Preparation and electrochemical characterization of activated carbons by chemical-physical activation

A process was proposed based on the combination of chemical and physical activation for the production of activated carbons used as the electrode material for electric double layer capacitor (EDLC). By material characterization and electrochemical methods, the influences of the activitation process on the specific surface area, pore structure and electrochemical properties of the activated carbons were investigated. The results show that specific surface area, the mesopore volume, and the specific capacitance increase with the increase of the mass ratio of KOH to char (m(KOH)/m(char)) and the activation time, respectively. When m(KOH)/m(char) is 4.0, the specific surface area and the mesopore volume reach the maximum values, i.e. 1 960 m²/g and 0.308 4 cm³/g, and the specific capacitance is 120.7 F/g synchronously. Compared with the chemical activation, the activated carbons prepared by chemical-physical activation show a larger mesopore volume, a higher ratio of mesopore and a larger specific capacitance. Foundation item: Project(2007BAE12B01) supported by the National Key Technology Research and Development Program of China     

Influence of nitrogen hetero-substitution on the electrochemical performance of coal-based activated carbons measured in non-aqueous electrolyte

Nitrogen-containing carbons were prepared by modification of activated carbons. The modified carbons were used as electrode materials with improved electrochemical performance. Precursor anthracite was activated by KOH (KOH: anthracite= 1:1), modified by melamine or urea and then treated at 1173 K to obtain the modified carbons. The porous structure, the chemical composition and the electrochemical characteristics of the carbons were investigated by nitrogen sorption, XPS and electrochemical methods respectively. Electrochemical experiments were performed in an organic electrolytic solution of 1 M (C2H5)4NBF4/PC.The samples modified by the different methods showed differences in chemical composition that introduced varying degrees of electrochemical performance enhancement. The presence of nitrogen enhanced the electron donor properties and the surface wettability of the activated carbons: this ensured a sufficient utilization of the exposed surface for charge storage.     

Bifurcation analysis for an SMIB power system with series capacitor compensation associated with sub-synchronous resonance

In this paper,an introduction to the bifurcation theory and its applicability to the study of sub-synchronous resonance (SSR) phenomenon in power system are presented. The continuation and bifurcation analysis software AUTO97 is adopted to investigate SSR for a single-machine-infinite-bus power system with series capacitor compensation. The investigation results show that SSR is the result of unstable limit cycle after bifurcation. When the system exhibits SSR, some complex periodical orbit bifurcations, such as torus bifurcation and periodical fold bifurcation, may happen with the variation of limit cycle. Furthermore, the initial operation condition may greatly influence the ultimate state of the system. The time-domain simulation is carried out to verify the effectiveness of the results obtained from the bifurcation analysis.     

陶瓷电容器的制备工艺概述

简介了新型陶瓷电容器的优点、功能、类型和发展现状及表面层陶瓷电容器、表面层型陶瓷电容器和晶界型陶瓷电容器的产生机理和区别，和影响陶瓷电容器性能的诸多因素，如显微结构、掺杂元素和包覆改性等；回顾了国内外陶瓷电容器的烧成工艺发展历史，如高温一次烧成、低温一次烧成、独石法和激光辐射法等；展望了陶瓷电容器在21世纪的研究和应用前景。     

基于超级电容的电梯能量再生系统

针对电梯采用制动电阻消耗回馈能量造成的极大浪费,介绍基于超级电容的电梯能量再生系统及其控制逻辑的设计。     

地铁再生制动储能装置参数设计

为了利用地铁列车制动过程产生的再生能量,维持牵引网电压的稳定,设计一种基于列车制动的超级电容型储能装置。根据北京地铁5号线的电动列车实际参数,通过对列车制动动力学和制动特性的对比和分析,更准确地计算出列车制动过程反馈到牵引网的再生能量;分析了储能装置的物理模型,根据限制条件确定了储能装置的主要参数和阵列配置;验证分析表明,该储能装置能满足地铁制动过程中各物理量的要求。     

Control strategy for energy recovery system in hybrid forklift

After analyzing the working condition of the conventional diesel forklift, an energy recovery system in hybrid forklift is considered and its simulation model is built. Then, the control strategy for the proposed energy recovery system is discussed, which is validated and evaluated by simulation. The simulation results show that the proposed control strategy can achieve balance of the power and keep the state of charge （SOC） of ultra capacitor in a reasonable range, and the fuel consumption can be reduced by about 20.8% compared with the conventional diesel forklift. Finally, the feasibility of the simulation results is experimentally verified based on the lifting energy recovery system.     

逆变弧焊电源中变压器的偏磁与防护

分析了全桥式逆变孤焊电源中变压器产生偏磁的原因及危害；阐述了在变压器一次侧串联电容或设置自动纠偏电路等防止偏磁的原理和方法。     

晶界对低压电解电容器铝箔腐蚀结构的影响

采用扫描电子显微镜和背散射电子取向成像技术分析研究了低压电解电容器用阳极铝箔的腐蚀结构、晶粒尺寸和晶界分布对比电容的影响及相关机理.结果表明,在铝箔的晶界附近,尤其是大角度晶界附近容易出现尺寸较大的腐蚀孔坑或沟道,造成腐蚀结构的不均匀性并降低比电容.该晶界优先腐蚀的现象起因于晶界的高缺陷密度和与之相应的腐蚀电流密度的局部集中.增加晶界密度可以降低杂质原子偏聚程度和电流密度分布的不均匀性,因此在一些特定的电化学腐蚀条件下可以借助减小晶粒尺寸的方式提高比电容.     

微量Mg对高压电子铝箔腐蚀结构的影响

采用立方织构定量检测以及扫描电子显微镜下观察腐蚀结构等手段, 对比了不同微量Mg元素含量的高压电解电容器阳极铝箔在织构和腐蚀结构上的差别, 研究了Mg含量对高压电解电容器阳极铝箔比电容的影响. 分析表明 Mg含量从0.0001%提高到0.0014%时, Mg会更多富集于铝箔表面, 促使腐蚀形成的氧化膜中出现含Mg的复合氧化物微小颗粒, 进而引起腐蚀隧道的侧向发展; 频繁的侧向发展可导致表层腐蚀组织剥落, 进而使铝箔在500 V的比电容从7.3×10-3 F/m2降低到4.3×10-3 F/m2.