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排序方式: 共有164条查询结果,搜索用时 15 毫秒
161.
162.
M.Y. Ho P.S. Khiew D. Isa T.K. Tan W.S. Chiu C.H. Chia 《Current Applied Physics》2014,14(11):1564-1575
In this study, a symmetric electrochemical capacitor was fabricated by adopting a lithium iron phosphate (LiFePO4)-activated carbon (AC) composite as the core electrode material in 1.0 M Na2SO3 and 1.0 M Li2SO4 aqueous electrolyte solutions. The composite electrodes were prepared via a facile mechanical mixing process. The structural properties of the nanocomposite electrodes were characterised by scanning electron microscopy (SEM) and Brunauer–Emmett–Teller (BET) analysis. The electrochemical performances of the prepared composite electrode were studied using cyclic voltammetry (CV), galvanostatic charge–discharge (CD) and electrochemical impedance spectroscopy (EIS). The experimental results reveal that a maximum specific capacitance of 112.41 F/g was obtained a 40 wt% LiFePO4 loading on an AC electrode compared with that of a pure AC electrode (76.24 F/g) in 1 M Na2SO3. The improvement in the capacitive performance of the 40 wt% LiFePO4–AC composite electrode is believed to be attributed to the contribution of the synergistic effect of the electric double layer capacitance (EDLC) of the AC electrode and pseudocapacitance via the intercalation/extraction of H+, OH−, Na+ and SO32− and Li+ ions in LiFePO4 lattices. In contrast, it appears that the incorporation of LiFePO4 into AC electrodes does not increase the charge storage capability when Li2SO4 is used as the electrolyte. This behaviour can be explained by the fact that the electrolyte system containing SO42− only exhibits EDLC in the Fe-based electrodes. Additionally, Li+ ions that have lower conductivity and mobility may lead to poorer charge storage capability compared to Na+ ions. Overall, the results reveal that the AC composite electrodes with 40 wt% LiFePO4 loading on a Na2SO3 neutral electrolyte exhibit high cycling stability and reversibility and thus display great potential for electrochemical capacitor applications. 相似文献
163.
This paper addresses the ring-cavity fiber laser system. A class of gray and black soliton solutions of the model are reported by adopting an appropriate envelope ansatz. Further more, the modulation instability (MI) of the equation is studied using the linear-stability analysis (LSA) technique and the MI gain spectrum is derived. Some physical interpretations and analysis of the results obtained are also presented. 相似文献
164.
Isa Nishiyama Boping Liu Hitoshi Matsuoka Hisayuki Nakatani Minoru Terano 《Macromolecular Symposia》2003,193(1):71-80
The formation, variation and conversion of isospecific active sites were investigated, based on the isotacticity distribution of the polypropenes analyzed by the temperature rising elution fractionation (TREF) method. Stopped-flow polymerization of propene was carried out with a MgCl2-supported Ziegler catalyst in the absence or presence of an internal or external electron donor so that the effects and roles of the electron donors could be clarified. The results showed that various kinds of active sites with different isospecificities, including the highest isospecific active sites responsible for producing the highest isotactic fraction (elution temperature: > 112°C) existed, even in the electron donor-free catalyst system. The isospecificity of the active sites in the donor-free catalyst might have originated from a surface monolayer multinuclear titanium species, namely an “island” of titanium species. The addition of the external electron donor converted a part of the aspecific and/or low isospecific active sites into the second highest isospecific active sites, but showed no effect on the formation of the highest isospecific active sites, whereas the addition of an internal donor played an important role in creating the highest isospecific active sites as well as suppressing the formation of the aspecific active sites. 相似文献