- 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)
Focusing on(Zr0.6336Cu0.1452Ni0.1012Al0.12)100-xErx(x=0, 0.5, 1, 1.5, 2, 2.5, 3, atom fraction) bulk amorphous alloys, the effect of Er on the structure, mechanical properties, thermal stability and amorphous forming ability of amorphous alloys was studied by changing the content of trace element of Er.The results show that all the samples are completely amorphous alloys after the addition of Er element.With the increase of the content of Er, the elastic modulus of each sample increases firstly and then decreases, and the compressive plastic strain is stepped up, and the plastic strain of samples at x=0, x=0.5 and x=1 is fluctuating in the range of 4%;the plastic strain of samples at x=1.5, x=2, x=2.5 in the range of 11%;the plastic strain of samples at x=3 is the highest, its value is 23.19%, the elastic modulus is 37.76GPa, the yield strength is 1604MPa, the compressive strength is 2068MPa, the fracture strength is 2060MPa.With the increase of Er content, the thermal stability of Zr based amorphous alloys and amorphous formation ability decrease firstly and then increase.
The effect of different process parameters on solidification of industrial gas turbine hollow blades via HRS(High Rate Solidification) and LMC(Liquid Metal Cooling) was studied by ProCAST software.The results show that the paste zone via LMC process is much narrower than that by HRS process and the shape of the S/L(solid/liquid) interface is more flat.The axial thermal gradient of the blade by LMC process is about three times higher than that by HRS process.The cooling rate of the blade is 0.3-2.00℃/s by LMC process, which is far higher than that by HRS process(0.05-0.16℃/s).In LMC process, low holding temperature can still ensure high temperature gradient and cooling rate of the blade; while in order to avoid blocking of stray grains to the initial grains at the platform of the blade, HRS process should adopt high holding temperature and lower withdrawal rate.The calculated and the measured results show that compared with the blade prepared by HRS process, the PDAS(primary dendrite arm spacing) is much finer in the blade prepared by LMC process.
Different primary recrystallized grain sizes were obtained by controlling decarburization process in grain oriented silicon steel produced by low temperature slab reheating technique.The effect of primary grain size on secondary recrystallization and magnetic properties was studied.The appropriate nitrogen content after nitriding was explored in case of very large primary grain size, and the effect of {411}〈148〉 primary recrystallized texture on the abnormal growth behavior was discussed.The results show that an increase in average primary grain size from 10μm to 15μm leads to an increase of secondary recrystallization temperature and a sharper Goss texture with higher magnetic permeability, in the condition of a very large average primary grain size of 28μm, the suitable amount of nitrogen increases to about 6×10-4.The {411}〈148〉 oriented grains in primary recrystallized microstructure can easily grow into larger sizes due to their size advantage, and thus hinder the abnormal growth of secondary grains, moreover, the hindering effect is more pronounced in the abnormal growth of Brass-oriented grains due to their misorientation with low migration rate other than Goss grains.
(Ti0.5Ni0.5)80Cu20 metallic glass composite samples with 3mm diameter were prepared by the levitation suspend melting-water cooled Cu mold process, microstructure of the alloy was characterized.The potential dynamic polarization curves in the different media were tested by electrochemical workstation in a three-electrode system, meanwhile, the electrochemical corrosion morphology and corrosion products were analyzed and characterized.The results show that the microstructure consists of amorphous matrix and shape memory crystal phase, exhibits gradient microstructure in casting process of temperature gradient, random dense pile of amorphous structure is formed in the edge area due to fast cooling rate, the main precipitation phase is overcooling austenite phase in the core area.In artificial seawater and simulated body solution(PBS), the alloy exhibits good corrosion resistance.Compared with crystalline TC4 alloy, the alloy exhibits high free corrosion potential that shows low corrosion thermodynamics tendency and has low corrosion current density as well as high polarization resistance that indicates low dynamic corrosion rate.Due to the low activity anion concentration in PBS solution, the alloy exhibits more excellent corrosion resistance than in artificial seawater.No pitting corrosion pits and corrosion products were found after electrochemical corrosion.The oxide film in the edge area is more compact and uniform than in the core area as well.
ZnCl2 and SnCl2 were added to the AlF3-CsF eutectic flux, which can be used for connecting aluminum alloy sheet by self-brazing at medium temperature.The influence of the amount of ZnCl2 and SnCl2 and the size of the T-joint area on the interface microstructure and the self-brazing joint mechanical properties was investigated.The interface microstructure, chemical compositions, defects and tensile fractography of the self-brazing joints were analyzed by metallographic microscope, scanning electron microscope and energy dispersive spectroscopy.The results show that the joints are soundly bonded when both the mass fractions of ZnCl2 and SnCl2 are about 4%;the replacement reactions between Zn2+, Sn2+ of flux and Al atoms of base metal occur during brazing, then the liquid metals of Sn and Zn appear, a great degree of Zn which has high solid solution with Al spreads rapidly to the base metal; Sn is distributed along the interface forming a low melting point metal layer with Zn and Al; the brazing of joints with small area can be realized easily; there are a lot of dimples on the fracture surface and the tensile strength of the brazing joint reaches(58±5)MPa.
The interface plays a key role on the mechanical properties of Cf/SiC composite prepared by GSI process.The ideal interface should not only prevent carbon fiber from being etched by Si vapor, but also adjust the bonding force between C fiber and SiC matrix.SiC coating prepared by CVD was chosen as the interface and its effect on the mechanical properties and fracture features of GSI Cf/SiC composite was discussed, and the influencing mechanism was analyzed.The results show that GSI Cf/SiC composite without CVD-SiC interface has poor mechanical properties, exhibiting brittle fracture feature.The bending strength, elastic module and fracture toughness are 87.6MPa, 56.9GPa and 2.1MPa·m1/2, respectively.The mechanical properties of GSI Cf/SiC increase with the increase of the thickness of CVD-SiC coating at first, then decrease with the continuous increase of the thickness of CVD-SiC coating.The Cf/SiC composite with 1.1μm thickness of CVD-SiC coating has the best mechanical properties, and the bending strength, elastic module and fracture toughness are 231.7MPa, 87.3GPa and 7.3MPa·m1/2, respectively.The action mechanism of CVD-SiC interface coating on the composite is mainly on the three aspects:load transfer, preventing C fiber from being etched by Si and adjusting fiber/matrix bonding status.
Al2O3 ceramic film was obtained by micro-arc oxidation (MAO) process on Al/C103 specimen, which was prepared by pack cementation aluminizing technology on C103 niobium alloy.With the aid of XRD and SEM equipped with EDS, chemical compositions and microstructures of the composite coatings before and after high-temperature corrosion were analyzed.The behavior and mechanism of the composite coatings in high-temperature oxidation and hot corrosion were also investigated.The results indicate that oxidation mass gain at 1000℃ for 10h of the Al/C103 specimen is 6.98mg/cm2, and it is 2.89mg/cm2 of the MAO/Al/C103 specimen.However, the mass gain of MAO/Al/C103 specimen (57.52mg/cm2) is higher than that of Al/C103 specimen (28.08mg/cm2) after oxidation 20h.After hot corrosion in 75%Na2SO4 and 25%NaCl at 900℃ for 50h, the mass gain of Al/C103 and MAO/Al/C103 specimens are 70.54mg/cm2 and 55.71mg/cm2 respectively, Al2O3 and perovskite NaNbO3 phases are formed on the surface; the diffusion of molten salt is suppressed, due to part of NaNbO3 accumulated in the MAO micropores.Therefore, MAO/Al/C103 specimen exhibits better hot corrosion resistance.
Micron texture was first introduced on aluminum alloy substrate by laser manufacturing.Subsequently, perfluorodecyltrichlorosilane(FDTS) was deposited on these surfaces by nanocoating technology through a self-assembly route to form hydrophobic/superhydrophobic aluminum alloy surface.Scanning electron microscope, surface profiler and contact angle measurement were used to characterize the surface properties, and wettability of specimens.The results indicate that the joint action of micron level rough structure of microtexture by laser manufacturing and SAMs plays an important role in preparing superhydrophobic surface.Contact angle of the water droplet on the substrate increases with pitch decreasing(50-100μm), and is related to the type of laser microtexture.The carrying capacity experiments of floating platform show that superhydrophobic surface is in accord with the Cassie-Baxter model state, and can effectively improve the carrying capacity of the floating platform.
Polydopamine-coated hollow glass microspheres were first prepared via the oxidative self-polymerization of dopamine in an aqueous solution. Then copper ions in electroless copper plating bath were adsorbed by polydopamine and reduced into the copper nanoparticles using dimethylamine broane (DMAB) as an exogenous reducing agent. Thus a copper layer was deposited on the surface of hollow glass microsphere. Copper-plated hollow glass microspheres were successfully fabricated. The surface morphology, chemical composition and crystalline structure of the composite microspheres were investigated by field-emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectra (FTIR), and X-ray diffraction (XRD). The results show that copper layers which successfully deposited on the polydopamine-coated hollow glass microspheres are continuous and compact. Compared with the traditional electroless plating, this approach is facile, low-cost and environment-friendly.
For conventional A356 aluminum alloy, the addition of rare earth elements is an effective way to modify its microstructures and improve its mechanical properties.The effect of rare earth Er on microstructures and properties of as-cast A356 aluminum alloy was studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD) and scanning electron microscopy (SEM).The results indicate that rare earth element Er is a good modifier for A356 aluminum alloy, which is able to improve obviously the microstructure of as-cast alloy.The addition of Er refines the primary α-Al phase, decreases the secondary dendrite arm spacing and the dendrite arm diameter, and modifies the eutectic Si in as-cast structure simultaneously.When the amount of Er reaches 0.4% (mass fraction, the same below), the refinement effect is the most significant, secondary dendrite arm spacing decreases from 53.6μm to 17.5μm and the morphology of eutectic Si transforms from thick lath-shaped to short rod-like or round granular.Compared with A356 alloy, the tensile strength and elongation of A356 aluminum alloy with the addition of 0.4%Er increase by 15.1% and 29.8% respectively.
The oxidation behavior of GH2984 alloy in pure steam at 750℃ and 850℃ was investigated by using X-ray diffractometer (XRD) and scanning electron microscope equipped with energy dispersive spectra (SEM/EDS). Results show that GH2984 alloy is oxidized parabolically with time. The temperature rising greatly promotes the external and internal oxidation and also the evaporation of Cr. The composition and microstructure of the oxide films change obviously. At 750℃, a compact and single-layered (Cr, Mn)2O3 film is formed on alloy surface; the number of voids in oxide scale increases at 850℃, whereas a three-layered oxide scale consisting of thin Fe2TiO5 outer layer and much thicker (Cr, Mn)2O3 middle layer and thinner (Nb, Mo)2O5 inner layer is formed at the elevated temperature. Ti and Al are internally oxidized preferentially along grain boundaries to be TiO2 and Al2O3, respectively; both the number and the size of the two internal oxides increase with the temperature rising.
The Automated Fiber Placement (AFP) of thermoplastic composite (TPC) realizes in-situ crystallization layer by layer and offers the potential to increase production rate and significantly reduces manufacturing cost when processing of large parts. Desired quality of composite parts depends intensively on the thermal history of the AFP, the heater moving with the AFP head and the case of layer continuously being added on bottom prepreg were simulated by the ANSYS software to obtain the temperature field distribution in the laminate. At the same time, a real-time temperature measurement system based on WinCC flexible was established, aiming at acquiring and memorizing the temperature during the experiments. The results show that the temperature curves of each layer appear several peaks and the peaks are gradually increasing with the increase of the temperature of hot gas, the higher the temperature of hot gas is, the bigger the peak temperature difference is and the smaller the difference between thermocouple and simulation is. The finite element simulation results are verified to be correct by comparing the peak temperature of the experimental results with the finite element simulation results. The results show that peaks are gradually decreasing with the increase of the speed of roll. In order to meet the requirements of the component, the maximum speed is 1.2m/min when the temperature of hot gas is 600℃.
Sandwich structural composites were prepared by aluminum foam as core materials with basalt fiber(BF) and ultra-high molecular weight polyethylene(UHMWPE) fiber composite as faceplate. The effect of factors of different fiber type faceplates, fabric layer design and the thickness of the corematerials on the impact properties and damage mode of aluminum foam sandwich structure was studied. The impact properties were also analyzed to compare with aluminum honeycomb sandwich structure. The results show that BF/aluminum foam sandwich structural composites has bigger impact damage load than UHMWPE/aluminum foam sandwich structure, but less impact displacement and energy absorption. The inter-layer hybrid fabric design of BF and UHMWPE has higher impact load and energy absorption than the overlay hybrid fabric design faceplate sandwich structure. With the increase of the thickness of aluminum foam, the impact load of the sandwich structure decreases, but the energy absorption increases. Aluminum foam sandwich structure has higher impact load than the aluminum honeycomb sandwich structure, but smaller damage energy absorption; the damage mode of aluminum foam core material is mainly the fracture at the impact area, while aluminum honeycomb core has obvious overall compression failure.
Nano silicon and multiwalled carbon nanotubes(MWCNTs) composites were used as active materials, paper fiber as substrate, MWCNTs as conductive agent, MWCNTs conductive paper was obtained to replace the copper foil current collector and applied in silicon based lithium ion battery. The morphology and the electrochemical performance of the composites were analyzed by scanning electron microscopy (SEM), transmission electron microscopy(TEM), galvanostatic charge-discharge tests and electrochemical impedance spectroscopy(EIS) tests. The results indicate that the lithium ion battery with MWCNTS paper/nano silicon composites reaches a specific capacity of about 1000mAh/g after 50 cycles in the current density of 80mA/g, and has good cycle stability even in the high current density of 2000mA/g.
Fe-doped V6O13 was synthesized via a facile hydrothermal method after preparing precursor in order to improve the discharge capacity and cycle performance of V6O13 cathode material at high-lithium state. XRD, SEM and XPS were employed to characterize the phase, morphology and valence of the Fe-doped V6O13. Meanwhile, the electrochemical performance was analyzed and researched. Different morphologies and electrochemical performances of Fe-doped V6O13 were obtained via doping different contents of Fe3+ ion. The sample 0.02 presented the largest thickness of nanosheets (the thickness of 600-900nm) and clearance between layers. The Fe-doped V6O13 has a better electrochemical performance than that of pure V6O13. The sample 0.02 exhibits the best electrochemical performance, the initial discharge specific capacity is 433mAh·g-1 and the capacity retention is 47.1% after 100 cycles.
Cu(NO3)2·3H2O and Ce(NO3)3·6H2O were used as modifier to make Cu-Ce/TiO2 by sol-gel method. The influences of Cu-Ce loading capacity, Cu and Ce molar ratio, sintering temperature on Cu-Ce/TiO2 performance were explored. Then, surface morphology, particle size distribution, pore structure and optical property of Cu-Ce/TiO2 were characterized by SEM, LPSA, BET and UV-Vis, respectively. The results show that:prepared Cu-Ce/TiO2 shows good photocatalytic-moisture performance when Cu-Ce loading capacity is 3%, Cu and Ce molar ratio is 1:1 and sintering temperature is at 500℃. Cu-Ce/TiO2 presents approximate sphere, with better uniformity and dispersibility and the particle size distribution is 1202.98-5364.48nm, with d50 2437.57nm. Cu-Ce/TiO2 has pore structure, approximate to an "ink bottle" with a narrow bottleneck, with the specific surface area 105.55m2/g, hole size 0.1200-0.1246mL/g, and average pore diameter 3.44-4.02nm. Cu-Ce doping promotes to form a new energy level inside Cu-Ce/fiO2 so as to improve the ability to capture e- and h+, enhance the efficiency of photon utilization, and promote red shift of absorption sideband.
A new type of environmental-friendly flexible nanofibers of aluminum doped zinc oxide (AZO) coated carbon (AZO@C) was successfully prepared by using polyvinyl alcohol (PVA) as raw materials. The as-spun PVA nanofibers were prepared via electrospinning and its water resistance was greatly improved after heat-treatment. Then, the PVA nanofibers with a layer of zinc aluminum hydroxide on the surface were synthesized by hydrothermal method. Thereafter, new AZO@C composite nanofibers was produced after sintering at 500℃ to the carbonization of PVA nanofibers and the dehydration of zinc aluminum hydroxide to form AZO nanoparticles. The structure and properties of the samples were characterized by Fourier-transform infrared spectrometer (FT-IR), thermal gravimetric analyzer (TGA) and scanning electron microscope (SEM). The average diameter of the AZO@C nanofibers is (320±45)nm. The photocatalytic property of the resultant composite fibers is demonstrated by degrading methyl orange under solar light.
The carbon fiber cloth was treated by surface treatment, and then it was used as the electrode substrate. The electrode material based on carbon fibers was synthesized by a galvanostatic electrodeposition method. The interface resistivity, electrochemical property and corrosion resistance of the CF/β-PbO2 electrode were characterized by four-probe method and electrochemical workstation, respectively. The results show that the surface roughness and chemical activity of the carbon fibers can be significantly improved through surface treatment. The carbon fibers possess the best chemical activity on the surface at the hot-air oxidation temperature of 400℃. Joint hot-air and liquid-phase oxidations show that the chemical activity of the carbon fibers on the surface is further improved, the grooves and pits on the surface of the carbon fibers are more obvious, after this treatment, the interface resistivity of the CF/β-PbO2 electrode reaches the minimum value of 6.19×10-5Ω·m, meanwhile, the conductivity and the electrochemical property of the CF/β-PbO2 electrode reaches the best, and with the best corrosion resistance, the corrosion rate is only 1.44×10-3g·cm-2·h-1.Thus, the interface resistivity, electrochemical property and corrosion resistance of the CF/β-PbO2 electrode depend on the the interface structure of the CF/β-PbO2 electrode obtained under different surface treatments.
Biological researches have attracted wide attentions in recent years, mimicking the morphology of creatures, learning the function of morphology and applying it to the engineering area have become the research focus. Investigating the special function of bionic surface texturing based on geometric morphology can provide us ideas to optimize surface properties of materials, extend the materials service life, widen the scope of application of materials, and improve the application values of materials. Through studying on the principle and application of hydrophobicity, bionic drag reduction, antifriction and wear-resistant due to the geometric morphology, the different functions of bionic texturing were explored, the future development directions of focusing on bionic patterns preparation and mechanism exploration were clarified, and further the surface treatment on materials was carried out to prepare the materials with more superior properties.
The basic principles and features of friction welding were introduced.The research progresses in friction welding of Mg alloys were reviewed. The process, joining mechanism, microstructure and mechanical properties of Mg-Mg similar and Mg-Al dissimilar friction welded joints were primarily discussed. Meanwhile, the current problems were analyzed. It was pointed out that the temperature field, stress-strain field and plastic flow during the friction welding process of Mg alloys require further investigation. Furthermore, the future development should focus on the optimization of process and intermediate layer to obtain high quality joints.
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