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In order to develop lithium-ion batteries with high energy density, prelithium technology has attracted extensive attention. Li5FeO4was successfully prepared by molten salt method with LiNO3-LiOH mixed lithium salt as reaction medium and lithium source, and nano Fe2O3 as iron source in this work. Li5FeO4 as cathode prelithiation additive is applied to lithium-ion batteries. The synthesis conditions of Li5FeO4 were optimized by orthogonal experiment, and the effect of synthesis conditions on the electrochemical properties of the material was discussed. Li5FeO4 was added to the surface of LiFePO4 positive electrode and assembled with graphite negative electrode to form a full cell. Its effect on the electrochemical performance of the full cells and the mechanism of reducing the initial capacity loss of lithium-ion batteries were studied. The results show that Li5FeO4 cathode prelithiation additives with high purity, small particle size and outstanding electrochemical performance can be prepared by molten salt method. When Li5FeO4 with a mass fraction of 2.8%(based on the percentage of active materials mass) was added, the discharge specific capacity of first cycle for the LiFePO4/graphite full cell was 150 mAh·g-1 at 0.05 C, which was 8.5% higher than that without adding, after 100 cycles at 0.2 C. the capacity still increased by 7.1%, and the irreversible capacity of the svstem was restored.

Flexible energy storage devices are at the forefront of next-generation power supplies, one of the most important components of which is the gel electrolyte. The dual network gel electrolyte for PAM/P123 zinc ion batteries was prepared by free radical polymerization. It was found that the addition of a small amount of triblock copolymer P123 can macroscopically improve the tensile strength, toughness and compressive strength of the gel electrolyte. Microscopically, the gel skeleton forms 0.6 μm mesopores and increases the surface pore distribution density, thereby improving the wettability of the electrolyte. The PAM/P123 series electrolytes not only have a high average swelling rate, but also have a higher conductivity than pure PAM electrolyte in the range of -30℃ to 65℃. Among which, PAM/P123-2 is a series of electrolytes with the best performance, with an average swelling rate of 1920.79%, and the conductivity at 0℃ is 36.2 mS·cm-1.The Zn/MnO2 battery prepared by using PAM/P123-2 gel electrolyte is stable during cycling at 0℃, with the capacity retention rate reaching 82.39% after 1000 cycles.

In recent years, zinc alloys have shown great potential as orthopedic plant materials because of their excellent biocompatibility, osteoinductive and biodegradation activities in vivo. The physiological function, degradation rate and mechanical properties of pure zinc were introduced in this review. Taking the gap between the above indicators and the clinical needs of orthopedics as the clue and the alloy elements as the classification basis, the existing achievements of researchers to improve the properties of zinc-based materials by changing the microstructure of materials and triggering the corresponding strengthening mechanism, and using the physiological synergistic function of added elements were expounded in this paper. The standard formulation, alloy design improvement and the introduction of new technologies such as additive manufacturing in the field of medical zinc based materials were discussed in order to meet the diversified needs of clinical diagnosis and treatment.

In order to investigate the solidification microstructures in typical section dimensions of a third generation single crystal superalloy DD9 turbine blade with 1500℃ and 1540℃ mould temperatures during directional solidification process, Optical microscopy (OM) and scanning electron microscopy(SEM) were used to analyse the solidification structure of typical sections of the blade. The results show that with increasing mould temperatures, the dendrite patterns have a tendency of becoming more refined, and the secondary dendritic arms tend to be highly developed. With the same mould temperature, the dendrite patterns in the blade aerofoil section are more refined than those in the tenon section. Also with increasing mould temperatures, the γ' precipitates of the interdendritic regions and the dendritic cores tend to be refined, the γ' precipitation size dispersion decreases, and the size distributions of the γ' precipitates follow the normal distribution law. Compared with the interdendritic regions, almost 61% reduction of the γ' precipitation average sizes is measured in the dendritic core. With the same mould temperature, the γ' precipitation sizes in the aerofoil section are more refined than those in the tenon section. Compared with the decreasing sectional areas, the increasing mould temperatures bring down the γ' precipitation sizes obviously. The sizes and contents of the γ-γ' eutectics decrease with increasing mould temperatures. The morphologies of γ-γ' eutectics show both sunflower-like shape and plate-like shape.

Solid state lithium battery is expected to be one of the next generation of battery systems with high energy density in the field of high energy. Based on the constructure characteristics and related formation mechanism of interface between solid polymer electrolyte and lithium anode, the impact of interface contact, interface chemistry and electrochemical reaction, and moreover, the growing process of lithium dendrite and other problems on the interface stability and compatibility were systematically discussed in this review.Thus, the application of doping modification, structure design, and other methods for the interfaces between polymer matrix and lithium anode were also emphasized. In addition, the common interface characterization methods and their applications on the interface between solid polymer electrolyte and lithium anode were also reviewed. Finally, based on the relevant strategies of designing and constructing a stable polymer solid electrolyte-lithium anode interface, the development prospects of interface optimization methods such as doping and core layer design were analyzed and prospected in this paper.

The polarization switching properties of P(VDF-TrFE) ultrathin films with different storage periods were measured. The dependence of polarization properties on temperature and storage period was investigated. The experimental results suggest that the relative remanent polarization (Pr/Pr0) remains on a relatively high level of 0.70 at 60℃, 106 polarzation swiching test, even to the ultrathin film capacitors stored in atmosphere for five months. The time stability model of polarization switching is predicted by the evolution of polarization switching with the number of electric field cycles. Moreover, when the changes of the molecular chain are simulated by different storage periods and testing temperatures, an inhibited hydrogen fluoride (HF) gas formation scheme in the capacitors was proposed. This work further validated the time stability model and microscopic dynamics associated with trapped charge. These results provide an effective method for designing an optimum protocol for flexible electronic devices based on P(VDF-TrFE) copolymer ultrathin films.

To meet the development needs of advanced aeroengines,the structure of aeroengine turbine blades is becoming increasingly complex, and the content of refractory elements is increasing in single crystal superalloys, which are the preferred materials for turbine blades. As a result, the tendency to form the grain defects increases during the preparation of single crystal turbine blades, which directly affects the quality of single crystal turbine blades. In this paper, a kind of grain defect that appears in the directional solidification process of single crystal superalloys—freckle was discussed. The research works on the formation mechanism, the criterion model and the control method of freckles formation during the directional solidification of single crystal superalloys in recent years was reviewed. The influence of the alloy composition, blade structure, directional solidification process and crystal orientation of single crystal castings on the formation of freckles was analyzed. Considering the influence of the alloying elements in different alloy systems and the parameters of the directional solidification process on the freckle formation, further studying the freckle formation mechanism of the single crystal turbine blade with complex structures, establishing an effective method for prediction and control of freckles are the future research directions.

In order to study the influence mechanisms of microstructure stability of high generation single crystal superalloys, the D1 and D2 alloys which contain 6%(mass fraction) Ru and 4.5%Ru respectively were prepared after complete heat treatment and long-term aging at 980 ℃ for 1000 h. The microstructure and alloying element distribution at different scales were examined and the results were analyzed combining with thermodynamic calculation. The results show that there are still high content of refractory elements segregating in the dendrite region after complete heat treatment, inducing to TCP precipitation in the dendrite after long-term aging. Ru and Re are the main forming elements of TCP in both D1 and D2 alloys, and more TCP phase precipitates in D1 alloy which contains more Ru than in D2 alloy. Because both Ru and Re can increase the d-orbital energy level of single crystal superalloy, higher Ru and Re content leads to more TCP phase precipitation. However, since Ru can reduce the segregation degree of Re in γ phase, the increase of Ru content can reduce the adverse effect of Re on the microstructure stability of single crystal superalloy. In this study, Ru plays a more significant role in promoting TCP phase precipitation, leading to more TCP phase precipitating in D1 alloy than in D2 alloy after long-term aging at 980 ℃ for 1000 h.

As the demand for large-scale batteries for electrical energy storage is increasing, sodium-ion batteries have attracted a lot of attention due to the abundance,cost-effectiveness of sodium resources and resemblance with lithium. In the key material selection of sodium ion battery, electrochemical performance and safety of a sodium-ion battery were affected by the electrolyte, which not only decides the electrochemical window and energy density, but also controls the electrode/electrolyte interfaces. In this paper, the basic requirements and classification of electrolyte of sodium ion battery were reviewed. The selective requirements of electrolyte in sodium ion batteries, the physicochemical properties of different sodium salts and the effects on solid electrolyte interface were discussed. Based on the compatibility of different solvents and materials as well as the energy storage mechanism of materials in different solvent systems, the solid electrolyte interface, rate and cycling performance obtained by materials in ether and ester based electrolytes were analyzed. Finally, the future development of sodium ion battery electrolyte in terms of matching with materials and key characterization methods were prospected.

At the conditions of 760℃/800 MPa, 980℃/250 MPa and 1100℃/137 MPa, the transv-erse stress rupture properties of a nickel-based third generation single crystal superalloy were investigated. The results show that the stress rupture life and elongation of the transverse specimens are lower than those of the longitudinal specimens at 760℃/800 MPa, 980℃/250 MPa and 1100℃/137 MPa. The dislocation configurations of the stress ruptured transverse and longitudinal specimens are the same. There are intersecting stacking faults in the γ' phases after stress ruptured at 760℃/800 MPa, and the dislocations are tangled and high densities of dislocation networks have formed at the γ/γ' interface after stress ruptured at 1100℃/137 MPa. The transverse and longitudinal specimens show quasi-cleavage and dimple mixture mode at 760℃/800 MPa, while they both show dimple mode at 980℃/250 MPa and 1100℃/137 MPa. The fracture mechanisms of transverse specimens of the first generation single crystal superalloy DD3, the second generation single crystal superalloy DD6 and the third generation single crystal superalloy in our study at medium and elevated temperatures are basically the same. The main reason for the transverse specimens have a lower stress rupture properties than the longitudinal specimens is that the external applied stress is perpendicular to the primary interdendritic interface formed during the directional solidification process.

The specimens of the fourth generation single crystal superalloy after heat treatment and at as-cast state were indented and annealed in vacuum at 1100, 1150, 1200, 1250, 1300℃ and 1340℃, respectively. The recrystallized microstructures of the alloy were examined by optical microscopy (OM), scanning electron microscopy (SEM) and electron back scattering diffraction (EBSD). The results show that cellular recrystallization (CRX) occurs in the standard heat treatment samples and as-cast samples after annealing treatment at 1100, 1150℃ and 1200℃. Mixed recrystallization occurs in standard heat treatment samples and as-cast samples after annealing treatment at 1250℃. Equiaxed recrystallization (ERX) develops when the standard heat treatment samples are annealed treatment at 1300℃, while mixed recrystallization occurs in as-cast samples at same condition. ERX develops when these two samples are annealed at 1340℃. The recrystallized layer depth of these two samples increases with the increase of annealing treatment temperature and the depth of standard heat treatment samples is obviously larger than that of as-cast samples.The recrystallized grain of standard heat treatment samples easily grows up at same condition. The interface between the recrystallization grain and original grain is low angle boundary and high angle boundary, while the interface between adjacent recrystallization grains is low angle boundary, high angle boundary, and twinning boundary. It can be inferred that the formation of twins can play an important role in the process of recrystallization.

The stabilities of microstructures and hardness of P92 steel samples austenitized at 1060℃ for 1h followed by air cooling (AC)/slow cooling (SC) and tempered at 760℃ for 2h and then aged at 650℃ for 1000h/3000h were studied by SEM-SE/BSE,EDS and multiphase separation technology (MPST). The results show that the microstructures of P92 steel aged samples consist of martensite and precipitations (M23C6 and Laves phase). The cooling modes after austenitization have an obvious effect on microstructures and hardness of the samples aged at 650℃. Compared with the AC samples, the total volume fraction of the precipitations/Vickers hardness of the SC sample is higher/lower and the volume fraction of the Laves/M23C6 phase is remarkably higher/lower. Moreover, the Laves phase particles of SC sample is much more coarsened. The hardness of the SC sample decreases after ageing treatment at 650℃ for 1000h/3000h, while that of the AC sample is not obviously varied. In addition, the stabilities of microstructure and hardness of P92 steel aged at 650℃ are related to the stability of the austenite which in return affects the stability of the martensite transformed during cooling. Therefore, the P92 pipes cooled from austenitization should dissipate heat as soon as possible in the manufacturing scene.

ZrC ceramics were prepared by mechanical axial compression of self-propagating high-temperature synthesis/single action pressing (SHS/SAP).The effects of pressure on microstructure and densification of the products,as well as the relationship between displacement/variation of the load curve and SHS reaction,were studied.The structure and properties of the products were investigated by XRD and SEM.In addition,the density was measured by the drain away liquid method.Meanwhile,universal testing machine was used to record the displacement and load curve alternations.The results indicate that products are mainly composed of ZrC phase,the process of exhaust are accelerated as the increasing of pressure as well,leading to the smaller size of porosity and crystal particles.Density manifested as an increasing pattern by the elevated pressure with no longer change at 80MPa.Due to the strong attenuation of pressure at the peak of temperature,the density of the production is only 65.7% in 120MPa.The end point of the SHS reaction and the plastic time of the products can be monitored by displacement and load curve.The results provide evidence for the application of self-propagating high-temperature synthesis/pseudo-hot isostatic pressing to further improve the density of ceramics.

Black phosphorus （BP） nanosheets have a special folded structure， which gives them an adjustable band gap， transmission anisotropy， and photoluminescence. These unique properties make BP nanosheets widely used in the construction of metal ion sensors and show great application potential in environmental monitoring and other research fields. In this paper， the preparation methods of BP nanosheets and their applications of different sensors in detecting heavy metal ions were introduced. Firstly， different preparation methods for BP nanosheets were introduced based on the “top-down” and “bottom-up” methods， and their advantages and disadvantages were summarized. Then， the research progress of BP nanosheets based field effect transistor （FET） sensors， electrochemical sensors， and photochemical sensors for the detection of heavy metal ions were described in detail. Among these sensors， the FET sensor shows an excellent detection limit， the electrochemical sensor has advantages of short response time and simple operation. The photochemical sensor shows a wider detection range than that of others. Furthermore， it is concluded that the types of heavy metal ions that BP nanosheets based sensors can detect are relatively limited， and the stability and selectivity need to be further improved. Finally， in view of the challenges faced by BP nanosheets for constructing different types of heavy metal ion sensors， we should develop low-cost and high-quality BP nanosheets preparation methods， and structure optimization and functional modification of BP nanosheets. In the aspect of expanding the application of BP nanosheets for the detection of heavy metal ions， it is expected to make a breakthrough in the practical applications by combining with novel technology.

Pure Mg has advantages of low density， good shock absorption performance and good biocompatibility， but its strength is low. Alloying is an important method to modify microstructure and properties of pure Mg. Sn has characteristics of low melting point， high eutectic temperature with Mg， high solid solubility in Mg， stable chemical properties and large output， which is appropriate to be an alloying element. The effects of alloying element Sn on microstructures and properties of Mg alloys were reviewed in this paper. Sn enriches at the front of the solid-liquid interface， dissolves in Mg matrix， reduces the ratio of critical resolved shear stress value of the pyramidal plane to that of the basal plane， and elevates the electric potential of Mg matrix. Mg2Sn precipitates can hinder dislocation and grain boundary movement， and form galvanic corrosion cells with Mg matrix. Therefore， effects of Sn addition include grain refinement， age hardening and strengthening， improving plasticity， accelerating or reducing corrosion rate， enhancing discharge efficiency and discharge potential. At present， the main problems restricting the development of Mg-Sn alloys are slow aging， low hardness and strength. In the future， endeavors should be made to develop rapidly age-hardenable Mg-Sn alloys with high strengths， wrought Sn-containing Mg alloys with good ductility， and Sn-containing structural-functional Mg alloys.

Cobalt-chromium-nickel (Co-Cr-Ni) alloys were prepared by two techniques of the sub-rapid solidification (SRS) and vacuum sintering (VS). The effects of the preparation processing and the content of Cr, Ni on the microstructure evolution were investigated in detail. Results show samples under SRS present a typical dual-phase dendrite microstructure of the face centered cubic (γ-fcc) crystal and the hexagonal closest packing (ε-hcp) crystal, which is independent of the raw material composition. The γ-fcc phase forms in dendrite arms, while the ε-hcp phase forms in inter-dendrites. With the increase of the solidification rate, the secondary dendrite spacing decreases. The main solute elements Cr and Ni take segregation between the two phases of γ-fcc and ε-hcp. Cr concentrates in inter-dendrites, and Ni exists in dendrite arms. The microstructure of cobalt chromium nickel alloy prepared by VS is determined by its composition, and the sintered body of low nickel content alloy is single-phase ε-hcp structure, the grains exhibit a sharp coarsening characteristic with the increase of sintering temperature. The sintered body of high nickel content alloy is γ-fcc+ ε-hcp dual phase structure, the grains are small and γ-fcc phase exhibits obvious twinning and stacking fault structures. Compared with the casted alloy, the sintered alloy exhibits a marked improvement in the uniform plastic elongation. The dislocation defect is the prime microstructural unit that promotes the improvement in the mechanical property of the sintered alloy with the single-phase structure of ε-hcp, while the defects of the crystal twins and stacking faults are considered as the key factors determining both the strength and toughness for those with the dual-phase structure of ε-hcp and γ-fcc.

CoCrFeNi-(Nb, Ta) high-entropy alloys (HEAs) were prepared by a vacuum arc melting process, and the synergistic effect of Nb and Ta concentrations on the microstructure evolution and mechanical properties was investigated in detail. Nb and Ta concentrations in the HEAs affect the microstructure compositions, eutectic phase lamella spacings, Laves phase size topographies, phase volume fractions and compositions. The alloy with an equal atomic ratio of Nb/Ta show an eutectic microstructure of the face centered cubic (FCC) crystal matrix and Laves phase, while those with non-equal atomic ratio of Nb/Ta exhibit the microstructure of the eutectic (FCC+Laves) phase and primary Laves phase. The volume fraction and grain size of the primary Laves phase monotonically increase with the increase of Nb/Ta atomic ratio. The compressive yield strength of HEAs is monotonously improved with the volume fraction of Laves phase, whereas the ultimate strength is hardly affected by the microstructure composition. Compression plasticity is negatively correlated with the volume fraction, type, and size distribution of Laves phase. The strengthening mechanism of CoCrFeNi-(Nb, Ta) HEAs was analyzed with theoretical calculation, and the relationship between the microstructure composition and the alloy strengths was established. The results indicate that the fine-grain strengthening and second phase strengthening of Laves phase are the main factors for the improvement of yield strength.