- 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)
The effects of non-metallic inclusions on the fatigue properties of iron and steel materials and their research status were reviewed. From the perspective of inclusions, the latest research progress on the extraction of non-metallic inclusions was first introduced from the experimental measurement methods and mathematical formulas. Secondly, according to the main principles of inclusions for fatigue damage, five kinds of widely used quantitative analysis of inclusion parameters and math-ematical model of steel fatigue performance were introduced.Then the influence of the characteristics of non-metallic inclusions on the fatigue properties of heavy-duty steel parts was investigated by taking the morphology, mechanical properties and the interaction between the inclusions and the matrix as the starting point. Finally, it was pointed out that the focus of future research in this field is to analyze the main action mechanism of non-metallic inclusions on steel fatigue properties from multiple perspectives and to build a prediction model of non-metallic inclusions on steel fatigue life.
Precipitation and evolution behavior of phases in Inconel 625 superalloy were reviewed, and the various types of phases in the alloy were emphatically introduced, including the γ' phase, γ″ phase, δ phase, Ni2(Cr, Mo) phase, three types of MC, M6C, M23C6 carbides and Laves phase. The precipitation and evolution behavior of phases in different forming processes, heat treatment and high temperature creep were elucidated. Further, the effects of different types of phases on the properties of the alloys were discussed. The main factors causing cracks during rapid forming and welding in Inconel 625 alloy were pointed out and it was proposed that an important development direction in the future is how to improve the thermal strength and thermal fatigue properties of the Inconel 625 alloy by selecting and controlling the phase precipitation.
Synthesis and control strategy of colloidal nanocrystals are mainly concerned with dynamic factors. Generally, theory of nucleation of liquid phase colloids and crystal growth are considered. Firstly, the strategies on colloidal nanocrystalline synthesis and morphology control at the stage of nucleation, growth and ripening were reviewed in this paper. Secondly, selective-adsorption mechanism, effective-monomer mechanism and oriented-attachment mechanisms were briefly introduced for the phenomena that can not be explained by classical crystal growth theory. It was also introduced briefly the joint action of some new mechanisms or multiple mechanisms on synthesis of nano-materials in recent years. Finally, perspectives on future development of nanocrystalline synthesis and morphology control were presented. It is believed that quantitative and precise structural control is of great importance and will be a huge challenge and development trend in nanocrystalline synthesis and morphology control.
Porous metal is a material that combines both structural and functional properties. It is widely used in various fields due to its low density, high porosity and controlled permeability. In this paper, the application progress of porous metal on the flow field of bipolar plates in proton exchange membrane fuel cell (PEMFC) was reviewed. Compared with the traditional flow channel, the high open porosity (>70%) porous metal has three-dimensional structure connected with each other, which can increase the uniformity of gas distribution, enhance gas mass transfer, enhance electron/heat conduction and water discharge, so eventually improve battery performance. In addition, the effects of porous metal parameters, flow field structure design, service parameters and materials on porous metal flow field in PEMFC applications were explored. At present, the biggest problem that hinders the application of porous metal in PEMFC is corrosion, and more challenges must be faced on the coating preparation process for the complex internal structure of porous metal. Therefore, how to effectively solve the corrosion problem of porous metal in PEMFC environment, which have great significance to promote the application of porous metal in fuel cell field.
SiCNW were prepared with different molar ratio of silicon to carbon on carbon fiber cloth by thermal evaporation method using acetylene black as carbon source. SiCNW-Cf/LAS(Li2O-Al2O3-SiO2) were prepared by using slurry-impregnation and vacuum sintering process with SiCNW-Cf as intermediate interlayer. The results show that as the molar ratio of silicon to carbon decreasing, the diameter of SiCNW decreases continuously, and the yield first increases and then decreases and reaches the highest when the molar ratio of silicon to carbon is 1:3. The SiCNW-Cf/LAS prepared with a molar ratio of silicon to carbon of 1:1 has a minimum reflection loss of -40.9 dB (7 GHz, 3 mm) for electromagnetic wave. The SiCNW-Cf/LAS prepared at a molar ratio of silicon to carbon of 1:3 has a maximum effective bandwidth for absorbing electromagnetic wave of 4.61 GHz (Ku band, 1.5 mm). The excellent absorbing properties of SiCNW-Cf/LAS composites can be attributed to their higher dielectric loss and scattering loss for electromagnetic wave and adjustment of LAS to material and space impedance matching.
In order to study the thermal response of carbon fiber epoxy resin composites in fire, considering the pyrolysis process in fire, the nonlinear thermal response equations were established, and a finite difference method was used to calculate and analyse the material's internal time-dependent temperature progressions and carbonization subjected to one-sided heat flux. The theoretical results from the established thermal response equations were validated against experimental data and a good agreement was observed.As the heating time increases, the carbonized layer range gradually expands, the temperature changes tend to be stable, and the distribution of material temperature with depth position is changed from nonlinear to linear. With the increment of the depth, temperature rise rate is decreased, the time of carbon fiber epoxy resin composites reaching the pyrolysis temperature is increased, the carbonization process is slowed down, and the peak change of density with temperature moves toward the low temperature with the increased depth. The residual mass fraction of materials at different depth in the pyrolysis reaction zone is slightly different at the same temperature, the residual mass fraction is decreased and the degree of carbonization is increased as the depth increases.
Molybdenum disulfide/reduced graphene(MoS2/RGO) composite catalyst was synthesized by one-step hydrothermal method in order to improve the catalytic activity and stability. X-ray diffractometer, scanning electron microscope, transmission electron microscope and rotating disk electrode were used to characterize the physical and chemical properties of the catalyst. The results show that the molybdenum disulfide compound with graphene has pear-shaped structure with few layers, and the layer spacing increases which is uniformly attached to the thin layer of graphene. The oxygen reduction process of molybdenum disulfide catalyst is mainly carried out in two-electron path, while MoS2/RGO composite catalyst can play a synergistic catalytic role in oxygen reduction process and the average number of electron transfer in the process is 3.58. The current density retention rate of the composite catalyst after 20000 s is up to 89.7%.
In view of the imperious demand for efficient anode catalyst in direct methanol fuel cell(DMFE), Ca-Mg-Pd-M(M=Cu, Ag) metallic glasses were designed and synthesized as precursors to prepare nanoporous Pd-Cu/Pd-Ag alloys with ligament-pore bicontinuous structure through dealloying in this paper. The proportion of elements as well as the ligament size of nanoporous metals can be adjusted by changing the composition of presurors. Pd elements can form continuous solid solution with Cu and Ag in a wide range, which can reduce the diffusion rate of Cu and Ag elements in solution, and refine the ligament size of nanoporous metals dramatically(from 100 nm to 10 nm). Moreover, catalytic performance of nanoporous Pd-Cu/Pd-Ag alloys in methanol electro-oxidation was investigated. Compared to nanoporous Pd, nanoporous Pd-Cu/Pd-Ag alloys exhibit more excellent catalytic activity and anti-poisoning effect. The electric current density of nanoporous Pd-Cu alloy can reach 45 mA/mg, and the ratio of Jf/Jb is 1.56. As a result, the nanoporous Pd-Cu/Pd-Ag alloys with lower cost has favorable application prospect in DMFE.
High nickel ternary cathode material LiNi0.8Co0.1Mn0.1O2 was prepared by high temperature sintering method, and the carbon nanotubes were treated in mixed acid. The single wall carbon nanotubes were obtained by centrifuging. Then dispersant (DMF)and LiNi0.8Co0.1Mn0.1O2 were mixed, and different amounts of carbon nanotubes were coated on the surface of LiNi0.8Co0.1Mn0.1O2by ultrasonic dispersion and spray drying method uniformly. CNTs/LiNi0.8Co0.1Mn0.1O2 composites were characterized and tested by SEM, XRD and electrochemical test system. The results show that the composite with 0.5%(mass fraction) carbon nanotubes has the best morphology and the best electrochemical performance. The first discharge specific capacities at different rates such as 0.1 C and 5 C are 215.587 mAh·g-1and 175.78 mAh·g-1, respectively. When charged at 0.1 C and discharged at a large rate of 5 C, the CNTs/LiNi0.8Co0.1Mn0.1O2 composites can still maintain the first discharge capacity of 81.54%, which is 10.48% higher than that of LiNi0.8Co0.1Mn0.1O2 which is not coated with carbon nanotubes. After 100 cycles at 1 C, the capacity retention rate is 93.02%, which is 15.42% higher than that of LiNi0.8Co0.1Mn0.1O2 which is not coated with carbon nanotubes.
EVOH-SO3Li/P(VDF-HFP)/HAP lithium ion battery separator was prepared by high-pressure blending electrospinning using polyethylene-vinyl alcohol sulfonate (EVOH-SO3Li), poly(vinylidene fluoride-hexafluoropropylene) (P(VDF-HFP)) and nano hydroxyapatite (HAP) as raw materials. The performance of the separator was characterized by FTIR, SEM, electrochemical workstation and battery detection system. The results show that the EVOH-SO3Li/P(VDF-HFP) composite separator forms an uniform and dense three-dimensional network structure, and the EVOH-SO3Li/P(VDF-HFP)/HAP composite separator presents a three-dimensional network of dendritic shapes after adding P(VDF-HFP) and HAP, which improves the porosity and liquid absorption rate of the separator. Compared with the pure EVOH-SO3Li separator, the porosity and liquid absorption rate of the EVOH-SO3Li/P(VDF-HFP)/HAP composite separator are increased by 37.5% and 91.6%, respectively. Meanwhile, the excellent electrochemical performance is also exhibited. The electrochemical stability window of the assembled lithium-ion battery is 5.65 V, and the interfacial impedance is decreased to 184.24 Ω, and the ionic conductivity is increased to 2.686×10-3 S·cm-1; Lithium-ion batteries assembled with EVOH-SO3Li/P(VDF-HFP)/HAP composite separator have a capacity retention rate of 96.69% after 100 cycles at 0.5 C discharge current, the properties of EVOH-SO3Li/P(VDF-HFP)/HAP composite separator are improved compared with EVOH-SO3Li.
Poloxamer is a thermo-sensitive polymer that can form gel at a concentration of 15.0%(mass fraction, the same as below)-30.0%.In order to decrease the gelatinization concentration and improve drug release properties of poloxamer at body temperature, thermo-sensitive N-acetyl glycol chitosan/poloxamer composite hydrogel was prepared by complexing N-acetyl glycol chitosan with poloxamer 407 (GC/P407).The structure, thermo-sensitivity, mechanical properties, morphology and in vitro drug release properties of GC/P407 were characterized by FT-IR, tube inverting method, rheometer, SEM and UV-vis spectroscopy. The GC/P407 solution shows reversible thermo-sensitive sol-gel transition behavior, and the sol-gel transition temperature is well controlled in the range of 25-37℃ by regulating the ratio of GC/P407, which shortens the gelation time and the gelatinization concentration(6%) of poloxamer 407 at body temperature. GC/P407 composite hydrogel, which has a highly porous three-dimensional structure with pore size of 10-60 μm as demonstrated by SEM, exhibits high mechanical properties. In addition, the GC/P407 composite hydrogel shows sustained release behavior of the anticancer drug gemcitabine, and the release time of the drug-loaded gel can reach 72 h. GC/P407 composite hydrogel shows the potential for biomedical application as injectable drug delivery carrier.
In order to obtain high-flux antifouling nanofiltration membrane, a series of ICIC/ZnO/HBPA nanofiltration membranes were prepared by interfacial polymerization of 5-isocyanato-isophthaloyl chloride (ICIC) and hyperbranched polyamide (HBPA) on the surface of polyacrylonitrile (PAN) ultrafiltration membrane, the nano-ZnO was incorporated into the polyamide separation layer. The existence of ZnO is confirmed by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The analysis results of water contact angle indicate that the membrane hydrophilicity is increased by incorporation of ZnO nanoparticles, the lowest water contact angle of the membrane is 22.7°. Compared with the membrane without ZnO, the flux and the salt rejection rate for NaCl, MgCl2, Na2SO4 and MgSO4 of the membrane containing ZnO increase. The largest flux of the ICIC/ZnO/HBPA membrane is about 102 L·m-2·h-1, which is nearly 2.6 times of the membrane without ZnO. The bacteriostasis of the membranes to E. coli is enhanced by incorporation more ZnO. Increasing the monomer content or prolonging the interfacial polymerization time is beneficial to increasing the salt rejection rate, but the order of the salt retention rate is changed. When HBPA is 0.8%, ICIC is 0.1%, content of ZnO is 0.02 g and reaction time is 10 min, the salt rejection rate for NaCl, MgCl2, Na2SO4 and MgSO4 of the prepared membrane are 60.8%, 96.4%, 95.1%, 96.7% and the flux is 53, 54.7, 53.7 L·m-2·h-1and 54.7 L·m-2·h-1, respectively.
The nano-TiO2 microspheres were prepared by a hydrothermal method with urea in ethanol/water solution in the presence of sodium sulfate. The prepared samples were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption and UV-Vis diffuse reflectance spectroscopy, the effects of hydrothermal temperature on the nano-TiO2microspheres morphology were investigated, and the photocatalytic activities toward gaseous benzene of the samples were studied. The results indicate that the microspheres are composed of tiny nanoparticles, the TiO2 microspheres pose high specific surface areas and uniform porous nanostructures, the optical absorption edges of the samples have "blue shift". The photocatalytic results confirm the benzene-degrading effectiveness of the TiO2 microspheres, especially, the results show that no benzene detected after 20 min reaction with TiO2 microspheres prepared at 180℃, however, the produced CO2 concentration continues to increase, it indicates that TiO2 microspheres with very high adsorptive capacity can enhance the subsequent photocatalytic reaction, and the mineralization ratio of this TiO2 microspheres can be as high as 5.5, which is double of P25 (2.7).
With chitosan mass fraction changing from 0% to 50% by 5%, relative to collagen mass, the collagen-chitosan scaffolds were crosslinked by γ-irradiation and EDC/NHS. Fourier transform infrared spectroscopy (FTIR) and SEM were applied to analyze the structure. Water absorption rate, porosity, collagenase degradation and mechanical property were used to detect the properties. The effects of γ-irradiation and EDC/NHS modification on the properties of scaffolds were studied. The results show that both γ-irradiation and EDC/NHS modification induce crosslinking in collagen-chitosan scaffolds and chitosan greatly reduce the damage to molecular structure caused by γ-irradiation.The microstructure crosslinked by γ-irradiation is worse than those crosslinked by EDC/NHS. The optimal chitosan mass fraction is 25% for both γ-irradiation and EDC/NHS. γ-irradiation and EDC/NHS scaffold modification can lead to orientation structure.
The effects of aging treatment on microstructure and properties of Al-Zr-Sc(-Er) alloys were investigated by TEM, STEM, hardness tests and electric conductivity tests systematically. Results show that the aging response speed, peak hardness and thermal stability of Al-Zr-Sc alloys are significantly improved by increasing Sc content, and increasing Zr content improves hardness and thermal stability, while decreasing the electric conductivity. Adding Er in Al-Zr-Sc alloys improves the aging response speed and promotes the precipitation of Zr and Sc. Hardness and electrical conductivity of alloy are improved, owing to the formation of Al3(Er, Sc, Zr) phases with core-double shell structure. For experimental alloys, one-stage aging at 300℃ provides the higher hardness but lower electric conductivity; one-stage aging at 400℃ can increase the aging response speed and electrical conductivity but decrease hardness; two-stage aging at 300℃/24 h+400℃ can lead to better match of conductivity, tensile strength and heat resistance.
The FGH95 superalloy was processed through HIP + HEX + HIF, then the alloy was conducted by two different aging treatments, and the microstructure, morphology of precipitate phase and mechanical properties were studied. The results show that there is no obvious effect of aging treatments on the grain size, but the amount, the size distribution are obviously different. Compared to single-step aging treatment, double-step aging treatment can more effectively promote the growth of inner-grain γ' phase, the average diameter of inner-grain γ' phase can reach 78 nm, while that is 67 nm for single-step aging treatment. Meanwhile, double-step aging is more beneficial to the precipitation of inner-grain strenthening phases, such as M3B2 and etc. The tensile strength of the alloy with different aging is similar, but the endurance life of alloy with double-step aging is lower, and the endurance plasticity is higher.
The Ni-Cr-P metal powder was prepared by vacuum melting and inert gas atomization method, and then an organic binder was added and stirred at high speed to prepare a Ni14Cr10P paste-like filler metal. The prepared pasty filler metal was used to braze the C/C composites in a vacuum furnace. Then the shear strength of the brazed joint was tested. The interface structure of the brazed joint was analyzed by OM, SEM, EDS and XRD. The results show that the shear strength of the joint obtained at the brazing temperature of 1000℃ and the holding time of 0.5 h reaches 28.6 MPa, and then the strength of the brazed joint is decreased with the increase of the brazing temperature or the holding time. It is found that the contact area between the brazing layer and the surface of the C/C composites is increased by the pasty brazing filler metal, which is favorable for blocking the pores on the surface of the C/C composites. A staggered distribution of Cr carbide phase buffer layer is formed at the interface, so that the interface exhibits a structure with an increased thermal expansion coefficient gradient, which helps to alleviate the thermal mismatch and improve the strength of the brazed joint.
The surface of TC4 titanium alloy was treated by wet shot-peening (SP). The residual stress relaxation during high and low cycle tensile fatigue was studied, and the effect of re-shot-peening (RSP) on fatigue life was discussed. The results show that relaxation of compressive residual stress still occurs under tensile stress. The fatigue load level has an important influence on the relaxation rate, degree and range of compressive residual stress field (CRSF) of shot peened TC4 titanium alloy. Residual stress relaxation during high cycle fatigue (HCF) mainly occurs in the near surface layer of 0-30 μm, and the relaxation rate is slow, while residual stress relaxation in low cycle fatigue (LCF) mainly occurs in the range of 0-80 μm, which is deeper and faster. RSP also has a great influence on the fatigue life of TC4 titanium alloy. It can significantly improve fatigue life at 25% and 50% of initial SP fatigue life, but has little effect on fatigue life at 75% of initial SP fatigue life. In addition, the strengthening effect of RSP is related to the level of fatigue load, which improves the HCF life obviously.
YSZ ceramic coating was prepared by PS-PVD process on K417G superalloy prefabricated with NiCoCrAlYTa bond coating. The tensile bond strength, particle erosion resistance and high temperature oxidation resistance of PS-PVD YSZ ceramic coating were tested by the universal tensile testing machine, particle erosion device and static oxidation furnace. The SEM and EDS were used to analyze the surface, cross-section morphology and element distribution. The results show that surface roughness has great influence on tensile bond strength, particle erosion resistance and high temperature oxidation resistance of YSZ ceramic coating. The bonding strength is increased first and then decreased with the increase of surface roughness. The coating prepared on the surface of Ra=0.40 μm has the highest bonding strength of 23.5 MPa. The tensile fracture occurs in the interior of YSZ ceramic coating at a distance of 40-70 μm from the bond coating. The erosion rate is decreased first and then increased with the increase of surface roughness. The coating prepared on the surface of Ra=0.40 μm has the best particle erosion resistance, and the erosion rate is 2.8×10-3 g/g. Small surface fluctuations and low porosity are two important reasons for preventing fast particle erosion. The YSZ coatings prepared with different surface roughness can produce dense and continuous TGO layer. Larger surface roughness causes larger fluctuation of growing TGO layer, which is more likely to cause local thickening and stress concentration, thus leading to failure.
The 45 steel was sealing treated for various time in 6%(volume fraction)KH560 solution after the hot-dip aluminizing-anode oxidation. An Al-Al2O3-silane composite coating was formed on the surface of the 45 steel. The microstructure of composite coating was studied. The corrosion resistance of composite coating and its effect on the galvanic corrosion between the 45 steel and 30%(mass fraction)Cf/nylon6 composite were investigated. The results show that the silane coating effectively seals the cracks in Al2O3 coating, prevents the corrosive liquid from attacking the substrate. Hence, the corrosion resistance of the 45 steel is improved. Meanwhile, the good insulation property of the Al-Al2O3-silane composite coating can reduce the driving force of the galvanic corrosion between the 45 steel and 30%Cf/nylon6 composite, consequently, the galvanic corrosion resistance of 45 steel also is improved. After treated with the optimal KH560 treatment process for 5 min, the self-corrosion current density of the hot-dip aluminized 45 steel decreases by 3 orders of magnitude compared with that of the single hot-dip aluminized sample while the electrochemical impedance increases by 2 orders of magnitude, and the galvanic corrosion current density between the 45 steel and 30%Cf/nylon6 composite decreases by about 75%.
BN, TiN and BN/TiN nano-additives were modified by oleic acid, characterized by Fourier transform infrared spectroscopy. The tribological properties of lubricating oil nano-additives were tested by four-ball friction and wear tester. The results show that oleic acid is grafted onto the surface of nanoparticles to improve their dispersibility. Compared with pure base oil, lubricating oil with nano-additives reduces friction coefficient by 11.7% and wear scar diameter by 29.5%, respectively. No peeling and falling off appears on the surface of wear scar, and the depth and width of groove are obviously reduced, compared with single nano-additive BN or TiN, BN/TiN displays synergistic lubrication when mixed nano-additive BN/TiN is used. The nano-BN and TiN particles can enter the friction pair, play the role of micro-bearing, reduce friction and wear. The nano-BN entering the friction pair and reacting with the matrix material of the friction pair can form boron nitride, boron oxide and iron oxide to repair the wear surface.
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