Abstract:Mesoporous MnO₂ was prepared by sol-gel method using KMnO₄ and P123. The structure and properties of the synthesized materials were characterized by XRD, N₂ adsorption and desorption, and FT-IR. The effects of reactant ratio and pH on the catalytic oxidation performance of the product were investigated. The optimum conditions of the preparation were as follows: the ratio of KMnO₄ and P123 was 10:1 and the pH was 7. The results shown that mesoporous MnO₂ has good catalytic oxidation performance to HCHO. Finally, the influencing factors of the catalytic oxidation of HCHO by mesoporous MnO₂ were discussed. The specific surface area of mesoporous MnO₂ (pH7-10:1) was largest. The oxidation performance was the strongest, and the degradation rate of formaldehyde was maintained at 95 %.

Abstract:Surface engineering is an effective means to improve photocatalytic activity of semiconductors. In this work, two-dimensional (2D) ZnO/Bi3.9Zn0.4V1.7O10.5 nanosheets were successfully prepared using Zn5(CO3)2(OH)6 nanosheets as substrate to anchor BiVO4 followed by calcination. As-prepared samples were characterized by X-ray diffraction and transmission electron microscopy with elemental mapping attachment. Results show that with the increasing Zn/Bi molar ratio, the surface composition of ZnO porous nanosheets evolves into Bi3.9Zn0.4V1.7O10.5 step by step. When the Zn/Bi molar ratio is above 1:0.02, additional BiVO4 begins to form and grow into particles in the Bi3.9Zn0.4V1.7O10.5 region. Diffuse reflectance spectra of as-prepared samples reveal that nanoscale heterostructures harvest visible light of 400 ~ 600 nm dependent on the varying Zn/Bi molar ratio. The experiment for photocatalytic degradation of rhodamine B under visible light (λ ≥ 420 nm) illumination shows that this 2D heterostructure with the Zn/Bi molar ratio of 1:0.0133 performs the best photocatalytic activity in spite of no remarkable visible-light absorption. Photoluminescence and photoelectrochemical tests indicate that the enhancement in catalytic activity is attributable to an effective separation and transfer of photoinduced carriers caused by the ZnO/Bi3.9Zn0.4V1.7O10.5 heterostucture. This 2D surface heterogenization can promote the photocatalytic process, being applicable to a wide range of 2D nanostructures.

Abstract:Due to their superior theoretical energy density and low to zero emissions etc, rechargeable lithium-air batteries have attracted significant attention as promising next-generation power sources for vehicle applications. But the main challenge is the sluggish kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on the cathode, which results in poor discharge performance and cyclability. In this work, we propose using Mn doped TiO₂ as cathode catalyst to improve the electrochemical performance of lithium-air batteries. Firstly, rutile Mn-TiO₂ was calcined by a facile hydrothermal treatment method. Secondly, Polyvinylidene fluoride (PVDF) was dissolved in an N-methyl-2-pyrrolidone (NMP) solvent. KB and Mn-TiO₂ were mixed with a PVDF/NMP solution to fabricate a cathode slurry. The last, the cathode slurry was coated onto circular carbon paper (diameter = 15 mm) and dried at 60 ℃ 3 hours in the oven to obtain the air cathode, And the cyclic voltammetry (CV) results show that the cathode withSMn-TiO₂ with KB as catalysts exhibits a higher peak current density.

Abstract:F-Mn Co-doped SnO₂ nanoparticles with rutile structure have been successfully synthesized by hydrothermal method at low temperature. In the hydrothermal method, surfactant plays an important dispersion role. The nanostructures have been characterized by means of XRD. XRD results show that the nanostructures are crystalline with rutile structure. The morphology of as-prepared samples was characterized by scanning electron microscopy (SEM). Effects of pH, dopant, surfactant and alkali source on morphology, dispersion, Crystal crystallinity and nanoparticles diameter are discussed.

Abstract:In this paper, hot deformation behavior of as-cast TC17 titanium alloy was investigated by isothermal hot compression tests at temperatures of 1073~1373K and strain rates of 0.01~20s_^-1. The four constitutive models, strain compensated Arrhenius-type (SCA), modified Arrhenius-type (MA), Johnson Cook (JC) and Modified Johnson Cook (MJC), were used to represent the elevated temperature flow behavior of as-cast TC17 titanium alloy. The suitability levels of these models were evaluated by comparing both the correlation coefficient R and the average absolute relative error (AARE). The results indicated that JC model the JC model is inadequate to predict the flow stress of as-cast TC17 titanium alloy; the SCA model has the highest accuracy to descript of flow behavior of TC17 alloy in the α+β two-phase region in the studied range. While the MJC model exhibits the highest accuracy in the β single-phase region. Within the whole deformation temperature range, the SCA model proposed in this paper can more accurately conform to the high-temperature rheological curve of as-cast TC17 titanium alloy.

Abstract:In this paper, against the background of the research on the performance of dampers for a certain type of spacecraft, a new type of shape memory alloy metal rubber (SMA-MR) which was made of Ni-Ti alloy wire processed by coil spring ,cold stamping and post-treatment damper is designed. Through theoretical and experimental research on SMA-MR dampers, the equivalent rigidity and energy dissipation coefficient of the damping system at different temperatures are analyzed. The law of mechanical properties of SMA-MR material with temperature is studied. Using the experimental results to analyze the relationship between equivalent rigidity, energy dissipation coefficient and temperature. The research results show that the mechanical and damping properties of SMA-MR dampers are subject to certain regularity due to temperature. The analysis results provide theoretical basis and data reference for the design of SMA-MR dampers and their application under extreme environment.

Abstract:In order to further investigate the micro-nano scale monocrystalline germanium cutting mechanism, the molecular dynamics method was firstly used to simulate the stress field distribution of material atoms and the influence of different tool angles on stress distribution. The average stress value of hydrostatic and Von Mises at various times during the cutting process are calculated by nearest neighbor average method. The results show that during the nano-cutting process of monocrystalline germanium, the maximum average stress value is concentrated in the subsurface region of the tool tip, and the maximum stess is 8.6Gpa. There is also a high stress in the chip, which is around 4.2Gpa. In addition, the angle of the tool also has an influence on the distribution of the stress field. The cutting force curves of different tool angles are drawn. It is found that the tool rake angle has a significant influence on the cutting force. The cutting force is the largest when cutting with a negative rake angle, while the relief angle has no effect on the cutting force, which is consistent with the macro cutting theory.

Abstract:Three potassium fluorozirconate (K2ZrF6) salts mixture (M) were prepared and added to the as-cast Mg-3Y-3.5Sm-2Zn alloys at three different temperatures. The microstructures and mechanical properties of the alloys were investigated by differential thermal analysis (DSC), X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and tensile test. The grain refinement mechanism of K2ZrF6 salts mixture was also discussed. The results show that the as-cast Mg-3Y-3.5Sm-2Zn alloy is composed from three phases, namely α-Mg, Mg12(Y,Sm)Zn and (Mg,Zn)3(Y,Sm). The addition of K2ZrF6 salts mixture does not lead to the formation of any new phase detectable by SEM and XRD. M3 salt (60wt% K2ZrF6-20wt% NaCl-20wt% KCl) added at 780°C exhibits the best grain refining effect. The mechanical properties of the as-cast Mg-3Y-3.5Sm-2Zn alloy are improved by three salts added at 780°C, where the alloy refined by M3 salt has the best mechanical properties. The grain refinement mechanism of K2ZrF6 salts mixture in the as-cast Mg-3Y-3.5Sm-2Zn alloy is attributed to the grain refining effect of fine Zr particles and zirconium-rich zones obtained by the reduction reaction between Mg and K2ZrF6.

Abstract:The effects of microstructure evolution on the strength and hardness of 7050 aluminum alloy during the process of two-stage aging were systematically studied in this paper. The results showed that a double-peak phenomenon occurred in the double-stage aging of 7050 aluminum alloy. Both the hardness and strength of the second aging peak were slightly higher than those of the first peak. Transmission electron microscopy (TEM) observations indicated that the increase of the hardness and strength for the second aging peak was caused by an increase in the number of h￠ phases. Additionally, the synergistic effect of h￠ phase and GP zones was better than the effect of GP zones on its own.

Abstract:In this research, pre-aging treatment has been performed on our newly developed Al-5.2Mg-0.45Cu-2.0Zn alloy. Results show that pre-aging treatment not only improves the stability of the alloy sheet at room temperature, which avoids the paint-baking softening, but also enhances the age hardening response during subsequent artificial aging at 180℃. The microstructure of the T4 sample in peak aged condition consists of coarse lath-like T-Mg32(AlZn)49 phase and needle-like S-Al2MgCu phase. However, the microstructure of the T4P sample in peak aged condition only consists of high density of finer and equiaxed T phase with the S phase disappeared. Unstable clusters formed during natural aging dissolve when imposed on 180℃, which retards the precipitation process of the alloy. Stable clusters formed during pre-aging treatment serves as the nucleis of the T phase during aging at 180℃, which enhances the age hardening response of the alloy.

Abstract:The high strength and high conductivity Cu-18vol.%Nb microcomposites (8733filaments) were fabricated by bundling and drawing process (ADB) for high pulsed magnets field. The influence of heat treatment on the microstructure、mechanical properties、 and magnetic properties of Cu-18vol.%Nb microcomposites were systematically investigated. The sample were characterized by XRD、 SEM、 and TEM. Results show that the intensity of <110>Nb texture decreased at first and then increased with the increases of annealing temperature. At the same time, the significant spheroidization and coarsening phenomenon of the Nb filaments were observed. The influence of the microstructural changes on the mechanical properties and the magnetic properties of the Cu-Nb microcomposites are discussed.

Abstract:Petal-like MoS₂ microspheres were synthesized via the hydrothermal reaction of Na₂MoO₄, CS(NH₂)₂, and H₂C₂O₄. The crystal form and micro morphology of MoS₂ were analyzed by XRD and SEM, and its thermogravimetric and gas precipitation properties were studied via TG–DSC–FTIR. Results indicated that product yield was influenced by the molar ratio of Mo/S, amount of reducing agent, reaction temperature, and reaction time. The crystal form of petal-like MoS₂ microspheres was hexagonal 2H-MoS₂, which petal-like microspheres diameter was about 1-2 μm with 15-20 nm average thickness of petal. The thermal loss process of MoS₂ could roughly be divided into two stages: transformation stage of MoS₂ and phase change stage of MoO₃, wherein, first stage mainly focused in 221.40 °С～603.15 °С, and second stage occurred in the temperature range of 603.15 °С～1220 °С. MoO₂ and MoO₃ were generated in the first stage which thermal loss decreased by 22.30%. A phase change of MoO₃ from solid to liquid and gas appeared in the second stage. FTIR data showed that there was no SO₂ gas at 603.15 °С, which proved MoS₂ completely transformation before 600 °С. Compared with common MoS₂, the petal-like MoS₂ microsphere acted out high reaction activity.

Abstract:Polycrystalline bulks Bi_2.1Sr_1.96Ca_1-xNa_xCu_2.0O_8+d (Bi-2212) with Na doping content of x=0, 0.02, 0.05 and 0.10 were fabricated by spark plasma sintering (SPS) process. The Bi-2212 precursor powders were synthesized by modified co-precipitation process, and NaOH powders were added into as dopants before calcination. The influences of Na^₊ ions doping on the lattice parameters, phase composition, microstructures as well as related superconducting properties were systematically investigated. The introduction of Na in Bi-2212 system could cause an obvious decrease of phase transition temperatures. Thus during the SPS process, although the sintering temperature has been greatly decreased accordingly, Na doped Bi-2212 bulks still tended to decomposed into Bi₂Sr₂CuO₆ (Bi-2201) phase, which led to the decrease of both superconducting phase content and texture degrees, and thus caused negative effects on superconducting properties. On the other hand, Na doping introduced more point defects into Bi-2212 matrix, which acted as flux pinning centers during current transport process, and contributed to the increase of current capacity under high field. Therefore, Na doping with optimized sintering parameters should be considered as a promising method for the enhancement of high field current capacity in Bi-2212 system.

Abstract:The composite coating NiCr-Ag was successfully prepared by lase clad on substrate of pure Ti in order to enhance space tribological properties of pure Ti, with hard phase NiCr as the reinforcing agent and Ag as the primary lubricating fillers. The composition and microstructure of the fabricated composite coating were investigated by X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectrometry (SEM-EDS), and high-resolution transmission electron microscopy (HRTEM). Furthermore, the space tribological properties were systematically evaluated by a ball-on-disc tribometer against AISI-52100 ball counterpart under simulated space environment including atomic oxygen (AO), ultraviolet irradiation (UV), and high vacuum (VC) in comparison with that in atmospheric environment (AR) through the space tribological test system. The results show that the composite coating has better tribological properties in atmospheric environment than those in simulation space environment. Findings indicate that the vacuum (without any moisture or hydrocarbons) and intense radiation in the space environment would induce severe oxidation on the surface of the coating, making the enhancement of the coating weak and the lubrication effect deteriorated. The wear mechanism is abrasive wear under atmospheric environment. Adhesion wear and plastic deformation are the predominant wear mechanism under space environment as peeling pits and transferred Ni, Cr, and Ti could be found on the worn surface and the surface of the counterpart, respectively.

Abstract:The current study presents a uniaxial compression testing of <110>-oriented single-crystalline Iridium micropillars with diameters ranging from 1000 nm to 7400 nm fabricated by focused-ion-beam (FIB). The tests were performed on a nanomechanical instrument. The results reveal that the yield strength of micropillars follow a power law depending on diameter, as reported in other face-centered cubic (FCC) metals. Unlike the mechanical behavior of bulk Iridium when performing uniaxial compression, the flow stress at micro- and nano-scale is found to increase with a decreasing of micropillar diameter, which is attributed to a size-dependent effect. Moreover, the plastic deformation shows a periodical jerky and strain bursts. This work mainly focused on the rate of strain bursts and the sensitivity of strain rate in Iridium micropillars under uniaxial compression. The experiments also indicate that the displacement jumps increase with the extending of durations and micropillar diameter. In addition, the strain rate sensitivity (SRS) index m increases with a decreasing diameter of Iridium micropillar.

Abstract:Herein we report an investigation of the piezomagnetic properties and the negative piezomagnetic effect in a Fe73.5Cu1Nb3Si13.5B9 amorphous alloy film. The results show that in its quenched state, the Fe73.5Cu1Nb3Si13.5B9 amorphous alloy film has a significant positive piezomagnetic property. Furthermore, the inductance of the alloy film decreases substantially in the 0–0.66 kPa pressure zone, whereas the compressive stress, σ, increases. At a σ value of 0.66 kPa, the piezomagnetic effect value, SI, reaches 5.5%; The ambient temperature has significant influence on the sensitivity of the piezomagnetic property. The films show optimal piezomagnetic properties and sensitivity stability in the temperature range of 20–30 °C. Increases in ambient temperature lead to increases in the piezomagnetic property and sensitivity values, and the inner stress state of the film changed after annealing treatment. At an annealing temperature of 350 °C, the piezomagnetic effect of the film changes from being "positive " to "negative." Furthermore, as the internal stress decreases, the value of |SI| decreases, and the piezomagnetic property of the film becomes less sensitive to changes in the ambient temperature. For an annealing temperature of 555 °C, the value of |SI| is minimum (0.59%), at a σ value of 0.44 kPa. When the annealing temperature reaches the crystallization temperature, the piezomagnetic property of the film becomes less sensitive to changes in the ambient temperature.

Abstract:The hot deformation behavior and microstructure evolution of metastable β-T51Z alloy during hot compression deformation was sdudied through EBSD and TEM by thermal simulation compression at Gleeble-3500 thermal-mechanical simulator under different deformed temperatures and strain rates.The results show that the compressing curves in hot deformation have a typical characteristic of single-peak dynamic recrystallization,and the degrees of increased stress increase gradually with decrease of deformed temperatures or increase of strain rates. Based on the peak stress,the constitutive equation of thermal deformation of alloy is established, and the activation energy Q is 159.57 kJ/mol,the deformed mechanism of alloy during hot compression is mainly related to the cross slip of dislocation.The deformed temperature and strain rate have a great influence on the deformation microstructure.Dynamic recovery exists throughout hot deformation process,with increase of deformed temperatures or decrease of strain rates, the fractions of dynamic recrystallization increase gradually. When deformed temperature is 800°C and strain rate is 10 s-1,the adiabatic shear band is easily formed and the macro/micro deformation is not uniform.

Abstract:The microstructure evolution of Ti-55531 alloy with (β + global α) microstructure composition under 1K/min heating condition was observed by thermal expansion and SEM, and it was found that the microstructure evolution was α lamellae precipitate, dissolute and α globes dissolute. The kinetics equations of the growth / dissolution of the lamerllar precipitate and spherical precipitate were established. The simulation results showed that the growth and dissolution of lamellar α was affected by the Gibbs-Thomson effect, which reduced the stability of α lamella tips, thus resulting in the dissolution of α lamella tips at lower than the equilibrium temperature. The elongation of the α lamella tips follows the kinetics controlled by the mixed mechanism of bulk diffusion and interfacial diffusion, while the lateral thickening is controlled by bulk diffusion, and the bulk diffusion control dissolution of α lamella. global α growth at low temperature is controlled by the volume diffusion of stable elements with a lower diffusion rate, and the solubility at high temperature is controlled by the volume diffusion of Al with a higher diffusion rate.

Abstract:The microstructure evolution of wrought GH720Li alloy with three different initial grain sizes during isothermal hot deformation was studied. Grain size finer than ASTM 6.5 is considered to be the key critical initial condition for the final fine-grain grain structure, and a wider hot deformation window is found for the initial grain size with ASTM 10 or higher. The obvious effect of initial grain size on hot flow behavior is observed. The coarser the grain structure, the greater the hot flow behavior of the alloy. Discontinuous and continuous dynamic recrystallizations play important roles for the alloy with the initial ASTM 3 grain size The alloy with the initial grain size coarser than ASTM 6.5 are mainly subjected to discontinuous dynamic recrystallization. Dynamic recrystallization and superplastic deformation mechanism play important roles for the alloy with the initial ASTM 10 grain size. The hot working window of GH720Li alloys with ASTM 6.5 and ASTM 10 grain size was further determined for the final uniform fine grain structure.

Abstract:In this paper, the dynamic mechanical properties and failure behavior of rolled and heat treated Ti-4.5Mo-5.1Al-1.8Zr-1.1Sn-2.5Cr-2.9Zn alloys were studied. After multi-pass rolled at 880℃, a duplex microstructure consisting of β matrix and non-uniformly distributed _^-1~3800s_^-1 show that the dynamic compression strength of rolled titanium alloys is about 200MPa~400MPa higher than that of heat treated titanium alloys, with a maximum value of 2133MPa, but the critical fracture strain is obviously lower, with a maximum value of only 10.8%. Although the dynamic compression strength of titanium alloys decreases after heat treated, the critical fracture strain can reach 23.6%, showing better matching feature of strength and plasticity. Further study found that the characteristic of high dislocation density and inhomogeneous structure distribution of rolled titanium alloys result in bifurcated adiabatic shear bands during dynamic compression tests. The fracture surfaces of rolled titanium alloys show two characteristics: smooth zone and dimple zone, indicating that the fracture mechanism is brittle fracture + ductile fracture, while that of heat treated titanium alloys is mainly dimple zone, indicating that the fracture mechanism is ductile fracture. The research provides theoretical and technical support for the engineering preparation and application of the new alloy.

Abstract:Magnesium alloys have poor plasticity at room temperature, which leads to uneven distribution and stress difference of microstructure during rolling. Therefore, it is important to analyze the mechanical characteristics and microstructure evolution from the angle of material properties. Based on this, a piecewise constitutive model of AZ31 magnesium alloy was established by experiments, and a cellular automata model including grain topology technology was constructed. With the aid of secondary development technology, the constitutive model, cellular automata and finite element software were combined to simulate, and the predicted results including stress, strain, grain size and distribution law were obtained. It is of certain significance to control the forming process of AZ31 magnesium alloy rolled by Pilger to realize the coordinated control of forming and properties, and the simulation results were verified by experiments.

Abstract:To have a better understanding of fretting wear for titanium alloys, the effect of wear particles distribution on coefficient of friction, wear volume, surface topography and danage mechanisms at various displacement amplitudes was investigated. The test results showed that the displacement amplitude has a significant influence on the distribution of the fretting wear particles. The ‘flake-like’ delamination formed by the central adhesive teard was stacked into a ‘ridge’ in a direction perpendicular to the fretting at a relative low fretting-amplitude.At a medium amplitude,the debris particles were scattered on the contact surface.When the amplitude was even increased,‘cluster-like’ debris were accumulated into a ‘ridge’ paralleled to the direction of the fretting.The various distribution of the wear particles leads to the change in the wear mechanisms from the adhesion to abrasive with slight adhesion,and finally the adrasion accompanied the oxidative wear.

Abstract:Continuous carbon fibre reinforced silicon carbide (C/SiC) composites exhibit superior properties such as high strength, low density and high temperature tolerance, however, their applications are limited because of the rapid oxidation of carbon fibre and SiC matrix at elevated temperature. In this work, a mullite/yttrium silicate bilayer coating was prepared by plasma spray method as the oxidation protective coating. The morphology, composition, microstructure and adherence strength of the coating were analyzed. The efficiency of the coating against oxidation was characterized by means of heat treatment of the C/SiC composites at 1500 °C in static air for 1 hour. The structural change of the coating was studied, the weight and flexural strength of the C/SiC composites before and after the heat treatment were investigated. The results indicated that the mullite/yttrium silicate bilayer coating exhibited excellent oxidation resistance as the flexural strength of the composites retained 95.3 % of the original strength.

Abstract:In order to realize the thermal protection of aluminum alloy structural materials in high temperature environment, the inorganic zirconium sol coating was prepared on the surface of aluminum alloy by sol-gel method. The stability of zirconium sol was prepared by using n-propanol zirconium and glacial acetic acid. The effect of PVP content on the size and viscosity of zirconium sol particles was studied. The mechanism of PVP on sol particles was analyzed. The inorganic coating was prepared by adding 60wt% SiO2, and the coating was ablated. The effects of different adhesives on the coating structure and thermal protection performance were compared. According to the macroscopic response and microscopic morphology of the coating in the ablation test, the thermal protection mechanism of the inorganic coating at high temperature was analyzed. The results show that the stability of zirconium sol is the best when the content of glacial acetic acid is 22wt%. After optimization of 7wt% PVP, the zirconium sol particles are uniform in size and have the best coating property. The silica sol-based coating has the best moldability. After the three kinds of adhesive coatings were ablated for 30s at 1300℃, the substrate was not broken, and the water glass-based coating peeled off after ablation; compared with other adhesive coatings, the zirconium sol-based coating had the best thermal protective ability. During the ablation process, the zirconium sol particles dehydrate and condense at high temperature to form nano-zirconia particles, which are dispersed around the filler and produce good synergistic heat insulation with the filler, so that the coating has good high-temperature thermal protection properties.

Abstract:In a reaction system using water as the main solvent, the stable TiO₂ nanocrystal sol was synthesized under the mild conditions of atmospheric pressure and low temperature (70^_oC) through the improved sol-gel method with controlling tetrabutyl titanate to fully hydrolyze and slowly polymerize. TiO₂/bentonite composite photocatalytic material was further prepared by the loading of TiO₂ nanocrystal sol on the surface of bentonite. XRD,SEM and BET were adopted to analyze the structure and morphology of as-prepared samples, and their photocatalytic activities were also investigated. The results show that the high water addition amount is conducive to the formation of TiO₂ nanocrystals. When the molar ratio of deionized water: etrabutyl titanate is higher than 167:1, the anatase TiO₂ nanocrystals appear in the sol system. TiO₂ nanocrystals are mainly loaded on the surface of bentonite rather than embed into the structure between bentonite layers. However, compared with a pure bentonite, the TiO₂ loading significantly increases the specific surface area of the material. When the molar ratio of deionized water: etrabutyl titanate is 192:1, the composite photocatalytic material shows the highest photocatalytic activity under UV light, and the degradation rate of methylene blue can reach to 93.8%.

Abstract:In this paper, MnO/carbon (MnO/C) composite was successfully synthesized by a facile biotemplating method combine with chemical bath deposition (CBD) method followed by calcination treatment. The natural pomelo peel and potassium permanganate were used as the biotemplate and potassium permanganate source. The phase composition, morphology and microstructure were investigated by XRD, TG-DTA, Raman, SEM and TEM, respectively. The result indicates that the pomelo peel was transformed to in-situ carbon matrix with a quality content of 30%, and MnO nanoparticles were uniformly dispersed onto the carbon matrix. The MnO/C composite presents excellent lithium-storage property, which exhibits a high reversible specific capacity of 644 mAh/g at a current density of 0.2 A/g after 100 cycles. Even at a high current density of 3 A/g, a remarkable reversible capacity of 430 mAh/g could still be maintained.

Abstract:Photon-generated carrier of ferroelectric photovoltaic effect is different from the carrier of traditional photovoltaic effect, which makes the ferroelectric photovoltaic effect much more excellent. It is of great significance to improve the photoelectric conversion efficiency, and overcome the shortcoming of large band gap of ferroelectric thin film, which has been an important subject of research in ferroelectric photovoltaic effect. In this work, BTO ferroelectric thin films with different doping concentration of Fe were prepared by sol-gel method to reduce the optical band gap. In order to study impact of different Fe doping concentration on photovoltaic effect of ferroelectric thin film, the film composition, microstructure, band gap and other factors were characterized. Research result shows that the doped Fe with concentration of (Bi4Ti3-xFexO12) changing from x = 0.8 to x = 1.2 does not transform the matrix structure of BTO; The doped film has good crystallinity, obvious reticular structure, well-proportioned spatial distribution and uniform grain size. The Fe-BTO ferroelectric thin films prepared by sol-gel method can significantly tune its band gap.

Abstract:A water based conductive ink was fabricated with HPMC as binder, FSO-100 as surfactant and silver nanowire (AgNW) as conductor and the transparent conductive film was fabricated on PET substrates by Mayer rod coating process. The effects of the concentration of HPMC, FSO-100 and AgNW on the opto-electrical properties of transparent conductive film were investigated. The results show that the addition of FSO-100 can significantly enhance the wettability between conductive ink and PET substrate, but excess FSO-100 results in the increase of sheet resistance. The introduction of HPMC reduces the aggregation of AgNWs and high concentration of HPMC decreases the conductivity. The high concentration of AgNWs decreases the sheet resistance and transmittance. With 2.6 mg/mL AgNW, the transparent conductive film researches a sheet resistance of 12 Ω/sq and transmittance of 94.02% at 550 nm, showing a figure of merit of (FOM) of 448.63, and a root-mean-square surface roughness of 7.28 nm, and the opto-electrical properties maintain after 1000 times of bending, providing great potential for the application in wearable devices and flexible organic light-emitting diodes.

Abstract:High-purity cubic zinc stannate nanopowder with spinel structure was successfully synthesized by chemical co-precipitation method with different zinc sources, tin sources and precipitants as raw matterials. Zinc stannate nanopowders as reinforced phase were applied to strengthen the properties of silver-based electrical contact materials. Ag/Zn2SnO4 electrical contact materials were prepared by Mechanical Alloying and Powder Metallurgy technique. In this work, effects of the processing parameters such as heat treated temperature, types of zinc sources and types of precipitants on the microstructure and physical performance of Ag/Zn2SnO4 electrical contact materials were investigated. The morphology and phase of zinc stannate nanopowder were characterized by Field Emission Scanning Electron Microscopy and X-ray Electron Diffractometry. The electrical resistivity, hardness and density of Ag/Zn2SnO4 electrical contact materials were also investigated in this paper. The results show that by using tin chloride, zinc chloride and sodium carbonate, under the condition of sintering temperature at 1000℃ for 3h, the optimal electrical resistivity, density and Vickers hardness of the Ag/Zn2SnO4 electrical contact material can reach 2.31μΩ·cm, 9.51g/cm3 and 65.63Hv0.5, respectively. Especially, the lower electrical resistivity of Ag/Zn2SnO4 contact prefers to that of traditional Ag/SnO2 electrical contacts. Compared with traditional Ag/SnO2 and Ag/ZnO electrical contacts, Ag/Zn2SnO4 electrical contact material has obvious advantages in electrical properties and density. And Ag/Zn2SnO4 electrical contact material also has more compact fracture morphology and shows better interface bonding performance.

Abstract:WSx/W/DLC/W multilayer films were prepared by using magnetron sputtering technique and alternate deposition of WSx, W and diamond-like carbon (DLC) layers on silicon substrates. The microstructure, mechanical properties and tribological behaviors in the atmosphere of the films were characterized by X-ray diffractometry, scanning electron microscopy, nano-indenter and ball-on-disk wear tester. The results show that the surface of all the multilayer films is smooth and dense. As the thickness of single W interlayer increases in the modulation period, α-W, W2C, and β-WC1-x crystalline phases are formed in the multilayer films. The hardness of the multilayer films is greatly improved (up to 17.3 GPa at single W interlayer thickness of 6 nm), the friction coefficient shows a downward trend, the adhesion to the substrate is gradually reduced and the wear rate decreases first and then increases. The multilayer film with single W interlayer thickness of 6 nm exhibits the best wear resistance, its wear rate is about 1.4×10-14 m3N-1m-1.

Abstract:Ag/SnO₂(x)-MeO(y) composite powders were obtained by means of mechanical alloying different contents of CuO or Fe₂O₃ powders with Ag and SnO₂ powders, and Ag/SnO₂(x)-MeO(y) electrical contact materials were prepared by hot pressing process. The microstructure and physical and mechanical properties of the materials were characterized by scanning electron microscopy, X-ray diffractometry, resistance tester, hardness tester and tensile tester. The results show that the density of Ag/SnO₂(x)-MeO(y) materials decreases with the increase of dopant content, and CuO is more conducive to improving the conductivity of Ag/SnO₂(x)-MeO(y) material than Fe₂O₃. The two dopants can obviously improve the capacity of plastic deformation of Ag/SnO₂(x)-MeO(y) material. The Ag/SnO₂(11.2%)-CuO(0.8%) material (i.e. CuO content =0.8%) exhibits the best comprehensive properties with the resistivity about 2.35 μΩ?cm, elongation about 9.1% (higher than that of Ag/SnO₂ material by 93.6%).

Abstract:Lanthanum nitrate, copper nitrate, strontium nitrate and so on were used as raw materials to synthesize the irregular granular (LSCO_g), mesoporous (LSCO_m) and lamellar (LSCO_l) LaSrCuO₄ (LSCO) powders by solid phase method, sol-gel method and co-precipitation method respectively. Ag/LSCO electrical contact materials were prepared by high-energy ball milling combined with initial pressing, sintering and hot pressing. The morphology of LSCO powders and the microstructure, physical and electrical properties of Ag/LSCO materials were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), conductivity instrument, Vickers hardness tester and electrical life tester. The results show that, compared with Ag/LSCO_m material and Ag/LSCO_l material, Ag/LSCO_g material exhibits a lower resistivity of 2.37 μΩ?cm, higher hardness of 800 MPa, higher average density of 9.32 g/cm^₃. Under the conditions of AC220V 12A, the arcing energy and arcing time of Ag/LSCO_g electrical contact material are 400 mJ and 23 ms for breaking state, 1500 mJ and 68 ms for closing state. The failure modes of Ag/LSCO electrical contact materials are droplet splashing, micro-cracks and micro-holes.

Abstract:By using Ag powder and nano-SnO₂ as raw materials , Ag/SnO₂ electrical contact materials and its rivets were prepared by mechanical alloying and hot extrusion and cold press-welding process. The phase composition of the commercial Ag powder and as-prepared SnO₂ and Ag/SnO₂ composite powders was analyzed by X-ray diffractometry (XRD). The surface morphology and arcing characteristics and mass loss of the rivets before and after the electrical life test were characterized by Scanning Electron Microscopy (SEM). Effects of different process parameters (working current and cycle number) on the arcing characteristics, arc eroded morphology, mass loss and degradation mode of Ag/SnO₂contacts were analyzed comparedly..The results showed that compared with pure Ag, Ag/SnO₂ electrical contacts had higher arcing time and arcing energy under arcing, and the average arcing time of making-arc and breaking-arc was 25.86ms and 51.78ms, which was 2.78ms and 4.87ms higher than that of pure silver, respectively; the average arcing energy of making-arc and breaking-arc was 493.85mJ and 988.14mJ, which was 58.76mJ and 104.93mJ higher than that of pure silver, respectively. As the number of cycle operations increased, the total mass loss of the Ag/SnO₂ electrical contacts was negative value, and its main failure degradation modes of droplet splatter and SnO₂ particles floating were manifested.

Abstract:Boron-doped vanadium dioxide (VO2) nanopowders were prepared by the sol-gel hydrothermal method. Effect of process parameters including the hydrogen peroxide (H2O2) concentration, hydrothermal time, annealing temperature, type of boron dopant and boron doping amount on the synthesis of boron-doped VO2 powders was investigated. The structure, morphology and phase transition properties of the boron-doped VO2 powders were characterized by the X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma (ICP), field emission scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results show that the superior synthesis process parameters are 15% for the H2O2 concentration, 72 h for the hydrothermal time, 600 °C for the annealing temperature, boric acid as the boron dopant, and less than 10 at.% for the boron doping amount. The obtained boron-doped VO2 powders have the size of around 100 nm with the morphology of coral-like structure. The boron atoms successfully replace the vanadium atoms in the VO2(M) lattice. The phase transition temperature is reduced by 7.2 °C, when the actual doping amount is 0.6 at.%.

Abstract:In this paper, powders of alkali tungsten bronze (M_xWO₃, M=Cs, Rb or one of them) were synthesized by sol-gel method. The tantalum and niobium were respectively doped and yttrium and lanthanum co-doped to tungsten bronze. The effect of powder crystal phase and morphology. X-ray diffractometer (XRD), X-ray energy spectrometer (EDS), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), UV-visible near-infrared spectroscopy (UV-Vis-NIR) The phase, morphology, optical properties and thermal insulation properties of the synthesized alkali tungsten bronze powder were characterized by a thermal film temperature tester. The results show that the alkali-tungsten bronze powder synthesized by sol-gel method has good crystallinity, small particle size and good dispersibility. The transparent adiabatic index of Cs and Rb co-doped K=150.34 is higher than that of Rb single doping. 23.92, improved the Cs single doping at 1076nm transmission rate mutation; Cs, Rb co-doping temperature difference (compared to the starting temperature) is 4.9 ° C than the Rb single doping temperature difference decreased by 5.7 ° C.

Abstract:A spray deposited 2195 Al-Li alloy ingot was extruded into plates. Some of the extruded plates were hot rolled down to the thickness of 6 mm with different finish rolling temperature, and others were cold-rolled down to the thickness of 6mm after different intermediate annealing. The surface layer of the plate with finish rolling temperature 290°C consists of coarse recrystallized grains, but the center layer cosnsits of non-recrystallized fine fibrous grains. As the finish rolling temperature is lowered to 220°C, the size of the recrystallized grain in the surface layer is decreased, but grains in the center layer are transferred to coarse elongated recystallized grains. As the intermediate annealing temperature was elevated from 330°C to 450°C, the number density of Cu-rich secondary phase particles with size larger than 1 mm increases, the recrystallized grain in the surface layer of the cold-rolled plate after solutionization coarsenes, and the center layer grain were transferred to small equi-axed recrystallized grains from coarse elongated recrystallized grains. After approporiate intermediate annealing followed by furnace cooling, the cold-rolled plate through thickness after solutionization developed into fine recrystallized grains. After a same T8 aging, the strength of the cold-rolled plates are higher than that of the hot-rolled plates, and that of the plate with a finish rolling temperature of 220°C is the lowest.

Abstract:The increasing demand for light-weight and high-performance materials for the aerospace industry in recent years has led to the development of metal matrix composites (MMCs). As typical MMCs, titanium matrix composites (TMCs) have been regarded as potential candidates due to their high specific strength, outstanding wear resistance as well as excellent mechanical properties at high temperatures. However, it is difficult to achieve a superior titanium matrix composites with high strength and high plasticity simultaneously. In this study, the in-situ reinforced titanium matrix composites were fabricated using low-oxygen HDH Ti powders and polycarbosilane (PCS) via a powder metallurgy method, including solution-assisted wet mixing and pressureless sintering. The effects of PCS addition on the oxygen inhibition, sintering densification, microstructure and mechanical properties of the composites were investigated. Results show that the solution-assisted wet mixing process makes the Ti powders coated with PCS, which can effectively control the oxygen contamination. The oxygen content of the fabricated Ti-1.0 wt.% PCS composite is 0.21~0.24 wt.%, much lower than that of 0.36~0.41 wt.% for CP-Ti. During sintering, the pyrolysis products of PCS can react with Ti matrix to in-situ synthesized TiC particles, while Si element is dissolved in matrix. The incorporation of PCS can improve the mechanical properties of the Ti matrix. The Ti-1.0 wt.% PCS composite sintered at 1200 °C for 2 h possesses the best mechanical properties, with a relative density of 98.4%, a Rockwell hardness of 47.3 HRC, a yield strength of 544 MPa, a ultimate tensile strength of 650 MPa, and a elongation of 14.5%, which is obviously higher than CP-Ti.

Abstract:Recently, Cu2Se-based liquid-like materials with high thermoelectric performance have attracted great attention from the thermoelectric community. However, as compared with the extensive study on the electrical and thermal transport properties of Cu2Se, few investigations were reported on the Cu2Se-based thermoelectric device. Barrier layer is an imperative component for thermoelectric power generators （TEG）since it can effectively depress drastic reactions between the thermoelectric material and the electrode at hot side. In this work, we firstly chose Mo as the barrier layer for Cu2Se and fabricated Cu2Se/Mo/Cu2Se thermoelectric joints with the one-step hot pressing method. It is found that the Cu2Se/Mo interface has ultralow electrical contact resistivity but poor tensile strength. Via introducing 5 wt.% Mn in Mo, we successfully improved the tensile strength by three times while still maintaining low electrical contact resistivity, which are attributed to the diffusion of Mn into Cu2Se during the hot pressing process. The evolutions of microstructure and contact resistivity at the interface during long-term aging at high temperatures (650℃ and 800℃) were investigated. After aging experiments, the interface remains integrity and with low contact resistivity which proves that the Mo-Mn mixed phase is a promising candidate as the the barrier layer for Cu2Se-based TEGs.

Abstract:An investigation was carried out to study the effect of squeeze casting process on the microstructure and properties of Al-7Si-0.4Mg-0.3Er alloy by OM, SEM and microhardness. The results show that the solidification sequence has great influence on the microstructure of different parts of bracket, the size of primary α-Al grains in the thick parts is smaller than the thin parts. The primary α-Al phase and Er-π-AlFeMgSi phase in bracket is smaller and more uniform distribution, which is fabricated by lower temperature of 650℃ and higher speed 2. The microhardness is 119HV and standard deviation is 5HV after heat treatment, the properties is more uniform distribution than the bracket fabricated by low temperature and high speed. Al-Si alloy engine bracket is suitable for low temperature pouring and high speed forming.

Abstract:In order to improve the magnetic properties and corrosion resistance of sintered Nd-Fe-B magnets, (PrNd)_15.5B₆Cu_0.1Fe_balMg(wt%, x=0.1-0.3)permanent magnet was sintered by binary alloy method with adding MgO/Mg nanopowders at grain boundary.The magnetic properties, microstructures and corrosion resistance of sintered Nd-Fe-B magnets with different amounts of MgO/Mg (mass ratio 1:2) nanopowders were studied by means of permanent magnet automatic measuring instrument, scanning electron microscopy, X-ray diffractometer and CHI660E electrochemical workstation. The results show that when the content of MgO/Mg nanopowders is 0.1wt%, the comprehensive magnetic properties of the magnet are the best. At this time, the coercivity of the magnet is 1183 kA/m, the remanence is 1.22T, and the maximum magnetic energy product is 288 kJ/m^₃. The Tafel curve shows that the corrosion potential increases from -1.093V to -0.929V and the corrosion current density decreases from 223.87μA/cm^₂ to 42.66μA/cm^₂ with the increase of MgO/Mg nanopowders content. The electrochemical impedance spectroscopy shows that the radius of the high frequency capacitive arc of the magnet with appropriate amount of MgO/Mg nanopowders is larger than that of the high frequency capacitive arc of the magnet is not added, increasing the charge transfer resistance.Therefore, the magnetic properties and corrosion resistance of sintered Nd-Fe-B magnets are improved by adding appropriate amount of MgO/Mg nanocomposite powder at grain boundaries.

Abstract:The multi-pass thermal compression experiments of hot isostatic pressed TC4 titanium alloy were carried out on the Gleeble-1500D thermal simulator at strain rate of 0.001s_^-1~5s_^-1, the total deformation was 70%. The hot isostatic pressed TC4 titanium alloy was treated by 935℃+60 min+water quench solution treatment, and520℃+ 4/6h+water quench and 560+4/6h+water quench aging treatment, respectively. After multi-pass deformation, the samples were treated by solution treatment at 945℃ +60min+water quench and aging treatment at 560℃ +6h+water quench. The results show that the content of secondary α phase of hot isostatic pressed TC4 titanium alloy decreases with the increase of aging temperature, while the equiaxed α phase increases with the increase of aging time, and the microstructure mainly consists of secondary strip α phase and equiaxed α phase. Meanwhile, the ideal tri-modal microstructure(equiaxed α phase + secondary strip α phase + β transformation phase) of hot isostatic pressed TC4 titanium alloy can be obtained by solution and aging treatment during multi-pass deformation at the deformation temperature from 950℃ to 850℃and strain rate of 0.1s_^-1.

Abstract:Three kinds of diamond-like carbon-based films of a-C, a-C:H and a-C:Cr were deposited by unbalanced magnetron sputtering technique on 316L steel and Ni60C spray-welding coating, respectively. Tribocorrosion resistance in 5 wt% sulfuric acid solution of two different protective systems were investigated. The result indicate that the carbon-based films deposited on Ni60C spray-welding coating show a significant improved adhesion and wear resistance compared with the one deposited on 316L. The friction coefficient and corrosion wear rate of the DLC films deposited on Ni60C spray-welding coatings were 0.05 ~ 0.14 and 0.66×10-8 ~ 5.7×10-8 mm3/N?m, respectively. The improvement of abrasion resistance of composite system was attributed to the Ni60C spray-welding coating as a hard support layer which can improve the bearing capacity of the DLC films, the graphitization process of DLC films in the process of tribocorrosion test was effectively inhibited.

Abstract:The wear resistant coatings of Ni₃Al alloy and Ni₃Al/Cr₃C₂ composites were prepared on 304 stainless steel substrate by laser cladding technique. The microstructure, hardness and wear resistance of Ni₃Al alloy and Ni₃Al/Cr₃C₂ composites were investigated. The results show that the microstructure of the cladding layer of Ni₃Al/Cr₃C₂ consists of matrix γ"-Ni₃Al phase and in-situ self-generated M₇C₃ (M=Cr,Fe) type carbides, and the fine near-circular M₇C₃ is dispersed in γ"- Ni₃Al matrix. Compared with the Ni₃Al alloy cladding layer, the micro-hardness of the Ni₃Al/Cr₃C₂ composites cladding layer is increased by 2.5 times, and the weight loss is only 28% of the vermicular graphite cast iron. Therefore, the laser cladding Ni₃Al/Cr₃C₂ composite cladding layer has good wear resistance.

Abstract:Effects of solution treatment, single aging treatment, and duplex aging treatment on the microstructure and mechanical property of Ti-4Al-5Mo-6Cr-5V-1Nb alloy are studied. After the solution treatment at 820 ℃ for 0.5 h, α phase completely dissolved. The hardness of single/ duplex aging treated alloys both increase at the beginning and then decrease. The alloy duplex aging treated at 300 ℃ for 8 h and 500 ℃ for 8 h processes the peak-aging hardness of 458 HV, ultimate tensile strength (UTS) of 1462 MPa and elongation of 3.4%, whose UTS is 6% higher than original alloy and even higher than single aging treated alloy. The calculation of interface energy indicates that ω phase can promote the precipitation of α phase and the refinement of α lath by decreasing the nucleation resistance of α phase by 50%, thus increasing the hardness, strength, and elongation of alloys.

Abstract:The paper investigated the formation and evolution of intermetallic compound at the interface of Ni/Sn with and without USV. Without ultrasonic treatment, the IMC layer are plain and compact at the interface of Ni/Ni₃Sn₄. Towards the solder side, Sn tends to wet and penetrate the grain boundaries to form the scallop-type Ni₃Sn₄. Moreover, intermetallic grains grow with a 1/2 power dependence on time, the growth was controlled by the bulk diffusion. With ultrasonic treatment, acoustic cavitation causes the interfacial Ni₃Sn₄to dissolve and forms many grooves, even forms is reopened and ultrasonic streaming promotes this dissolution. With prolong of ultrasonic time, elongated Ni₃Sn₄grains which was "neck" connection are broken up by the ultrasonic cavitation and fall into the liquid solder. Interfacial IMC was gradually reduction. The Ni₃Sn₄ grains falling into the liquid are further dissolved and broken by ultrasonic cavitation. Finally many fine Ni₃Sn₄ grains are evenly distributed in the joint.

Abstract:The regulation mechanism and deposition behavior of sprayed particles in vertical groove were studied by means of groove constrained electro-explosive spraying. The results show that when the constraint depth reaches 20 mm, i.e. the spraying distance is 100 times of the wire diameter, the continuous and uniform coatings can still be obtained. With the constraint width decrease from 6mm to 2mm, the morphology of coating surface changed from "Hill-like" to "pancake-like"，and the coating thickness increases significantly; Increasing energy density from 57J/mm3 to 152J/mm3 can also improve coating thickness and uniformity. By analysis the collected spraying particles, it was found that reducing the constraint width and increasing the energy density can effectively refine the spraying particles and make the particle size distribution more uniform. It is concluded that the "thermal expansion effect" caused by Joule heating and the "pressure effect" associated with breakdown arc can work together to regulate the sprayed particles with the change of energy density and constraint parameters, which will resulting in different deposition behavior.

Abstract:In this paper, a Ni-28.5Al-43V (at%) hypereutectic alloy was prepared by liquid metal cooling technology (LMC), The microstructure evolution and mechanical properties of the alloy were investigated by optical microscopy (OM), scanning electron microscopy (SEM) and three-point bending (3PB) test. Under the experimental conditions(Temperature gradient G_L=310K/cm, Growth rate V=6～150μm/s), the results show that the steady-state growth microstructure of NiAl-43V is composed of primary V dendrites and eutectic structure (NiAl lamellar +V lamellar). 3PB test shows that the maximum room temperature fracture toughness(RTFT) of NiAl-43V hypereutectic alloy is four times higher than that of NiAl alloy.The RTFT decreases from 22.679 MPa.m ^_1/2 at 6 μm/s to 18.422 MPa.m ^_1/2 at 150 μm/s as the growth rate increases.The reason is that the fine-grained strengthening effect caused by the increase of growth rate is weaker than the adverse effect of increased primary V dendrites and inter-cell regions on fracture toughness. Fracture morphology analysis of alloys indicates that alloy fracture is quasi-cleavage fracture.Crack blunting, crack renucleation, crack deflection, interfacial debonding, crack bridging and linkage of microcrack toughening mechanism contribute to the improvement of room temperature fracture toughness of NiAl-43V alloy in crack propagation. The precipitation of primary V dendrites reduces the fracture toughness of the alloy.

Abstract:Paracostibite (CoSbS), as a thermoelectric material, has attracted much attention recently. It has many advantages such as low cost and environment-friendly. However, the thermoelectric performance is limited by the high thermal conductivity. In addition, the preparation of this material need a long-duration heating process and a complicated process by conventional method. In this paper, CoSbS1-xSex based solid solution alloys were facile and rapidly prepared by one-step high pressure method. Their structures and thermoelectric properties were investigated. The results show that high pressure can accelerate the reaction rate and fabricate single-phase CoSbS quickly. Alloying with a small amount of Se can simultaneously optimize three thermoelectric parameters: increasing Seebeck coefficient, reducing resistivity and thermal conductivity. CoSbS0.8Se0.2 has the largest figure of merit ZT~0.25 at 673 K, which is about four times as much as that of the parent material CoSbS. Moreover, the ZT of high-pressure synthesized samples at the same temperature is higher than that of CoSbS1-xSex prepared by the traditional solid-state reaction combined with spark plasma sintering method. These results indicate that high pressure method is an effective method for preparing CoSbS based thermoelectric materials.

Abstract:Stem from its high specific strength, low density, low elastic modulus, excellent toughness, fatigue and corrosion resistance, titanium alloy has become a kind of attractive candidate material for oil country tubular goods(OCTG) and offshore components in harsh service environment. Because the oil gas exploration environment of China is more rigorous, certain titanium alloy OCTG will occur corrosion problems especially crevice corrosion, in this service environment, which will lead to the seal failure of titanium alloy OCTG premium connection and cause huge economic losses. In this paper, 5 kind typical titanium alloys materials((Ti-6Al-4V, Ti-6Al-4V-0.1Ru, Ti-6Al-2Sn-4Zr-6Mo,Ti-3Al-8V-6Cr-4Zr-4Mo and Ti-5.5Al-4.5V-2Zr-1Mo))used for oil gas exploration were investigated, the influence of different alloy compositions on anti-corrosion properties of these titanium alloys in China typical service environment were studied by high-temperature high-pressure autoclave simulation test, the corrosion morphology and corrosion products were also analyzed is analyzed and summarized by using scanning electronic microscopy (SEM)and energy dispersive spectrometer (EDS),the corrosion resistance mechanism of different alloys was discussed by electrochemical method. The results showed that the corrosion reactions of all titanium alloy materials were anode controlled under the test conditions, the uniform corrosion rates of all tested titanium alloy were lower than 0.001mm/a, and the resistance to stress corrosion cracking of all titanium alloys were excellent. However, Ti-6Al-4V and Ti-5.5Al-4.5V-2Zr-1Mo alloys had obvious pitting and crevice corrosion problems. The corrosion mechanism results showed that, under the test conditions, the self-corrosion potential, polarization resistance of all titanium alloys decreased and the corrosion current increased with the decrease of pH value, which illustrated that corrosion resistance of titanium alloys were reduced, especially for Ti-6Al-4V. The research results provide a theoretical basis for material selection and crack corrosion prevention of titanium alloy OCTG used in oil and gas exploration.

Abstract:Ni-Mg co-doped LiNi0.03Mg0.10Mn1.87O4 cathode material was synthesized by solid-state combustion method at 500℃ for 1 h and further calcined at 650℃ for 6 h. The structure, morphology, phase and electrochemical properties of the material were tested by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction spectrometry (XPS) and electrochemical tests. The results show that the LiNi0.03Mg0.10Mn1.87O4 has a cubic spinel structure with a particle size of 100-200 nm, which is a polyhedral morphology. The synthesized LiNi_0.03Mg0.10Mn1.87O4 has good electrochemical performance with initial discharge capacity of 107.6 mAh.g-1 at 1 C, and the first discharge capacity of 10 C is 68.7 mAh.g-1. The initial discharge capacity is 103.7 mAh?g-1 at a high temperature of 55℃. CV and EIS tests show that the LiNi0.03Mg0.10Mn1.87O4 has a large lithium ion diffusion coefficient of 1.038×10-11 cm2.s-1 and a small activation energy of 32.69 kJ.mol-1. The material after 1000 cycles shows that the crystal structure and particle morphology are basically unchanged, doping appropriate amounts of Ni and Mg ions can effectively improve the capacity attenuation and structural stability of the spinel LiMn2O4, thereby suppressing the Jahn-Teller effect.

Abstract:Tungsten reinforced bulk metallic glass composites (BMGCs) possess the high strength, hardness, wear resistance and excellent armor penetration performance, resulting in a promising application prospect in military industry. In the past decades, scholars all over the world have paid much attention to the preparation methods, mechanical properties (quasi-static/dynamic) and armor penetration behavior of tungsten reinforced BMGCs. It has been found that the performance of tungsten reinforced BMGCs is closely related with many factors, such as the morphology, size and volume fraction of tungsten, and also the environmental temperature and strain rate etc. The review summarizes the research progress of tungsten reinforced BMGCs, including the preparation methods, mechanical properties and armor-piercing properties under different influencing factors. Finally the direction of research and development of tungsten reinforced BMGCs are also prospected.

Abstract:High-entropy alloys(HEAs) were a new class of alloys that have attracted physical and chemical properties. The light-weight high-entropy alloys with light elements have high specific strength, specific hardness and corrosion resistance. Light-weight HEAs have attracted worldwide attention for their outstanding potential value in the field of engineering application. Therefore, in this paper, the research status of light-weight high-entropy alloys was elaborated, including that the design rules and methods of light-weight HEAs were assessed, the microscopic phase structure of lightweight HEAs were analyzed, and different properties of HEAs were summarized. Accordingly, current problems of light-weight HEAs are also discussed, and the development trend of light-weight HEAs is proposed.