Al-based composite coatings containing 30%Al₂O₃ were prepared on AZ31 Mg-alloy via cold-spraying technique. Then the pore feature and cracking behavior of Al-based composite coatings during reciprocating friction testing was assessed by means of a wear-testing machine, as well as and the location of crack initiation for relevant pores on the cross section of coatings. Meanwhile, models for composite coatings of elliptical-, triangular-, and rectangular-pores, and pore-free were respectively established using Abaqus and Python scripts, then the maximum stress of pores during friction and the residual stress on the top surface after friction were analyzed for the composite coatings. The relationship between stress finite element results and the size of cracks induced by reciprocating friction was discussed. The research findings indicated that stress concentration for elliptical-, triangular-, and rectangular-pores mainly occurred at the endpoints of the major axis or at their corners during friction. From the top surface to the interface, the residual stress transformed from tensile stress to compressive stress and then back to tensile stress. For elliptical-, triangular-, and rectangular-pores, the maximum Mises stress and average residual stress on the surface gradually increased. Cracks initiated and propagated from the endpoints of the major axis for elliptical pores, while cracks in triangular- and rectangular-pores originated from the corners, with corresponding increases in crack length and width. Finite element analysis revealed that the increase in the maximum Mises stress of poresduring friction led to an increase in the average residual stress on the surface after friction. This, in turn, resulted in larger crack dimensions, consistent with the findings from the reciprocating friction experiments.

Metal fatigue crack growth monitoring has been a hot topic in the study of material properties. In this study, high sensitive acoustic emission technology is used to conduct online monitoring of metal fatigue crack growth. A quadratic K-entropy method is proposed for the first time, the calculation results of which are used as a new parameter to analyze this uncertain process. The experimental results indicate that the acoustic emission signal in metal fatigue growth shows chaotic characteristics, and its trend has a clear corresponding relationship with the process of fatigue crack growth after the quadratic K-entropy treatment, and the fatigue fracture information can be obtained in advance. The advance rate is more than 8% of the whole process, which effectively provides a basis for the prediction of fatigue fracture.

In the present study, AZ31 Mg-alloy sheets with bimodal non-basal texture were subjected to heating treatment (520^oC/5 h), and then immediately water-quenched and quenched into liquid nitrogen for 12 h. Then, their ambient temperature mechanical performance and microstructure evolution were studied by means of uniaxial tension testing, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). The results show that nano-precipitates Mg₁₇Al₁₂ and Al₈Mn₅ all exist in AZ31 Mg-alloy sheets. However, compared to the Mg-alloy sheet subjected to water-cooling treatment, the volume fraction and size of precipitates increase about 65.5% and 78.7% respectively for the sheet subjected to cryogenic treatment. Meanwhile, the volume fraction of {\mathrm{10}\overline{\mathrm{1}}\mathrm{2}} extension twin (ET) increases by 38.0% and 36.7% for the sheet being subjected to 6% and 12% deformation, respectively. The yield strength (YS) and ultimate tensile strength (UTS) of the cryogenic treated sheets are increased by 43.8% and 5.2%, respectively, compared with the water-cooling treated ones, however, the fracture elongation (FE) decreases by 20.4%. The increase in YS and UTS may mainly be due to the generation of high-density dislocations and precipitation strengthening by Mg₁₇Al₁₂ and Al₈Mn₅ precipitates during cryogenic treatment. The decrease in FE is mainly due to the accumulation of high-density dislocations near {\mathrm{10}\overline{\mathrm{1}}\mathrm{2}} ET boundaries during tensile deformation at room temperature, which would hinder the movement of basal slip and benefit in propagation of microcracks to expand to this region.

Rock salt-type high entropy oxide (Co_0.2Cu_0.2Mg_0.2Ni_0.2Zn_0.2)O as anode material for lithium-ion battery has attracted widespread attention due to its unique synergistic effect of multiple elements. Zn and part of Co elements provide the main source of electrode capacities, while MgO stabilizes the crystal structure, Ni, Cu, and the reduced residual Co may form a 3-dimensional network to enhance the conductivities of the oxide. In this study, a series of rock salt-type high entropy oxides (Co_0.22Cu_0.22Mg_0.22Ni_0.22Zn_0.12)O,(Co_0.2Cu_0.2Mg_0.2Ni_0.2Zn_0.2)O and (Co_0.18Cu_0.18Mg_0.18Ni_0.18Zn_0.28)O with different Zn contents were prepared by solution combustion method, while the effect of Zn ion concentration on the electrochemical performance of rock salt-type HEOs was also assessed. The results suggest that with the increasing Zn content, the electrochemical performance of the electrode material was enhanced. Although the (Co_0.2Cu_0.2Mg_0.2Ni_0.2Zn_0.2)O electrode exhibits a higher lattice distortion and oxygen vacancy concentration, resulting in a slightly higher intrinsic conductivity and lithium ion diffusion coefficient, however, the (Co_0.18Cu_0.18Mg_0.18Ni_0.18Zn_0.28)O electrode showed the most excellent electrochemical performance with the highest initial discharge specific capacity (777.06 mAh·g^-1) and cycling stability (capacity retention rate nearly 100% after 150 cycles) at 200 mA·g^-1, as well as excellent rate performance (specific capacity of 140.2 mAh·g^-1 at 3000 mA·g^-1), and it even shows the best cycling stability after 150 cycles at a high current density of 1000 mAh·g^-1 (specific capacity of 198.1 mAh·g^-1). The excellent electrochemical performance of the (Co_0.18Cu_0.18Mg_0.18-Ni_0.18Zn_0.28)O electrode may be attributed to the complete conversion of Zn element during the redox reaction. The higher Zn content is beneficial to increase capacities, while the appropriate oxygen vacancy concentration and lattice distortion may provide more channels for Li ion migration, thus resulting in higher cycle stability of the electrode.

Herein, the effect of heat treatments (solution, solution+single aging and solution+double aging) on the microstructure and mechanical properties of a novel Ti-based alloy Ti-6Al-2Mo-2V-3Nb-2Fe-1Zr was investigated through microstructure characterization and tensile testing. The microstructure observations indicate that the alloy prior to heat treatment possesses a bimodal microstructure consisted of primary α_p phase, secondary α_s phase, and β phase, and the volume fraction of the primary α_p phase and secondary α_s phase is 22% and 21%, respectively. After solution treated in the dual phase zone, a portion of the original α_p and α_s phases was replaced by β phase and the alloy microstructure is comprised of metastable β phase, equiaxed primary α_p phase, and coarse lamellar secondary α_s phase. After single aging, a large number of evenly distributed needle-like nano secondary α_s phases are precipitated within the β phase; After double aging, the volume fraction of α phase increases significantly, while the grain size of primary α_p phase and secondary α_s phase increases with the increasing aging time. Quasi-static tensile test results reveal that alloys subjected to solution treatment in the dual phase zone exhibit significant enhancements in elongation compared to the as hot-rolled ones, but yielding at lower stress levels. Single aging results in significant increase of strength, thereby presenting an improved strength-ductility balance of the alloy. In comparison with the hot rolling process, the double aging process is unfavored to the ductility, moreover, with the increasing aging time, the strength decreases and elongation increases gradually. Finally, the variation in the work hardening rate of the alloy subjected to different heat treatments may be explained by work hardening rate-strain curves. Based on the experimental data, the modified Hall-Petch constitutive model is fitted, whilst the results predicted by this constitutive model have high coincidence with the experimental data.

N and O co-doped carbon electrode materials were synthesized by pyrolysis of Zeolitic Imidazolate Framework-8 (ZIF-8) at high temperature in air using a salt-sealing technique, aiming to solve the issue related with the low energy density of conventional carbon materials for supercapacitors. Compared with the conventional carbon materials prepared by direct pyrolysis of ZIF-8 in nitrogen atmosphere, the novel carbon materials prepared by this proposed technique have an open hollow structure with appropriate distribution of mesoporous and microporous, and higher specific surface area of 1589 m²·g^-1. The co-doping of heteroatoms N and O can improve the wettability of the material, while the open hollow structure is conducive to the diffusion of the electrolyte ions from both internal and external surfaces to the interior of the electrode material. Therefore, more solvated ions are adsorbed and desorbed in the pores, and the effective specific surface area is increased for the electrode material, therewith, more active sites of heteroatoms N and O can participate in the redox reaction, introducing higher Faraday capacitance. As a matter of course, the symmetrical supercapacitor assembled with the novel electrode material shows an energy density of 11 Wh·kg^-1 at power density of 250 W·kg^-1.

In order to comprehensively evaluate the influence of alloy structure on the competition mechanism of slip-cleavage failures during ultra-high cycle fatigue process of Ti-alloy, a competition failure model considering the maximum stress (σ_max) was constructed, and then the competition mechanism among failure modes was quantitatively described. Furthermore, the influence of microstructure (surface defects, \alpha-grain size and α-grain content) on the competition mechanism was revealed in detail by means of the control variable method. Meanwhile, ultra-high cycle fatigue tests of TC4 Ti-alloy under stress ratios of -1, -0.3 and 0.1 were carried out at room temperature. The S-N curves obtained under three stress ratios were bilinear, and TC4 Ti-alloy showed three failure modes, namely surface slip failure, surface cleavage failure and internal cleavage failure. The GP extreme value distribution function is used to clarify the distribution characteristics of the surface defect size, and the predicted extreme size of the surface defect is 5.69 μm, which is defined as the thickness of the sample surface area. Next, the coupling effect of microstructure variables such as control volume, external load, α-grain content and α-grain size, the increase or decrease of σ_max value is taken as the main factor of fatigue failure mode transformation of TC4 Ti-alloy and the competitive failure model is constructed. The calculation results show that the model prediction results have a good correlation with the experimental data. Finally, the effect of W value, α-grain size and α-grain content on the slip-cleavage competition failure mechanism of TC4 Ti-alloy was investigated by the control variable method. It is concluded that smaller W value, larger α-grain size and less α-grain content are beneficial to the internal cleavage failure of TC4 Ti-alloy. The value of W does not affect the probability of surface slip failure, and the increase of α-grain size or the decrease of α-grain contentis beneficial to the surface slip failure of TC4 Ti-alloy; The smaller W value, larger α-grain size and less α-grain content is all conducive to internal cleavage failure of TC4 titanium alloy.

The nest-like bismuth-containing precursor was prepared by hydrothermal method with sodium gluconate as auxiliaries. The effect of the hydrothermal temperature and reactant concentration on the morphology and composition of the prepared precursor were systematically studied, and the formation mechanism of the precursor was elucidated. Then, calcination of the precursor was carried out at 150^oC~400^oC, during which the precursor decomposed to Bi₂O₃. At the same time, the carbon generated by high-temperature carbonization of the gluconic acid involved in the skeleton of the precursor can in situ reduce Bi³⁺ to Bi nanoparticles. The phase transition during calcination process can be described as: precursor→Bi/β-Bi₂O₃ (150^oC~280^oC) →Bi/β-Bi₂O₃/α-Bi₂O₃ (300^oC~350^oC)→Bi (400^oC). The degradation of levofloxacin hydrochloride (LVFH) was used as a probe to evaluate the visible-light photocatalytic performance of the as-prepared Bi/β-Bi₂O₃ heterojunctions. Among others, the Bi/β-Bi₂O₃ heterojunction obtained at 280^oC exhibited the best visible-light photocatalytic activity, and the degradation rate of LVFH can reach 97.75% after 140 min of visible-light irradiation. Its superior photocatalytic performance was attributed to the nest-like hierarchical structure and the SPR effect of the in situ generated Bi-nanoparticles, which improved visible-light harvesting and promoted the separation of photogenerated carriers. In addition, the Bi/β-Bi₂O₃ heterojunction photocatalyst showed good recyclable and reusable performance.