- 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)
Thermal management systems, controlling the dispersion, storage and conversion of heat, were widely used in various fields of national economy and defence applications etc. Advanced thermal management materials form the material basis of the thermal management system, while the thermal conductivity was the critical property of all the thermal management materials. The application, classification, and physical mechanism of heat conduction of advanced thermal management materials were reviewed in this paper. The research progress and existing problems of thermal interface materials, high thermal conductivity packaging materials, thermal storage materials and thermoelectric materials were introduced. It is pointed out that molecular dynamics, density functional theory and large-scale parallel computing technology will play increasingly import roles in revealing the multi-scale heat transfer mechanism in the homogeneous and composite materials.
There is a growing interest in the application of graphene-based nanocomposites in light-driven technology. Graphene has excellent physical chemical properties, especially the high specific surface area, thermal conductivity and mechanical strength, promoting the development of light-driven technology in remote control intelligently. The light-driven actuator based on graphene nanocomposites provides a kind of bright-future driving technology for precision machinery and optical fields and etc. By reviewing recent advances based on light-driven technology of graphene-based nanocomposites, this paper aims to prospect the research focus on its synthesis method and the ability of graphene to be a filler in light-driven composite and the application prospect in the field of bionic study, micro-robot and biomedical.
Silicate clay minerals possess unique chemistry compositions, micro morphology structures, and physicochemical properties, which make them useful in a broad application in antibacterial fields. Through chemosmosis, some antibacterial elements in silicate clay minerals can directly react with the cell membrane and cytoplasm. By controllable adjustment of the surface charge, silicate clay minerals can be adsorbed to the surface of the bacteria and release the antibacterial agents with controllable amount. The micro morphology structures enable silicate clay minerals to serve as a matrix to load the antibacterial inorganic and organic materials, which can improve the antibacterial effects and undermine the bio-toxicity to prepare the antibacterial nanocomposites with high stability, strong and durable antibacterial effect. The two antibacterial mechanisms of silicate clay minerals including chemiosmosis and physical absorption were reviewed in this paper, the synergistic effects and antibacterial product applications of antibacterial nanocomposites based on silicate clay minerals were further discussed to explore the feasibility of silicate clay minerals in industrial applications of the antibacterial fields.
Boron nitride interface was deposited on SiC fibers by chemical vapor deposition at different temperatures from BCl3-NH3-H2 mixtures.The effect of temperature on deposition rate, morphology, composition and structure of the interface was studied.The results show that in the low temperature range of 700-900℃, the deposition rate increases with increasing temperature complying with Arrhenius law, and the apparent active energy calculated is 57.2kJ/mol.The interface is smooth and dense and uniformly deposited on fibers, the deposition rate is controlled by surface reaction.At 900℃, the deposition rate reaches a maximum(174nm/h), at the same time, surface reaction control is changed to be mass-transportation control. Above 900℃, the deposition rate decreases with the increasing temperature due to the gas-phase nucleation, and the interface surface becomes loose and rough. BN interface is turbostratic structure with stoichiometric ratio 1:1, and the order degree increases with increasing temperature.
ZnFe2O4 nanoparticles were synthesized by polyol process. The influence of reaction conditions, such as the refluxing time, heating rates and refluxing temperature on the size, morphology and magnetic properties was investigated. The structure, morphology and magnetic properties of resultant products were characterized by X-ray diffraction(XRD), transmission electron microscopy(TEM), fourier transform infrared (FTIR) and vector network analyzer. The results show that the obtained ZnFe2O4 nanoparticles have uniform size and good dispersibility. The particle size increases with the increase of the reflux time and the reflux temperature. ZnFe2O4 nano ferrites synthesized at the refluxing temperature of 270℃ have maximum saturation magnetization of 35.09A·m2/kg with less remanence and the coercive force is 4.2kA/m.ZnFe2O4 nanoferrites show a typical ferrimagnetic behavior.
LiFePO4-C/graphene composite was successfully prepared by a facile approach of grinding, ultrasonic dispersion, stirring and drying and used as the cathode material for lithium-ion batteries.The structure and morpholgy of as-prepared LiFePO4-C/graphene composite material was characterized with transmission electron microscopy, scanning electron microscopy, X-ray diffraction and Raman spectroscopy, and the electrochemical performance was tested using coin cells assembled in an argon-filled glovebox. SEM images show that in the as-prepared material, graphene nanoflakes are adhered on the surface of LiFePO4-C particles, and uniformly dispersed in the composite material forming an effective 3D conducting network. Electrochemical tests show that after adding 2% of graphene, rate and cycling performances of the LiFePO4-C/graphene composite material are obviously improved. For the rate performance, a high reversible capacity of 94.2mAh·g-1 is achieved at 5C rate, which is more than 2.53 times higher than that of pristine LiFePO4-C; For cycling performance, the composite material shows a low capacity decay rate of 9.6% when cycles under 1C rate for 100 times, which is lower than pure LiFePO4-C (43.5%). The electrochemical performance enhancement can be mainly ascribed to the effective 3D conducting network formed by graphene nanoflakes with superior conductivity.
The effect of sodium tungstate in insulation coating solution of grain-oriented silicon steel on the microstructure and properties of the prepared phosphate insulation coating was investigated by using scanning electron microscopy (SEM), Epstein square, insulating resistance tester and Fourier transform infrared spectrum (FTIR) et al. The results show that, with the gradually increasing content of sodium tungstate in the coating solution, the wetting angle between the coating solution and the grain-oriented silicon steel substrate first decreases and then increases; the interlamination resistance, lamination factor and magnetism induction intensity of grain-oriented silicon steel first increase and then decrease, the iron loss first decreases and then increases. When the sodium tungstate content is 2.0%(mass fraction), the coating solution shows the best wettability on the grain-oriented silicon steel substrate, the wetting angle is 39.3°; at the same time, the formed insulation coating is dense and smooth, there is a diffusion area about 0.8μm at the junction between the insulation coating and the magnesium silicate bottom layer, furthermore, the humidity resistance of the insulation coating is not significantly changed; the interlamination resistance, lamination factor, magnetism induction intensity and iron loss of grain-oriented silicon steel reach the optimal values, which are 14073Ω·mm2, 97.0%, 1.893T and 1.051W·kg-1, respectively.
Ti6Al4V substrates were anodized in aqueous solution containing 0.15mol/L HF+2mol/L H3PO4. After that, hydroxyapatite coatings is deposited on the anodized Ti6Al4V substrates surface by hydrothermal-electrochemical method at a constant current in an electrolyte containing 0.02mol/L CaCl2, 0.012mol/L K2HPO4·3H2O and 0.139mol/L NaCl. The influence of current density on the coating compositions, microstructure, thickness, bioactivity and bonding strength between the coating and substrate was investigated by XRD, SEM, EDS, step profiler and universal testing machine during deposition process. The results indicate that HA coatings can be successfully obtained on anodized Ti6Al4V surface by hydrothermal-electrochemical deposition with different current densities. The coatings appear a layered growth and parts of crystals are characterized by flower-shape. The thickness of the HA coatings increases firstly and then decreases with increasing current density. When the current density is 1.25mA/cm2, the thickness of the HA coatings reaches the maximum 26.4μm, the coating is the most dense and the bonding strength is near 20.0MPa.The simulated body fluid (SBF) immersion test can quickly promote the deposition of calcium phosphate with a maximum diameter of 7-8μm.
Straight polarity direct current method(DCSP A-TIG) was applied to join 2219 high strength aluminum alloy, and the effects of single-component(AlF3, LiF), three-component (AlF3+30%LiF+10%KF-AlF3) and four-component (AlF3+30%LiF+10%KF-AlF3+10%K2SiF6) activating flux on weld face forming, weld quality (porosity), arc shape, weld penetration, joint microstructure and mechanical properties were studied. The results show that adding activating flux helps to remove the oxide film on the weld face of the 2219 aluminum alloy, improve the weld surface forming quality; the four-component activating flux of weld face forming is the best; compared with the weld quality of variable polarity TIG welding (VPTIG), DCSP A-TIG welding method significantly reduces the porosity generation in 2219 aluminum alloy weld; AlF3 single-component activating flux obviously increases the weld penetration, which has obvious dragged arc phenomenon; DCSP A-TIG welded seam has the same structure component as the parent metal. Welding current has a greater influence on DCSP A-TIG weld microstructure, increasing current may result in the coarsening of the joint microstructure. The strength and elongation of the DCSP A-TIG welding joint, which are coated with four-component activating flux are the highest, and the mechanical properties are nearly the same as VPTIG welding. The DCSP A -TIG welding method of 2219 high strength aluminum alloy is of great value to the engineering application.
The crack initiation and propagation of 7A04 aluminum alloy in 3.5%NaCl solution at pH=1, 4, 7, 12 during slow strain rate test (SSRT) were investigated by the method of combining phase shift with electrochemical impedance spectroscopy. The feasibility of the method was verified by electrochemical noise (EN). The results show that the more corrosive the solution is, the susceptibility of the 7A04 aluminum alloy to stress corrosion cracking is greater; in the solution at pH=1, the phase shift method shows that crack initiates at 1h and propagates at 4.5h, and the electrochemical impedance spectroscopy in situ method shows the crack initiation and propagation are discontinuous, and in stages; the EN results show that the crack initiation occurs at a certain moment among 3000-5000s and propagates obviously at a certain moment among 13500-22500s accompanying with obvious periodical current and potential noise peaks.
This research has produced Al-Zn-Mg-Cu alloy containing 20%(mass fraction, the same below) alloying elements by the Hot-top semi-continuous DC casting equipment, which has adopted purifying and refining on-line technologies. This alloy has broken the limit of 7000 Al-alloy containing no more than 14% alloying elements. The microstructure and fracture of the alloy were investigated by optical microscopy (OM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM), the temperature of phases transformation was investigated by differential scanning calorimetry (DSC), and the hardness and tensile properties were also tested. The tensile strength, yield strength and elongation of this alloy can be up to 810.3, 799.3MPa and 3.4% by RRA heat-treatment after extrusion. Through the study on the single and tertiary-stage ageing treatment kinetics, the optimum ageing temperature 120℃ is identified and a wider range of aging time can be chosen. Moreover, no other precipitates are found in the alloy containing 16.1%Zn element, and the joint strengthening comes from the undissolved second phase and the ageing precipitation η' phase.
The WCp/Hadfield steel composite and a composite-steel composite structure were manufactured by the squeeze casting method, the impact wear resistance of the WCp/Hadfield steel composite and the composite structure were investigated.Pure Fe powder was added into the WC particle preform and the surrounding region to control the structure of the interface between the steel and the composite in the composite structure. The results show that no melt of WC and no transition layer are formed at the interface between the steel and composite region in the composite structure, because the Fe powder absorbs a lot of heat and melt, however which is present in the composite. The wear rate of the composite is higher than the Hadfield steel, because of the material avalanched at the edge of the worn surface, but the wear resistance of the composite structure is improved by 1.34 times than Hadfield steel. Through the wear morphology analyzing, the reasons of the composite avalanching and the impact wear resistance mechanism for the composite structure were discussed.
CsF-AlF3 based composite fluxes with different Ge contents which are in the form of GeO2 were developed by the method of solution synthesis, and their melting characteristics, phase structures and microstructures were observed and analyzed subsequently. Meanwhile, 2024 aluminum alloy was brazed successfully at 480℃ under the active effect of CsF-AlF3 flux with 4% (mass fraction, the same below) Ge doped. The results show that the liquidus temperature decreases from 477℃ to around 440℃and has the main phase composition of CsAlF4 and Cs2GeF6 when content of Ge exceeds 4%. And the new Cs2GeF6 changes the morphology of CsF-AlF3 flux to more regular polyhedron structure with fewer flocculent agglomerates. On the other hand, the flux with 4% Ge immensely promotes the spreading of Zn-15Al filler metal on the 2024 aluminum alloy at 480℃ and the shear strength of brazing lapping joints reaches 110MPa, with homogeneous structure of the joints, and with no obvious defects observed.
The mechanical properties of Cu/Ni film composed of substrate Cu and impurity Ni, and the influence of impurity sizes and shapes on yield strength was studied under tensile loading. Based on the embedded-atom-method potential, molecular dynamics simulations were carried out to analyze the interactions between the impurity and dislocations. The results show that the introduction of impurity Ni decreases the yield strength of the nano-crystalline. However, the impurity hinders the movement of dislocations because of the interface between Cu and Ni, and it strengthens the substrate due to the strong interaction force of Ni in the plastic deformation stage. The films with the shape of square, transverse rectangular, circular and vertical rectangular impurities have similar yield strengths at the cross-sectional size 6.9nm2; if the cross-sectional size is 15.7nm2, the film with transverse rectangular impurity has the largest yield strength 7.41MPa; at the cross-sectional size 3.1nm2, film with circular impurity has the highest yield strength 6.93MPa.
Based on the generalized Newtonian fluid constitutive equation, using ARD-RSC fiber orientation model, numerical simulation was used to predict fiber orientation distribution of the long-glass fiber reinforced composite injection molding components by considering the interaction between fibers. The fiber homogenized RVE model of long glass fiber reinforced composites was established through the composite material micromechanics Eshelby inclusion theory and Mean Field homogenization method. By using composite meso-scale modeling, discrete RVE model field, injection molding and structural finite element analysis techniques, the strength of long glass fiber reinforced composites analytical method was proposed. The strength analysis of the thrust-rod injection molded part shows that the simulated dangerous position is in good agreement with the actual damage location. On the basis, the structure of thrust rod is improved, the results show that the maximum principal stress of the rod is reduced by 57.18% under the tensile load and 71.25% under the compressive load.
The non-isothermal crystallization kinetics of glass fiber reinforced polypropylene for automated fiber placement was studied by differential scanning calorimetry (DSC) and Avrami equation. To investigate the influence of cooling rate and cooling time on non-isothermal crystallization behavior of matrix material and solve the maximum processing speed at different cooling speed, the non-isothermal crystallization kinetics model and the heat transfer model were derived and the cooling conditions in the process of automated fiber placement were set up. The result shows that the crystallinity of the polypropylene decreases along with the increase of cooling speed. The initial and final crystallization temperature are both moving in the direction of low temperature with the increase of cooling speed. The relative crystallinity is closed to the S type curve along with the change of temperature. The compress strength and the interlaminar shear strength are all increasing with the increase of the crystallinity, however, the impact strength is decreasing along with the increase of the crystallinity which is opposite to the compress strength and the interlaminar shear strength.
The cavity pressure sensors were mounted in the self-developed injection compression mold. Comparison and analysis on cavity pressure of conventional injection molding and injection compression molding were conducted by changing process parameters. The results show that injection compression molding can greatly decrease the injection pressure and cavity pressure, and make the cavity pressure field more uniform. During the conventional injection molding, the influence of mold temperature on the cavity pressure is the most significant factor, followed by melt temperature, pressure holding time and holding pressure. During the injection compression molding, the compression speed influences the most, followed by melt temperature, mold temperature and compression stroke. The technological advantages and pressure field characteristic of injection compression molding were further validated with the low residual stress and small warpage, indicating the cavity pressure plays a major role in guiding processing properties.
The influence of overmolding injection parameters such as packing pressure, racking time, melt temperature, mold temperature and the injection speed on the warpage of PMMA-PC composite boards was investigated. The result shows that the warpage of PMMA-PC composite boards exhibits the tendency of decreasing first and then increasing with the increase of packing pressure; However, the prolongation of packing time is beneficial to reduce the warpage of composite boards, increasing melt temperature and injection speed will lead to the increase of the warpage composite boards. When mold temperature increases, the composite boards bend towards the PMMA side. Asymmetrical cooling in the mold resulting in internal residual thermal stress in composite boards is the main reason of the increase of the warpage, when the mold temperature is 90℃, no warpage occurs in the composite boards. Among these parameters studied, mold temperature and packing time influence the most significantly on the warpage of the composite boards.
Toray T700S and domestic T700 carbon fibers were used as reinforcements to prepare bismaleimide composites by autoclave moulding. Surface physical and chemical states of the carbon fibers, as well as interfacial of the composites and interlaminar shear strength were studied. The results show that the domestic T700 carbon fibers can form better physical adhesion with the resin matrix, which have more grooves on the surface and higher surface roughness than T700S carbon fibers. Although the two kinds of oxygen functional groups of carbon fiber are equivalent, the domestic T700 carbon fibers can form better chemical adhesion with the resin matrix, as they have more oxygenic functional groups than T700S carbon fibers. Hence, the interfacial shear strength of domestic T700 carbon fibers is higher than that of T700S carbon fibers by about 14%, and the interlaminar shear strength is higher by about 19%.
The glass fiber reinforced polypropylene (GF/PP) composite plate with different glass fiber contents was fabricated by the laminated hot-pressing experiment method using the glass fiber felt and polypropylene film, then tensile experiments were carried on under different loading rates. The strain rate sensitive properties of the composites were investigated, and the feasibility of the Burgers model fitting to predict the constitutive relation of the material was analyzed. The results show that the GF/PP composite in the low strain rates is sensitive to strain rate, with the increase of strain rate, the fracture stress and tensile strength increase, and with the increase of the glass fiber content, the strain rate effect decreases. Meanwhile, the Burgers model can effectively fit to predict the tensile stress-strain curves of the composites, then compared with the experimental curves, which further validates the strain rate sensitive properties of the GF/PP composites and its trend.
An experiment was conducted for the composite hat-stiffened panels with different forming process types with boundary constraint, in order to study the effect of secondary bonding and co-curing on the compression stability and carrying capacity of composite hat-stiffened panels, while the thickness of skin and polymethacrylimide (PMI) foam were taken into account on the effect on axial compression characteristics. In the test, strain gage was pasted to monitor the local bucking, acoustic emission was detected and fracture section was observed to investigate the fracture mechanism. The results show that the thickness of skin has significant influence on the compression properties of panels, PMI foam can slightly increase the buckling load while has no impact on the ultimate load. Both buckling load and ultimate load of co-cured panels almost decrease by 18% compared with that of secondary bonded panels, damage can be observed in the former prior to the latter, delamination induces collapsing for the former panels while debond is the key point of breaking for the latter panels.
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