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51.
Gino Bontempelli Nicola Comisso Rosanna Toniolo Gilberto Schiavon 《Electroanalysis》1997,9(6):433-443
Electroanalytical sensors, suitable for the analysis and monitoring of electroactive analytes present in gaseous phase or low-conductive liquid media, and based on electrodes in close contact with perfluorinated ion-exchange polymers are reviewed. The basic operative mechanism of these sensors, in which ion-exchange polymers act as solid polymer electrolytes (SPE's), is thoroughly discussed, while stressing the fundamental reasons why their behavior differs from that of conventional membrane electrodes. The procedures for preparing composite working electrodes by coating one side of ion-exchange membranes with stable porous films of conductive materials are described, along with the most common strategies followed to assemble this type of sensors. Useful examples of measurements in electrolyte-free media of inorganic and organic electroactive species of interest mainly for environmental analysis are given. Future prospects for the development of these sensors are also discussed. 相似文献
52.
Polypyrrole composite cation- and anion-exchange membranes (CEM and AEM), in which polypyrrole (PPY) coated on one surface of the membrane as a thin layer, were prepared by chemical polymerization of pyrrole in the presence of high oxidant concentration (Na2S2O8). Existence of polypyrrole layer on the both types of ion-exchange membranes were confirmed by recording their coating density, SEM images and conductivity. These membranes were extensively characterized by recording their properties such as water uptake, ion-exchange capacity, contact angle, permselectivity and membrane conductivity as a function of polymerization time such as. It was observed that due to coating of PPY for 2 h, membrane permselectivity of CEM for NaCl (0.907) was reduced to 0.873, while it was increased from 0.747 to 0.889 in the case of AEM. Similar behaviors were also obtained for bi-valent electrolytes. Electrodialysis experiments were also conducted with polypyrrole composite ion-exchange membranes using mixed electrolytic systems. Relative dialytic rates for NaCl with respect to other bi-valent electrolyte were varied in between 5 and 8 (depending on bi-valent electrolyte), which suggested the feasible and efficient separation of mono-valent from bi-valent electrolyte. Slower electro-migration of bi-valent electrolyte (CaCl2, MgCl2 and CuCl2) in comparison to NaCl was explained on the basis of synergetic effect of sieving of bulkier bi-valent cations by tight and rigid polypyrrole layer and the difference in electrostatic and hydrophobic–hydrophilic repulsion force between bi-valent cations and mono-valent cation. It was concluded that these composite membranes are suitable for the efficient separation of same type of charged ions by electro-driven separation techniques. 相似文献
53.
The composite material of polyaniline/NiO/sodium dodecylbenzenesulfonate (SDBS) is synthesized in SDBS micelles. The composite material has satisfactory conductivity and thermostability, and the particle length, width, and thickness are about 200–500 m, 3–5 m, and 40–96 nm, respectively. 相似文献
54.
55.
A new ion exchange membrane based on polyvinylidene fluoride (PVDF) and sulfonated poly(styrene-
divinylbenzene) was prepared by in-situ polymerization. The incorporation of sulfonic groups into the polyvinylidene fluoride composite membrane was confirmed by infrared spectroscopy (IR), ion exchange capacity (IEC) and energy dispersive X-ray analysis (EDAX). Area resistance, IEC and water uptake of the treated membrane were evaluated. When 20% of the crosslinked membrane was sulfonated at 80°C for 22 h, the PVDF ion exchange membrane can attain 0.8 Ω·cm2area resistance in NaCl aqueous solution at 25℃, IEC is as high as 2.43 millimoles per gram of the wet membrane. The
hydrophilicity of PVDF membrane is also significantly improved after treatment. When 60% of crosslinked membrane was sulfonated at 80 ℃ for 6 h, water uptake of the treated membrane can attain 64.7%. 相似文献
56.
Fine particle superacidic sulfated zirconia (SO42−/ZrO2, S-ZrO2) was synthesized by ameliorated method, and composite membranes with different S-ZrO2 contents were prepared by a recasting procedure from a suspension of S-ZrO2 powder and Nafion solution. The physico-chemical properties of the membranes were studied by ion exchange capacity (IEC) and liquid water uptake measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, thermogravimetry–mass spectrometry (TG–MS) and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the IEC of composite membrane increased with the content of S-ZrO2, S-ZrO2 was compatible with the Nafion matrix, the incorporation of the S-ZrO2 could increase the crystallinity and also improve the initial degradation temperature of the composite membrane. The performance of single cell was the best when the S-ZrO2 content was 15 wt.%, and achieved 1.35 W/cm2 at 80 °C and 0.99 W/cm2 at 120 °C based on H2/O2 and at a pressure of 2 atm, the performance of the single cell with optimized S-ZrO2 was far more than that of the Nafion at the same condition (e.g. 1.28 W/cm2 at 80 °C, 0.75 W/cm2 at 120 °C). The 15 wt.% S-ZrO2/Nafion composite membrane showed lower fuel cell internal resistance than Nafion membranes at high temperature and low relative humidity (RH). 相似文献
57.
Donghui Wang Zhengping Hao Daiyun Cheng Xicheng Shi Chun Hu 《Journal of molecular catalysis. A, Chemical》2003,200(1-2):229-238
Composite oxide MOx/Al2O3 supported gold catalysts for low-temperature CO oxidation were prepared and investigated. The presence of transition metal oxide was proved to be beneficial to the improvement of catalytic performance of Au/Al2O3 catalysts for low-temperature CO oxidation. Furthermore, the influence of various pretreatment conditions on Au/MOx/Al2O3 catalysts was studied carefully. The image of TEM showed that gold catalyst with small gold particles only in the form of a fine dispersion exhibited highly catalytic activity. The XPS, Fourier transform infrared (FTIR) spectroscopy characterization results of Au/FeOx/Al2O3 catalyst showed that gold catalysts having partially oxidized gold species have the best catalytic performance. One possible pathway for CO oxidation on Au/FeOx/Al2O3 catalyst is that the CO adsorbed on gold particles reacts with adsorbed oxygen, which is possible to occur on oxygen vacancies on the support or at the metal–support interface. 相似文献
58.
59.
《Electroanalysis》2003,15(21):1719-1722
Composite‐electroplating of zinc particles with polytetrafluoroethylene at a zinc substrate resulted in a working electrode which could be used at high negative potentials (to ?2.5 V vs. Ag/AgCl) without significant hydrogen evolution. The electrodes were characterized by SEM and CV and were used to detect organochloride compounds in a water‐acetonitrile mixture, by potential step methods. 相似文献
60.
Aiming to develop a high performance fiber reinforced rubber of SBR, a special technique using electron beam (EB) irradiation-induced graft-polymerization was applied to ultra-high molecular-weight polyethylene (UHMWPE) fibers. Although UHMWPE is chemically inert, N-vinyl formamide (NVF) could be graft-polymerized onto the UHMWPE fiber surface with this special technique. A maximum grafting percentage of 23.6% was achieved. The composite of SBR and grafted UHMWPE fibers with maximum grafting indicated a linear increase in the initial modulus and strength with the fiber content. At the fiber content of 10%, the initial modulus was improved about five times with respect to that of the pure SBR, while the strength was done about twice. At this moment, only a small reduction could be observed in the strain compared with that of pure SBR. The fiber reinforced rubber with a good performance was obtained in the system of SBR and grafted UHMWPE fibers. 相似文献