Synthesis of well-defined Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods/N-doped graphene for lithium-ion batteries

The geometric size and distribution of magnetic nanoparticles are critical to the morphology of graphene (GN) nanocomposites, and thus they can affect the capacity and cycling performance when these composites are used as anode materials in lithium-ion batteries (LiBs). In this work, Fe₃O₄ nanorods were deposited onto fully extended nitrogen-doped GN sheets from a binary precursor in two steps, a hydrothermal process and an annealing process. This route effectively tuned the Fe₃O₄ nanorod size distribution and prevented their aggregation. The transformation of the binary precursor was characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). XPS analysis indicated the presence of N-doped GN sheets, and that the magnetic nanocrystals were anchored and uniformly distributed on the surface of the flattened N-doped GN sheets. As a high performance anode material, the structure was beneficial for electron transport and exchange, resulting in a large reversible capacity of 929 mA·h·g^–1, high-rate capability, improved cycling stability, and higher electrical conductivity. Not only does the result provide a strategy for extending GN composites for use as LiB anode materials, but it also offers a route for the preparation of other oxide nanorods from binary precursors.

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Electromagnetic wave absorption in reduced graphene oxide functionalized with Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Fe nanorings

We report the preparation of nanocomposites of reduced graphene oxide with embedded Fe₃O₄/Fe nanorings (FeNR@rGO) by chemical hydrothermal growth. We illustrate the use of these nanocomposites as novel electromagnetic wave absorbing materials. The electromagnetic wave absorption properties of the nanocomposites with different compositions were investigated. The preparation procedure and nanocomposite composition were optimized to achieve the best electromagnetic wave absorption properties. Nanocomposites with a GO:α-Fe₂O₃ mass ratio of 1:1 prepared by annealing in H₂/Ar for 3 h exhibited the best properties. This nanocomposite sample (thickness = 4.0 mm) showed a minimum reflectivity of–23.09 dB at 9.16 GHz. The band range was 7.4–11.3 GHz when the reflectivity was less than–10 dB and the spectrum width was up to 3.9 GHz. These figures of merit are typically of the same order of magnitude when compared to the values shown by traditional ferric oxide materials. However, FeNR@rGO can be readily applied as a microwave absorbing material because the production method we propose is highly compatible with mass production standards.

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Fabrication of flexible reduced graphene oxide/Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> hollow nanospheres based on-chip micro-supercapacitors for integrated photodetecting applications

Micro-supercapacitors (MSCs) as important on-chip micropower sources have attracted considerable attention because of their unique and advantageous design for optimized maximum functionality within a minimized sized chip and excellent mechanical flexibility/stability in miniaturized portable electronic device applications. In this work, we report a novel, high-performance flexible integrated on-chip MSC based on hybrid nanostructures of reduced graphene oxide/Fe₂O₃ hollow nanospheres using a microelectronic photo-lithography technology combined with plasma etching technique. The unique structural design for on-chip MSCs enables high-performance enhancements compared with graphene-only devices, exhibiting high specific capacitances of 11.57 F·cm^-3 at a scan rate of 200 mV·s^-1 and excellent rate capability and robust cycling stability with capacitance retention of 92.08% after 32,000 charge/discharge cycles. Moreover, the on-chip MSCs exhibit superior flexibility and outstanding stability even after repetition of charge/discharge cycles under different bending states. As-fabricated highly flexible on-chip MSCs can be easily integrated with CdS nanowire-based photodetectors to form a highly compacted photodetecting system, exhibiting comparable performance to devices driven by conventional external energy storage units.

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An efficientfficient,controllable and facile two-step synthesis strategy: Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@RGO composites with various Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles and their supercapacitance properties

An efficient,controllable,and facile two-step synthetic strategy to prepare graphene-based nanocomposites is proposed.A series of Fe3O4-decorated reduced graphene oxide (Fe3O4@RGO) nanocomposites incorporating Fe3O4 nanocrystals of various sizes were prepared by an ethanothermal method using graphene oxide (GO) and monodisperse Fe3O4 nanocrystals with diameters ranging from 4 to 10 nm.The morphologies and microstructures of the as-prepared composites were characterized by X-ray diffraction,Raman spectroscopy,nitrogen adsorption measurements,and transmission electron microscopy.The results show that GO can be reduced to graphene during the ethanothermal process,and that the Fe3O4 nanocrystals are well dispersed on the graphene sheets generated in the process.The analysis of the electrochemical properties of the Fe3O4@RGO materials shows that nanocomposites prepared with Fe3O4 nanocrystals of different sizes exhibit different electrochemical performances.Among all samples,Fe3O4@RGO prepared with Fe3O4 nanocrystals of 6 nm diameter possessed the highest specific capacitance of 481 F/g at 1 A/g,highlighting the excellent capability of this material.This work illustrates a promising route to develop graphene-based nanocomposite materials with a wide range of potential applications.     

Pt/Y<Subscript>2</Subscript>O<Subscript>3</Subscript>:Eu<Superscript>3+</Superscript> composite nanotubes: Enhanced photoluminescence and application in dye-sensitized solar cells

Y(OH)3:Eu3+ nanotubes were synthesized using a facile hydrothermal method,and then,Pt particles were grown on the surface of the nanotubes using a combination of vacuum extraction and annealing.The resulting Pt/Y2O3∶Eu3+ composite nanotubes not only exhibited enhanced red luminescence under 255-or 468-nm excitation but could also be used to improve the efficiency of dyesensitized solar cells,resulting in an efficiency of 8.33％,which represents a significant enhancement of 11.96％ compared with a solar cell without the composite nanotubes.Electrochemical impedance spectroscopy results indicated that the interfacial resistance of the TiO2-dye|I3-/I-electrolyte interface of the TiO2-Pt/Y2O3:Eu3+ composite cell was much smaller than that of a pure TiO2 cell.In addition,the TiO2-Pt/Y2O3:Eu3+ composite cell exhibited a shorter electron transport time and longer electron recombination time than the pure TiO2 cell.     

Thermally stable Ir/Ce<Subscript>0.9</Subscript>La<Subscript>0.1</Subscript>O<Subscript>2</Subscript> catalyst for high temperature methane dry reforming reaction

In this study,the use of a thermally stable Ir/Ce0.gLa0.1O2 catalyst was investigated for the dry reforming of methane.The doping of La2O3 into the CeO2 lattice enhanced the chemical and physical properties of the Ir/Ce0.9La0.1O2 catalyst,such as redox properties,Ir dispersion,oxygen storage capacity,and thermal stability,with respect to the Ir/CeO2 catalyst.Hence,the Ir/Ce0.gLa0.1O2 catalyst exhibits higher activity and stabler performance for the dry reforming of methane than the Ir/CeO2 catalyst.This observation can be mainly attributed to the stronger interaction between the metal and support in the Ir/Ce0.gLa0.1O2 catalyst stabilizing the catalyst structure and improving the oxygen storage capacity,leading to negligible aggregation of Ir nanoparticles and the Ce0.gLa0.1O2 support at high temperatures,as well as the rapid removal of carbon deposits at the boundaries between the Ir metal and the Ce0.gLa0.1O2 support.     

锂离子电池正极材料LiCo1/3Ni1/3Mn1/3O2的研究进展

综述了近几年锂离子电池正极材料层状三元过渡金属氧化物LiCoxNiyMn1-x-yO2的研究进展，重点讨论了综合性能优异的LiCo1/3Ni1/3Mn1/3O2的电化学性能、结构、制备方法以及存在的不足，LiCo1/3Ni1/3Mn1/3O2与其它商业化正极材料相比具有高容量、热稳定性好、高倍率放电等诸多优异的性能，若能解决循环、存放等问题，将有望成为新一代锂离子电池正极材料。     

Superconducting YBa<Subscript>2</Subscript>Cu<Subscript>3</Subscript>O<Subscript>7−δ</Subscript> thick film (T<Subscript>c</Subscript>(0) = 92 K) on a newly developed perovskite ceramic substrate

A complex perovskite oxide, YbBa₂NbO₆, as a non-reacting substrate for YBa₂Cu₃O_7-° super-conducting film has been developed. The dielectric constant and loss factor values of the material are in the range suitable for its use as substrate for microwave applications. A YBa₂Cu₃O_7−δ superconducting thick film dip coated on YbBa₂NbO₆ substrate gave a T_c (0) of 92 K and current density of ∼ 1.3 × 10⁴ A cm⁻².     

Minimizing Thermal Residual Stress in Ni/Al₂O₃ Functionally Graded Material Plate by Volume Fraction Optimization

The thermal residual stress in the fabrication of functionally graded material (FGM) systems can give rise to various mechanical failures. For a FGM system under a given fabrication environment, the thermal residual stresses are determined by the spatial distribution of its constituent components. In this study, we optimize a Ni/Al₂O₃ FGM plate aiming at minimizing the thermal residual stresses through controlling its compositional distribution. Material properties are graded in the thickness direction following a power law distribution in terms of the volume fractions of constituents (P-FGM). An analytical model and a hybrid genetic algorithm with the pattern search are employed to predict and to minimize the thermal residual stresses, respectively. Simulation results show that an optimal design of the FGM plate could help fulfill its potential in reducing the thermal residual stresses.     

Polar nanodomains and relaxor behaviour in (1 − x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 crystals with x = 0.3–0.5

Phase transitions and dielectric properties of the (1 − x)Pb(Mg_1/3Nb_2/3)O₃–xPbTiO₃ crystals with x = 0.3–0.5 are studied. The solid solutions in this composition range are shown to be relaxor ferroelectrics. The crystals with low x demonstrate a diffused maximum in the temperature dependences of the dielectric permittivity at T_m. T_m varies with frequency according to the Vogel–Fulcher law. The polarizing microscopy investigations reveal a first-order phase transition from the relaxor phase to the low-temperature ferroelectric phase at T_C, which is several degrees below T_m. The permittivity peak in the crystals with x = 0.5 is sharp, and T_m is equal to T_C and does not depend on frequency, as is typical of the transition from a ferroelectric to an ordinary paraelectric phase. Nevertheless, the relaxor, but not the paraelectric, phase is observed at T > T_m. This conclusion is confirmed by the observation of the temperature behaviour of complex dielectric permittivity at T > T_m, which is typical of relaxors and related to the existence of polar nanodomains.     

掺杂对0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3陶瓷结构和电学性能的影响

用传统的固相反应法、通过铌铁矿预合成路线制备了1mol%ZnO、MnO2和CuO掺杂的0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3(0.7PMN-0.3PT)陶瓷。XRD分析表明掺杂的0.7PMN-0.3PT陶瓷都呈现纯三方钙钛矿结构。烧成的陶瓷具有较高的致密度,其中CuO掺杂的0.7PMN-0.3PT陶瓷达到理论密度的93.79%。掺杂的0.7PMN-0.3PT陶瓷都呈现宽化、弥散的介电响应峰,然而介电常数的频率色散现象明显减弱。CuO掺杂的0.7PMN-0.3PT陶瓷呈现优良的综合电学性能:介电常数最大值εm达到21000左右,剩余极化强度Pr达到27.49μC/cm2,压电应变常量d33达到548pC/N。     

Effects of growth conditions on the domain structure and dielectric properties of (1 − x)Pb(Sc1/2Nb1/2)O3–xPbTiO3 single crystals

The studies of the (1 − x)Pb(Sc_1/2Nb_1/2)O₃–xPbTiO₃ (PSN–PT) single crystals reveal that the chemical and physical properties of the materials are affected by the growth conditions. By the measurements of the dielectric constant as a function of temperature upon cooling, it is found that crystals grown from the same charged stoichiometric composition (x = 0.425), but under different flux environments (i.e. the composition of flux and the flux to PSN–PT ratios are varied), show anomalies (i.e. phase transitions) at different temperatures. This phenomenon is attributed to the complex local chemical structure of the PSN–PT solid solution single crystals with B-site random occupancy of three different cations (Sc³⁺, Nb⁵⁺ and Ti⁴⁺). The dielectric and domain structure of the PSN–PT crystals with composition near the morphotropic phase boundary (MPB) are investigated, showing much more complex situations compared with Pb(Sc_1/2Nb_1/2)O₃.     

掺钾对PMN基陶瓷有序微区及介电和电致伸缩性能的影响

使用二次合成法制备了不同钾含量的0.80Pb(Mg1/3Nb2/3)O3-0.20PbTiO3陶瓷，首先研究了掺钾对PMN基预烧粉体和陶瓷试样相组成的影响，在此基础上详细研究了掺钾对PMN基陶瓷有序微区、介电和电致伸缩性能的影响规律。掺钾对PMN基预烧粉体和陶瓷的相组成影响很小；理论计算和Raman散射光谱分析都表明掺钾使PMN基陶瓷的有序微区的尺寸稍微减小；掺钾也小幅度地减小了PMN基陶瓷的介电和电致伸缩性能，最后分析了掺钾降低介电和电致伸缩性能的原因。     

New 3-((2′:2″,5″:2-terthiophene)-3″-yl) acrylic acid as active layer for organic field-effect transistor

Most functionalized thiophenes are difficult to electropolymerize due to nucleophilicity that will attack the radical cation inhibiting polymerization. However, we have successfully electrodeposited a newly synthesized functionalized terthiophene monomer 3-((2′:2″,5″:2-terthiophene)-3″-yl) acrylic acid (TAA) as an active layer of a organic field-effect transistor (OFET). The polymer was then oxidized in order to increase its conductivity. Various oxidizing potentials were experimented and their effect on the OFET's charge mobility was examined. A mobility of 0.25 cm² (V s)⁻¹ is achieved with an oxidizing potential of 0.9 V after vacuum drying.