一种高电导率PVA聚合物电解质的制备与表征

A type of polymer-in-salt electrolyte composed of poly( vinyl alcohol), KOH and water was prepared by a solution casting method. X-ray diffraction proves that the high concentration of KOH in the electrolyte is in an amorphous state. The ionic conductivities of the PVA-KOH-H2O electrolytes increased as the concentration of KOH increased, and the alkaline electrolyte with PVA/KOH 1/3 (mass ratio) exhibited the highest ionic conductivity of 0. 15 S/cm at room temperature, as measured by electrochemical impedance spectroscopy. The temperature dependence of the conductivity is found to be in agreement with the Arrhenius equation. The potential stability window at the metal/electrolyte interface was of 1.4 V for the nickel electrode determined by cyclic voltammetry.     

Mesoporous amorphous MnO<Subscript>2</Subscript> as electrode material for supercapacitor

A kind of novel mesoporous, electrochemical active material, amorphous MnO₂ has been synthesized by an improved reduction reaction and using supramolecular as template. The synthesized sample was characterized physically by thermogravimetric analysis, X-ray diffraction, transmission electron microscope (TEM), and Brunauer–Emmett–Teller (BET) surface area measurement, respectively. Electrochemical characterization was performed using cyclic voltammetry and chronopotentiometry in 2 mol/l KOH aqueous solution electrolyte. The results of BET and TEM analysis indicated that supramolecular template plays an important role in the process of big specific surface area mesoporous material forming. After sintering at 200 °C, the sample still remained an amorphous structure, and its specific capacitance reached 298.7 F/g and presented a very stable capacitance after 500 cycles. In addition, the electrochemical process, such as ion transfer and electrical condition, was also investigated with electrochemical impedance spectroscopy.     

Production of biodiesel through transesterification of soybean oil using ZIF-8@GO doped with sodium and potassium catalyst

One pot encapsulating (hydrothermal) method was used to synthesize ZIF-8@GO hybrid nanocomposites. Na/ZIF-8@GO doped with potassium were synthesized by the hydrothermal treatment of ZIF-8@GO precursor with a 10 M alkali solution containing both NaOH and KOH. The final product (KNa/ZIF-8@GO) was characterized by FTIR, XRD, BET, TGA, and SEM. The structure of graphene oxide remains intact following various modifications, as shown by absorption–desorption analysis, while spectral techniques indicate successful immobilization of the neat ZIF-8 between the GO sheets. Furthermore, soybean oil has been used as the feedstock in the preparation of biodiesel by KNa/ZIF-8@GO-catalyzed transesterification process. The effects of various reaction parameters, including methanol/oil molar ratio, reaction time, catalyst mass, and reaction temperature were investigated. A remarkable conversion of 98% was obtained using a 8% (wt/wt oil) of KNa/ZIF-8@GO catalyst, methanol/oil molar ratio of 18 : 1, and reflux temperature of methanol over a period of 8 h. The solid catalyst can be reused over at least three cycles under mild reaction conditions.

     

纳米银的电解质效应

向2种不同电性的纳米银溶胶中分别加入KCl、KBr、KI、KNO3、Mg(NO3)2、Al(NO3)3、K2CO3、K2SO4、KOH和HNO3电解质溶液,利用透射电子显微镜、紫外-可见分光光度计等研究电解质对纳米银的显微结构和光谱学性质的影响。结果表明,不同电解质离子在纳米银胶体表面吸附程度以及导致纳米银胶体聚集和生长程度不同,从而对纳米银胶体的分散状态和表面电势产生不同影响。这种影响的结果导致其对相同电性纳米银粒子和不同电性纳米银粒子的显微结构和光谱学性质影响不同。     

Effect of surfactant on the morphology and capacitive performance of porous NiCo2O4

A promising nickel cobaltite oxide (NiCo₂O₄) composite electrode material was successfully synthesized by a sol-gel method and followed by a simple sintering process. The microstructure and surface morphology of NiCo₂O₄ modified by hexadecyltrimethylammonium bromide (CTAB) and polyvinyl alcohol were physically characterized by powder X-ray diffraction and scanning electron microscopy. Meanwhile, electrochemical performance was widely investigated in 2 M KOH aqueous electrolyte using cyclic voltammetry, galvanostatic charge-discharge test, and electrochemical impedance spectroscopy. The results show that evident porous microstructure was successfully fabricated by CTAB. The NiCo₂O₄ controlled by CTAB exhibited highly specific capacitance of 1,440 F?g^?1 at a current density of 5 mA?cm^?2. Remarkably, it still displays desirable cycle retention of 94.1 % over 1,000 cycle numbers at a current density of 20 mA?cm^?2. The excellent electrochemical performance suggests its potential application in electrode material for electrochemical capacitors.     

Synthesis and electrical–magnetic properties of polyaniline composites

Composites of polyaniline (PANI) with both conducting and ferromagnetic feature were synthesized by an improved method proposed by the authors. The electrical and ferromagnetic properties of the composites were measured as a function of the concentration of KOH solution used during polymerization. The conductivity of the composites at room temperature decreases with the increase of the concentration of KOH; the maximum conductivity of 8.0 × 10⁻¹ S/cm can be obtained when 25 wt % of concentration of KOH was used. For a high concentration of KOH, ferromagnetic properties of the composites including a high saturated magnetization (∼ 10.0 emu/g) depending on the concentration of KOH solution and a lower coercive force (H_c ≈ 0) independent of the concentration of KOH solution were observed. It has been demonstrated that magnetic particles (Fe₃O₄) with nanometer size in the composites can be attributed to the ferromagnetic properties of the composites observed. For a lower concentration of KOH solution, on the other hand, the magnetic properties of the composites can be decomposed to Curie susceptibility χ_c depending on the temperature and Pauli susceptibility χ_P independent of the temperature. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2799–2805, 1998     

Role of surface roughness and lubricant film thickness in nanolubrication of sliding components in adaptive optics

Silver-coated copper particles with various silver loading were prepared by a direct liquid-to-particle conversion process in spray pyrolysis reactor system. The prepared particles were completely densified at 900°C within a residence time of 2.1 s and had core-shell structure, of which formation mechanism was proposed. The mean diameter of particles was 0.45 μm. Copper particles of 20 wt.% of silver loading were stable under air and 95% of copper remained as metallic copper even after 1 month of exposure to air. This enhanced air-stability contributed to the enhanced electrical property of conductive film obtained from the coated particles. The conductive film obtained from 15 wt.% of silver-coated copper particles had a sheet resistance of 1.2 mΩ square(-1). This low resistance resulted from the lack of oxide layer and low sintering temperature of silver layer.     

Effect of the Copper Oxide Sintering Additive on the Electrical and Electrochemical Properties of Anode Materials Based on Sr<Subscript>2</Subscript>Fe<Subscript>1.5</Subscript>Mo<Subscript>0.5</Subscript>O<Subscript>6–δ</Subscript>

The effect of introducing 1–3 wt % copper oxide sintering additive on the electrical and electrochemical characteristics of promising anode materials for solid oxide fuel cells based on Sr₂Fe_1.5Mo_0.5O_6–δ was studied. The total conductivity increases with increasing amount of copper oxide. The maximum conductivity in humid hydrogen at 800°C, 45 S cm^–1, was reached on introducing 3 wt % CuO. The sintering additive enhances the electrochemical activity of Sr₂Fe_1.5Mo_0.5O_6–δ and Sr₂Fe_1.5Mo_0.5O_6–δCe_0.8Sm_0.2O_1.9 anodes. A decrease in the sintering temperature of the anodes containing CuO with the electrolyte based on lanthanum gallate directly correlates with the electrochemical activity of the anodes. The minimum value of the polarization resistivity, 0.15 Ω cm² at 800°С in a humid hydrogen atmosphere, was obtained for the composite anode with 3 wt % CuO sintered at a temperature of 1050°С.     

Electrochemical Recovery of Silver from Secondary Raw Materials

Electrolysis of silver in 95-84 wt % sulfuric acid with addition of 40 g l^-1 of silver sulfate was studied at electrolyte temperature of 40°C. The optimal conditions of silver electrolysis in 84-85 wt % sulfuric acid were determined. Semicommercial tests of the electrochemical recovery of silver from silver coatings on copper, brass, aluminum, and steel articles were performed.     

Indirect Atomic Absorption Spectrometric Determination of Ammonia,Thiosulfate and Cyanide in an Unsegmented Flow System

Abstract

A flow injection analysis method (FIA), has been developed for the determination of cyanide, thiosulfate and ammonia by atomic absorption spectrometry (AAS). Aqueous solution of the analyte was injected into an on-line column containing glass beads and packed with silver chloride and deionized water was used as the carrier. The analyte dissolves the silver chloride and the dissolved silver complex is introduced to the nebulizer of the AAS. This method has proved to be sensitive, simple and precise. Detection limits of 1.0 × 10^?7 M, 5.0×10^?7 M and 5.0x10^?6M were obtained for thiosulfate, cyanide and ammonia, respectively. The precision of the technique was 2.0%, 2.4% and 1.4% in case of thiosulfate, cyanide and ammonia, respectively. The effects of flow rate and sample volume on the FIA/AAS signals are presented.     

Polyaniline‐tailored electromechanical responses of the silver/epoxy conductive adhesive composites

In this article, the electromechanical properties of silver‐in‐epoxy conductive adhesives with the polyaniline (PANI) micron particles as cofillers have been investigated. PANI is a conductive polymer and has a moderate conductivity in between those of silver and epoxy. It was found that PANI can be used to tailor both the adhesive's electrical contact resistance and its relaxation behavior; however, the effects of adding PANI were complex. The addition of small amount of PANI (2 wt %) dramatically increased the contact resistance; it might block the electrical contacts among silver flakes and was not able to form a continuous path among themselves. The addition of more PANI showed a moderate increase in contact resistance, which increased with the weight fraction of PANI from 6 to 15 wt %. Interdependent behavior of compressive strain and relaxation in electrical contact resistance is characterized to evaluate the origin of this relaxation. The addition of PANI made the relaxation in electrical contact resistance more sensitive to the compressive strain and the electromechanical coupling to deviate from the linear relationship. These research findings provide insights into the way to use PANI to tailor the electromechanical properties of the adhesive bonds or joints in the development of advanced functional devices. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2013, 51, 1448–1455     

The effects of a eutectic modifier on microstructure and surface corrosion behavior of Al-Si hypoeutectic alloys

Hypoeutectic aluminum–silicon alloys can have significant improvements in mechanical properties by inducing structural modification in the normally occurring eutectic. The eutectic modification may affect not only the mechanical properties but also the corrosion resistance of such alloys. It is well known that structural parameters such as grain size and interdendritic spacing can significantly affect corrosion resistance of alloys. However, to date, few researches have been performed to experimentally evaluate the effects of an effective modification of eutectic morphology on surface corrosion behavior of Al–Si alloys. In the present study, modified and unmodified samples of an Al 9 wt.% Si alloy were solidified under similar solidification conditions, and after metallographic procedures, the corrosion resistance was analyzed by both the electrochemical impedance spectroscopy technique and the Tafel extrapolation method carried out in a 0.5 M NaCl test solution at 25 °C. The impedance parameters and corrosion rate were obtained from an equivalent circuit analysis. It was found that the Al-9 wt.% Si alloy casting in the modified condition tends to have its corrosion resistance decreased when compared to the unmodified alloy.     

CaZrO3-based powders suitable for manufacturing electrochemical oxygen probes

Calcium zirconate powders doped with a small amount of CaO were synthesised using the Pechini method. X-ray analysis revealed that solid solution was formed in the concentration up to 51.5% mol CaO. For synthesis of stoichiometric CaZrO₃, the highest temperature was required (1150°C), but introduction of excess CaO from 50.5 to 51.5% mol enabled us to lower the synthesis temperature to 800°C. The sintering behaviour of such samples under non-isothermal conditions was studied by dilatometric methods. Deviations were found in stoichiometry; by increasing the CaO concentration in CaZrO₃ sinterability improved in comparison to CaZrO₃ with stoichiometric composition. The presence of CaO as second phase caused deterioration of the sinterability of the CaZrO₃-based samples. Pellets sintered at 1500°C for 2 h reached 96–98% of theoretical density. SEM and TEM observations were used to characterise the microstructure of the prepared samples. The electrical properties of CaZrO₃-based samples were investigated by the AC-impedance spectroscopy method. It was found that introduction of excess CaO into the CaZrO₃ structure caused an increase in ionic conductivity up to the solubility limit. The possibility of using CaZrO₃-based samples for constructing prototype electrochemical oxygen probes to determine activity of oxygen dissolved in molten copper is also demonstrated.      

活性炭/钴氧化物干凝胶电化学电容器性能

以高性能活性炭作为负极材料, 将颗粒平均粒径为40~60 nm的纳米钴氧化物干凝胶作为正极材料组成电化学电容器, 研究了电容器在7 mol/L的KOH水溶液中的电化学性能, 其充放电电压可以达到1.4~1.6 V, 以材料本身重量计算的比能量和比功率分别达到15.4 W·h/kg和23.5 kW/kg.     

Preparation and Crystallization of Magnetic Glass-Ceramics from the Residues after Sulfur Release and Iron Recovery from Copper Ore Tailings with Varied CaO Content

To comprehensively reuse copper ore tailings (COT), the fabrication of glass-ceramics by the direct sintering method was investigated, where the residues after sulfur release and iron recovery from copper ore tailings were used as raw materials. The effect of the CaO added on the fabrication of glass-ceramics was emphasized. After analysis of chemical composition and thermodynamics, crystallization kinetics were analyzed by Differential Scanning Calorimetry (DSC) and fitted to the Kissinger equation. The crystal phase and microstructure of sintered glass-ceramics heated between 1080 °C and 1100 °C were estimated by X-Ray diffraction analysis (XRD) and Scanning Electron Microscopy (SEM), respectively. Furthermore, the effects of the addition of CaO on the properties of the sintered glass-ceramics have been discussed. The results showed that the magnetic glass-ceramics were sintered by the residues successfully, the color of which was lighter than that of glass-ceramics sintered by raw materials before iron recovery. According to the XRD analysis, hedenbergite, wollastonite and sekaninaite were formed with traces of maghemite and quartz. In terms of crystallization kinetics and sintering results, a decrease in the activation energies of crystallization and in sintering temperature were observed for an increase in the addition of CaO of up to 10 wt.%. Moreover, the properties of the sintered glass-ceramics, including bulk density, linear shrinkage and flexural strength, were enhanced, while water absorption and true density were reduced with the increase of the amount of CaO added.     

Effect of sintering temperature on microstructure,electric and optical properties of Ce<Subscript>0.8</Subscript>Gd<Subscript>0.2</Subscript>O<Subscript>2−δ</Subscript> + 2 mol % TiO<Subscript>2</Subscript>

The effect of the sintering temperature of the Ce_0.8Gd_0.2O_2?δ + 2 mol % TiO₂ on its microstructure, electric, and optical properties was studied using the methods of x-ray spectroscopy, scanning electron microscopy (SEM), conductivity and ellipsometry. It is shown that the electrolyte lattice parameter decreases at an increase in the sintering temperature. The pattern of the sample surface obtained using the SEM method points to the dominating role of the sintering temperature in the formation of the electrolyte microstructure. Variation of optical properties as dependent on the synthesis temperature is also determined by the microstructure parameters of ceramics: presence of pores, formation of grain interfaces.     

热处理对线团状二氧化锰结构及其电化学性质的影响

以氯化锰与高锰酸钾为原料, 在低浓度下大数量合成由无数片状纳米层组成的线团状二氧化锰粒子. 采用X衍射, 扫描电镜, 液氮等温吸附脱附、循环伏安、交流阻抗及恒流充放电等方法研究了温度对产物结构及电化学性质的影响. 结果表明处理温度升高, 微孔减少, 比表面积减小, 孔径变大, 在300 ℃以下二氧化锰粒子的结构保持无定型结构. 交流阻抗测试显示随着处理温度的升高, 样品的法拉第电荷传递能力和离子在电解液与活性材料界面的扩散能力均得到提高. 比电容测试显示在200 ℃处理的二氧化锰具有最高的比电容, 以1 mol·L^-1 Na₂SO₄为工作介质, 扫速为2 mV·s^-1时, 其比电容是210.6 F·g^-1. 该研究表明: 材料的电化学性质可以通过热处理进行调整, 适当的热处理能提高该材料作为超级电容器活性材料的性质.     

Methane conversion into aromatic hydrocarbons over Ag-Mo/ZSM-5 catalysts

Nonoxidative methane conversion into aromatic hydrocarbons over ZSM-5-type high-silica zeolites modified with nanosized powders of molybdenum (4.0 wt %) and silver (0.1–0.5 wt %) is reported. The acidic properties of the catalysts have been investigated by temperature-programmed ammonia desorption. The microstructure and composition of the Ag-Mo/ZSM-5 catalytic systems have been studied by high-resolution transmission electron microscopy and energy-dispersive X-ray spectroscopy. The doping of the Mocontaining zeolite with silver enhances its activity and stability in nonoxidative methane conversion into aromatic hydrocarbons.     

Nanocomposite solid polymeric electrolyte of 49% poly(methyl methacrylate)-grafted natural rubber–titanium dioxide–lithium tetrafluoroborate (MG49-TiO2-LiBF4)

A nanocomposite polymer electrolyte consisting of 49% poly(methyl methacrylate)-grafted natural rubber (MG49) as a polymer matrix, lithium tetrafluoroborate (LiBF₄) as a dopant salt, and titanium dioxide (TiO₂) as an inert ceramic filler was prepared by solution casting technique. The ceramic filler, TiO₂, was synthesized in situ by a sol–gel process. The ionic conductivity was investigated by alternating current impedance spectroscopy. X-ray diffraction (XRD) was used to determine the structure of the electrolyte, and its morphology was examined by scanning electron microscopy (SEM). The highest conductivity, 1.4 × 10⁻⁵ S cm⁻¹ was obtained at 30 wt.% of LiBF₄ salt addition with 6 wt.% of TiO₂ filler content. Ionic conductivity was found to increase with the increase of salt concentration. The optimum value of conductivity was found at 6 wt.% of TiO₂. The XRD analysis revealed that the crystalline phase of the polymer host slightly decreased with the addition of salt and filler. The SEM analysis showed that the smoother the surface of the electrolyte, the higher its conductivity.

     

三元复合材料PANI／Ag／MWNT的电化学行为和比电容

通过原位聚合的方式在银纳米粒子/多壁碳纳米管（Ag/MWCNT）复合材料的表面成功聚合苯胺单体制备了聚苯胺/银纳米粒子/多壁碳纳米管（PANI/Ag/MWCNT）三元复合材料苯．通过对三元复合材料的结构以及表面形貌进行分析,表明聚苯胺层完全包覆了Ag/MWCNT复合材料,形成了核壳式结构．同时银纳米粒子则以单质晶体的形态存在于多壁碳纳米管与聚苯胺层之间．三元复合材料电极在1 mol/L的KOH溶液中具有极低的阻抗,而与聚苯胺电极相比,这些复合材料电极则表现出更低的电阻、更高的电化学活性和更好的循环稳定性．尤其是当苯胺和Ag：MWCNTs质量比为5：5时,该复合材料电极在0.25 A/g的电流密度下表现出最大的比电容值为160 F/g．