Free-standing anion-exchange PEO–SiO2 hybrid membranes

Free-standing anion-exchange polyethylene oxide (PEO)–SiO₂ hybrid membranes with higher flexibility and good mechanical strength (tensile strength (TS) as high as 20.55 MPa) as well as high temperature tolerance (thermal degradation temperature in air, T_d, in the range of 220–240 °C) were prepared through sol–gel reaction of different precursors: charged alkoxysilane-functionalized PEO-1000 (PEO-[Si(OCH₃)₃]₂(+)), N-triethoxysilylpropyl-N,N,N-trimethylammonium iodine (A-1100(+)), monophenyltriethoxysilane (EPh) and in some cases also tetraethoxysilane (TEOS). Properties of the hybrid membranes, such as the thermal stability, tensile properties, hydrophilicity, and electrical performances, can be controlled by changing the feed ratio of the different sol–gel precursors. The results showed that some of the membranes have relatively good conductivity (∼0.003 S/cm) and so may find potential applications in alkaline membrane fuel cells.     

Performance of double layer electrolyte cells Part I: Model behavior

The present work reports on the estimated performance of double layer electrolyte based cells, including one yttria stabilized zirconia (YSZ) electron blocking layer. In order to evaluate the impact of the relative magnitude of the materials properties on the cell performance, a range of electrical properties has been considered, taking YSZ as reference. At constant temperature, the open circuit voltage, the oxygen permeability and the oxygen partial pressure profiles in such two layer electrolyte cells are related to the materials ionic and electronic transport properties, layers thickness and overall cell oxygen partial pressure boundary conditions. The effectiveness of the electron blocking characteristics of YSZ layers is demonstrated for a variety of materials, but consideration of the exact electrical properties (the n-type but also the p-type and ionic conductivities) of the second electrolyte layer is shown to be a fundamental requirement for proper design of such cells.     

燃料电池的发展和应用

燃料电池是一种新型的能量转换技术。文中扼要介绍了燃料电池发展过程及其在航天、发电站、便携式电源以及电动汽车方面的应用和发展状况。     

Prediction of flow over helically ribbed surfaces

Fully developed, steady flow through an annulus with a multistart, helical-ribbed inner cylinder is numerically predicted and compared with available data. To facilitate comparison, the transverse-ribbed case is included. It is predicted that substantial differences exist between turbulent flow over helical ribs and that over transverse ribs. The predictions clarify the experimental finding that helical-ribbed cylinders can be expected to have better pressure drop and heat transfer characteristics than transverse-ribbed cylinders. For this work the AERE Harwell code FLOW3D Release 2 was used.     

MEMS微型燃料电池及其基于压电风扇的换气方法

介绍了基于MEMS的微型燃料电池的国内外研究动态 ,对其技术关键进行了阐述。在此基础上 ,对微型燃料电池的换气方法进行了研究。提出一种低功耗、体积小的压电风扇 ,对其力学模型进行了分析 ,并进行了风速、振幅、功耗等方面的实验研究 ,初步证明其应用于微型燃料电池换气的可行性     

燃料爆炸抛撒过程的实验研究

 通过高速录像对3种量级（5、20、50 kg）FAE装置的静爆实验进行了现场记录，通过对燃料爆炸抛撒形成云雾的成长过程的实时记录结果，把燃料的爆炸抛撒过程分为3个阶段：喷出阶段、过渡阶段和膨胀阶段，其依据是爆炸驱动力和气动阻力的相互作用而导致的云雾径向膨胀速度的变化；对于结构相似的FAE装置，爆炸抛撒各阶段结束时刻及最终的云雾直径与装填燃料量的立方根成正比，说明小型装置可以模拟大型FAE武器；此外对应于不同阶段结束时刻的云雾直径与装置直径的比值分别为5.5、30和45。     

Two-Layer Fuel Cell Electrolyte Structure by Sol-Gel Processing

Thin layers of yttria-stabilized zirconia (YSZ) at 11 mol% Y₂O₃ doping level was deposited on a sintered disk of Y₂O₃ doped ceria electrolyte by spin-coating from an alkoxide solution. Dense sintered films were obtained by heat-treatment at 600°C. Open circuit voltage (OCV) was measured across the disk in a fuel cell mode with hydrogen fuel on the ceria side and pure oxygen on the YSZ side. Marked improvement of OCV was obtained on the two-layer electrolyte structure with the sol-gel YSZ film.     

Rare earth hydrogen storage alloy used in borohydride fuel cells

Fuel cell using the borohydride as the fuel has attracted much attentions because of high energy density and working potential. In this work, LaNi_4.5Al_0.5 hydrogen storage alloy used as the anodic material to replace noble metals has been investigated. Experimental results showed that H₂ evolution was unavoidable during discharge process because of the hydrolysis of , but the utilization of the fuel increased with the increasing current densities. At high discharge current, the alloy electrode showed the lowest hydrogen generation rate and higher utilization of the fuel because, the generated hydrogen was absorbed and oxidized to produce electric energy similar to the behavior of hydrogen storage alloy in nickel–metal hydride batteries. The reaction mechanism of borohydride on the surface of electrode made of hydrogen storage alloy also has been discussed. Hydrogen storage alloy would be a promising material as the anodic catalyst in borohydride fuel cell.     

Fuel quality and operational issues for polymer electrolyte membrane (PEM) fuel cells

Polymer electrolyte membrane (PEM) fuel cells are susceptible to degradation due to the catalyst poisoning caused by CO present in the fuel above certain limits. Although the amount of CO in the fuel may be within the permissible limit, the fuel composition (% CO₂, CH₄, CO and H₂O) and the operating conditions of the cell (level of gas humidification, cell temperature and pressure) can be such that the equilibrium CO content inside the cell may exceed the permissible limit leading to a degradation of the fuel cell performance. In this study, 50 cm² active area PEM fuel cells were operated at 55–60 °C for periods up to 250 hours to study the effect of methane, carbon dioxide and water in the hydrogen fuel mix on the cell performance (stability of voltage and power output). Furthermore, the stability of fuel cells was also studied during operation of cells in a cyclic dead end / flow through configuration, both with and without the presence of carbon dioxide in the hydrogen stream. The presence of methane up to 10% in the hydrogen stream showed a negligible degradation in the cell performance. The presence of carbon dioxide in the hydrogen stream even at 1–2% level was found to degrade the cell performance. However, this degradation was found to disappear by bleeding only about 0.2% oxygen into the fuel stream.     

Effect of the initial matrix material on the structure of radiation‐grafted ion‐exchange membranes: Wide‐angle and small‐angle X‐ray scattering studies

Seven different fluoropolymer films were used as matrix materials for radiation‐grafted ion‐exchange membranes. The crystallinity and preferred orientation of these membranes were studied with wide‐angle X‐ray scattering, and the lamellar structure of the membranes was examined with small‐angle X‐ray scattering. The crystallinity of poly(vinylidene fluoride) (PVDF)‐based matrix materials varied between 57 and 40%, and the crystallinity of the sulfonated samples varied between 34 and 23%. The lamellar periods of PVDF‐based matrix materials were about 115 Å, and the lamellar periods of poly(ethylene‐alt‐tetrafluoroethylene) and poly(tetrafluoroethylene‐co‐hexafluoropropylene) were 250 and 212 Å, respectively. When the samples were grafted, the lamellar periods increased. Correlation function analysis showed very clearly that the long‐range order decreased because of grafting and sulfonation processes. For those samples that showed good proton conductivity, the lamellar period also increased because of sulfonation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1539–1555, 2002