查看更多>>摘要：NASICON (Na superionic conductor) type electrode materials are known for their wide range of electrochemical potentials, high ionic conductivity, and most importantly their structural and thermal stabilities. Li2M2(MoO4)3 (M=Zn, Cu), belonging to molybdenum-based NASICON family, are successfully synthesized by simple sol-gel method. The structure evolution caused by the substitution of Zn2+ by Cu2+ within Li2Zn2-xCux(MoO4)3 (0 ≤ x ≤ 2) has been investigated. Rietveld refinement results reveals that the priority order of copper atoms replacing zinc atoms in Li2Zn2(MoO4)3. Furthermore, both Li2Zn2(MoO4)3 and Li2Cu2(MoO4)3 electrodes deliver excellent electrochemical performance, and high reversible capacities of 864 mAh g?1 and 747 mAh g?1 can be acquired at a current density of 0.1 A g?1, respectively. In addition, the in-operando X-ray diffraction measurements indicate the formation of cubic mesophase Li4MoO5 both in Li2Zn2(MoO4)3 and Li2Cu2(MoO4)3 during the initial lithium insertion, which irreversibly converts into the amorphous phases on further discharge at subsequent discharge and charge process.
查看更多>>摘要：In this work, NaNb0.018V2.982O8 (NVO-0.018Nb) composite was served as the cathode of sodium-ion batteries (SIBs) to deliver a superior Na-storage capacity of 187 mA h g?1 at the current density of 1 C and voltage range of 1.5–4.0 V, and favorable energy density (419.3 Wh kg?1). Electrochemical impedance spectroscopy (EIS) measurements displayed decreased charge transfer resistance in the NVO-0.018Nb composite. The detailed kinetic analysis revealed enhanced surface-controlled behaviors, leading to improved sodium-storage capability. Scanning electron microscopy (SEM) and X-ray powder diffraction (XRD) analyses demonstrated that NVO-0.018Nb composite exhibited unique structure with signi?cantly enhanced structural stability during fast cycling. In sum, the proposed method looks promising for the design of future advanced electrode materials of SIBs.
查看更多>>摘要：With rapid advances in the portable electronics industry, the creation of microwave absorbing materials with high-performance to dissipate the unwanted electromagnetic wave is an important prerequisite. Herein, unique ternary organic-inorganic composites (C/Ni/PPy) were fabricated by hydrothermal method combined with in-situ polymerization approach. The correlation between structure, components, and microwave absorption capability is investigated in detail. The carbon matrix was prepared through a typical “carbonization-activation” procedure. Then, the PPy particles were decorated on the surface of the biomass carbon matrix incorporated with Ni particulates via an in-situ polymerization method. The microwave absorbing results suggest that the C/Ni/PPy ternary composites exhibit stronger dielectric loss and microwave absorption capabilities than C/PPy binary composites. A reflection loss of ? 42.09 dB and an outstanding effective absorption bandwidth of 5.24 GHz are achieved simultaneously with a thickness of only 2.4 mm. The excellent microwave absorbing performances can be ascribed to the unique microstructure, enhanced polarization and the synergistic effects between dielectric loss and magnetic loss. The present work achieves a new paradigm to improve microwave absorption characteristics through the combination of dielectric components with magnetic materials. Furthermore, a prototype is proposed, which has broad application prospects for applications in next-generation wearable and portable electronics.
查看更多>>摘要：Carbonaceous materials are used as the anode for rechargeable lithium-ion batteries (LIBs), however, lithium dendrites are easily formed during cycling due to the low lithium insertion potential (~0.1 V versus Li+/Li). As alternative anodes, transition metal oxides based on conversion mechanism have attached much attention. But the high lithiation potential (>1.0 V vs. Li+/Li) usually leads to a low output voltage and energy density when used in a full cell configuration. Herein, Zn-substituted Co3O4 submicron spheres are successfully synthesized by a facile solvothermal reaction and subsequent calcination method. When used as the anode for LIB, the optimized sample shows a specific capacity of 686 mAh g?1 at 0.8 A g?1 after 500 cycles, and a specific capacity of 692.9 mAh g?1 at a higher current density of 3.2 A g?1 in a half-cell. Thanks to the controlled Zn substitution, the discharge voltage plateau is 0.16 V lower than that of the pure Co3O4 anode at a current density of 0.4 A g?1. Further investigation of the 0.5Zn-Co3O4//LiCoO2 full cells also displays a high capacity (400.7 mAh g?1 after 200 cycles at 0.4 A g?1) and an excellent rate capability (658.1 mAh g?1 at 1.6 A g?1) compared with the Co3O4//LiCoO2 full cells. This work confirms that substituting suitable metal elements into sub-micron conversion based anodes can reduce the voltage plateau, which is of great significance for the practical applications in high performance energy storage devices.
查看更多>>摘要：Strong absorption and emission are the key the features of any phosphor. The results obtained during this study demonstrate the difficulty of the incorporation of tantalum ions into the garnet structure and reveal that only the combination of Sol-Gel synthesis method together with Molten-Salt technique enable to obtain a single-phase cubic garnet structure. Note that, the Sol-Gel synthesis assisted by further processing by Molten-Salt technique can be a potentially new way of material preparation reported in literature. This work also proves that this combination of synthesis methods is much more capable of incorporating ions with large ionic radii into the garnet structure as compared to traditional Sol-Gel method. Moreover, samples synthesized using this new technique exhibit 30% higher emission intensities as compared to the ones prepared by the original Sol-Gel method, while also reducing the needed sintering temperature by 200 °C. To the best of our knowledge, the modification of yttrium aluminum garnet (Y3Al5O12, YAG) by co-doping it with Ca2+ and Ta5+ ions by Sol-Gel assisted Molten-Salt route has been investigated for the first time.
查看更多>>摘要：In this paper, a pyrolysis method is used to synthesize high quality VO2 powder. Black carbon and V2O5 powder are mixed and annealed at 650 °C or 800 °C under argon flow to initiate a carbo-reduction reaction. The 650 °C VO2 powder presents submicron particle size with an amorphous fraction estimated at 11.5%. With the increase of the annealing temperature up to 800 °C, grains become larger than the micron while the crystallinity goes up to 98.5% (i.e. amorphous fraction drops to 1.5%). This one-step process allows the preparation of quantities up to 10 g of VO2 powder and should be easily transferable to large-scale production. An innovative sintering process is then adopted to produce high quality thermochromic VO2 ceramics from the as-prepared VO2 powder. First, SPS process is used to obtain high-density VO2 pellet. Then, the VO2 pellet is post-annealed in a homemade induction furnace at 1300 °C under a controlled atmosphere to allow grain growth by coalescence and improve pellet surface quality. According to a surface topography analysis, the mean amplitude roughness parameter (Ra) of the obtained VO2 ceramic is found to be 2.93 ± 0.01 nm. A large resistance change by three orders of magnitude along the phase transition is observed, which makes the as-prepared smooth VO2 ceramic a promising candidate for various applications requiring optical and/or electronic switching behavior depending on temperature.
查看更多>>摘要：AA2195 sheets treated by artificial aging to an ultra-high strength were subjected to electromagnetic forming (EMF) to overcome the distortion of formed components during heat treatment. The deformation behavior and corresponding strengthening effect of a conical-shape workpiece were evaluated by strain analysis and Vickers hardness testing, respectively. The limiting dome height (LDH) and limiting effective strain of the conical workpiece during electromagnetic bulging were 26.7 mm and 46.3%, respectively. Hardness in the undeformed area of the conical workpiece was 180 HV, which increased with increased deformation during electromagnetic bulging, reaching 200 HV at the effective strain of 35%. Microstructure characterization showed that grain distribution increased in uniformity with increase in strain, accompanied by small and equiaxed grains. Dislocation density and low-angle grain boundaries increased with increasing strain, which improved the strength of the bulged specimen. Texture evolution indicated that the {110}<112>orientation of the Brass texture component increased significantly as the deformation increased. Considerable helical dislocations were formed during electromagnetic bulging, which led to the improved hardness with an increase in strain. This study proves the feasibility of forming ultra-high-strength aluminum alloys at room temperature.
查看更多>>摘要：3 mol% yttria-stabilized zirconia (3YSZ) and a nickel-based superalloy (GH3128) were robustly joined in seconds using a Cu interlayer at 1000 °C under the application of an electric field. The shear strength of the joints reached 190 ± 6 MPa within 2 s of energization and increased to 250 ± 15 MPa with the extension of the energization time to 30 s. The electric field-induced electrochemical reactions greatly accelerated atomic interdiffusion, generated Cu?Zr eutectic liquid at the interface and enabled the interfacial gap to be rapidly filled due to the good wettability of 3YSZ by the melt, thus yielding the strong joints in seconds. The key joining parameters (current density, time and temperature) were investigated and the correlations between interfacial structural evolution and fracture characteristics were addressed. This work provides a reliable method for ultrafast and robust joining of zirconia to metals.
查看更多>>摘要：Spherical LiNi0.4Co0.2Mn0.4O2 powders are synthesized via the modified hydrothermal method with the presence of urea and polyvinyl pyrrolidone (PVP). For comparison, LiNi0.4Co0.2Mn0.4O2 powders are also synthesized via the normal hydrothermal method without urea and PVP. In the normal hydrothermal process, incomplete compound formation with extra Li2MnO3 phase is observed. Whereas, phase-pure LiNi0.4Co0.2Mn0.4O2 powders with the well-ordered layered structure are obtained via the modified hydrothermal process. The modified hydrothermal process considerably reduces the cation disorder of Li+/Ni2+ and yields spherical-shaped particles. The LiNi0.4Co0.2Mn0.4O2 powders synthesized via the modified hydrothermal process delivers a high discharge capacity of 159 mAh/g at 0.1 C with the capacity retention of 94% at 0.3 C after 100 cycles. On contrary, the powder synthesized via the normal hydrothermal process delivers a low specific capacity of 126 mAh/g at 0.1 C with capacity retention of only 74% at 0.3 C after 100 cycles. Based on the results of electrochemical impedance and galvanostatic intermittent titration, the charge transfer resistance and charge diffusion coefficient of the sample synthesized via the modified hydrothermal process are found to be 16 ohm and 7.5 × 10?12 cm2/s, respectively. The present study reveals the feasibility to prepare phase-pure LiNi0.4Co0.2Mn0.4O2 cathode with a promising high-rate performance by adding PVP and urea during the hydrothermal synthesis process.
查看更多>>摘要：The n-type CuInS2 nanoparticles were deposited successfully on n-type TiO2 nanotube surface via the successive ion layer absorption and reaction (SILAR) technique. Compared with the pure TiO2, the photoresponse of CuInS2/TiO2 films is expanded to the visible region, indicating an excellent visible light utilization rate and improved photoelectric conversion efficiency. Benefiting from the favorable n-n heterojunction structure, the photocurrent density of CuInS2/TiO2 photoanode under visible light irradiation exceeded 40 μA/cm2, which was 8 times that of the TiO2. The potential of the coupled 316L stainless steel in 3.5 wt% NaCl aqueous solution was droped by ? 850 mV in the presence of CuInS2/TiO2 films, which showed a remarkable photocathode protection performance of n-n type CuInS2/TiO2 heterojunction materials.
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