- 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)
With the increase of the thrust-weight ratio of the aero-engine, CMC-SiC composites with low density, high strength and toughness, high thermal stability, long lifetime, good ablation resistance and oxidation resistance need to be developed to meet the requirements of the complicated and aggressive environments in the aero-engine. The characteristics, fabrication methods, applications on the hot components of the abroad advanced aero-engines, the domestic research achievements and the open problems of the CMC-SiC composites were introduced. The research tendencies in the high performance fibers, parts design and fabrication, environmental barrier coatings, non-destructive testing technologies, evaluation and verification method and repairing technologies were put forward.
As an attractive candidate for anode materials, silicon has attracted extensive attention. The instability of electrode/electrolyte interphase due to the inherent volume variation upon (de)lithiation is one of the major factors that limit the commercialization of Si materials. The in-depth understanding of the interface reaction of Si is helpful to modify the interface properties of Si, and further improve the electrochemical performance. This review summarizes the research on the interface reaction mechanism of Si during (de)lithiation process, including Li-Si alloying process, the reactions of primary oxide layer and the formation of passivation film on the Si surface. Moreover, the effect of the three processes on the Si electrochemical performance are also discussed.
Compatibilization of immiscible polymer blends is by far the most general and efficient strategy to convert multiphase polymer blends with poor miscibility into high performance polymer alloys. The concept and necessity of compatibilization of immiscible polymer blends were analyzed. Various compatibilization methods were introduced to improve the miscibility of polymer blends, including the addition of block or graft copolymers, reactive polymers, low molecular weight chemical compound and functionalized nanoparticles, etc. In addition, the development of compatibilization methods was reviewed and the effect of compatibilization on the phase morphology and final properties of the blends was discussed, such as mechanical properties, thermal properties, electrical properties, etc. Finally, it was proposed that nanoparticle compatibilization will become a popular method in the field of blend compatibilization. This method not only can increase the capacity, but also increase the mechanical strength and possibly bring new properties to the blend.
Titanium carbide(TiC)nanoparticles were synthesized in situ by direct current(DC)arc-discharge method under the mixture of methane and argon gas atmosphere. The physical characterization including X-ray diffraction(XRD)and transmission electron microscope(TEM)show that TiC nanoparticles have cubic structure with grain sizes of 40-90nm. Cyclic voltammetry(CV)measurement indicates that TiC nanoparticles are efficient bi-functional catalysts toward both oxygen reduction reaction(ORR)and oxygen evolution reaction (OER)for Li-O2 batteries, which can effectively compensate for the weak catalytic activity of OER of carbon materials. The results of galvanostatic charge-discharge measurement present that the TiC nanoparticles can reduce the charge-overpotential by 280mV compared to general carbon materials(Super-P), and the TiC electrode delivers an initial discharge capacity of 1267mAh·g-1 at 50mA·g-1. Even at a high current density of 150mA·g-1, the discharge capacity still maintains 778mAh·g-1, indicating excellent rate performance of lithium-air batteries with TiC nanoparticles as catalysts. The TiC electrode displays 10 cycles at a fixed capacity of 500mAh·g-1 and at a current density of 100mA·g-1.The characterization of XRD, Fourier transform infrared(FT-IR)and scanning electron microscopy(SEM)show that the formation and decomposition of Li2O2 have great reversibility under the bi-functional catalysis of TiC nanoparticles, which can significantly alleviate the accumulation of undesired byproducts, and eventually improve the electrochemical performance of Li-air batteries.
Using solid-phase reaction process to synthesize La0.7Ca0.3CrO3-δ(LCC) primary powder, composite hollow fiber membrane of NiO/LCC (1:1) was prepared by phase-conversion spinning method and then sintered at 1400℃ in air as micro-tubular solid oxide fuel cells (SOFC) support. The particle size distribution, TG-DTA thermal analysis, structure, morphologies, electrical conductivity, thermal expansion and bending strength were characterized by laser particulate size analyzer, thermal analyzer, X-ray diffraction, scanning electron microscopy, standard DC four-probe technique, thermal expansion dilatometer and universal material testing machine. Results indicate that LCC and NiO powders have considerable chemical and sintering compatibilities at SOFC co-firing temperature (1400℃). The fracture section of the hollow fiber membrane exhibits a sandwich-like structure with homogeneous porous surfaces. Two layers of obviously bigger parallel finger-like pores distribute uniformly between the inner and outer surfaces of the microtubule section. The porosity of the sample is 60.6%, and increases to a relatively high value of 68.1% after reduction. Electrical conductivity of the sintered specimen decreases as the temperature increasing in pure H2. The value reaches 10.8S·cm-1 at 700℃. Bending strength before and after reduction are 39.6MPa and 33.2MPa respectively. Thermal expansion coefficient (TEC) value of the NiO/LCC hollow fiber membrane gets to 12.4×10-6K-1, which is very close to that of other SOFC components, such as NiO/YSZ anode and LCC interconnect.
Two types of ultrathin-flaky δ-MnO2 electrode materials (denoted as δ-MnO2-A and δ-MnO2-B) were synthesized through the reduction of potassium permanganate with manganese acetate and ethanol separately.The crystalline structure, chemical component, microstructure and pore size distribution of these nano-materials were determined by XRD, XPS, SEM/TEM and BET analysis.The electrochemical test demonstrates two δ-MnO2 electrode materials own similar specific capacitance and rate capability.Comparing to δ-MnO2-A, however, electrode material δ-MnO2-B contains a higher potassium and manganese vacancy content, and the lamellar structure of δ-MnO2-B is more legible and stable, therefore it displays a much more superior cycling stability.In 0.5mol/L Na2SO4 electrolyte, the specific capacitance of δ-MnO2 reaches 227F·g-1(1mV·s-1) and the capacitance retention rate is achieved 87.6% after 5000 cycles at 100mV·s-1.
Montmorillonite(MMT) was utilized to absorb three types of cationic photosensitizers, namely, meso-tetra(4-N-methylpyridyl)porphyrine tetratosylate (TMPyP), Zn(Ⅱ) meso-tetra (N-methyl-4-pyridyl) porphine tetrachloride (Zn-TMPyP) and methylene blue (MB), the as-obtained mixtures were then evenly dispersed in aqueous polyvinyl alcohol-styrylpyridine salt condensate (PVA-SbQ) solution, corresponding photoactive MMT/PS hydrogels were prepared by the assay of UV cross-linking eventually. Transmission electron microscopy (TEM) was employed to analyse morphology of MMT and one as-prepared MMT/PS hydrogel. Scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) were applied to analyse the internal morphology and thermal properties of the as-prepared hydrogels. Finally, swelling properties and antibacterial effect against staphylococcus aureus (S. aureus) were investigated. The results show that three photoactive MMT/PS hydrogels are successfully prepared with good swelling properties. The as-prepared hydrogels exhibit inactivation against S. aureus to some extent, furthermore, the hydrogel which immobilizes Zn-TMPyP reveals best inactivation efficacy, with a sterilization rate of 98.49%.
Carbonized nano-Co3O4 particles and diatomite were used for preparation of the composite of carbonized nano-Co3O4/diatomite by pyrolysis method, the magnetic and absorption properties were studied. The composite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometer. The results show that the superparamagnetic nano-Co3O4 particles with average size of 50nm and amorphous activated carbon are uniformly dispersed in the surface and pores of diatomite to form a stable composite. Carbonized nano-Co3O4/diatomite composite indicates high magnetic and microwave absorption performance with maximum reflection loss of -14.7dB, < -10dB frequency range about 14-18GHz and bandwidth of 4GHz.
ANSYS finite element simulation software was used to simulate the heating process of silver coated yarns in fabric. The thermal filed distribution of heating fabric in different condition was analyzed by adjusting the distance between the silver coated yarns and output voltage. The heating fabric was prepared by the results of finite element simulation. The electrical heating property of heating fabric was researched and contrast with the results of finite element simulation. The result shows that, the equilibrium temperature of silver coated yarns rise with the increase of output voltage. The temperature is 109.7℃ by the output voltage is 7V. The distance of silver coated yarn in fabric is 3mm, which makes the surface temperature of heating uniform while the cost of silver coated yarns is lower. The equilibrium temperature and the heating speed rise with the increase of power density. The results of simulation are consistent with the actual results and the deviation is less than 4.5%. The results of finite element simulation can be important reference to guide the fabrication of heating fabric based on silver coated yarns.
Two bicrystal specimens containing high angle grain boundary (about 20 degrees) were prepared by seed crystal method. The effect of Hf on the as-cast, heat-treated grain boundary microstructure, composition and stress rupture properties under 1100℃/100MPa was investigated in Ni-based single crystal superalloy contained Re with different contents of Hf (mass fraction:0%, 0.4%). The results show that Hf addition results in the increase of the volume fraction of (γ+γ') eutectic and MC along the grain boundary. The volume fraction of cellular recrystallization microstructure is significantly decreased after heat treatment with Hf addition. The transverse stress rupture life is observed to increase significantly under 1100℃/100MPa in the Hf-containing alloy. The stress rupture properties are closely related to the type, morphology, content and composition of the precipitation phase along grain boundary, but the obvious segregation of Hf is not observed. This study can be helpful for the understanding of Hf's role of strengthening mechanism in grain boundary in advanced Ni-based single crystal superalloy.
The plastic deformation with respect to dislocation distribution of titanium foil under ultrasonic vibration was studied. The influencing rule of different ultrasonic vibration modes on the stress-strain, elongation and dislocation distribution of titanium foil during plastic deformation was studied by uniaxial tensile test and microstructure analysis. The results show that the flow stress of titanium foil can be reduced by about 80% and the elongation can increase from 40.33% to 54.46% during ultrasonic vibration. TEM shows that the dislocations tend to be parallel to each other without large amount of entanglement, and the distribution of dislocations in the samples without ultrasonic vibration is chaotic and seriously entangled.
The effect of various amounts of Sr (0%-0.09%, mass fraction, the same below) and homogenization treatment on the as-cast microstructure and mechanical properties of Al-Mg-Si-Cu-Mn alloy was investigated by optical microscopy, scanning electron microscopy, differential thermal analysis, X ray diffraction analysis and hardness test, electrical conductivity test and tensile test. The evolution of the second phase in as-cast microstructure and homogenization annealing process were also studied. The results show that the Al-Mg-Si-Cu-Mn alloy mainly includes AlCuMgSi, Mg2Si, AlSi, Al2Cu, Al(MnFe)Si, AlMnSi and Al(MnCrFe)Si phases. The addition of 0.06%Sr in the alloy can transform the needle-like AlSi phase into spherical AlSi phase, and promote the formation of AlFeSi spherical crystalline phase which reduces the stress concentration and improve the strength and plasticity of the alloy. During homogenization, the bulk-like phases and low melting eutectics are dissolved. The Al(MnCrFe)Si phase turns from the original trigonometric and needle-like phases into fine granular phases which are more favourable for the material processing. The homogenization heat treatment process of 540℃ for 8h is suitable for Al-Mg-Si-Cu-Mn-Sr alloy.
The hot compression test of the new ultra strength Al-Zn-Mg-Cu-Zr-Sc alloy at high temperature was carried out by using the Gleeble-1500 thermal simulator. The flow stress and microstructure evolution during the deformation process of the new alloy were investigated at the deformation temperature 370-460℃, the strain rate 0.001-10s-1. The results show that the flow stress in the early deformation stage increases with the increase of the strain rapidly, and then the peak stress decreases gradually and reaches a steady state. The flow stress increases with increasing strain rate, and decreases with the increase of deformation temperature. The flow stress can be described with hyperbolic sine relationship, and material parameters such as activation energy can be calculated by linear fitting, thus the constitutive equation of flow stress can be presented finally. With the increase of the deformation temperature and the decrease of the strain rate, the deformation degree of the original grain increases significantly, and the recrystallization fraction increases obviously.
Several (Cu-Ni-Fe)-xNiFe2O4(x=50, 60, 70, 80, mass fraction/%) composite inert anodes with different contents of alloy phase were prepared using Cu, Ni, Fe and high-temperature synthetic NiFe2O4 by cold-pressing sintering method. The effect of Fe on the composition and microstructure of the (Cu-Ni-Fe)-xNiFe2O4 composite inert anodes during sintering and electrolysis process was studied. It is found that the redox reaction between Ni/Fe and NiFe2O4 phase occurs, leading to the dissociation and regeneration of NiFe2O4. In addition, the film-forming process and corrosion behavior of the (Cu-Ni-Fe)-xNiFe2O4 anodes were studied through low-temperature aluminium electrolysis test. The results indicate that the cell voltage is stable during electrolysis and the impurities in the produced aluminium are less than 0.7% (mass fraction), which indicates that (Cu-Ni-Fe)-xNiFe2O4 composite inert anode is one of the most promising inert anode materials, and the poor thermal stability of the ceramic anode is expected to be solved.
WCP/steel surface composites were endowed with gradient structure and prepared by powder metallurgy. The mechanical properties, thermal fatigue properties and microstructure of the composites with different W content in the transition layers were analyzed by scanning electron microscopy, metallographic microscope, compression and thermal shock tests, and the influence of W addition on the composites performances was examined. The results show that the composition and structure between the composite layer and the substrate layer are varied by adding tungsten powder in the transition layer, the conflicts in stress, strain, and thermal expansion between the composite layer and the substrate layer are decreased. With the mass fraction of tungsten powder increasing, the W can diffuse both into the substrate layer and the composite layer, which leads to a new phase appearing in the transition layer. The bond between the substrate layer and the composite layer is reinforced. When the W content in the transition layer reaches 30% in mass fraction, the compressive strength reaches 553MPa, and thermal fatigue resistance of WCP/steel surface composite is improved.
The corrosion inhibition effect and adsorption behavior for N80 steel in HCl solution were investigated by using electrochemical method and scanning electron microscope, meanwhile, the corrosion inhibition mechanism of inhibitors was analysed from the point of view of the thermodynamic. The results indicate that when Mannich base is added into HCl solution, the charge transfer resistance increases, thereby the corrosion rate of metal surface is reduced. When Mannich base is compound with sodium tungstate, the saturated adsorption capacity of inhibitors on metal surface increases, and the corrosion resistance of N80 steel in HCl solution increases significantly, showing a good synergistic effect. When the molar ratio of Mannich base to sodium tungstate is 1:1.5, the highest inhibition efficiency can reach 99.65%. The adsorption of inhibitors on the surface of N80 is in accordance with the Langmuir adsorption model, and it mainly belongs to chemisorption. The process of adsorption on N80 surface is spontaneous and irreversible endothermic reaction.
Reciprocating sliding friction and wear tests were carried out on polyetheretherketone (PEEK) and natural patella cartilage using the pin-on-disk configuration at different normal loads, slipping velocity and friction pairs under 25% fetal bovine serum, where natural femoral cartilage and CoCrMo were used for comparison to PEEK. The influence of normal load, slipping velocity and friction pair on the friction and wear behavior was studied. The results show that under 25% fetal bovine serum conditions, the friction coefficient of femoral cartilage/patella cartilage is the smallest among that of PEEK/patella cartilage and CoCrMo/patella cartilage, the coefficient of friction of PEEK/patella is obviously lower than that of CoCrMo/patella and the wear surface of CoCrMo/patella is more seriously damaged than that of PEEK/patella. The friction coefficient of PEEK/patella decreases with the increase of normal load especially under the low loads (10-20N) and increases with the increase of slipping velocity especially under the high slipping velocity conditions (10-20mm/s). The wear surface damage increases with the increase of normal load and slipping velocity. The normal load is more effective than slipping velocity.
Integral bending is an efficient and economical method to manufacture curved sandwich panels, and its forming characteristics and springback prediction are a major concern. The equivalent elastic constants of bi-directional trapezoidal sandwich were deduced by the semi-analytic approach with finite element, then the deformation characteristics of face sheets and core and the change of the stress neutral layer in the bending forming were analyzed. On this basis, the theoretical calculation model of plane strain bending springback of sandwich panels was established and applied to predict the stress and springback, then compared with the numerical simulation and experimental results of multi-point bending. The results indicate that springback of sandwich panels is small; it is easy to control the forming precision. the theoretical predicted cross section tangential stress and springback are overestimated, the stress relative deviation of the top face sheet is less than 2.9% and the bottom face sheet is less than 6.5%, the error of vertical center cross section line between is within 1.0mm, all kinds of deviations are in a minor range, so the accuracy of the analytical model is verified.
The technique of quantitative characterization for the physical structure of the surface on PAN-based carbon fiber filaments was established through analyzing the cross sectional morphology which was obtained by scanning electron microscopic (SEM), followed by the image processing with Photoshop software and self-written Matlab program. The parameters such as the width, depth, and the number of surface groove structure were obtained by statistic calculation. Then the circularity, ratio of depth to width, density of groove structure along circle direction, and irregularity were also calculated to characterize the physical structure systematically. Furthermore, the groove structure of carbon fiber was regulated and controlled by adjusting the coagulation environment during the spinning process of PAN precursor, and it is found that the depth and width of groove structure on the surface of carbon fiber are decreased gradually, the shape of grooves also tends to flatten due to the decreased ratio of depth to width, the irregularity is decreased by about 7.5%, while the density of groove structure is increased by about 50% when the temperature of coagulation bath is increased from 25℃ to 45℃. The above carbon fibers with different surface physical structures were used as reinforcements to prepare composites, the results of microdroplet debonding test indicate that the interfacial shear strength (IFSS) of composites is increased with the increasing of groove size and aspect ratio, as well as the surface irregularity of carbon fibers.
VRAM (vacuum resin absorbable molding) process was used to prepare the epoxy resin matrix hybrid composites with ramie fiber cloth and glass fiber cloth.The storage modulus, the loss factor and the mechanical property of the composites were tested.Vibration characteristics were estimated through the resonance frequencies and free vibration decaying curve via the single cantilever beam vibration test.Meanwhile, the damping factors were obtained by calculation.Finally, the finite element simulation software was used to do some simulation analysis on the resonance frequencies and free vibration decaying experiments.The results show that the contradiction between the damping properties and the mechanical properties can be balanced by the hybrid plies of the ramie fiber cloth and the glass fiber cloth.Therefore it can realize the controllable regulation of the damping properties and the mechanical properties and give full play to the remarkable designing advantages of composites.Among them, loss factor and tensile strength of the composites with RGR lay-up are 1.4 times more than the pure glass fiber cloth composite, and 3 times more than the pure ramie fiber cloth composite, respectively.The finite element simulation curves of free vibration are basically consistent with the experiment results.It shows that virtual vibration test of laminated composite can be realized by simulation software, so as to provide convenience for material performance prediction and design.
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