- 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)
Solid phase additive manufacturing based on friction stir is a new technology for manufacturing of large lightweight alloy components, which has become one of the hot research topics in advanced manufacturing field at home and abroad.The research status of metal solid phase additive manufacturing technology based on friction stir and related process mechanism were analyzed and summarized. The solid phase additive manufacturing technology based on friction stir can be divided into three categories.One is friction stir additive manufacturing(FSAM), which is based on the principle of friction stir lap welding, the plates are stacked layer by layer. Another is additive friction stir deposition(AFSD) technology, which usually uses a hollow tool to conduct AFSD by additive powder or wire through the hollow.The third one is friction surfacing deposition additive manufacturing (FSD-AM) technology, which is based on the principle of friction surfacing by using a rotating consumable bar to deposit materials to form the designed components. The research and application status of solid phase additive manufacturing technology of metal materials based on friction stir were analyzed, and the characteristics, advantages and disadvantages of three kinds of solid phase additive manufacturing technology based on friction stir were compared.Finally, the future research direction of solid phase additive manufacturing technology based on friction stir was proposed, including revealing their process mechanism, integrated controlling of the formation and property of the AM components, modifying the process assisted with second energy, application of new materials and optimization with artificial intelligence, etc.
The lightweight of vehicles is one of the important means to solve the energy crisis and environmental problems, which has been paid great attention by scholars at home and abroad.Carbon fiber-reinforced polymer (CFRP) composites and light alloys such as aluminum and magnesium alloys have a series of excellent mechanical properties and processing performance, representing lightweight materials with great application prospects. It has become a hot research topic to realize the effective joining between the CFRP and aluminum/magnesium alloys which are the promising lightweight materials. However, due to the significant differences in physical and chemical properties between these dissimilar materials, the mixed application of a variety of lightweight materials in the production process is still facing great challenges.The research progress, advantages and disadvantages, and development trend of bonding, mechanical fastening, friction stir welding and its variants were summarized and analyzed. The micro morphology of joints obtained under different bonding methods was investigated. Three mechanisms of friction stir joining between CFRP and aluminum/magnesium light alloys were preliminarily summarized through investigating the micro morphology of joints, including macro anchoring, micro mechanical chimerism and chemical bonding. Finally, based on the above joining mechanism, it is pointed out that the key to further improving the performance of hybrid joints is to increase the surface roughness of the base metal, increase the area of the molten polymer and adopt the hybrid joining techniques.
Friction pull plug welding is one of the key technologies in the manufacturing process of rocket tank.The geometrical shape and its effect on microstructure and mechanical properties of friction pull plug welding for the 8 mm thick 2219-T87 aluminum alloy were studied. The results show that the geometry of hole and forming ring has an important effect on the interface quality of the joint. When the welding parameters are 7000 r·min-1 rotation speed, 35 kN axial tensile force and 16 mm axial feed, the use of tapered straight hole can effectively prevent the neck of plug during the welding process, so as to eliminate the lack of bonding defect. The stepped shaped forming ring can improve the stress state of interface and prevent the weak bonding defects. The microstructure analysis shows that dynamic recrystallization occurs at the base material side adjacent to the interface, and obvious plastic deformation occurs at the thermo-mechanical affected zone. The microstructure adjacent to the bonding interface is obviously softened by the welding thermal cycle and the rotary extrusion of the plug; and the lowest hardness value is about 90HV, which occurs in the thermal mechanical affected zone. When the joint has weld defects, the tensile strength of the joint significantly reduces compared with that of base material.The tensile strength and elongation of the joint without weld defects can reach 360.1 MPa and 6.45%, respectively, the joint coefficient is 0.828, and the fracture mode is ductile fracture.
A novel ultrasonic vibration enhanced friction stir welding (UVeFSW) process was employed to join the 6061-T6 aluminum alloy and QP980 high-strength steel. The macro morphology, microstructure and tensile shear properties of the joint with or without ultrasonic energy were compared and analyzed. Meanwhile, the effects of ultrasonic energy on the welding load were studied. The results show that the ultrasonic vibration applied to the base metal before welding can soften the base metal, promote the plastic flow of the material, expand interface zone and nugget zone of the aluminum/steel, make more steel particles rotate into the aluminum alloy side with the stirring needle, forming a hook structure at the edge of the interface zone which can improve the failure load of the joint. The fracture position and fracture morphology of FSW joint are changed by ultrasonic, and the mechanical properties of FSW joint are improved. Under the welding parameters conducted in the experiment, the maximum average failure load of the joint is 4.99 kN. Under the conditions of a welding rate of 90 mm/min and a depth of 0.1 mm, the application of ultrasonic vibration makes the average failure load of the joint increase by 0.98 kN and the tensile shear performance increase by 28.24%. After applying ultrasonic vibration, the axial force Fz, the tool torque Mt and the spindle power decrease by 2.46%, 6.44% and 4.59% respectively.
MXenes, as a new 2D transition metal carbides/nitrides/carbonitrides, have wide potential application in physics, chemistry, material science and nanotechnology fields. Since MXenes inevitably possess defects and —O, —OH, —F terminal groups during the preparation, behaving high conductivity and large surface area, MXenes have a good electron transfer rate and can be used as an excellent electrochemical catalyst. In this review, the various synthesis methods and development of different doping types of MXenes were introduced. The application and mechanism of MXenes in electrocatalytic hydrogen production, oxygen production, oxygen reduction, CO2 reduction and nitrogen reduction processes were mainly discussed. It was pointed out that the preparation methods of MXenes should possess the characteristics of environmental friendliness, morphology controllability, the inoxidizability and high adjustability, meanwhile, different types of MXenes should be applied to different electrocatalytic reactions.
The electrocatalytic CO2 reduction reaction (CO2RR) can not only alleviate the negative effects caused by excessive CO2, but also produce the carbon-containing fuels to alleviate energy shortages. However, the reactive paths of CO2RR are relatively complicated, and the problems such as low selectivity, low current density and poor stability exist. It is urgent to develop efficient and inexpensive catalysts to promote its development. Ultra-thin materials have the advantages of large specific surface area, fully exposed active sites, accelerated kinetic mass transfer, and adjustable electronic structure. They are expected to break the bottleneck of CO2RR, thus receiving widespread attention. Here, the synthesis and application of ultra-thin materials in the past four years in electrocatalytic CO2RR to produce liquid fuels (formic acid, methanol, acetic acid) were briefly summarized. The advantages of ultra-thin materials over bulk materials and their influence on catalytic activity, selectivity and reaction paths were discussed. Also, some suggestions for future development trends, including the synthesis methodology of ultra-thin materials, their potential as supports, mechanism analysis and machine learning were put forward.
With the increasing demand for lithium-ion batteries, lithium-ion batteries with high energy density and high power density have become one of the research hotspots. Material modification and new material development can effectively increase the energy density of lithium-ion batteries. In addition, the microstructure parameters of the electrode such as porosity, pore size and distribution, tortuosity and electrode composition distribution are also factors that determine the performance of the electrode and battery. Improving the performance of high specific energy batteries by optimizing the electrode structure design has gradually become the focus of attention. The research progress of porous electrode structure design optimization for lithium ion batteries was reviewed in this article, the design factors and preparation methods of porous electrode structure were summarized. Then the future development of electrode structure design optimization and the promotion of novel preparation technologies for large-scale application in the field of high specific energy lithium ion batteries were prospected in the field of high specific energy lithium ion batteries.
Nickel-based single crystal superalloys are widely used for hot components of advanced turbine engines due to their excellent mechanical properties at elevated temperature. Ru is the symbol element of the fourth and fifth generation nickel-based superalloys. During the past decades, many efforts have been made to provide insight into the role of Ru addition in superalloys. In this paper, the research progress in the effect of Ru on the solidification characteristics, as-cast microstructures, precipitation of topologically close-packed (TCP) phases, and creep properties of nickel-based single crystal superalloy was reviewed. The effect of Ru on the solidification characteristics such as solidification path, solidification transition temperature, micro-segregation, and the solidification microstructures such as eutectic, carbide were analyzed systematically. And the reasons why the addition of Ru can inhibit the precipitation of TCP phase and improve the creep property of superalloy were emphatically studied. The composition design and optimization of Ru-containing superalloy are more challenging due to the complexity of the multi-component interaction on microstructure and properties. It was suggested that the future research on Ru-containing superalloys could be explored from the following aspects: the cause of the precipitation of the new Ru-rich phases and the method of inhibiting its precipitation, the effect of Ru addition on solidification defects, the mechanism of the interaction between Ru and other elements on the "reverse partitioning effect" and the precipitation of TCP phases. It could provide significant guidance for the composition optimization and performance improvement of the new Ru-containing nickel-based single crystal superalloys.
As one of the important materials for new generation aeroengines, Ti2AlNb alloy has many good properties, including good processability, great comprehensive mechanical properties and low density. In order to widen the application field of Ti2AlNb alloy, the optimization of alloy composition and the control of process and microstructure need to be carried out to further enhance the oxidation resistance property of traditional Ti2AlNb alloy. In this study, the compound method of Mo, Zr, W alloys on traditional Ti-Al-Nb alloy was designed to improve the oxidation resistance property of Ti2AlNb alloy. The oxidation mass gain behaviour, the oxide layer structure, surface oxides and the alloy composition distribution of these Ti2AlNb alloys during the high temperature oxidation process at 750 ℃ and 850 ℃ were analyzed and compared. It is found that the oxidation resistance of Ti2AlNb alloy with Mo alloying element decreases obviously when temperature increases from 750 ℃ to 850 ℃, while the oxidation resistance of Ti2AlNb alloy with Zr alloying element still keeps excellent; the oxide scale microstructure of these Ti2AlNb alloys is made up of oxidation layer, oxygen enrich layer and interstital affected layer according to the SEM morphology analysis of these cross-sections samples. It is believed that Zr and W alloying elements have the coordination repression effects on the formation of different oxide layers during the oxidation process at 850 ℃. Therefore, the kind of Ti2AlNb alloy with both Zr and W alloying elements was recommended as the promising anti-oxidation Ti2AlNb alloy.
Ti45Al-8Nb-0.3Y-mCo (m=0, 0.5, 1, 2, atom fraction/%) alloys were prepared by vacuum arc non-consumable melting method. The microstructure and high temperature oxidation resistance of the alloys were investigated. The results show that the microstructure of TiAl-Nb alloy can be significantly refined by addition of Co element. However, Co can remarkably inhibit the formation of α2+γ lamellar while promote the formation of Co-rich B2 precipitations in the alloys. The oxide films formed on the Ti45Al-8Nb-0.3Y-mCo alloys mainly consist of relatively loose TiO2 and Al2O3 mixtures, after oxidation at 1000 ℃ for 100 h in air. With the increase of Co content, the mass gains of the TiAl-Nb-0.3Y alloys after oxidation increase obviously, while much better anti-spalling performance of the oxide films can be obtained. Addition of Co can reduce the internal stress of the oxide film to a certain extent, which is beneficial to the anti-spalling performance of the oxide film. However, the coarse B2 precipitation caused by Co weakens high temperature oxidation resistance of the alloy.
Electrochromic materials have good development prospect under the development concept of promoting low carbon and energy saving. In order to explore the efficient, simple and excellent preparation process, the polymer electrochromic film was prepared by the electrostatic spray method combined with the in-situ elution method. According to the color adaptability and solubility of the electrolyte salt, tetrabutylammonium perchlorate (TBAP) was selected as the template, and different proportions of electrolyte salt were added to the easy-to-process TPA-OMe-PA solution, then film was deposited on the surface of the ITO glass by electrostatic spray technology. After that, the electrolyte salt was precipitated by in-situ washing method. The morphology of the film was analyzed using scanning electron microscope, and the electrochromic properties of the film were studied using the electrochemical workstation combined with ultraviolet/visible/infrared spectrometer. The research results show that the polymer film prepared by electrostatic spray technology and in-situ elution method have multi-level pore structure and excellent electrochromic properties. Especially when the electrolyte content is 33.3%(mass fraction), the multi-layer porosity is the highest, and the electrochromic performance is the best. The bleaching time/coloration time is reduced to 0.6 s/1 s, and the coloration efficiency reaches 608.2 cm2·C-1, which is the best record for the polyamide based electrochromic film.
Lightweight and cellular-structured graphene-pyrrole (G-P) aerogels /epoxy composites were prepared basing on the three-step fabrication process which involving infiltration of epoxy resin into G-P aerogels under vacuum atmosphere. The microstructure of G-P aerogels possesses uniform three-dimensional structure, which can also be preserved well in epoxy composite. The three-dimensional interconnected graphene network serves as fast channels for charge carriers. The conductive property of the composite is improved significantly, 67.1 S/m with only 0.23%(mass fraction) filler content (1G-1%P, 1300 ℃). The electromagnetic interference shielding effectiveness (EMI SE) of the composite (1G-1%P, 1300 ℃) can reach 33 dB in the frequency range of 8-12 GHz. More importantly, the G-P aerogel network also enhances the mechanical properties of epoxy matrix. Flexural strength and flexural modulus are increased by 60.93% and 25.98% respectively (10G-5%P, 180 ℃). Implication of the results suggests that the three-dimensional structure is an effective method for preparing composites with both excellent EMI SE and mechanical properties.
4, 4'-diaminodiphenyl ether (ODA) and pyromellitic dianhydride (PMDA) were used as monomers. Carbon nanofiber (CNF) was used as the reinforcing agent. CNF reinforced polyimide (PI) composite aerogels were prepared with acidified CNF (a-CNF) via sol-gel process followed by freeze-drying technology. The morphologies, thermal insulation, microwave absorption as well as compression properties of PI composite aerogels were characterized. The results show that the volume of PI composite aerogels is shrunk from 45.52% to 35.32%, and the density is decreased from 0.084 g/cm3 to 0.069 g/cm3 with the increase of a-CNF content. The composite aerogels exhibit bigger pore sizes and wider pore size distribution after the introduction of a-CNF as well. CNF in PI matrix play roles for reducing the shrinkage of PI composite aerogels, thereby the thermal conductivity is reduced. Additionally, the reflection loss (RL) of PI composite aerogel with 15%(mass fraction) of a-CNF (15% CNF/PI) reaches -9.7 dB at 8.3 GHz. This is due to the fact that the introduction of CNF induced the conduction loss and the porous structure of aerogels provides better impedance matching. The compressive strength and modulus of PI composite aerogels with 15% of a-CNF content are increased by approximately 1.5 times and 2 times compared with pure PI aerogel, respectively.
The stitched foam-core sandwich composites with different stitching methods and stitch density were manufactured using vacuum assisted resin infusion (VARI) molding process. The effect of stitching parameters on their flatwise tensile, three-point flexural, core shear and climbing drum peel properties was investigated. The results show that although stitching makes flatwise tensile strength and core shear strength of foam-core sandwich composites to decrease obviously, it can improve flexural properties as well as substantially enhance climbing drum peel properties. Modified lock stitch method is better than tufting stitch method. Properly increasing stitch space has certain positive effect for mechanical properties, but it is not conducive to the enhancement of climbing drum peel properties. For modified lock stitched foam-core sandwich composites with the stitch density of 30 mm×10 mm, flatwise tensile strength and core shear strength are reduced by 14.75% and 24.79%, respectively, whereas flexural strength and average peel strength are respectively increased by 7.96% and 80.78% compared to those of unstitched foam-core sandwich composites.
The hydrophobic magnetic materials of HMC-1 and HMC-2 were obtained by blending synthesized Fe3O4 nanoparticles and commercial CaCO3 powder with stearic acid solution, which is used as hydrophobic modifier. HMC-2 was loaded on the PU sponge for the further improvement of the applicability. The structural properties of the two materials were detected by X-ray powder diffractometer and infrared spectrometer. Thermal stability of HMC-2 was analysed by differential scanning calorimeter. The hydrophobic properties of the samples were determined by contact angle meter. The results show that HMC-2 has more stable hydrophobic properties than HMC-1. HMC-2 exhibits more stable hydrophobic performance. The contact angle remains nearly unchanged (about 150°) after oil removal. HMC-2 shows no release of Fe(Ⅲ) ions, which has taken place during the oil removal experiment using HMC-1. PU sponge loaded with HMC-2 can remove 98% oil in 3 s. The oil removal rate remains 95%, after 20 times of repeated oil absorption. The mass ratio of oil adsorption/adsorbent is larger than 100.
To improve the interface strength between aramid fiber (PPTA) and NBR composites, the silane coupling agent (A172) and graphene oxide (GO) were used to have the graft modification treatment to the aramid fiber surface and analyze the chemical construction, surface topography and H-pull test of aramid fiber before and after treatment. The microstructure of the pull out fiber surface and section of the rubber-based aramid fiber reinforced polymer(AFRP) was analyzed by SEM. The results show that the oxygen-containing groups on the fiber surface are increased and the chemical activity is improved after the secondary surface modification to the aramid fiber is conducted with the silane coupling agent and GO. The obvious attachments can be found on the surface after treatment. The fiber structure has no obvious damage and its surface roughness is improved substantially. The H-pull test after treatment increases with an optimal effect of aramid fiber H-pull test after the secondary modification with GO (improved to 48.748 MPa from 18.192 MPa). The interface bonding strength between the aramid fiber and NBR is improved dramatically, thus confirming the effectiveness of the silane coupling agent and GO in the secondary modification to the aramid fiber, which provides reference for the study of the performance of the rubber-based AFRP.
Cu/Cu2O cermet composites were prepared with hot pressing graphite reduction methods. The DC electrical conductivity of Cu/Cu2O cermets, with various volume contents and random distribution status of the conducting phase was tested. To quantitatively characterize the shape, size, and distribution status of the conducting phase, the fractal dimensions of the conducting phase(Cu) were calculated through the binarized image analysis. The percolation behavior was analyzed, and the relationship between microstructure and electrical properties was studied. The results show that the quantities of the percolation infinite cluster and backbone increase with the increasing volume fraction of the conducting phase, but the backbone density fluctuates near the percolation threshold. Furthermore, the difference of fractal dimension between Cu/Cu2O cermet composites perpendicular to hot pressing direction and the parallel to hot pressing direction is about 0.1.An approach is provided to quantitatively characterize the microstructure of the conducting phase in dual-phase conductor/insulator composites, which is beneficial to predict the properties of composites with a randomly distributed second phase.
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