查看更多>>摘要：The B2 structure based MIL composites was fabricated by a two-step processing: the stacked Al and Fe foils were firstly hot pressed under eutectic reaction to form the Al-rich intermetallic phase(Fe2Al5) layer by consuming all the Al foils. And then, for forming the Fe-rich intermetallic phase (FeAl with B2 structure), three kinds of experiments were carried out to transfer the Al-rich phase layer to B2 structure: annealing at eutectic temperature for a long time; hot pressing or Spark plasma sintering (SPS) at higher temperature (1000 °C). The EDS, EBSD, XRD, micro-hardness tests and quasi-static compression are applied to study microstructure evolution, phase transformation and identification during fabricating the B2 structure based MIL composites. Mechanical properties of the B2 structure based MIL composites has proved the reduction of the stress concentration on the interface.
查看更多>>摘要：In this paper, a sphere-like MoS2 and porous TiO2 composite film was prepared on Ti foil by plasma electrolytic oxidation and magnetron sputtering methods. The prepared film was assembled as a binder-free anode in the lithium-ion battery and a Li foil served as the counter electrode. The specific capacity and cycling stability of the electrode were evaluated, together with the cyclic voltammograms and electrochemical impedance spectra. The TiO2/MoS2 composite film anode combined the advantages of TiO2 with high structural stability and MoS2 with high theoretical capacity. The electrochemical performance exhibited a specific capacity above 400 mAh g?1 at the current density of 100 μA cm?2, which was much higher than that of the TiO2 anode. Besides, after cycling under a high current density of 1000 μA cm?2, the capacity came back to 91% of the initial capacity, showing a good rate capability. The porous TiO2 prepared by plasma electrolytic oxidation can provide a significant number of internal channels for the Li+ diffusion, resulting in a high porosity of 33.5–41.6%, and a high Li+ diffusion coefficient of 3.12 × 10?14–6.67 × 10?14 cm2/s, which was beneficial for the enhanced electrochemical performance.
查看更多>>摘要：The work reports the fabrication of CoSe2@NiSe2 nanoflowers on nickel foam substrates via one-step microwave method, in which the Ni foam serves as a skeleton and a nickel source. The as-prepared CoSe2@NiSe2 nanoflowers display high capacitance value of 1434 F g?1 at the current density of 1 A g?1 and excellent cycling performance of 87.5% retention after 20,000 cycles at 10 A g?1. In addition, the supercapacitor device using CoSe2 @NiSe2 nanoflowers as the positive electrode and activated carbon (AC) as the negative electrode not only can exhibit wide voltage window of 1.6 V, but also deliver a maximum high energy density of 20.4 Wh Kg?1 at power density of 798 W Kg?1 and 86.6% of capacity retention after 20,000 cycles.
查看更多>>摘要：We studied the effect of Mn on the structure and properties of Cd3?xMnxAs2 crystals with x = 0–0.24, synthesized by direct fusion of high-purity elements. Obtained X-ray diffraction patters suggest that the incorporation of Mn promotes a structural phase transition from primary α-Cd3As2 (x = 0) phase to the α''– Cd3As2 (x = 0.24) phase, while at intermediate compositions both phases can coexist. In addition, the increase of Mn content results in the decrease of lattice cell parameters, which effectively saturates for x > 0.13. Microstructural, calorimetric and magnetometry studies suggest that at high Mn content (x = 0.24) secondary MnAs phase appears. Using obtained results, we estimated the solubility limit of Mn in Cd3As2 as x~0.13, which corresponds to the formation of ternary Cd3?xMnxAs2 compound where Cd atoms are partially substituted by Mn. Formation of ternary compound was also suggested by the results for Cd3As2 + MnAs composite systems, where we also observed the presence of CdAs2 phase, which is a byproduct of corresponding reaction. Additional studies suggested that the CdAs2 phase formation in composite system can be prevented if one uses the Cd3?xMnxAs2 compound instead of pure Cd3As2 as a matrix material.
查看更多>>摘要：SnO2/carbon hybrids with porous carbon as the carrier are considered as promising candidates for substituting graphite anode in Li-ion batteries (LIBs). However, in these composites, the active SnO2 particles are usually agglomerated and exposed on the surfaces of carbon matrix, which will lead to weak structure stability of the electrode, insufficient electric contact area between SnO2 and carbon, as well as more side reactions. To overcome these drawbacks, herein, a three-dimensional (3D) N-doped mesoporous carbon (NMC)/SnO2 composite with polypyrrole (PPy) coating layers (NMC/SnO2@PPy) is synthesized through a wet-impregnation and subsequent in situ vapor-phase pyrrole polymerization method, in which ultrafine SnO2 particles with monodisperse morphology are well encapsulated between porous carbon matrix and PPy coating layer. This novel structure can effectively reduce SnO2 aggregation, enhance electrical conductivity and depress excessive side reactions. The NMC/SnO2@PPy anode shows a reversible capacity of 775 mAh g?1 at a current density of 500 mA g?1 after 300 cycles. And a high reversible capacity of 591 mAh g?1 is obtained at a high rate of 1 A g?1 even after 1000 cycles. The successful preparation of NMC/SnO2@PPy anode can provide a rational approach to devise metal oxide-carbon hybrid anodes with 3D porous structures for LIBs development.
查看更多>>摘要：The challenge of enhancing the high-temperature oxidation resistance of titanium alloys is hereby addressed by the addition of TiB whiskers and nano-silicide. The cyclic oxidation tests results showed that the weight gains of the composites with reinforcements were less than that of titanium alloy, and the oxidation film of the silicide/composite only appears little peeling after heating at 1123 K for 100 h. The grains were refined by the introduction of reinforcements, thus the high-density grain boundary can be also used as the nucleation site of oxidation products to refine the oxide grains and effectively inhibit the internal diffusion process of oxygen. Additionally, nano-silicide distribution at grain boundaries cause short-circuit diffusion, resulting in preferential oxidation at grain boundaries thus forming a network structure, which effectively hinders the inward diffusion of oxygen and better inhibits the growth of oxidation scale. DFT calculation shows that TiBw and nano silicide reinforcement with weak oxygen binding ability can reduce the adsorbed oxygen atoms and prevent the further oxidation growth of the matrix.
查看更多>>摘要：The effectiveness of simultaneous etching and W-doping has been demonstrated in improving the quantum-dots anchoring and charge transport properties of CdS/TiO2 heterojunction films, thereby enhancing their photoelectrochemical performances. After the process of etching and doping, a rough and amorphous W-doped TiO2 shell is formed on the TiO2 nanorods surface. It can not only provide more active sites and larger surface areas for quantum-dots loading, light-harvesting and photoelectrochemical reaction, but also protect the electron-hole pairs from recombination at the interface. Furthermore, W-doping plays a role in motivating the separation and transfer of photo-generated carriers by introducing the intermediate energy level and inducing the positive shift of TiO2 conduction band, meanwhile prominently increase the amount of electrons due to the intrinsic valence difference between W6+ and Ti4+. Based on the above advantages, the uniform and compact deposition of CdS quantum-dots on the surface of etched and W-doped TiO2 nanorods pose a great influence on the establishment of the built-in electric field, heterojunction areas, light-capture ability, and the separation and injection efficiency of photo-generated carriers. Therefore, the optimal photocurrent density of improved CdS/TiO2 photoelectrodes is 7.05 mA cm?2, approximately 12 and 2.6-fold enhancement compared with conventional TiO2 and CdS/TiO2 photoelectrodes, respectively.
查看更多>>摘要：The in-situ TiC/Ti2Ni reinforced CrTi4-based laser cladding composite coating was fabricated on Ti811 alloy. The phased composition and microstructure of the composite coating was studied, and the interface relationship between CeCrO3 and Ti2Ni was investigated in detail. The results show that the formation phases of the coating contain TiC, Ti2Ni, CrTi4, and CeCrO3. The density functional theory (DFT) calculation suggests that the CeCrO3(121ˉ)//Ti2Ni(2ˉ42ˉ)interface was stable with ionic bonds, and the charge transfer number at the interface was confirmed.
查看更多>>摘要：In this work, we investigate the hysteresis effect of the current-voltage characteristic for the magnetron sputtered molybdenum disulfide (MoS2) nanocrystalline films. The field emission hysteresis of MoS2 cold cathode is studied by sweeping mode with voltage upward/downward, the vacuum pressure has a remarkable effect on the hysteresis of the emission current and overall the hysteresis becomes more prominent as pressure rises. Besides, we also demonstrate the current-voltage behaviors of MoS2 film using thermal evaporated Al dot as top electrode and copper foil substrate as bottom electrode. The Al/MoS2/Cu configuration device presents an obvious current hysteretic effect and the current increases with the increase of the voltage sweeping times. The possible mechanism of the hysteresis has been proposed herein and also investigations provide a great promise for the development of magnetron sputtered MoS2 nanocrystalline films in applications such as field emitters and memristor devices.
查看更多>>摘要：Temperature sensor and field emission displays (FED) are the intensive topics for Sm3+ activated red phosphor. In this study, a novel lithium nitride red phosphor Li2CaSi2N4:Sm3+ was successfully prepared by solid phase method. The photoluminescence and cathodoluminescence performances were systematically studied to explore the possibility in FED and temperature sensor applications. The results indicate that the Li2CaSi2N4:Sm3+ phosphor features intense red emission under the UV light and cathode ray excitations. The phosphor also has a long red afterglow with an afterglow time of 12.7 min. Most importantly, Li2CaSi2N4:Sm3+ exhibits excellent temperature sensitivity with the relative sensitivity of 4.8% K?1 @473 K, which is higher than other temperature sensor materials. The thermal quenching mechanism was proposed based on a configurational-coordinate model. Moreover, excellent cathode ray saturation and aging resistance were observed in Li2CaSi2N4:Sm3+. The results indicate that Li2CaSi2N4:Sm3+ is a potential temperature sensor and FED materials.
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