Investigation of titanium liquid/gas diffusion layers in proton exchange membrane electrolyzer cells

In a proton exchange membrane electrolyzer cell (PEMEC), liquid/gas diffusion layer (LGDL) is expected to transport electrons, heat, and reactants/products to and from the catalyst layer with minimum voltage, current, thermal, interfacial, and fluidic losses. In addition, carbon materials, which are typically used in PEM fuel cells (PEMFCs), are unsuitable in PEMECs due to the high ohmic potential and highly oxidative environment of the oxygen electrode. In this study, a set of titanium gas diffusion layers with different thicknesses and porosities are designed and examined coupled with the development of a robust titanium bipolar plate. It has been found that the performance of electrolyzer improves along with a decrease in thickness or porosity of the anode LGDL of titanium woven meshes. The ohmic resistance of anode LGDL and contact resistance between anode LGDL and the anode catalyst play dominant roles in electrolyzer performance, and better performance can be obtained by reducing ohmic resistance. Thin titanium LGDLs with straight-through pores and optimal pore morphologies are recommended for the future developments of low-cost LGDLs with minimum ohmic/transport losses.     

氟碳涂料实验室循环盐雾试验后防腐蚀行为研究

目的 研究氟碳重防腐涂层在循环盐雾试验后的防护性能.方法 开展氟碳涂层的实验室循环盐雾试验,通过电化学阻抗谱、附着力、光泽、色差测试等方法对氟碳涂层的各性能进行分析表征,并使用等效电路图对电化学阻抗谱数据进行拟合,评价涂层在盐雾试验后的腐蚀保护性能.结果 循环盐雾试验1440 h后,涂层无失光、变色、粉化等现象,模值由1.42×1011?·cm2下降至7.26×1010?·cm2,下降幅度较小.结论 经循环盐雾试验后的氟碳涂层仍具有优异的防护性能.     

可伸缩接地装置在浮顶罐中的应用

介绍了浮顶罐浮盘与罐壁之间的电气连接--可伸缩接地装置,它易于安装、检测和维护,能快速对地泄放雷电电荷和静电电荷,同时降低雷电流频率下的趋肤效应,尽可能地消除二次电弧,防止油罐密封处产生火花放电引起的火灾.     

流动海水环境中人工破损有机涂层的劣化过程研究

目的研究流动海水环境中人工破损有机涂层的劣化过程。方法使用电化学阻抗谱(EIS)技术对比研究流动海水与静止海水环境中破损涂层的劣化行为,跟踪观察涂层宏观形貌演变。结果根据EIS响应特征,发现流动海水中的人工破损有机涂层劣化更快,且在浸泡后期流动海水中破损涂层没有形成扩散阻抗。根据涂层宏观形貌发展,发现静止海水中涂层仅围绕破损处出现了面积较小的锈点和鼓泡,而流动海水中涂层因劣化而产生的锈点和鼓泡面积更大且大量分布在整个涂层表面。结论当人工破损有机涂层在流动海水和静止海水环境的浸泡过程中,涂层劣化首先从人工破损处开始。破损处成为局部腐蚀反应主要的阳极区,破损处周围的区域和涂层内在缺陷处成为扩展腐蚀反应的阴极区。流动海水中涂层的腐蚀产物累积与脱落更加频繁,导致涂层劣化速度加快和基体金属腐蚀加剧。     

硝酸盐浓度对微生物燃料电池阳极产电性能的影响

采用以假单胞菌Pseudomonas sp.C27为阳极优势菌属的微生物燃料电池(MFC)为研究对象,重点考察了进水中的硝酸盐浓度对于MFC系统产电及污染物去除的影响.实验结果表明,硝酸盐对于MFC的库仑效率(CE)影响较大,当硝酸盐浓度为250 mg·L~(-1)时,其电压下降段库仑效率仅为0.17%,而阳极未加入硝酸盐时,库仑效率为9.3%.当阳极初始硝酸盐浓度由0 mg·L~(-1)增加到250 mg·L~(-1)时,系统的传荷内阻由16.3Ω下降至11.2Ω,输出电压经短暂的电压下降后迅速回升至稳定,其稳定阶段输出电压与未受抑制阶段基本持平,最大输出功率可达到120 m W·m~(-2)左右.当硝酸盐浓度大于300 mg·L~(-1)时,硝酸盐对阳极微生物产电活性造成不可逆的抑制作用,系统产电能力大幅度下降且无法恢复至未受抑制阶段.可见,阳极生物反硝化过程对阳极生物产电具有电子竞争作用,过高的硝酸盐浓度会造成阳极生物膜产电性能降低甚至完全丧失.     

Methods Currently Used in Testing Microbiological Degradation and Deterioration of a Wide Range of Polymeric Materials with Various Degree of Degradability: A Review

Biodegradation of polymeric materials affect a wide range of industries, information on degradability can provide fundamental information facilitating design and life-time analysis of materials. Among the methods currently used in testing, traditional gravimetric and respirometric techniques are tailored to readily degradable polymeric materials mostly and polymer blends with biodegradable components, but they are not applicable to the new generation of engineering polymers which are relatively resistant to biodegradation. However, electrochemical impedance spectroscopy (EIS) has been tested for monitoring biodeterioration of high strength materials and the technique has very high sensitivity. A wide range of materials including electronic insulation polyimides, fiber-reinforced polymeric composites (FRPCs) and corrosion protective polyurethane coatings have been successfully measured under inoculation of degradative microorganisms using EIS. In addition, the mechanism of degradation of high strength polymers is mainly due to the presence of plasticizers in the polymer matrices. The information on various methods discussed in this review is intended to illustrate a suite of methods for those who are interested in testing biodeterioration of polymeric materials under different environmental conditions and in selecting appropriate techniques for specific applications.     

EMI有源滤波器与阻抗失配问题的分析

EMI滤波器的阻抗失配往往使得滤波器不仅起不到应有的作用，反而加剧了干扰分量的强度，为了弄清有源滤波器的结构类型与阻抗匹配之间的关系，本文从滤波器的主要性能参数插入损耗的基本定义入手。推导了不同结构有源滤波器的插入损耗与阻抗、滤波器增益关系的表达式。由此得出滤波器结构类型与阻抗失配情况的合理搭配．经过实验验证该结论对选用和设计EMI有源滤波器有直接的指导意义。     

A Sensitive Electrochemical Impedance Spectroscopy Method for Detection of Polyimide Degradation by Microorganisms

An electrochemical impedance spectroscopy (EIS) technique was evaluated for monitoring microbial degradation of electronic packaging polyimides. The microbial inoculum was a mixed culture of fungi isolated previously from deteriorated polyimides. The active fungal consortium comprised Aspergillus versicolor, Cladosporium cladosporioides, and a Chaetomium species. After inoculation, fungal growth on the polyimides resulted in distinctive EIS spectra indicative of polymer insulation failure, which directly related to polymer integrity. Degradation appeared to occur in a number of steps and two distinctive stages in the decline of film resistance were observed in the inoculated EIS cells within the 2 and 10 weeks after inoculation. The early stage of resistance decrease may be related to the ingress of water molecules and ionic species into the polymeric materials, whereas the second stage probably resulted from partial degradation of the polymers by fungal growth on the polymer film. The relationship between changes of impedance spectra and microbial degradation of the polymer was further supported by scanning electron microscopy (SEM) observations of fungi growing on the surface of the inoculated polyimides. Our data indicate that the EIS can be used in detection of early degradation of resistant polymers and polyimides that are susceptible to biodeterioration.     

基于电化学阻抗的航空有机涂层加速老化动力学规律研究

目的研究有机涂层的加速老化动力学规律。方法针对某飞机实际服役环境条件特点,编制有机涂层加速老化试验谱,开展0~9 a的当量加速老化试验。借助PARSTAT 4000电化学工作站,测试老化试验后涂层试件的电化学阻抗值。结果得到了不同老化周期有机涂层的Bode图、等效电路、孔隙率、吸水率和电化学阻抗,表征了加速试验条件下的老化动力学规律。结论低频阻抗|Z|0.01可以作涂层防腐蚀性能的评价指标,涂层老化过程大致可分为初期、中期和后期三个阶段,分别对应三个不同等效电路。     

Rapid determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration

A rapid, simple and sensitive method was demonstrated for the determination of phenolic compounds in water samples by alternating-current oscillopolarographic titration. With the presence of sulfuric acid, phenol could be transferred into a nitroso-compound by reacting with NaNO2. The titration end-point was obtained by the formation of a sharp cut in the oscillopolarographic with infinitesimal NaNO2 on double platinum electrodes. The results showed that phenol concentration had an excellent linear relationship over the range of 4.82×10-6-9.65×10-3 mol/L, the RSD of the proposed method was lower than 1.5%, and the spiked recoveries of three real water samples were in the range of 95.6%-106.9%.