Single-crystal sapphire fibers with diameter of 400-1000 μm and length of 500 mm were successfully grown by the edge-defined film-fed growth (EFG) method. The cross section is roughly circular without noticeable faceting on the lateral surface of the fiber. The diameter variation was within 40 μm in the whole fiber. Crystal defects such as micro-bubbles, inclusions and growth stripes were observed and analyzed. Most micro bubbles in the crystal are spherical and exist on the periphery of the fiber. A small amount of Mo inclusions were observed on the periphery of the fiber. The new dies produce greater number of Mo inclusions at the first several uses, and Mo inclusions decrease after several uses. Size and distribution of micro-bubbles in sapphire fiber have been studied by experimental and numerical simulation of the fluid flow in the meniscus. Results of experimental and numerical simulation presented excellent agreement. The micro-bubbles distribution depends on the fluid flow in the meniscus. Vortex of the fluid flow drove these micro-bubbles to move to the atmosphere under thermo-capillary convection. Absorption loss at 633 nm was 9 dB/m. Inclusions and surface irregularities increase the scattering losses.

Ceramic coatings can effectively prevent the corrosion of steel bars in marine environments. In this study, we prepared phosphate ceramic coatings on the surface of carbon steel. X-ray diffraction and X-ray fluorescence were used to analyze the phase structure and composition of the ceramic and the results show that the main crystal composition of ceramic is P2O5 and SiO2. Scanning electron microscopy was used to characterize the morphology of the surface and the section and results showed that the surface was cracked, and the thickness of ceramic was 349 μm. Meanwhile, a number of high-resolution images of internal structure of solids were obtained by non-destructive X-ray computed tomography (X-CT). Matlab and Mimics software were used to conduct the three-dimensional reconstruction of the CT images. Matrix and holes are distinguished by threshold segmentation in grayscale images, and the porosity of the ceramic coatings was calculated to be 14.0%. In addition, mercury intrusion porosimetry was used to verify the calculation results. Therefore, X-CT can be a useful and reliable tool for the visualization of the internal structure of ceramic coatings.

To reduce the F deficiency defect in MgF2 thin films deposited with magnetron sputtering, SF6 was added to the working gas Ar2 as the reactive gas, and MgF2 thin films were prepared on quartz glass substrates with radio frequency (RF) magnetron sputtering. The effects of sputtering power on the chemical compositions, microstructure and optical properties of MgF2 thin film were investigated. The results show that with sputtering power increase from 115 to 220 W, the atomic ratio of F to Mg increased continuously, and reached 2.02 at 185 W, close to ideal stoichiometric ratio of 2: 1. The crystallinity of MgF2 film improved first, then decreased, and finally changed into amorphous state. Profile of particles composing MgF2 film became clearer at first, and finally became blurred. Refractive index of MgF2 film decreased firstly and then increased, and got the lowest value at 185 W, 1.384 at 550 nm wavelength which is very close to that of MgF2 bulk crystal. The integral transmittance of the coated glass within 300-1100 nm (hereinafter referred to as the transmittance of the thin film) increased first and then decreased, and reached 94.99% at 185 W, higher than that of the bare glass substrate by 1.79%.

BiVO4 film was synthesized via template method, the ferroelectric material BiFeO3 was prepared by Sol-Gel method to modify BiVO4. By means of dual-ferroelectric semiconductor composition, the photochemical properties of BiVO4 was greatly improved. The electrochemical test results show that the superior photoelectrochemical properties of BiVO4 film are achieved after spin-coating with BiFeO3 for 5 times. It owns an optimal photocurrent density of 0.72 mA·cm-2, which is 67.4% higher than that of pure BiVO4. The energy band bending regulation via electric field polarization could further boost the photoelectrochemical property of BiVO4/nBiFeO3 ferroelectric composite. The highest photocurrent density of the composite after polarization at 20 V reaches 0.91 mA·cm-2, which is more than twice of pure BiVO4 film. The combination of BiFeO3 and BiVO4 is favorable for forming heterojuncting, generating and separating of photogenic electrons and holes. The electric field polarization regulating band bending accelerates the photogenic charge transfer, which is the main reason for the improved photoelectrochemical properties of ferroelectric composite.

Electronic structure and photocatalytic performance of 2D novel Zr2CO2/InS heterostructure was systematically investigated using first principle calculations. The calculated results demonstrate that the Zr2CO2/InS heterostructure is a direct bandgap semiconductor with a lattice mismatch less than 3% and a formation energy of -0.49 eV, indicating a stable structure. Band gap of the Zr2CO2/InS heterostructure is 1.96 eV, which should have a wide visible light absorption range, and the absorption coefficient is up to 105 cm-1. The heterostructure has a typical type-II band alignment, and its valence band and conduction band offsets are 1.24 and 0.17 eV, respectively, demonstrating the transfer of photo-generated electrons from Zr2CO2 layer to InS layer and vice versa for holes, which indicates that the electrons and holes can be separated effectively in space. In addition, InS is an indirect band gap semiconductor material, which can further reduce the recombination of electrons and holes. Therefore, the novel Zr2CO2/InS heterostructure is a potential visible-light photocatalyst.

Hierarchically porous silica-aluminum is an important support material for metal-catalysts, because of its excellent properties. Herein, an efficient hydrothermal approach for the production of hierarchical aluminum- doped silica (Al-SiO2) architectures was reported by employing aluminum nitrate as an aluminium source and TEOS as silicon source. Effects of the structure-oriented agent on the structure of Al-SiO2 were investigated. Structural features of Al-SiO2 were characterized by XRD, SEM and N2-physisorption. The results showed that hierarchical Al-SiO2 with "worm-like" porous of 30-40 nm can be synthesized by using TPAOH as the structure-oriented agent and hydrothermal treatment at 80 ℃. The cobalt catalysts were prepared by the wetness impregnation method. Compared with commercial SiO2 supported cobalt catalysts, the Fischer-Tropsch synthesis performance of the catalyst Co/Al-SiO2 is significantly enhanced, i.e., CO conversion nearly doubled, CH4 selectivity reduced by 19.3wt%, C2-C4 selectivity reduced by 13.3wt%, and the selectivity of gasoline products (C5-C12) reached 53.3wt%.

Phosphorus is an important nutrient element that affects the growth of algae. The sorption of phosphorus on the sediments plays an important role in its bio-geochemical cycle, with metal oxides such as alumina being one of the important active components for the process. The sorption behavior of phosphorus on two kinds of alumina (γ-Al2O3, amorphous alumina) was studied through batch methods. Both kinetics and thermodynamics of the process were investigated, as well as the effects of temperature, salinity, and pH of the medium on the process. The sorption kinetic curves could be described by a two-compartment first order equation, and the isotherms fit Freundlich equation well. The amorphous alumina has a larger specific surface area, and its sorption ability is stronger than that of γ-Al2O3. Based on the results of surface acid-base titration, the sorption behavior is also considered to be related to the surface acidity and alkalinity of the aluminum oxides. Compared with NaNO3 medium, the sorption of phosphorus in seawater was weakened. The sorption capacity decreases with the increase of the ionic strength. pH significantly affected the sorption ability of the oxides with the maximum capacity at pH=5. Higher temperatures are favorable to the sorption progress, which is endothermic and spontaneous with entropy increasing. The difference in the thermodynamic parameters of the two alumina seemed unremarkable.

CoFe2O4 nanofibers with fishbone-like structure were prepared by a electrospinning method followed with high temperature calcination, using polyvinylpyrrolidone (PVP), iron nitrate nonahydrate (Fe(NO3)3·9H2O) and cobalt nitrate hexahydrate (Co(NO3)2·6H2O) as raw materials. Results show that the crystallinity and grain size of nanofibers become larger with increasing calcination temperature. Meanwhile, the surface morphology of CoFe2O4 nanofibers changes from smooth to rough and porous. The morphology of CoFe2O4 nanofibers exhibits a fishbone-like structure with calcination temperature exceeding 800 ℃. The diameter of the fiber is gradually decreased with the increase of calcination temperature, and the average diameter of CoFe2O4 nanofibers calcined at 900 ℃ reaches 80.3 nm. By vibration sample magnetometer (VSM) test, the saturation magnetization (Ms) of CoFe2O4 nanofibers increases with the increase of calcination temperature, and the Ms of CoFe2O4 nanofibers calcined at 900 ℃ is 87.13 A·m2/kg. In a result of vector network analyzer (VNA) analysis, the microwave absorption performance is significantly different with calcination temperature changing. Among them the fibers calcined at 800 ℃ have the highest wave absorption ability. The microwave absorption mechanism of CoFe2O4 nanofibers mainly includes hysteresis loss and eddy current loss. The morphology of porous and fishbone-like generated by calcination can increase the reflection loss, for the reason that this morphology is beneficial for microwave reflection multiple times on the fiber surface.

In order to investigate the influence of precursors on impregnation behaviors of C/SiC composites, C/SiC composites (C/SiC-0,C/SiC-Ⅰand C/SiC-Ⅱ) prepared with three different precursors (solid polycarbosilane, PCS(s)), liquid polycarbosilane PCS-Ⅰ(l) and PCS-Ⅱ(l)) were prepared via precursor infiltration and pyrolysis (PIP) method. Impregnation behaviors of different precursors were studied to mainly focuse on the combination of mechanical properties as well as microstructures of C/SiC composites with different PIP cycles. Results showed that C/SiC-Ⅰ composites exhibited the highest flexural strength of 336 MPa. The microstructures of C/SiC composites showed that the internal pores of C/SiC-0 composites were distributed between carbon fiber bundles, C/SiC-I composites were dense and the pores were evenly distributed. The pores of C/SiC-II composites were inside carbon fiber bundles and SiC matrix. Gel permeation chromatography (GPC) results showed that due to the difference of molecular weights of the impregnating solution, the macromolecules cannot impregnated into the carbon fiber bundles, which resulted in the lack of SiC matrix and degradation of mechanical properties for the composites after PIP cycles.

Metal-organic frameworks (MOF) as piezoelectrical materials used in mechano-catalytic degradation of organic dye are rarely investigated. In this work, NH2-UiO-66 was synthesized by the solvothermal method and applied in mechano-catalytic degradation of Rhodamine B under ultrasonic vibration. The results show that NH2- UiO-66 behaves a high mechano-catalytic decomposition efficiency of 80% for Rhodamine B within 5 h vibration and possesses a good stability. The piezoelectrically induced electric charges on the surfaces of NH2-UiO-66 via the piezoelectric effect could induce hydroxyl radicals as strong oxidants to decompose Rhodamine B. The piezoelectrical effect of MOFs is potential in utilizing vibration energy for dye wastewater treatment.

Polyoxometalate is a new type of catalyst, which has good application in many fields. The properties of phosphomolybdate (PMo) can be regulated by changing the metal cations. In this work, phosphomolybdic acid (PMA) anions were reacted with three different metal ions (Ni, Na and Zn) to form PMos, which were used as catalysts to improve the flame retardant efficiency of polypropylene/intumescent flame retardant (PP/IFR). The results show that the PP composites can obtain the UL-94 V0 grade of flame retardant efficiency by adding 25wt% IFR. However, if PMo is introduced into PP/IFR system, only 14.5wt% IFR and 0.5wt% sodium phosphomolybdate (NaPMo) or sodium phosphomolybdate (ZnPMo) are needed for PP to achieve the UL-94 V0 grade. While under the same formulation, nickel phosphomolybdate (NiPMo) can only make PP composite obtain the UL-94 V1 grade. Different metal ions have different catalytic activities in PP/IFR, among which NaPMo and ZnPMo match with IFR better than NiPMo. PMos can promote the reactions among IFR, slow down the heat release rate during combustion, and form a char layer with better barrier effect, so as to improve the matching of PP and IFR, and improve the flame retardant efficiency in the UL-94 test.

Flexible thermoelectric devices have received a great deal of interest due to their capability of direct convert human body heat into electrical energy. In this work, we synthesized the tellurium nanowires by using hydrothermal method. The effects of hydrothermal temperature and reducibility of the reaction solution (with or without ascorbic acid) on morphology and thermoelectric properties of tellurium nanowires were investigated. Compared to the nanowires prepared in strong reducing solution, those prepared in relatively weak reducing solution (without ascorbic acid) reveal a higher aspect ratio up to 200 and the as-assembled film exhibits better electrical conductivity up to 26 S·m-1. It is also found that the wet-press method can enhance the micro-densification of the film, resulting in a tighter connection among the micro-nanowires. Therefore, the carrier mobility and carrier concentration of the tellurium nanowire film are significantly increased. As a result, its electrical conductivity is improved by 18.3 times, reached 476 S·m-1. Simultaneously the optimal tellurium nanowire film exhibits good performances including Seebeck coefficient (282.9 μV·K-1) and power factor (38 μW·m-1·K-2).

As a new promising thermoelectrical material in the range of intermediate temperature, BiCuSeO attracts much attention due to the combination of low intrinsic thermal conductivity and relatively high Seebeck coefficient. In this study, the effects of substituting variable-valence rare-earth element Eu for Bi site on the microstructure and thermoelectric performance of BiCuSeO-based material were investigated. The results indicate that ions of two valence states, Eu2+ and Eu3+, coexist in the doped BiCuSeO samples. The doping of Eu not only improves the concentration of the carriers, but also modifies the band structure of BiCuSeO matrix, resulting in effective improvement of electrical transport properties. The electrical conductivity of Bi0.85Eu0.15CuSeO reaches 98 S·cm-1 at 823 K, which is 6 times as high as that of the undoped sample. The power factor of 0.32 mW·m-1·K-2 and ZT of 0.49 can be achieved at 823 K for Bi0.975Eu0.025CuSeO sample. This study shows that the doping of variable-valence rare-earth elements can effectively improve the thermoelectric properties of BiCuSeO.

Proton conducting oxide BaCe0.7Zr0.1Y0.2O3-d (BCZY7) was synthesized by high temperature solid-state reaction method, which crystal structure and microstructure morphology were characterized. The anode-supported button solid oxide fuel cell (SOFC), NiO-BCZY7/BCZY7/La0.6Sr0.4Co0.2Fe0.8O3-δ(LSCF)-BCZY7, was fabricated by combining the dip-coating and co-sintering processes. It operated by using H2 (containing 3vol% H2O) as fuel and ambient air as oxidant. The maximum power density of the cell reaches 203, 123 and 92 mW×cm-2 at 600, 550 and 500 ℃, respectively. However, traditional SOFCs based on (ZrO2)0.92(Y2O3)0.08 electrolyte usually display only tens of milliwatts output per unit area at 600 ℃. Proton conducting electrolyte greatly improves the low and medium temperature performance of SOFCs and provides a promising solution to reduce SOFCs’ operating temperature.

Membrane-based gas separation is one of the critical technologies in filtration and separation industry, since it is more efficient, energy-saving and environmentally friendly compared with traditional separation technologies. Novel inorganic two-dimensional materials (2DMs) for gas separation are expected to achieve both high selectivity and high permeability, breaking through the trade-off between selectivity and permeability of commercial polymer membranes. This review begins with a brief explanation of gas separation mechanisms for membranes. Afterwards, special attention will be given to the recent advances in novel inorganic 2DMs including graphene and their derivatives, TMDs and MXene, about their design, fabrication and application in gas separation. The gas separation characteristics of different materials, their challenges and directions for future research are summarized. Moreover, the application of other novel inorganic 2DMs, such as LDH, h-BN and mica nanosheets in gas separation technology is also discussed. Finally, the perspectives and challenges for future research of novel inorganic 2DMs in gas separation field are outlined.

In recent years, the development of new energy vehicles industry is accelerating. Lithium nickel cobalt manganese/aluminum oxide ternary cathode materials (NCM/NCA), especially with the nickel content ≥50%, has aroused great interest in both academia and industry. This is mainly due to the fact that the aggregative parameters of performance and cost of NCM/NCA are superior to those of traditional cathode materials, such as LiCoO2 and LiFePO4. However, the application of NCM/NCA is affected by a number of drawbacks, including poor safety and insufficient cycle stability and so on, which are mainly attributed to its crystal and surface structure. Researchers have carried out various efforts to solve these problems and further improve the performance of NCM/NCA. Some remarkable results have been achieved in the past few years. In this review, the latest research progress on coating and doping of Ni-rich ternary cathode materials is summarized from the view on the mechanism of structural and electrochemical improvement of NCM/NCA. Finally, the perspective for the development of NCM/NCA cathode materials is also prospected.