiber pull-out to uneven with fiber pull-out. During the thermal expansion process, the dL/L0of ZrW2O8-Cf/E51 composites show three stages: increase, decrease and slow increase under the combined action of carbon fiber and ZrW2O8 particles. When ultrasonic time increases from 5 min to 20 min, the average thermal expansion coefficient of ZrW2O8-Cf/E51 composites decreases by about 130%, and the ultimate tensile strength increases by about 8%.
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