Ca₅Mg₄(VO₄)₆ microwave dielectric ceramic was prepared by a solid-phase reaction method. Mg element in Ca₅Mg₄(VO₄)₆ ceramic was substituted by Co element in order to improve the microwave dielectric properties. The phase composition and microscopic morphology of the ceramics were determined by X-ray diffraction and scanning electron microscopy. Also, the internal laws of the microwave dielectric properties were analyzed via theoretical calculations, such as bond energy. The formation of solid solution after Co substitutioncan decrease the sintering temperature. The density dominates the change of ε_r at a higher relative density. However, ε_r is mainly affected by the ion polarizability per unit volume at a lower relative density. The grain size reduction caused by the substitution is beneficial to the promotion of the Q×f value. τ_f is closely related to the bond energy and changes with the bond energy of the V—O, which is the maximum bond energy in ceramics. Ca₅Mg₃Co(VO₄)₆ ceramic has the optimum microwave dielectric properties (i.e., ε_r=9.65, Q×f=54 685 GHz, and τ_f = -55.3×10^-6℃^-1).

The ZnO-A1₂O₃-MgO-TiO₂-SiO₂-Fe₂O₃ linear ceramic resistance were prepared by solid state sintering method. The effect of Fe₂O₃ doping on the microstructure, impedance, temperature-resistance characteristics and impedance-frequency characteristics was investigated. The results show that the ZnO linear ceramic resistance doping with 0.75% (mass fraction) Fe₂O₃ has the optimum comprehensive performance. This resistance synthesized has nonlinear coefficient of 1.12, and resistance temperature coefficient of -8.23×10^-3/℃.

A pressure rapid sintering process of tetragonal zirconia ceramics was proposed. The effects of sintering parameters (i.e., temperature, voltage, current and pressure) on the density, microstructure and phase composition of zirconia were investigated. The process superimposed a flash burning effect based on hot pressing sintering, and the high-temperature conductive zirconia was instantly densified and sintered at a high electric field strength. The results show that the pressure-assisted flash sintering process involves the advantages of hot pressing sintering and flash sintering. Zirconia powder was used as a raw material to simplify the green pressing process. Low temperature and instantaneous flash firing inhibit the high-temperature phase transformation of zirconia. Hot pressing in sintering process ensures the diffusion and flow of zirconia powder and enhances the density.

Boron carbide matrix composites containing boron carbide (B₄C), titanium diboride (TiB₂) at 20% (mass fraction) and 30%, and titanium carbide (TiC) were fabricated at 2 130℃ using a pressure-less sintering method. Different amounts of TiB₂ and TiC particles were added to B₄C. TiB₂ content was chosen as the main variable to study the effect on the composites. The density, hardness, bending strengths and fracture toughness measurements were performed to obtain the physical and mechanical properties of the samples. The results indicate that by adding 30%TiB₂ sub-micron particles at 2 130℃, the bending strength and fracture toughness of 277.6 MPa and 5.38 MPa·m^1/2 were obtained for the composite. Particle pullout and crack micro-bridging play an effective role in toughening the composite ceramics. The main toughening mechanisms of the B₄C-TiB₂ composites are noted to possess microcrack and crack deflection toughening owing to the residual stresses resulting from the mismatch of the thermal expansion coefficient between TiB₂ and B₄C.

BiFeO₃ (BFO) and Bi_0.8La_0.1Ho_0.1FeO₃ (BLHFO) materials were prepared by a solid-state reaction method. The dynamic process of melting and solidification of the samples was observed in real time by high temperature polarizing microscopy. The phase composition, microstructure and element distribution of the solidified samples were analyzed by X-ray diffraction, scanning electron microscopy and energy dispersive spectrometry. It is indicated that BFO and BLHFO samples both have polyhedral Fe₂O₃ grains precipitated along with the melting and further grow in the cooling process. Based on the results by SEM, a continuous Bi₂O₃ phase is mixed with a small amount of micron-sized Fe₂O₃ grains and a large amount of micron-sized BiFeO₃ grains. BiFeO₃ grains in the undoped samples are irregular, while La-Ho doped samples form regular cubic BiFeO₃ crystals. In addition, Fe₂O₃ grains in the co-doped sample only contain La element. La and Ho can be co-doped into BiFeO₃ polyhedral grains.

A single planar solid oxide fuel cell model considering various temperature-dependent physical and chemical properties of the materials was proposed via multi-physics coupling based on the COMSOL multiphysics simulation platform. The effects of residual stress and nickel volume fraction in the anode material on the internal thermal stress of the fuel cell were investigated. The results show that the existence of residual stress increases the maximum tensile and compressive stresses of the electrolyte and the cathode electrode under working conditions, reduces the maximum tensile stress of the anode electrode and increases its maximum compressive stress. The increase in the volume fraction of nickel in the anode electrode firstly decreases and then increases the maximum tensile stress of each component of the SOFC. The optimal percentage of nickel volume fraction in the anode electrode is 40%-60%.

Solution-based approaches are regarded as one of great potential methods for preparing Cu₂ZnSn(S,Se)₄ thin film solar cells due to the advantages of simple operation, high material utilization, and low material cost. This review systematically summarized recent development on the solution-based approaches for preparing Cu₂ZnSn(S,Se)₄ thin film solar cells, i.e., spray pyrolysis, bath-based aqueous solution, nanoparticle solution and direct solution coating methods. Recent research results on solution-based high-efficient Cu₂ZnSn(S,Se)₄ thin film solar cells based on the optimization of cation ratio, sintering conditions and selenium conditions, as well as Na, Ge and other metal elements doping were represented. This review gave the advantages and problems in the process of solution-based preparation. t In addition, the future research could also focus on membrane composition and reaction pathway, as well as some effective methods to reduce the intrinsic defects of Cu₂ZnSn(S,Se)₄ absorber layer.

A series of porous carbon based supercapacitor electrode materials (GCO600) were synthesized via simple oxidative carbonization (GCO) with K₂CO₃ activation using grapefruit peel as a resource. The optimized product GCO600-14 has massive network pores and a specific surface area of 661.7 m²/g. In the three-electrode system, the specific capacitance of GCO600-14 is 413 F/g at 1 A/g, and the specific capacitance can still reach 289 F/g when the current density increases to 30 times, which is 70% of the initial value. The cycling stability has a capacitance retention of 96% after 5 000 cycles. For GCO600-14//GCO600-14 symmetric supercapacitor, the energy density is 26 (W·h)/kg at a power density of 720 W/kg and 20.2 (W·h)/kg at a power density of 20 800 W/kg, respectively. It is indicated that GCO600-14 could have potential application prospects in environmentally friendly energy storage materials.

A composite with low crystallinity nickel manganate (NiMn₂O₄) on reduced graphene oxide (rGO) was synthesized by a solvothermal method. Velvet-like NiMn₂O₄ was deposited evenly on rGO nanosheets. The coverage of NiMn₂O₄ effectively prevents agglomeration between graphene flakes. The NiMn₂O₄/rGO composite has a large specific surface area and an excellent electrical conductivity due to the unique structure, and the specific capacitance is 1 675 F·g^-1 at 1 A·g^-1. The specific capacitance retention rate of NiMn₂O₄/rGO nanoflowers composite is 91% at 5 A·g^-1 after 2 000 cycles.

The nano-crystalline ferroelectric films composed of BiFe_0.95Mn_0.05O₃ and Bi_0.9Nd_0.1FeO₃ were fabricated on the fluorine-doped tin oxide/glass substrates via the simple and cost-effective chemical solution deposition method combined with spin-coating and the subsequent layer-by-layer annealing technique. Microstructures and ferroelectric properties of the samples were investigated. Results show that either BiFe_0.95Mn_0.05O₃ or Bi_0.9Nd_0.1FeO₃ film has a single polycrystalline perovskite phase structure with fine and homogeneous grains and smooth surface in addition to a compact and dense structure. Both film samples exhibited well-saturated polarization-electric field hysteresis loops. Especially, the BiFe_0.95Mn_0.05O₃ film showed more preferential upward polarization orientation and superior ferroelectric properties than the Bi_0.9Nd_0.1FeO₃ film, which was reflected by a high remanent polarization (P_r) of 60 μC·cm^-2 and stable ferroelectric responses to frequency and temperature in the ranges of 1 to 50 kHz and 25 to 200℃ in addition to retention capability of 1×10³ seconds and fatigue endurance over 1×10⁹ cycles.

Two-dimensional titanium carbide (Ti₃C₂T_x) material with an organ-like morphology was prepared by a selective etching reaction strategy, and the surface-treated Ti₃C₂T_x samples were obtained by O₂-Ar microwave plasma technology under different temperatures to regulate the terminal functional groups. The microstructure evolution and surface oxygen functional group changes of Ti₃C₂T_x were investigated at different plasma treatment temperatures. The effect of activated Ti₃C₂T_x on gaseous formaldehyde, benzene, toluene and xylene were analyzed. A possible gas-sensing mechanism was discussed based on the perspective of the variation of the surface oxygen functional groups. The results show that O₂-Ar plasma treatment can increase the content of surface oxygen functional groups of activated Ti₃C₂T_x. The gas sensitive response of a sample treated by plasma at 500℃ can reach 169 for 0.01% formaldehyde at an optimal operating temperature, and this sample also exhibits a good selectivity to gaseous formaldehyde.

In order to improve the photocatalytic oxidative desulfurization (PODS) activity of TiO₂, a composite of TiO₂ and g-C₃N₄ was supported on bimodal mesoporous silica (BMMS) to synthesize TiO₂-g-C₃N₄/BMMS. The dodecane solution of dibenzothiophene (DBT) was used as a simulated oil to evaluate the catalytic performance of the samples. The reaction conditions were optimized and the catalytic reaction mechanism was proposed. The results show that TiO₂-g-C₃N₄/BMMS has a bimodal mesoporous structure. As an active composite, TiO₂-g-C₃N₄ can be dispersed on BMMS. Compared to pure TiO₂, the light absorption ability of TiO₂-g-C₃N₄/BMMS is enhanced and the catalytic activity is improved. The desulfurization rate of TiO₂-g-C₃N₄/BMMS obtained under optimized reaction conditions (i.e., the catalyst amount of 3% (in mass fraction), the molar ratio of O∶S of 10∶1, and the volume ratio of solvent to oil of 1∶1) can reach 96.6%, and the desulfurization rate remains more than 85% after 8-run repeated reactions. The main active species in the PODS process are ·O₂^- and h⁺.

Titanium dioxide based organic-inorganic hybrid film containing azobenzene was prepared by a sol-gel technique and a spin-coating method. The surface morphology, transmission mode, refractive index, thickness and photochemical structural properties of the hybrid film were characterized at different heat-treatment temperatures. The results show that the hybrid film is a good optical waveguide material with the smooth and dense surface. Also, the refractive index is adjustable when the heat-treatment temperature is lower than 300℃. The absorbance of the sample irradiated by a ultraviolet light at 365 nm and a visible light at 450 nm was examined to investigate the optical switching property of the hybrid film. It is indicated that the hybrid film has good optical switching properties. In addition, the hybrid film with a fatigue resistance also has promising application prospects in photonics.

Zinc oxide (ZnO) is widely used as a photocatalyst in the treatment of organic pollutants in wastewater due to its wide bandgap, high photocatalytic efficiency, and stable chemical properties. Based on the results by X-ray diffraction and transmission electric microscopy, synthesized ZnO remains a highly disordered structure because the crystallization of ZnO is suppressed by ultrasonic atomization. Amorphous ZnO nanoparticles were synthesized by a ultrasonic atomization-assisted microwave sintering method. Amorphous ZnO nanoparticles with a highly disordered structure enhance the absorption at a wavelength of 300 nm. The UV absorption of amorphous ZnO nanoparticles shifts to the lower energy side and is greater than that of crystal ZnO nanoparticles. The forbidden bandwidth of amorphous ZnO nanoparticles reduces to 3.17 eV. The photocatalytic efficiency of amorphous ZnO nanoparticles is improved, and the photocatalytic degradation efficiency of amorphous ZnO nanoparticles on Rhodamine B (RB) is 37% greater than that of crystal ZnO nanoparticles. Ultrasonic atomization-assisted microwave sintering method could be an effective method for preparing amorphous ZnO nanoparticles at a low temperature and a low energy consumption. Amorphous ZnO nanoparticles are a highly efficient photocatalyst. However, since the photocatalytic efficiency of amorphous ZnO nanoparticles could decrease with increasing the catalytic cycles, the stability and dispersion of amorphous ZnO nanoparticles should be thus further improved.

This paper mainly investigated a relationship between clay mineral type/clay powder content in crushed dust and methylene blue (MB) value, and analyzed the effect of the adsorption properties of clay minerals on the MB value. The results show that the MB value gradually increases, but is far less than 1.00 with the increase of crushed dust content. Clay powder and mixed clay powders both have an influence on the MB value, showing a linear relationship. Montmorillonite and montmorillonite-based mixed clay powders can affect the MB value, i.e., 8.00 and 4.20, respectively. The maximum MB values of kaolin and illite are 1.75 and 1.05. The maximum MB value of two mixed mud powders with its main components is 2.10 and 1.95. Mixed clay powders with different clay minerals can affect the MB value rather than single clay powder. The methylene blue value is more sensitive to clay mineral type, and the sensitivity in an order is montmorillonite>kaolin>illite. That is, montmorillonite has a greater adsorption capacity.

The Berkovich indenter was used to conduct nanoindentation tests on the (100) and (010) crystal planes of gallium oxide by a constant load method, and the creep stress index of the gallium oxide crystal was obtained by data fitting. The creep stress index of single crystal gallium oxide crystal face (100) ranges from 15.5 to 27.8, and the creep stress index of crystal face (010) ranges from 46.1 to 63.4. The nanoindentation method can effectively determine the creep deformation of gallium oxide. The two crystal planes of gallium oxide show two stages of initial creep and steady-state creep. Among them, the crystal plane (100) has an obvious initial creep. The initial creep phase of the crystal plane (010) is not obvious. The holding load is positively correlated to the creep displacement and equivalent indentation stress of gallium oxide, and has no significant effect on the creep stress index. The creep stress index of different crystal planes of gallium oxide is different. The crystal plane (010) has a larger creep stress index rather than the crystal plane (100), which has a more intense creep resistance and is more suitable for precision machining.

Homogeneous cellulose and hetergenous oak leaves with montmorillonite as a catalyst were used as a biomass to investigate bio-gas and bio-oil. The results show that the loading of montmorillonite promotes the conversion of cellulose pyrolysis to β-elimination pathways, leading to an increase in activation energy and DTG peak temperature, but has little effect on the pyrolysis characteristics of oak leaves. Montmorillonite can catalyze the secondary cracking of biomass pyrolysis liquid products, which reduces the liquid yield and increases the gas yield, but has little effect on the solid product yield. Pyrolysis gases are mainly H₂, CH₄ and CO₂. The surface and layers of montmorillonite contain the Lewis and Brønsted acid sites, which can catalyze the decarboxylation reaction of carboxylic acids in situ and degrade their yield, and has a promoting effect on the furfural and levoglucosenone enrichment of bio-oil.

Zeolite is a kind of aluminosilicate crystal with a regular pore structure, which is widely used in gas adsorption separation, industrial catalysis, and heavy metal ion pollution treatment. The hydrothermal synthesis of zeolite often uses silicon and aluminum-containing chemical products and organic template as raw materials, which is expensive and pollutes the environment. It is thus important to develop green synthetic zeolite using natural clay minerals as a raw material. This review represented recent studies on clay-based zeolite from the aspects of the activation and depolymerization process natural clay, clay-based zeolite of green synthesis process and mechanisms and some application on clay-based zeolite as solid acid catalyst, gas adsorption separation and heavy metal adsorption. In addition, the future work on clay-based zeolite was also given.

A high-purity quartz sand was prepared by a mixed acid leaching method with quartz sand in Donghai County as a raw material, hydrochloric acid, oxalic acid and citric acid as leaching agents. The influences of acid concentration, liquid-solid mass ratio, acid leaching temperature and acid leaching time on the phase structure and leaching efficiency of quartz sand were investigated, and the kinetic model of leaching quartz sand with mixed hydrochloric acid, oxalic acid and citric acid was deduced. The results show that the acid concentration, liquid-solid mass ratio, acid leaching temperature and acid leaching time all have an effect on the efficiency of acid leaching. The mixed acid leaching process follows a diffusion control model, and E_a is 13.22 kJ/mol. Fe content in quartz sand decreases from 342.62 mg/kg to 90.21 mg/kg, and the iron removal rate is 73.67% a after leaching at a hydrochloric acid concentration of 4.5 mol/L, an oxalic acid concentration of 0.05 mol/L and a citric acid concentration of 0.01 mol/L under normal pressure at 80℃ for 6 h. In this case, the total impurity content decreases from 523.79 mg/kg to 194.39 mg/kg, the impurity removal rate is 62.89%, and the purity of SiO₂ is 99.97%, which meets the requirements for the use of crystalline glass.

The phase composition and reaction mechanism of aluminum-spinel (Al-MgAl₂O₄) composite were investigated after being treated at 580℃ for 8 h and 1 700℃ for 3 h in flowing high purity nitrogen. The results show that after being treated at 580℃ for 8 h, the Al-MgAl₂O₄ composite forms an area phenomenon with the aluminum-aluminum nitride (Al-AlN) core-shell structure in the outside area. When the temperature increases up to a critical value, the Al-AlN core-shell structure in the outside area breaks, Al(l/g) reacts with N₂ to form AlN and with O₂ to form Al₂O(g). This process prompts formation of an MgAl₂O₄ spinel with stoichiometric ratio that allows decomposition into Al₂O₃-rich spinel and Mg(g). On the one hand, AlN reacts with Al₂O₃-rich spinel to form MgAlON spinel, and on the other hand, AlN is transformed into (Mg,Al)(N,O) through the solid solution reaction of Mg(g) and O₂(g) into AlN. Phase composition of the inside area is different from the outside area in which MgAlON with flake crystal morphology forms via a gas-gas phase reaction: Al₂O(g)+O₂(g)+N₂(g)+Mg(g)→MgAlON(s) or Al(g)+O₂(g)+N₂(g)+Mg(g)→MgAlON(s) in which Al₂O₃-rich spinel doesn't further form MgAlON spinel.

ZrNiSn bulk thermoelectric materials were synthesized by a self-propagating high-temperature synthesis (SHS) process. Phases and microstructure of ZrNiSn were investigated. Its thermoelectric property was tested. The results show that there are a large number of nuclei and high concentration of dislocation groups and stress fluctuation area inside the dense material, greatly enhancing the phonon scattering and reducing the phonon mean free paths, thus leading to the decreased lattice thermal conductivity of the materials. The thermoelectric properties of the material were optimized, and the ZT value is 0.54 at 873 K.