Scalable nanostructured membranes for solid-oxide fuel cells

The use of oxide fuel cells and other solid-state ionic devices in energy applications is limited by their requirement for elevated operating temperatures, typically above 800°C (ref. 1). Thin-film membranes allow low-temperature operation by reducing the ohmic resistance of the electrolytes. However, although proof-of-concept thin-film devices have been demonstrated, scaling up remains a significant challenge because large-area membranes less than ~ 100 nm thick are susceptible to mechanical failure. Here, we report that nanoscale yttria-stabilized zirconia membranes with lateral dimensions on the scale of millimetres or centimetres can be made thermomechanically stable by depositing metallic grids on them to function as mechanical supports. We combine such a membrane with a nanostructured dense oxide cathode to make a thin-film solid-oxide fuel cell that can achieve a power density of 155 mW cm?2 at 510 °C. We also report a total power output of more than 20 mW from a single fuel-cell chip. Our large-area membranes could also be relevant to electrochemical energy applications such as gas separation, hydrogen production and permeation membranes.     

A monolithic silicon-based membrane–electrode assembly for micro fuel cells

Technical Physics Letters - We report the basic possibility of creating a micro fuel cell (MFC) with a monolithic silicon-based membrane–electrode assembly (MEA), which employs a porous...     

The Ionic Resistance of a Nanostructured Membrane Electrode Assembly under Nonequilibrium Conditions

Technical Physics Letters - The ionic resistance of the membrane electrode assembly (MEA) of O2/H2 fuel cells is studied in situ in a broad range of MEA compositions by using electrochemical...     

Thin-film sensor for emergency shutdown of electrochemical generator

A thin-film sensor for detection of emergency situations in fuel cells of electrochemical generators is proposed. Experimental results of emergency modeling are presented. It is shown that the thin-film sensor can function as a high-speed warning device. A system is proposed for emergency shutdown by means of a thermal pulse from the thin-film sensor. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 64–65, July, 2000.     

Humidity, Pressure, and Temperature Measurements in an Interdigitated-Flow PEM Hydrogen Fuel Cell

In situ measurements of humidity, temperature, and pressure are demonstrated for a polymer electrolyte membrane (PEM) fuel cell of interdigitated gas flow channel layout. Sensors are embedded at the flowfield edges, sampling air, and hydrogen at several positions along the flow channels. The measurements provide, for the first time, real-time localized data for this configuration of fuel cell. The results show that, for the interdigitated flowfield, moisture freely permeates through the membrane electrode assembly (MEA). This is in contrast to lower net moisture transmission through the same MEA used in a serpentine flowfield.     

Coupling electrodeposition with layer-by-layer assembly to address proteins within microfluidic channels

Two thin-film assembly methods are coupled to address proteins. Electrodeposition confers programmability and generates a template for layer-by-layer (LbL) assembly. LbL enables precise control of film thickness and the incorporation of labile biological components. The capabilities are demonstrated using glucose oxidase (GOx) based electrochemical biosensing within a microfabricated fluidic device.     

利用生物质材料合成高性能氢氧燃料电池氧还原催化剂（英文）

制备廉价、高活性氧还原催化剂对于发展氢氧燃料电池清洁能源极为重要.在本论文中,我们利用黑木耳作为生物质材料,通过一种便捷的方法合成了高活性氧还原催化剂.黑木耳经水热和热解两个步骤,碳化形成BF-N-950催化剂.该催化剂在酸性和碱性溶液中的半波电势分别为0.77和0.91 V.采用BF-N-950催化剂作为膜电极得到的氢氧燃料单电池,峰值功率可达255 mW cm^-2.本文提出了使用生物质材料合成高性能氧还原催化剂的方法,为氢氧燃料电池的应用提供了有益探索.     

Measurement of gamma and neutron radiations inside spent fuel assemblies with passive detectors

During operation of a fission nuclear reactor, many radionuclides are generated in fuel by fission and activation of ²³⁵U, ²³⁸U and other nuclides present in the assembly. After removal of a fuel assembly from the core, these radionuclides are sources of different types of radiation. Gamma and neutron radiation emitted from an assembly can be non-destructively detected with different types of detectors. In this paper, a new method of measurement of radiation from a spent fuel assembly is presented. It is based on usage of passive detectors, such as alanine dosimeters for gamma radiation and track detectors for neutron radiation. Measurements are made on the IRT-2M spent fuel assemblies used in the LVR-15 research reactor. During irradiation of detectors, the fuel assembly is located in a water storage pool at a depth of 6 m. Detectors are inserted into central hole of the assembly, irradiated for a defined time interval, and after the detectors removed from the assembly, gamma dose or neutron fluence are evaluated. Measured profiles of gamma dose rate and neutron fluence rate inside of the spent fuel assembly are presented. This measurement can be used to evaluate relative fuel burn-up.     

PEMFC膜电极电催化层的制备和性能

膜电极催化层的组成和电催化剂的活性对质子交换膜燃料电池的性能有很大影响．采用浸渍还原法制备出了Pt平均粒径为3．1nm的Pt／C催化剂．催化剂中Pt的粒径和在碳黑载体（VulcanXC-72）表面的分散程度采用透射电镜（TEM）进行测试．用Pt／C催化剂、适量的Nation溶液和PrFE乳液制备出质子交换膜燃料电池（PEMFc）膜电极的催化剂层,并研究了该催化剂层中PTFE含量对其性能的影响．实验表明,PTFE强烈的疏水性可以迫使部分水分向阳极反扩散,催化层中加入适量的PTFE可以使膜电极具有一定的水管理能力,在去掉辅助增湿系统的条件下具有良好的极化性能．     

新型MOX燃料组件的控制

MOX燃料组件的控制有别于常规UO2燃料,采用蒙特卡罗方法对MOX燃料组件的控制材料进行了分析。计算结果表明,控制棒价值随其B4C材料中10B的富集度及其直径的增加而增加,而控制棒插入深度对组件功率分布影响不大;随着MOX燃料PuO2含量的增大,可溶硼的价值减小,临界硼浓度随PuO2含量增大而增大,可溶硼浓度增大,慢化剂负温度系数绝对值减小,有利于改善MOX燃料组件径向功率分布的不均匀性。计算结果对压水堆新型MOX燃料组件控制设计有参考意义。     

Synthesis and characterization of Nafion/TiO2 nanocomposite membrane for proton exchange membrane fuel cell

In this study, the syntheses and characterizations of Nafion/TiO2 membranes for a proton exchange membrane fuel cell (PEMFC) were investigated. Porous TiO2 powders were synthesized using the sol-gel method; with Nafion/TiO2 nanocomposite membranes prepared using the casting method. An X-ray diffraction analysis demonstrated that the synthesized TiO2 had an anatase structure. The specific surface areas of the TiO2 and Nafion/TiO2 nanocomposite membrane were found to be 115.97 and 33.91 m2/g using a nitrogen adsorption analyzer. The energy dispersive spectra analysis indicated that the TiO2 particles were uniformly distributed in the nanocomposite membrane. The membrane electrode assembly prepared from the Nafion/TiO2 nanocomposite membrane gave the best PEMFC performance compared to the Nafion/P-25 and Nafion membranes.     

薄膜超材料减振特性研究

根据薄膜超材料共振耗能机理,设计并制备了薄膜减振超材料样品。利用振动测试系统对薄膜超材料减振特性进行了试验研究。结果表明,1.3 mm厚的薄层材料可实现对控制对象9 dB的减振效果,所设计的超材料结构厚度小,减振效果佳。     

质子交换膜燃料电池CCM的制备条件对其性能的影响

采用催化剂涂覆的膜(CCM)和碳纸扩散层组成质子交换膜燃料电池的膜电极.CCM采用直接喷涂的方法制备,研究了与直接喷涂技术相关的影响因素,包括催化层中Nafion的含量和分布、有机溶剂的种类、喷涂操作条件等.CCM的表面形貌和孔结构采用扫描电镜(SEM)方法表征,MEA的电化学特性通过单体PEMFC的I-V曲线进行评价.实验结果表明,在优化条件下制备的CCM膜电极的结构和性能有明显的改善.     

Measurements of water distribution in through-plane direction of PEFC by using neutron radiography

Fuel gas (hydrogen gas) and oxidant gas (air) are supplied to a polymer electrolyte fuel cell (PEFC). Protons pass through the electrolyte membrane, and combine with oxygen to form water in the cathode reaction site. The generated water must be supplied appropriately to the membrane for proton conduction. On the other hand, the generated water may affect the fuel cell performances because of the blocking of oxygen from reaching the cathode reaction site. Therefore, water management in the PEFC is important, and water distribution during the operation in the through-plane direction has been of wide concern. In order to obtain the water distributions in a membrane electrode assembly (MEA) and a gas diffusion layer (GDL), a borescope system was newly employed using neutron radiography. The system could obtain the water distribution in the MEA and the GDL, and pixel size of 6.5 μm was achieved. Furthermore, the system was applied for a tilted converter system. The pixel of 1.0 μm at an angle of 81° was achieved, and improvement of the spatial resolution was confirmed.     

A new high density magnetoresistive tape head

An 8-track magnetic tape head for high-frequency, high-density applications is described. It includes an unshielded magnetoresistive read head and two thin-film record heads for bidirectional operation with write verification. The MR sensors are biased by specially shaped thin-film permanent magnets (PM) that provide fields along both sensor axes to linearize output and eliminate Barkhausen noise. Nearly all films in the head are deposited using dry processes. Deposition conditions for the PM have been optimized to produce a high-coercivity, high-remanence isotropic film. The final head assembly has a contour that utilizes longitudinal slots to achieve intimate contact with low head-to-tape pressure. The associated data channel uses both read and write equalization to obtain the desired output pulse shape from the unshielded head     

Media requirements and recording physics for high density magneticrecording

Relevant aspects concerning the ultimate achievable recording densities for particulate as well as for thin-film media are discussed. This review covers the entire range starting from micromagnetics of individual single domain particles, moving on to their magnetic behavior in a particle assembly under particular consideration of the structure being actually obtained in the process of manufacturing recording media, and finally embarking on an outline of recording physics. These considerations are not only carried out for longitudinally and perpendicularly oriented recording media but also for media having an arbitrary orientation of the easy axis of magnetization. All aspects are discussed and illustrated for the first commercially available thin-film medium on a flexible substrate, which is the metal evaporated tape, i.e., the obliquely deposited Co-Ni-O layer for the Hi8 video system     

Nitrogen‐Induced Surface Area and Conductivity Modulation of Carbon Nanohorn and Its Function as an Efficient Metal‐Free Oxygen Reduction Electrocatalyst for Anion‐Exchange Membrane Fuel Cells

Nitrogen‐doped carbon morphologies have been proven to be better alternatives to Pt in polymer‐electrolyte membrane (PEM) fuel cells. However, efficient modulation of the active sites by the simultaneous escalation of the porosity and nitrogen doping, without affecting the intrinsic electrical conductivity, still remains to be solved. Here, a simple strategy is reported to solve this issue by treating single‐walled carbon nanohorn (SWCNH) with urea at 800 °C. The resulting nitrogen‐doped carbon nanohorn shows a high surface area of 1836 m² g^?1 along with an increased electron conductivity, which are the pre‐requisites of an electrocatalyst. The nitrogen‐doped nanohorn annealed at 800 °C (N‐800) also shows a high oxygen reduction activity (ORR). Because of the high weight percentage of pyridinic nitrogen coordination in N‐800, the present catalyst shows a clear 4‐electron reduction pathway at only 50 mV overpotential and 16 mV negative shift in the half‐wave potential for ORR compared to Pt/C along with a high fuel selectivity and electrochemical stability. More importantly, a membrane electrode assembly (MEA) based on N‐800 provides a maximum power density of 30 mW cm^?2 under anion‐exchange membrane fuel cell (AEMFC) testing conditions. Thus, with its remarkable set of physical and electrochemical properties, this material has the potential to perform as an efficient Pt‐free electrode for AEMFCs.     

Rational Design of Ultrathin Gas Barrier Layer via Reconstruction of Hexagonal Boron Nitride Nanoflakes to Enhance the Chemical Stability of Proton Exchange Membrane Fuel Cells

Hexagonal boron nitride (hBN) has great potential as a promising gas barrier layer in proton exchange membrane fuel cells (PEMFCs) as it shows high proton conductivity as well as excellent gas‐blocking capability. However, structural defects and mechanical damage during the transfer of the hBN layer and membrane swelling have limited the application of hBN sheets to PEMFCs. Here, an ultrathin gas barrier layer is successfully fabricated on a proton exchange membrane via reconstruction of mechanically exfoliated hBN nanoflakes using a direct spin‐coating process. The hBN‐coated layer effectively suppresses the gas crossover and inhibits the formation of reactive oxygen radicals in the electrodes without reducing the proton conductivity of the membrane. It is also demonstrated that the structural advantages of hBN‐coated gas barrier layers promise high performance of a unit cell even after a open‐circuit voltage (OCV) hold test for 100 h. Furthermore, through in‐depth postmortem analyses, a time‐dependent degradation mechanism of membrane electrode assembly under the OCV condition is rationally proposed.     

高性能被动式微型直接甲醇燃料电池的设计及制作

对一种被动式微型直接甲醇燃料电池进行了设计、制作及测试.利用微模具成型工艺,以ABS为基底材料制作了电池双极端板.采用200 μm厚的不锈钢薄片作为集电极,利用激光切割技术制作进料通道,并在集电极两侧溅射金层以防止电化学腐蚀.有效面积为0.49 cm2的膜电极则采用催化剂覆盖电解质膜的方法制备而成.测试结果表明,室温环境下(25℃)该被动式微型直接甲醇燃料电池在甲醇浓度为6 mol/L时最大功率密度可达22.14 mW/cm2.该性能对于被动式直接甲醇燃料电池的便携式高性能应用具有较大意义.     

Evaluation of water distribution in a small operating fuel cell using neutron color image intensifier

Neutron radiography is one of the useful tools for visualizing water behavior in operating fuel cells. In order to observe the detailed information about the water distribution in membrane electrode assembly (MEA) and gas diffusion layer (GDL) in fuel cells, a high performance neutron imaging system is required. A neutron color image intensifier (NCII) is a high spatial resolution and high sensitivity neutron image detector. We have developed an imaging system using an NCII for visualizing the behavior of water in fuel cells. The pixel size of the imaging system is around 4.7 μm in the small view field. By using this system, water distribution of a small sized fuel cell was observed continuously every 20 s at the Thermal Neutron Radiography Facility (TNRF). In the results, the water area appears from the GDL and MEA regions, and expanded to the cathode side channel with time. However, the voltage was gradually reduced with time, and steeply dropped. It is considered that the reduction and the drop of voltage were caused by a blockage of gas flow due to accumulation of water in the GDL and the gas flow channel in the cathode side.