Lithium cobalt oxide is a leading cathode material for 3C electronic products because of its high bulk energy density, excellent rate capacity and good cycle performance. The existing gram capacity of lithium cobalt oxide material in practical application is approximately 65% of the theoretical capacity, and this material has a potential for further development. In this paper, a lithium ion cobalt oxide cathode material was coated with lithium ion conductor material LiAlSiO4 by a sol-gel method. The effects of LiAlSiO4 and heat treatment temperature on the structure, morphology and electrochemical properties of the material were investigated. The results show that during the heat treatment, Al3+ enters the LiCoO2 lattice to form a solid solution LiCo1-xAlxO2, and an inert coating layer is formed on the surface of the lithium cobalt oxide particles LiAlSiO4 coating, effectively improving the cycle and rate performance of the lithium cobalt oxide material at a high voltage. The optimum overall performance of the lithium cobalt oxide material coated with LiAlSiO4 can be obtained at a heat treatment temperature of 600 ℃. In a voltage range of 2.75-4.55 V, the specific discharge capacity at room temperature at 0.5 C rate is 209.3 mA·h/g, and the discharge specific capacity after 50 cycles is 201.6 mA·h/g (at a capacity retention rate of 96.3%), and the specific capacity is 160.0 mA·h/g at 8 C.

The morphology of nanomaterials can affect their electrochemical performance. It is a challenge to design metal oxide nanostructures with controllable morphology/size and good electrical conductivity for their application in electrochemical supercapacitors and other energy storage devices. NiMn2O4 electrode materials with different amounts of polyvinylpyrrolidone (PVP) were prepared by a co-precipitation method. The effect of PVP (0, 0.2, 0.4, 0.8 g) amount on the microstructure and capacitance properties of NiMn2O4 was investigated. The results show that the microstructure of NiMn2O4 changes from an agglomerated granular to loose flocculent and fine powder with the increase of PVP content. The optimum capacitance performance of NiMn2O4 can be obtained at PVP amount of 0.4 g, and the specific capacitance of NiMn2O4 is 1 464 F/g at a current density of 1 A/g. At PVP amount of 0.8 g, the excessive amount of PVP is easy to cause residue in NiMn2O4 in the cleaning process. During the electrochemical test, the amount of active substances involved in the redox reaction is relatively reduced, leading to the decrease of the capacitance performance of NiMn2O4-0.8. The specific capacitance is 1 010 F/g when a current density is 1 A/g.

SnO2 is widely investigated as one of anode materials for lithium-ion batteries due to its natural abundance, low discharge potential (less than 1.5 V) and high theoretical capacity. However, the low electrical conductivity and large volume expansion (300%) during Li+ insertion/extraction results in the poor cyclability and rate capability of SnO2, thus restricting its practical applications. In this study, SnO2@C/rGO nanocomposites were prepared by an one-step hydrothermal method with SnCl2, L-ascorbic acid and GO as reactants. The L-ascorbic acid-derived amorphous carbon served as a spacer to inhibit the stacking of rGO sheets and acted as a coupling agent to strongly anchor SnO2 nanoparticles on the rGO sheets. The as-obtained SnO2@C/rGO nanocomposite delivers a specific capacity of 731 mA·h/g after 180 cycles at a current density of 0.1 C (1 C= 783 mA/g) and a high reversible capacity of 410 mA·h/g at a large current rate of 5 C. This study provides a promising route for the preparation of high-performance SnO2 anode materials.

Due to the difference of thermal expansion coefficient between the components in the solid oxide fuel cell (SOFC), there are some residual thermal stresses in the cell in fabrication. Introducing the functional gradient layer is an effective technique to relieve the residual thermal stress in fabrication. The residual thermal stress and failure probability were calculated by a commercial package named ANSYS. The effects of gradient distribution factor n, sublayers number w in the gradient layer and gradient layer thickness H on the thermal residual stress and failure probability were investigated. The results show that the functional gradient layer can reduce the stress and failure probability in the cell. The increase of the number of sublayers w has little effect on the decrease of the stress and failure probability when the w number exceeds 2. The optimum w number of sublayers is 2. When the gradient distribution factor n is small, the anode failure probability decreases with the increase of gradient layer thickness. In addition, the gradient parameter for the composition functionally graded anode layer was also optimized.

Gradient anode is an effective way to improve the electrical performance of anode-supported solid oxide fuel cell (SOFC). However, the porosity is closely related to the thermomechanical properties and thermal stress distribution of the anode. It is thus important to investigate the comprehensive effect of porosity on the thermal stress and electrical performance of SOFC. A single planar SOFC model considering various porosity-dependent properties of the materials was proposed via multi-physics coupling based on the COMSOL Multiphysics simulation platform. The electrochemical performance and thermal stress distribution of the SOFC with a gradient-porosity-anode design at working stage were investigated. The results show that the gradient porosity-anode design effectively improves the thermomechanical matching of the positive-electrolyte-negative structure, while maintains the high electrochemical performance of the SOFC. Compared with the usual uniform porosity anode designed SOFC with a porosity of 0.4, the output power of SOFC is increased by 3.5%, while the maximum first principal stress of the electrolyte is reduced by 68.5%. The results of this study provide the theoretical and data supports for optimizing anode structure design of SOFC.

Silver anode for direct carbon solid oxide fuel cell (DC-SOFC) has great chemical stability and resistance to sulfur and carbon deposition. However, the electrochemical performance of DC-SOFC is still unsatisfactory due to the poor catalytic performance. Strontium cobalt doped lanthanum ferrite (LSCF) is an electrode material with good catalytic performance as well as electronic and ionic conductivity. In this paper, silver anode (silver-gadolinium doped cerium oxide, Ag-GDC) was modified with LSCF to improve the catalytic performance of the silver anode and the output performance of the corresponding cell. At 850 ℃, the maximum power density of the corresponding DC-SOFC increases from 224 mW/cm2 to 264 mW/cm2. According to the results by impedance spectroscopy for the corresponding half-cell, microscopic morphology and crystal structure of the electrode material, and constant current discharge tests, the polarization resistance of Ag-GDC decreases from 0.543 Ω·cm2 to 0.373 Ω·cm2, the microstructure and crystal structure of the electrode become stable, and the fuel utilization of the corresponding cell increases from 51.3% to 57.9% after the LSCF modification. Therefore, LSCF-modified Ag-GDC is an ideal anode material for DC-SOFC with good performance and chemical stability, which is expected to promote the further development of DC-SOFC.

Developing cathode materials with superior electrochemical activity is of great importance to the application of intermediate-temperature solid oxide fuel cell (IT-SOFC). In this paper, Bi1-xCaxFeO3-δ (BCFx, x=0.1, 0.2 and 0.3) compounds were synthesized via solid-state reaction as a cathode material for IT-SOFC. The phase structure, electrical conductivity, oxygen transport performance, and the electrochemical performances of these compounds were evaluated. The as-prepared BCFx compounds show a single-phase perovskite structure. Among the BCFx materials, Bi0.8Ca0.2FeO3-δ (BCF0.2) oxide has the maximum electrochemical catalytic activity. The polarization resistance of BCF0.2 cathode on symmetrical cell is 0.06 Ω?偸cm2 at 750 ℃ in air. Meanwhile, the maximum peak power density of Ni-(Y2O3)0.08(ZrO2)0.92(Ni-8YSZ) anode-supported single cell reaches 730 mW?偸cm2 at 750 ℃. As is indicated by the electrical conductivity relaxation, the favorable oxygen reduction reaction catalytic activity of BCF0.2 can be ascribed to the higher oxygen bulk diffusion and surface exchange coefficient. The results of oxygen reduction kinetics reveal that the dissociation of adsorbed molecular oxygen is a limiting step for oxygen reduction reaction on BCF0.2 cathode.

In order to solve a problem of Sn-loss and reduce the thickness of MoS2 during the sulfurization process, the oxygen containing Cu-Zn-Sn precursor thin films were prepared on Mo-coated soda lime glasses via magnetron sputtering ZnO/SnO2/Cu. The results show that the Sn-loss and the formation of MoS2 are well inhibited by the utilization of SnO2 and ZnO. The single-phase CZTS absorbed thin films with the smooth surface, dense grains and good crystal structure can be prepared at 590 ℃. Also, the CZTS solar cells from oxygen containing precursors annealed at 590 ℃ have an optimum power conversion efficiency (PCE) of 5.12% with an open circuit voltage of 590 mV, a short circuit current density of 22.09 mA/cm2 and a fill factor of 39.28%.

It is imminent to develop and utilize solar energy to solve the increasingly serious environmental crisis. In order to improve the utilization rate of sunlight and the performance of photocatalysts, this work innovatively proposed to prepare Z-Scheme MoS2/RGO/Fe2O3 ternary composites by an in-situ growth method combined with a surface electrostatic adsorption method.MoS2/RGO hetero-structured binary composites were firstly synthesized by a hydrothermal method, and then all-solid-state Z-Scheme MoS2/RGO/Fe2O3 photocatalyst was constructed via adjusting the solution pH value to create the same charges of MoS2 and Fe2O3 and the opposite charges of RGO and MoS2. According to the results by scanning electron microscopy and transmission electron microscopy, MoS2 nanosheets and Fe2O3 nanoparticles are uniformly distributed on the surface of two-dimension RGO, and MoS2 nanosheets and Fe2O3 nanoparticles display a stable hetero-structure onto RGO nanosheets. The RGO-based all-solid-state Z-Scheme photocatalyst possesses a superior photocatalytic reduction degradation performance under the simulated solar-driven illumination. Especially, the all-solid-state Z-Scheme photocatalyst MR0.43F has the optimum photoreduction degradation efficiency within 60 min for heavy metal Cr (VI) in a solution as a degradation indicator, which is 1.5 times greater than that of binary MoS2/RGO composites. The all-solid-state Z-Scheme photocatalyst has wide-spectrum absorption, high separation efficiency of photogenerated carriers and surface chemical reaction efficiency, thus improving the photocatalytic properties.

Combining the photocatalytic activity with the superhydrophobicity of coating is an effective approach for the self-cleaning effect. In this paper, the porous aluminum surface was coated with trialkoxy-terminated polydimethylsiloxane/titanium dioxide (PDMS/TiO2) coating (APT) by a solution immersion method. According to the analysis by Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy, a bond (Ti-O-Si) between PDMS and TiO2 is formed. The results by scanning electron microscopy and energy dispersive spectroscopy show that the superhydrophobicity is due to the interconnected hierarchical sheet structure and the PDMS with a low surface energy. The surface of APT coating has a stable superhydrophobicity with a water contact angle (WCA) of 161.6° and a sliding angle of less than 10°. The stability of superhydrophobicity with WCAs greater than 150°remains after 24 h ultraviolet irradiation. The ATP coating has an effective photocatalytic activity and an ability to degrade dyes and remove some organic substances on the surface.

Cordierite glass-ceramics exhibit low dielectric constant, dielectric loss and thermal expansion. The stoichiometric cordierite MgO-Al2O3-SiO2 (MAS) glass is due to the surface crystallization. In this paper, MAS glass-ceramics with various contents of TiO2 as a nucleation agent were prepared by a melting method and subsequent heat treatment. The effect of TiO2 content on the crystallization behavior and properties was investigated. The results show that the glass transition temperature and the first crystallization peak temperature decrease with the increase of TiO2 content, indicating that TiO2 can effectively promote the crystallization. TiO2 enters into the glass network structure, and facilitates the formation of μ-cordierite and magnesium aluminum titanate crystalline phases in the glass, and then form α-cordierite at a higher temperature. The crystallization mechanism of glass with more than 5% (in molar fraction) TiO2 becomes the bulk crystallization. As TiO2 content increases to 10%, the glass-ceramics heat-treated at 800 ℃ for 10 h and 1 000 ℃ for 5 h have a high density of 2.95 g/cm3, a hardness of 9.67 GPa, and a thermal conductivity of 2.13 W/(m·K). At 8.2-12.4 GHz, its dielectric constant is 6.3-6.5 and the dielectric loss fluctuates from 10-2 to 10-3. At 1 MHz, the dielectric constant is 10.8 and the dielectric loss is 0.024 4.

Nb2O5 has a variety of crystalline states. However, the intermediate process of forming a long-range ordered structure is still unclear. Nb2O5 precursor was prepared by a sol-gel method. The intermediate-state samples in the crystallization of amorphous Nb2O5 were obtained at 460 ℃-520 ℃. The crystal structure, morphology, pore structure and crystallization kinetics of the intermediate-state samples were investigated. The results show that the atomic ordering process of the sample is from 1.0 nm short-range order with an amorphous state, to 1.0 nm short-range order with a small amount of crystal and amorphous mixed state, to 1.5 nm medium-range order with a pseudo hexagonal and amorphous mixed state, and then to more than 2.0 nm long-range order with a pseudo hexagonal, orthorhombic and a small amount of amorphous mixed state. The crystallinity of the samples at >495 ℃ increases rapidly from 20% to 86%. The samples are formed due to the crisscross accumulation of massive flaky particles and a small amount of rod-shaped particles. From a short-range order to a long-range order, the growth process of flake particles is the main process, while the rod-shaped particles have little change. The particles are mesoporous, and the size of the main pore becomes 10 nm as the calcination temperature increases. The Avrami index (n) of the samples is 1-2, and the main nucleation mode is the surface nucleation. During the transformation from short program to medium program, there exists a crystallization incubation period. This study provides a working basis for the investigation of Nb2O5 crystallization intermediate state.

Statistical structure modeling can help to establish the glass formulation design models to meet the vitrification requirements of different types of high-level waste liquids due to its advantages of high efficiency and accuracy. Taking the glass transition temperature Tg, thermal expansion coefficient α and element leaching rate of Li, Na, B as target properties, we utilized a statistical structure simulation method for the development of nuclear waste glass curing formula. The results show that Tg, α and chemical stability of the glasses can be well simulated with the statistical structural data. It is also indicated that the data predicted by the model are in a reasonable agreement with the measured results at a simulation desirability 0.94. Statistical structure modeling can assist to establish the formula database of the high-level liquid waste vitrification.

The infrared films with ultra-high reflection is the key and basic materials for the realization of low loss optical device, infrared stealth, etc.. According to the transmission matrix principle of multilayer optical films, the reflectance and transmittance expressions of one-dimensional photonic crystals were obtained, and the energy band structure of one-dimensional photonic crystals was analyzed. Using the principle of transmission matrix, we designed a 28-layer λ/4 one-dimensional photonic crystal structure with Ge and SiO2 as dielectric materials. Also, the first and second band gaps of the photonic crystal calculated by the finite element method to be 2.01×1013~4.11×1013 Hz and 8.13×1013~1.02×1014 Hz, respectively. The optimized λ/4 one-dimensional photonic crystal structure has as low as 14 layers, thus achieving high reflections of 3~5 μm and 8~14 μm.

Carbon foam composites with a unique porous structure can be widely used in the fields of thermal insulation, energy storage, and absorption. In order to improve their mechanical and thermal-insulation properties, carbon foam composites were modified. Silica (SiO2) aerogels reinforced carbon foam composites were prepared via compression molding and carbonization with zirconium modified phenolic resin as a carbon origin, SiO2 aerogels as a reinforcement, and phenolic hollow microspheres as a closed phase. The effect of SiO2 aerogels amount on the microstructure, compressive and oxidation resistance of carbon foam composites was investigated by scanning electron microscopy, universal testing machine, specific surface area analysis and pore size distribution measurement, respectively. The thermal conductivity of pure carbon foam and modified carbon foam composites were characterized by laser-flash thermal conductivity measurement, and their high-temperature heat transfer behavior was then analyzed. The results show that SiO2 aerogels disperse in the ligaments or on the surface of microspheres, and barely contribute to cell structure of carbon foams. When the SiO2 aerogels amount is 2% (in mass fraction), the maximum compressive strength and specific compressive strength both reach 19.39 MPa and 42.17 MPa·cm3/g, respectively. Compared to the pure carbon foam, the compressive strength and specific compressive strength of carbon foam are increased by 106.7% and 79.8%, respectively. A proper addition of SiO2 aerogels can restrict the heat transfer path and internal radiative heat transfer. When the SiO2 aerogels amount is 5%, carbon foam composites have the optimum thermal insulation and oxidation resistance. The thermal conductivity at 800 ℃ is 0.447 W/(m·K), which is 38.9% lower than that of pure carbon foam. The optimum oxidation resistance can be obtained, i.e., the mass loss of 18% during the isothermal oxidation at 700 ℃ for 30 min.

Improving the thermal stability of silica (SiO2) aerogel plays a crucial role in expanding its heat insulation application. In this work, heat treatment in argon atmosphere was adopted to avoid the thermal oxidative decomposition of hydrophobic groups, which inevitably occurred in the heat treatment in air atmosphere. Also, the physicochemical properties were analyzed. The results show that the hydrophobicity of SiO2 aerogels still maintains at a contact angle of 140° after heat treatment in argon atmosphere at 700 ℃. In the differential scanning calorimetry test in air atmosphere, the peak temperature in exothermic reaction (Tpeak) of heat treated SiO2 aerogels reaches 584 ℃, which is approximately 300 ℃ higher than that of untreated SiO2 aerogels, thus improving the thermal stability. The results obtained also indicate that hydrophobic SiO2 aerogels could be used at high temperatures due to the improved thermal stability and safety.

Geopolymers have a low immobilization efficiency to oxyanions, such as Se(VI) and Cr(VI). Effects of Ca, Mg and Fe(II) additives on the immobilization of Se(VI) and Cr(VI) in geopolymer were thus investigated. The results indicate that the leaching amount of Se or Cr ions is greater than 60% for the geopolymers without any additives. CaO or Fe(II) has a limited depressive effect on Se(VI) or Cr(VI) leaching from geopolymers, and the corresponding leaching amount of Se(VI) or Cr(VI) is still greater than 40%. However, the leaching amount of Se(VI) or Cr(VI) is lower than 10% for the geopolymers with the addition of MgO. According to the LCF fitting results, Cr(VI) can also exist in the geopolymer network through electrostatic interaction as Se(VI). Besides, MgO or CaO can promote Fe(II) to release its reducibility, thereby reducing approximately 15% of Cr(VI) to Cr(III). Se(VI) can have a bonding interaction with Ca. Fe(II) does not present its reducibility during the solidification of Se(VI). To some extent, MgO, CaO and Fe(II) have a synergistic effect on the leaching of Se(VI) and Cr(VI) from geopolymers. In addition, the mechanical strength of geopolymers with or without these additives can satisfy a requirement for industrial landfill.

Methyltrimethoxysilane (MTMS) based silica aerogels (MSA) with a controllable skeleton size were synthesized in pure water via adjusting the cetyltrimethylammonium bromide (CTAB) content. The results show that the content of CTAB has little effect on the surface chemical composition of MSA, while the skeleton size and pore size of MSA decrease with increasing the CTAB content. The average skeleton diameter (d) of MSA decreases from 2.39 μm to 0.55 μm, and the adsorption capacity for organic liquids decreases simultaneously when the CTAB content increases from 0.01 g to 0.03 g. When the CTAB content is 0.01 g, the as-prepared MSA has good adsorption properties for alcohols and alkanes, where the maximum adsorption capacity reaches 10 g/g, the adsorption rate of the pumping application is 1.04 g/s, and the capillary rise speed of organic liquids can reach 2.1 mm/s. Furthermore, the high thermal stability (456 ℃) of MSA ensures the realization of thermal desorption. A preparation method of MSA with a controllable skeleton size to obtain aerogels with specific adsorption properties.

In this paper, the adsorption behavior and mechanism of Cu2+、Pb2+、Zn2+ and Mn2+ ions in the leachate of polymetallic sulfide tailings with vermiculite from Yuli Xinjiang, China were investigated. The results indicate that the adsorption capacities of vermiculite for Cu2+, Pb2+, Zn2+, Mn2+ ions are 49.53 mg/g, 108.00 mg/g, 44.11 mg/g, 32.47 mg/g, respectively, and the monolayer adsorption process follows the Langmuir isothermal adsorption model. The adsorption mechanism is due to a combined effect of interlayer ion exchange, surface static electricity and surface complexation. Vermiculite as a filler reaches the equilibrium concentration for 528 h, and the running time is longer under the dynamic adsorption condition. This work can provide a guidance for the design and optimization of vermiculite as an adsorbent for removal of heavy metal ions in groundwater.

Hexavalent chromium (Cr(VI)) has attracted much attention due to its high toxicity. In order to improve the efficiency of Cr(VI) removal by adsorption, core-shell structured polyethyleneimine (PEI) functionalized composite nanoparticles (Fe3O4@SiO2-NH2) were synthesized to remove Cr(VI) in water. The chemical structure, morphology and magnetic properties of the nanoparticles were investigated. The effects of initial concentration, contact time, solution pH value and inorganic anions on the Cr(VI) adsorption efficiency were analyzed. The results show that Fe3O4@SiO2-NH2 has an excellent performance in removing Cr(VI), and its maximum adsorption capacity is 251.83 mg/g. The adsorption process is pH value-dependent, spontaneous, and endothermic. Fe3O4@SiO2-NH2 is protonated, and the adsorption of Cr(VI) is completed due to the electrostatic attraction. Also, according to the results by X-ray photoelectron spectroscopy, part of Cr(VI) can be reduced to low-toxic Cr(VI). Fe3O4@SiO2-NH2 has a good reusability after removing Cr(VI) in water, and the duration for effective magnetic separation after the removal is just 50 s.

Zeolite chabazite (CHA) membranes with a higher Si/Al mole ratio in the zeolite framework were prepared to improve their stability and separation performance. Pure zeolite CHA membranes were synthesized with imidazolium-based ionic liquids (ILs) as a structure-directing agent, which could improve the Si/Al ratio in the framework. ILs could be used repetitively at least 3 times for the synthesis of high-crystallinity zeolites. Under the optimized synthetic conditions, a continued zeolite CHA membrane obtained from an initial gel containing 1-buthyl-3-methylimidazolium bromide (［Bmim］Br) on the mullite tubular supports has a high water flux of 6.3 kg/(m2·h) with a high ion rejection (100%) for pervaporation (PV) separation of 3.5% (in mass fraction) NaCl aqueous solution at 75 ℃. The effects of temperature and feed concentration on the desalination performance of ILs-CHA membranes were also investigated. The water flux increases to 10.3 kg/(m2·h), and their salt rejections are 100% when the operating PV temperature increases at 90 ℃. Zeolite CHA membranes prepared have the superior separation performance even for desalination of 10% NaCl aqueous solution. Furthermore, the ILs-CHA zeolite membrane has a stable separation performance with a stable water flux as well as a high salt rejection in 3.5% NaCl aqueous solution at 75 ℃ for 3.5 d.

The tetrahedral amorphous carbon (ta-C) films were fabricated by 45° double-bent filtered cathodic vacuum arc technique, and the wettability, surface energy, roughness, surface topography, friction coefficient and microstructure evolution of ultrathin ta-C film as functions of incident angles of carbon ions were investigated. The results reveal that as the incident angle of carbon ions increases from 0° to 60°, the water contact angle of films slightly increases from 77.6° to 82.4° and the glycerin contact angle of films slightly increases from 64.7° to 71.2°, indicating that all the films are hydrophilic. The total surface energy decreases from 33.9 mJ/m2 to 28.0 mJ/m2. The slight increase of observed contact angle is attributed to the decrease of surface energy and increase of surface roughness. Also, the average friction coefficient increases from 0.140 to 0.217. According to the near edge X-ray absorption fine structure data, little change for the hybridized sp3 bond content in the deposited ta-C films appears, regardless of the change of incident angle in a range of 0°-60°.

Calcium silicate hydrate (C-S-H) gels shrink upon drying and swell upon on wetting due to the specific water sensitivity, making that the pore structure of cement-based material depends on its water content. The representativeness and accuracy of the pore structure characteristics and its development obtained in a totally dry state are questionable because of the influence of drying preconditioning. To explore the evolution of pore structure of cement-based materials with respect to water to cement (w/c) ratio, several typical white cement mortars were investigated by low-field nuclear magnetic resonance (LF-NMR) and mercury intrusion porosimetry (MIP). Meanwhile, their permeability coefficients to water were also measured. The results show that the discrete pore size distribution (PSD) achieved by LF-NMR in a water-saturated state can be used to predict the water permeability through a classical Kozeny-Carman model based on the parallel cylindrical pores. The effect of w/c ratio on the pore structure of water-saturated mortars is consistent with that on the water permeability. However, the PSD curves measured by MIP scatter remarkably, which cannot reflect the effect of w/c ratio on the pore structure of mortars. As a result, the pore structural characteristics obtained in a dry state are limited, which makes the typical pore classifications questionable. Since the pore structure plays a fundamental role in interpreting almost all the properties of hardened cement-based materials, it is essential to detect the more relevant pore structure in a water-saturated state through LF-NMR to avoid the effect of drying preparation.

To reveal the law of influence of hybrid fibers on the mechanical properties and deformation behavior of strain hardening cementitious composites (SHCC), the tensile and compressive properties of basalt-polyvinyl alcohol(PVA) fiber strain hardening cementitious composites (SHCC) were investigated at a constant fiber content of 2% (in volume fraction), different content ratios of basalt fiber and PVA fiber (i.e., 3:1, 1:1 and 1:3), and different ratios of fly ash to cement (FA/C) (i.e., 1.2, 1.5 and 2.0). The direct tensile and compressive strengths of hybrid fiber SHCC with different fly ash contents were analyzed. The horizontal and vertical strain evolution and crack development of the sample during compression were discussed via digital image correlation (DIC). The results show that the compressive strength of the mixed fiber specimens is greater than that of the single fiber specimens, indicating that the hybrid fiber can effectively improve the compressive strength. At FA/C ratios of 1.2 and 1.5, the optical fiber type is B0.5P1.5 (i.e., the volume fraction of basalt fiber is 0.5% and PVA fiber is 1.5%). At a FA/C ratio of 2.0, the optical fiber type is B1P1. The optical fiber type is different for different fly ash admixtures, indicating that the fly ash admixture affects the optical fiber type. In the hybrid fiber specimens, basalt fibers mainly play a role in improving the strength, but it is not suitable for the ductility of the material. In contrast, incorporating PVA fibers can effectively enhance the material's ductility, the addition of hybrid fibers can enhance the mechanical properties. The DIC can effectively characterize the strain evolution and crack formation and propagation process of the material, thus providing an effective method for investigating the material damage and crack evolution in the loading process.

In recent years, research concerning layered double hydroxides (LDHs) topological transformation materials in the field of photocatalysis and electrocatalysis, such as hydrogen production, and chemical transformation of C1 species, has been widely reported. Research shows that not only the dispersion of active site can be improved, but also phase composition, specific crystal plane and interface structure can be regulated by selecting different calcination temperature, atmosphere and other topological transformation conditions. This kind of materials thus exhibits superior performance in catalytic conversion and utilization of various energy sources. In this review, we will introduce the process and mechanism of LDHs topological transformation, and then review the research progress of LDHs topological transformation materials in energy catalysis from the aspects of photocatalysis and electrocatalysis.

The energy crisis and environmental pollution are the existing global problems for humanbeings. It is a priority to reduce the emission of carbon dioxide (CO2) and other greenhouse gases and to achieve carbon neutrality. The “artificial ecological cycle” for “(energy supply-storage-consumption-resupply)” enables to recycle and obtain material and energy via the consumption of CO2 to alleviate these problems. Aerogels with a ultra-high porosity, a large specific surface area and a ultra-low density, and a continuous three-dimensional network structure can provide abundant charge transfer channels, and can be used as carriers to dope or load various organic or inorganic active materials to obtain composite materials with excellent catalytic performance for a wide range of applications in “artificial ecological cycle” system, i.e., photochemistry, electrochemistry, energy storage materials and other fields. In this review, we outlined the relevant applications of aerogels in photochemistry, electrochemistry, artificial nitrogen fixation, hydrogen storage and thermoelectric materials in the artificial ecological cycle, as well as outlooked the development prospects of aerogels.

Solar arrays can convert light energy into electrical energy as an important component of spacecraft energy systems. And solar cells made of photovoltaic effect are an important carrier of energy acquisition. Through the development and application from Si solar cell to GaAs solar cell and from single junction to multi-junction technology, this review analyzed the current situation and bottlenecks of various space solar cells combined with the lattice mismatch, multi-node growth, flip-chip structure and thin film solar cell preparation technology. According to the structural composition and rigidity of the substrate, the characteristics and future development directions of body-mounted, rigid, semi-rigid, flexible and concentrator solar arrays were described to provide a technical support for the realization of high efficiency, light weight, high quality power ratio battery circuit energy function.

Ti3C2 MXene is a novel two-dimensional carbide with an accordion-like lamellar structure. The flakes of Ti3C2 MXene can slide or stack under tension or compression, which can change the number and length of internal conductive paths and directly affect the output electrical signals. Thus, Ti3C2 MXene can be used as sensing materials to measure the change of stress/strain. Combined with the elastic substrates, this material is used to make flexible sensors to monitor the motions and health signals of human-beings. This paper described the working principle of flexible stress/strain sensors made by Ti3C2 MXene composites. Recent methods to prepare the sensors were reviewed, i.e., electrospinning, filtration/coating, impregnation, screen printing, freeze drying, and freeze thawing. The key factors of the methods, i.e., flexible substrate, sensing parameters, sensor structure, detection limit, cycle times, sensing rage, responsive time and gauge factor, were represented. Some applications of the MXene-based sensors were discussed. Finally, the promising development of Ti3C2 MXene flexible sensors was outlooked and the problems to be solved were summarized.