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排序方式: 共有68条查询结果,搜索用时 15 毫秒
1.
Enn Lust Gunnar Nurk Silvar Kallip Indrek Kivi Priit Möller 《Journal of Solid State Electrochemistry》2005,9(10):674-683
The analysis of the medium temperature half-cell Ce0.8Gd0.2O1.9|70 wt% La0.6Sr0.4CoO3- (LSCO) + 30 wt % Ce0.8Gd0.2O1.9 (CGO) has been made by electrochemical impedance, cyclic voltammetry and chronoamperometry. The shape of complex impedance plots depends on temperature and cathodic polarisation of the electrode. Nyquist (Z, Z-) plots were fitted by equivalent circuit taking into account the electrolyte properties (at very high frequencies), charge transfer process at grain boundaries (at high frequencies), and medium and low frequency O2 reduction process at the cathode surface and inside the porous cathode material. Two different time constants have been obtained for the cathode process, i.e. for electroreduction of oxygen. It was found that the addition of CGO into the cathode material (LSCO) only somewhat decreases the surface catalytic activity but the noticeably higher low-frequency resistance (i.e. mainly diffusion-like mass transfer resistance RD) values at lower temperatures have been calculated. It was found that the mainly bulk diffusion-limited process at T773 K deviates toward the kinetically mixed process (diffusion + charge transfer) with increasing temperature. 相似文献
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The synthesis of N-[2-(heteroarylhydrazono)ethyl]benz-amides starting from (Z)-2-benzoylamino-3-chloro-2-propenoic acid and heteroarylhydrazines is reported. 相似文献
6.
Cyclic voltammetry and electrochemical impedance spectroscopy have been applied for investigation of electrochemically polished Bi(111) electrode in 1-ethyl-3-methyl imidazolium tris(pentafluoroethyl)trifluorophosphate (EMImFAP), 1-ethyl-3-methyl imidazolium tetracyanoborate (EMImTCB) and 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMImBF4) ionic liquids. The region of ideal polarizability, series resistance and capacitance, limiting high-frequency and low-frequency capacitances have been calculated. The lower series capacitance values at electrode potential less negative than the potential of the minimum in the capacitance vs. voltage curve for Bi(111)|EMImFAP than that for EMImBF4, and especially for EMImTCB, have been explained by the bigger diameter of FAP?, higher cation and anion sizes symmetry, and less expressed surface activity (i.e. lower closest approach of the FAP? mass centre to an electrode surface) compared with BF4? and TCB? anions. 相似文献
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Air-coupled ultrasound (ACU) provides a tool to evaluate wood samples of small or moderate thickness (<30 mm) thereby avoiding direct contact or liquid coupling. Results of through-transmission ACU measurements on wood veneer samples and related products are reported with respect to a wide variety of quality aspects. Fluctuations in the averaged received signal levels appear to be correlated to the presence of natural or machine-induced thickness and density variations, flaws and grain damage, errors produced by the manufacturing process, insufficient bonding on a substrate, etc. In addition it is seen that the variability of the signal levels enables to distinguish between quarter and crown areas. 相似文献
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S. Sepp K. Vaarmets J. Nerut I. Tallo E. Tee H. Kurig J. Aruväli R. Kanarbik E. Lust 《Journal of Solid State Electrochemistry》2017,21(4):1035-1043
Fuel cell electrodes were prepared from Pt nanocluster activated hierarchical microporous-mesoporous carbon powders. The carbon supports were synthesized from molybdenum carbide applying the high-temperature chlorination method. Six different synthesis temperatures within the range from 600 to 1000 °C were used for preparation of carbon supports. Thermogravimetric analysis, X-ray diffraction, low-temperature nitrogen sorption, and high-resolution scanning electron microscopy methods were used to characterize the structure of the electrode materials and symmetrical membrane electrode assemblies (MEAs). The MEAs prepared were used to conduct the proton exchange membrane fuel cell (PEMFC)single-cell measurements. The polarization and power density curves for single cells were calculated to evaluate the activity of the catalyst materials synthesized. The electrochemically active surface area (from 2.4 to 11.9 m2 g?1) was obtained in order to estimate the contact surface areas of platinum and Nafion® electrolyte. The values of the electrolyte resistance, polarization resistance, and cell degradation rate were calculated from electrochemical impedance spectroscopy data. The carbon materials synthesized within temperature range from 600 to 850 °C were found to be the most suitable supports for PEMFCs, having higher maximum power density values and better stability (cell potential degradation 240 μV h?1) than commercial carbon-based (Vulcan XC72; 670 μV h?1) single cells. 相似文献
9.
Jaanus Eskusson Raivo Jaaniso Enn Lust 《Applied Physics A: Materials Science & Processing》2008,93(3):745-749
DLC (Diamond-like carbon films) were prepared by pulsed laser ablation of a liquid target at substrate temperatures from 18
to 600°C using 248 nm KrF excimer laser. The sp3 hybridization state carbon formation was additionally promoted by gaseous H2O2 flow through the reaction chamber and substrate excitation by the same laser beam.
Deposited DLC films were characterised by Raman scattering spectroscopy and atomic force microscopy (AFM). Comparative AFM
and Raman study shows that the increase in the content of sp3 type bonding in DLC is in correlation with the increase of the surface roughness of the samples prepared. 相似文献
10.
Condić-Jurkić K Perchyonok VT Zipse H Smith DM 《Journal of computational chemistry》2008,29(14):2425-2433
High level ab initio and density functional calculations have been employed to determine the most appropriate manner in which to truncate an arginine-bound carboxylate motif, using the substrate mechanism of Pyruvate Formate-Lyase as a case study. The results show that, both qualitatively and quantitatively, a neutral carboxylic acid provides a more realistic approximation to the salt bridge arrangement than does a bare anionic carboxylate substituent. 相似文献