CoNiO₂/Ti₃C₂T_x composite was prepared by a facile co-precipitation method and subsequent heat treatment. The as-prepared samples were characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, nitrogen adsorption-desorption measurement, cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The results demonstrate that CoNiO₂/Ti₃C₂T_x composite with a CoNiO₂∶Ti₃C₂T_x mass ratio of 30∶1 exhibits the optimum electrochemical performance. The specific capacitance of CoNiO₂/Ti₃C₂T_x composite is 389 F/g at a current density of 1 A/g, which is approximately 6 times greater than that of Ti₃C₂T_x. CoNiO₂/Ti₃C₂T_x composite has the specific capacitance of 309 F/g when the current density increases to 20 A/g, and shows a cycle stability with 82% capacitance retention after 1 500 charge-discharge cycles at a current density of 10 A/g.

The high-purity r-BN nanosheets were synthesized at 1 100℃ by using KBH₄ and NH₄Cl as raw materials, NaCl and KCl as molten salt medias. The effects of salt-free and molten-salt methods on the phase composition and crystal morphology of r-BN were studied. And the electrochemical performance of r-BN was tested. Compared with the salt-free method, the molten-salt method can be used to prepare high-crystallinity and good-shaped sheet r-BN at the same temperature. r-BN shows good cycle stability. The specific capacitance of r-BN at a current density of 1 A/g is 16.35 F/g, and r-BN shows a small charge-transfer resistance and internal resistance.

Li_1.02Ni_0.05Mn_1.93O₄(LNMO) cathode materials were synthesized via liquid flameless combustion at 500℃ for 1 h and subsequent calcination at 700℃ for 3, 6, 9 h and 12 h. The effect of calcination time on the structure, morphology, electrochemical and kinetic properties of the LNMO samples was investigated. The results show that all the samples synthesized have a spinel structure of LiMn₂O₄, and the particle size and crystallinity increase with the increase of calcination time. The LNMO-6 sample has a superior electrochemical performance (i.e., the first discharge specific capacity of 118.7 mA·h/g and the capacity retention rate of 87.0% after 200 cycles at 1 C). At high rates of 5 C and 10 C, the LNMO-6 sample still maintains capacity retention rates of 76.3% and 75.5% after 1 000 cycles. Based on the results by cyclic voltammetry and electrochemical impedance spectroscopy, the LNMO-6 sample has the maximum diffusion coefficient (i.e., 3.74×10^-15 cm²/s) and the minimal apparent activation energy (i.e., 22.72 kJ/mol).

The structure stability, electronic structure properties and mechanical properties of Li_xCoO₂(0≤x≤1) as cathode material for lithium-ion battery were investigated by the first principles method based on density functional theory. The results show that the crystal structure of Li_xCoO₂ changes from hexagonal structure to monoclinic P2/m structure as x = 0.5, and then changes to hexagonal structure as x = 0. The conduction band of Li_xCoO₂ is partially filled and the valence band is completely filled with the de-intercalation of Li atom. As a result, the metal property and the electron conductivity of Li_xCoO₂ both increase, and the spin polarization phenomenon appears. The Co—O bond in Li_xCoO₂ is a covalent bond partially with an ionic bond. The ionic properties of Co—O bond weaken and the covalent properties increase with the de-intercalation of Li atom. The bulk modulus (B), shear modulus (G) and Young's modulus of Li_xCoO₂ decrease with the de-intercalation of Li atom, while the Poisson ratio and the anisotropy index increase. The change of G/B value shows that LiCoO₂ is brittle and then changes to ductile during de-intercalation process.

Some phase change materials (PCM) suitable for the thermal management of lithium-ion batteries were analyzed based on their types and characteristics, and recent research work on the selection and preparation of the PCMs were described. The main research aspect is to obtain the composites with a high thermal conductivity and a high latent heat. From the perspective of heat transfer mode, research progress on the passive and active phase change material-based thermal management systems was reviewed, and the future development direction was forecasted.

Studies on sodium-ion battery originated from the 1970s and 1980s, but it has not been paid much attention due to its low energy density. With the increasing shortage of lithium resources and the rising cost of lithium-ion battery preparation, sodium ion battery becomes a hot spot in the field of energy storage due to the abundant sodium resources, high energy conversion efficiency, long cycle life and good safety performance. Prussian blue analogues (PBAs) have excellent sodium storage properties due to their unique open framework structure, abundant sodium storage sites and large sodium ion migration channels. However, crystal water and structural defects are easy to occur in the synthesis process, leading to the decline of electrochemical properties. The structure and electrochemical characteristics of PBAs were introduced, and the preparation and modification methods were represented. In addition, the future development of PBAs as acathode for sodium ion battery was also prospected.

Potassium-ion batteries (KIB) are expected to replace lithium-ion batteries (LIB) as a new generation of energy storage devices due to their high energy density and abundant potassium resources. Carbon material is considered as a potential KIB anode material due to its low cost, easy availability and environment friendly. However, the development of carbon materials for KIB is restricted due to the presence of some problems (i.e., huge volume expansion and structural deformation during intercalation/deintercalation process), thus leading to low reversible capacity, inferior rate performance, and poor cycling stability. In order to solve the problems and increase the KIB performance, some approaches were summarized, such as heteroatom doping, structural designing and so on. This review summarized recent research progress on different types of carbon anode materials for KIB, including graphite, graphene, hard carbon, soft carbon and porous carbon. In addition, the critical issues, challenges, and perspectives for the development of KIB were also proposed.

The layered-structure materials of LaSrCoO_4±δ and PrBaMn₂O_5+δ as cathode materials for solid oxide fuel cell were analyzed by the first principle method. Effect of A site atom arrangement (i.e., layered and mixed) on the electronic structure, defect forming energy and oxide ion migrating energy was investigated. The results show that for LaSrCoO_4±δ, La/Sr atoms layered arrangement favors the formation and migration of interstitial oxygen ions, and for PrBaMn₂O_5+δ, Pr/Ba mixing arrangement benefits the formation and migration of oxygen vacancy. The electronic density distribution in real space was calculated. The results also indicate the reason for different oxygen defects (interstitial ions or vacancy) forming and migrating in each structure and provide a specific micro-image for the material research and optimization.

Micro thermoelectric devices based on thermoelectric films have promising applications in various fields such as micro-zone refrigeration and power generation. Thermoelectric films with high power factor and large ZT values are critical materials in these devices. Sb₂Te₃-based materials are outstanding p-type thermoelectric materials at room temperature. However, the thermoelectric properties of Sb₂Te₃-based thin films cannot meet the requirement of practical applications. The research background of thermoelectric materials is briefly introduced, the crystal structure of Sb₂Te₃ is discussed, the preparation techniques of Sb₂Te₃-based thin films are outlined, and the methods of improving the power factor and reducing the thermal conductivity of Sb₂Te₃-based thin films are summarized. In particular, the effects of microstructure on thermoelectric properties are focused on to elucidate the mechanism of improving thermoelectric properties of the films, which includes defects, preferential orientation, nanoparticles, superlattice, organic-inorganic hybridization, and so on. In addition, the future research directions for Sb₂Te₃-based thermoelectric thin films are discussed.

Hierarchical porous carbon with massive pores and intersections has a great potential in microwave absorption due to the low density, high specific surface area and high dielectric properties. This review represented the source, structure, composition and characteristics of hierarchical porous carbon materials. The research progress on hierarchical porous carbon as a wave absorbing material was summarized, and its future development was prospected.

FeCo@nano-SiO₂ was prepared via a modified Stöber method using tetraethyl orthosilicate using FeCo as raw materials. The results show that the powder has a uniform core-shell structure. The reflection loss (R_L) of FeCo@nano-SiO₂ reaches -36.1 dB with the thickness of 2.6 mm, and the effective absorption bandwidth with R_L<-10 dB is 3.2 GHz when the content of SiO₂ is 35% (in mass fraction). The mass of FeCo@nano-SiO₂ only increases 2% from room temperature to 800℃, and the optimum oxidation resistance can be obtained at the content of SiO₂ of 65%. The SiO₂ shell optimizes the impedance matching of FeCo, further facilitating the electromagnetic wave absorption, and prevents the contact between FeCo and oxygen at a high temperature, thus improving the oxidation resistance.

A flexible, lightweight and efficient electromagnetic shielding material was prepared with activated carbon fiber felt (ACF) with the density of 0.055 g/cm³. The phase compositions and micro-morphology were characterized by X-ray diffraction and scanning electron microscopy, respectively. The electromagnetic parameters of samples at 8.2-12.4 GHz were examined by a rectangular waveguide method. The results show that high-temperature treatment can improve the degree of carbon ordering in ACF. The conductivity and electromagnetic shielding efficiency of ACF are improved after high-temperature treatment. The total electromagnetic shielding effectiveness of ACF is 39 dB after high-temperature treatment at 1 400℃, which is 23 dB greater than that of the raw material of ACF (i.e., 16 dB). It is indicated that high-temperature treatment could improve the electromagnetic shielding performance of ACF.

Metal V films were prepared on quartz substrates via magnetron sputtering, and then converted to VO₂ films via vacuum annealing. The effect of annealing temperature on the surface morphologies, crystalline structures, optical properties and electric properties of VO₂ films was investigated. The results show that the crystallinity of the films increases with the increase of annealing temperature from 300℃ to 450℃. The films annealed at 400℃ and 450℃ are a pure monoclinic phase. The grains grow better and the grain boundaries are clear. The valent states of V element for different samples include +4 and +5 states. The presence of V⁵⁺ in the films is due to the oxidation in atmosphere. The annealing temperature has little effect on the visible transmittance, but the solar modulation efficiency increases. The metal-insulator transition (MIT) temperature and the resistance of semiconductor phase increase with increasing the annealing temperature. The resistance change amplitude across the MIT for the films annealed at 400℃ and 450℃ is more than 2 orders of magnitude. The hysteresis width and the MIT temperature of the film annealed at 450℃ are 14.6℃ and 61.0℃, respectively.

This review represented the electrochromic mechanism of Prussian blue (PB), and summarized recent research work on the improvement of the electrochromic performance of PB. The main methods of preparing PB thin films and the relationship between the process and the properties were described. The mechanism of improving the properties of electrochromic devices by combining PB with other materials was emphatically given. It is indicated that increasing the contact area with the ion layer and improving the conductivity of the base both are effective approaches to improve the electrochromic devices of PB. In addition, the future development of PB electrochromic devices is integrated with flexible materials to expand the application range of electrochromic devices besides the improvement of the optical and electrical performance.

Zinc indium sulfide (ZnIn₂S₄)/MIL-125 composites were synthesized by a two-step hydrothermal method. The effect of ZnIn₂S₄ on the phase, morphology, chemical state, spectral response and photocatalytic performance of the composite was evaluated in detail. The results show that a small amount of ZnIn₂S₄ results in the morphological evolution of MIL-125 from discoid block to pie shape, and a gradual decrease of the specific surface area. The photocatalytic degradation activity towards rhodamine B dye is greatly improved at the optimal ratio of 0.8% (in mole fraction). The degradation efficiency for the composite is 97.7% while the degradation efficiency for pure MIL-125 is only 70.3% within 50 min. It is indicated that a small amount of ZnIn₂S₄ suppresses the carrier recombination and improves the carrier transport, finally resulting in the enhancement of photocatalytic activity. In addition, the possible mechanism is also proposed.

The effects of attapulgite thermally activated at different temperatures, formaldehyde concentration and gas residence time on the formaldehyde removal efficiency were investigated. The reaction mechanism of formaldehyde on the surface of attapulgite particles was investigated by In-situ-diffuse reflectance infrared spectroscopy. The results show that attapulgite (Pal-250) thermally activated at 250℃ has an optimum formaldehyde removal rate. Oxygen enhances the removal of formaldehyde in the presence of Pal-250, indicating that the removal mechanism of attapulgite thermally activated for formaldehyde is physical adsorption and the catalytic mineralization process. The adsorbed formaldehyde can be partially mineralized into methylene dioxymehtylene, formate, carbonate and other species.

Modified tobermorillonite (AHTOB) with a specific surface area of 570 m²/g was prepared by heating and acidification of tobermorillonite (TOB). The structure and specific surface area and pore size of the modified tobermorillonite were characterized by X-ray diffraction and N₂ adsorption-desorption. The adsorption properties of three adsorbents on methylene blue solution (MB) were investigated by static adsorption experiments, and the adsorption mechanism of modified TOB on MB was analyzed. The effects of adsorbents, solution pH value, initial MB concentration, adsorption time, and temperature on the adsorption behavior were investigated, and the thermodynamic and kinetic behaviors of AHTOB adsorbed on MB solution were investigated. The adsorption of MB was analyzed in 50 mL of MB at a concentration of 10 mg/L. The results show that the adsorption rates of unmodified TOB, HTOB, and AHTOB on MB are 50.00%, 53.72%, and 97.35%, respectively. At different initial concentrations of MB, the maximum adsorption capacities of TOB and HTOB are 102.36 mg/g and 113.80 mg/g, and the adsorption capacity of AHTOB on MB is 248.01 mg/g. The adsorption efficiency of AHTOB modified by heating and acidification compound is improved. The optimal conditions for adsorption are pH value of 5-7, shaking time of 30 min, and temperature of 20-25℃.

Thick thermal barrier coatings (TTBC) have good thermal insulation properties and can effectively improve the gas inlet temperature before aero-engine turbine or gas turbine. Plasma spraying is a common method for preparing TTBCs. This paper reviewed recent research work on plasma sprayed TTBCs, and pointed out the challenges for TTBCs. The splat effect, the structure and properties of coatings were emphatically discussed. In addition, the future development was also prospected.

Two-dimensional continuous carbon fiber toughened silicon carbide composite (2D C/SiC) z-pinned joint was prepared by a chemical vapor infiltration method. The microstructure features and the tensile behaviors were investigated, and the corresponding failure mechanism was analyzed. The results show that the joint is porous, non-uniform bonded with non-uniform clearance. The average joint shear strength reaches 157.77 MPa, which exceeds the 2D C/SiC in-plane shear strength. The main failure mechanisms involve debonding of the lap interface, bearing between the pin and the hole and fibers shear-off within the pin. Three typical damage morphologies appear around the hole, i.e., intact morphology, matrix crushing and pin-hole debonding.

The growth processes (i.e., growth rate, inward/outward growth and compositions) of micro-arc oxidation coatings formed on AZ31 Mg alloys in different electrolytes (i.e., aluminate, silicate and phosphate, respectively) were investigated. The surface and cross-sectional morphologies with elemental distribution and the cross sections of the micro-arc oxidation coatings were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). The phase compositions of three micro-arc oxidation coatings with different coating thickness were determined by X-ray diffraction (XRD). The corrosion resistances of the micro-arc oxidation coatings were evaluated by electrochemical measurements and hydrogen evolution test. The growth processes in different electrolytes indicate the reasons for different anti-corrosion performances of the micro-arc oxidation coatings. The results show that the growth of micro-arc oxidation coating in aluminate is mainly due to the anionic compound deposition, and the coating grows outward, and the growth of the micro-arc oxidation coatings in silicate and phosphate is mainly due to the oxidation of the substrate, leading to the coating to grow inward. It is indicated that the growth processes of micro-arc oxidation coatings with 15 μm thickness in different electrolytes result in that different corrosion resistances (i.e., AZ31-Si> AZ31-P>> AZ31-Al).

Attapulgite (ATP) nano-powder was functionalized by ionic liquid (IL) and silane coupling agent, and then functional ATP reinforced epoxy (EP) composite was prepared. The tribological properties of the composite rubbing against GCr15 bearing steels were investigated under dry friction conditions in a model TRM-1000 pin-on-disc tribometer. The tribological mechanism was analyzed based on the characterization of interfacial microstructures and tribo-chemical reactions. The results show that the surface functionalization of ATP significantly restrains the agglomeration and promotes its uniform dispersion in the resin. Moreover, the maximum wear resistance is achieved by filling EP with functionalized ATP modified by IL (3%, in mass fraction). The wear resistance is enhanced by 60%, compared to neat EP. Iron oxide and silicon oxide-based tribofilm formed at the friction interface mitigated the direct contact of the friction pairs, thus improving the wear resistance of EP materials. It is indicated that ATP could be used as a promising friction functional mineral filler in wear-resistant polymer.

Biofilm and the microscopic properties of mortar were investigated by electrochemical impedance spectroscopy, scanning electron microscopy, thermal analysis and X-ray diffraction. The results show that a mature biofilm can be formed on the surface of mortar at 30 d. In a macroscopic study, the biofilm is a transparent and viscous substance containing white matter. In a microscopic study, the biofilm is a film structure formed by rod-shaped sulfur-oxidizing bacteria wrapped with extracellular polymeric substances (EPS). The biofilm on the surface of 90 d mortar is in the disintegration stage. The thickness, protein optical density (OD) value and microorganism number OD value of the 30 d biofilm are 1.59 mm, 0.086, and 1.614, respectively, which are higher than those of the 90 d biofilm. Based on the results of a microscopic study, the plate-like mineralized gypsum gradually occurs in mortar, the semicircular diameter of the first half of the electrochemical impedance spectrum gradually becomes larger and the inclination angle of the second half of the straight line becomes larger, and some pores in mortar fill with gypsum when the test age increases. Compared to the 30 d test age, the 90 d gypsum content is relatively larger, and the 90 d adhered biofilm dehydrated content of gypsum is 0.248% greater than the 90 d unattached biofilm dehydrated content of gypsum. This indicates that the biofilm formed by sulfur-oxidizing bacteria could have a corrosive deepening effect on mortar.

The damage of ultra-high performance concrete (UHPC) under load-temperature coupling was evaluated by using the indexes of ultrasonic pulse velocity, mass loss rate, bulk density and thermal conductivity. The results show that the ultrasonic pulse velocity (UPV) of UHPC decreases, and the damage increases gradually with the increase of load. The temperature has little effect on the UHPC damage and the UPV fluctuates at 4.55 km/s. The bulk density decreases slightly with the increase of load and temperature, i.e., only 0.73% and 1.80%, respectively, at a stress ratio of 0.5 and a temperature of 90℃. The test results of mass loss rate show the similar regularity. Load and temperature both have a greater influence on the thermal conductivity of UHPC. The thermal conductivity decreases with the increase of the increase of load and temperature. At 3 d, the thermal conductivity of UHPC in the presence of a stress ratio of 0.5 is decreased by 21.80%, compared to that in the absence of load, and the thermal conductivity of UHPC at 90℃ is decreased by 14.90%, compared to that at 30℃. A meso model of thermal conductivity of the UHPC under load-temperature coupling was proposed based on the assumption that the thermal conductivity of solid phase in UHPC could increase linearly with increasing saturation and eliminate the effects of load and temperature on the UHPC porosity. It is indicated that the theoretical values calculated by the model could be in reasonable agreement with the measured data.