Effect of magnetron sputtered anode functional layer on the anode-supported solid oxide fuel cell performance

Nickel oxide-yttria stabilized zirconia (NiO-YSZ) thin films were reactively sputter-deposited by pulsed direct current magnetron sputtering from the Ni and ZrY targets onto heated commercial NiO-YSZ substrates. The microstructure and composition of the deposited films were investigated with regard to application as thin anode functional layers (AFLs) for solid oxide fuel cells (SOFCs). The pore size, microstructure and phase composition of both as-deposited and annealed at 1200 °C for 2 h AFLs were studied by scanning electron microscopy and X-ray diffractometry and controlled by changing the deposition process parameters. The results show that annealing in air at 1200 °C is required to improve structural homogeneity of the films. NiO-YSZ films have pores and grains of several hundred nanometers in size after reduction in hydrogen. Adhesion of deposited films was evaluated by scratch test. Anode-supported solid oxide fuel cells with the magnetron sputtered anode functional layer, YSZ electrolyte and La_0.6Sr_0.4Co_0.2Fe_0.8O₃/Ce_0.9Gd_0.1O₂ (LSCF/CGO) cathode were fabricated and tested. Influence of thin anode functional layer on performance of anode-supported SOFCs was studied. It was shown that electrochemical properties of the single fuel cells depend on the NiO volume content in the NiO-YSZ anode functional layer. Microstructural changes of NiO-YSZ layers after nickel reduction-oxidation (redox) cycling were studied. After nine redox cycles at 750 °C in partial oxidation conditions, the cell with the anode NiO-YSZ layer showed stable open circuit voltage values with the power density decrease by 11% only.     

Effects of accession,spacing and pruning management on in-situ leaf litter decomposition of Jatropha curcas L. in Zambia

Jatropha curcas L. leaf litter decomposition and subsequent nutrient release was monitored in three experimental J. curcas plantations in Zambia, comparing accessions from six countries, pruned versus non-pruned and different plant spacings. Leaf litter production was low (267–536 kg ha⁻¹ at the end of the growing season) and contained, on average, 1.23% N, 0.14% P and 2.61% K. Litter decomposed rapidly, losing 80% of total mass between 70 and 105 days after incubation in the field and followed a negative exponential pattern with an average decomposition constant, k, of 0.08 week⁻¹. No significant effects of plant accession, plant spacing or pruning on the decomposition rate were detected. K, P, Mg and Na had nutrient release rates exceeding mass loss, explained by their high mobility and solubility, together with high soil temperature and rainfall conditions. Others, such as Ca and Mn, were initially retained in the decaying leaf litter before later release. The rate of N release closely approached that of mass loss. J. curcas litter can be a supplemental source of nutrients in areas known for nutrient deficiency and low organic matter, which represents an additional input in intercropping systems above biofuel production. Considering that the total primary nutrient input through J. curcas litterfall to the soil is limited (for example, for nitrogen between 9.7 and 14.2 g kg⁻¹ and for phosphorus between 0.8 and 1.9 g kg⁻¹), organic or mineral fertilizer application remains crucial to satisfy fully the nutrient requirements of surrounding crops.     

Dislocations,texture and stress development in hydrogen-cycled Pd thin films: An in-situ X-ray diffraction study

For Pd thin films, microstructural changes involved during hydrogen cycling provide the information needed to predict and optimize the film's mechanical strength. In this paper, a systematic study of the morphology, microstructure, texture, and stress has been performed on Pd thin films during hydrogen loading and deloading cycles at room temperature. Pd thin films of similar morphology were prepared by magnetron sputtering on substrates of different compliances, i.e., Si-oxide, Titanium (Ti) and Polyimide (PI). The evolution of the morphology, grain-orientation distribution (texture), state of stress, and dislocation densities are analyzed for each of the film substrate types for 20 hydrogen loading/deloading cycles. The lattice expansion and contraction caused by the transition from Pd to Pd-hydride and back result in a strong stress increase. This stress increase stabilizes after a few cycles by grain boundary motion that leads to a gradual enhancement of the (111) texture and changes in the dislocation density for Pd films that are strongly clamped on to an oxidized Si(100) wafer substrate with an intermediate layer (Ti or PI). For Pd on PI, the stress is also partly released by a crack-based (crack widening/growth/propagation) pathway. Pd films on Ti and PI do not buckle or blister after 20 hydrogen cycles. By providing a sufficiently compliant substrate the traditional problems of buckle-delamination of a film on a stiff substrate are mitigated.     

沥青混合料饱水过程的强度演化规律及机理分析EI北大核心CSCD

为研究SBS改性沥青混合料在饱水过程中的力学强度演化过程,提出了一种基于圆孔孔边应力集中效应的力学模型,分别计算了非饱水和饱水孔隙的孔边应力.对不同沥青含量的SBS改性沥青混合料试件进行水敏感性试验(MIST)和恒温浸水试验,采用间接拉伸强度(ITS)和拉伸强度比(TSR)来表征沥青混合料的强度演化过程,分析孔隙水压循环次数、水浴时间、孔隙水压力和温度对沥青混合料强度的影响.结果表明:在劈裂荷载作用下,孔隙水压抗力消散了薄弱孔隙的应力集中;随着孔隙水压循环次数或恒温水浴时间的增加,试件的ITS先减小后增大,TSR持续增大;沥青混合料在饱水过程中的强度增加,实际上采集到的是沥青混合料自身强度与孔隙水压力的加和;温度对沥青混合料强度的影响比孔隙水压力的影响更加显著.     

WaSSI-C模型GIS可视化模拟系统的设计、实现与验证

为实现WaSSI-C(Water Supply Stress Index-C)模型地理信息系统(GIS)可视化模拟系统,为区域水碳资源分析和模拟决策提供模型工具,在解析WaSSI-C模型理论框架和运行机理的基础上,对模型计算过程进行模块化分解和结构化设计;采用C/S模式构建软件体系架构,基于时空数据模型设计E-R模型图,并应用Geodatabase空间数据库与SQLite关系型数据库联合管理模型参数和时空数据;在.Net开发环境下,基于ArcGIS Engine二次开发组件,使用C#语言进行混合编程,实现WaSSI-C模型GIS可视化模拟系统的功能,进而以焉耆盆地为试验对象进行应用验证。结果表明:系统同时支持文本和空间数据格式输入,能够在GIS可视化环境下自动化输出研究区月尺度蒸散、径流和总生态系统生产力等水碳耦合过程变量的模拟地图,系统模拟结果率定期R²和NS均值分别为0.83和0.81,验证期两指标均值分别为0.8和0.76,总体上显示出良好的模拟效果。系统具有简单易用、运算效率高、普适性强等特点,可为相关领域研究提供有力工具支撑,也可为生态学、水文学等专业领域模型可视化研究提供借鉴思路。     

Effect of SiC whiskers on thermal cycling performance of YSZ-Based sealing coating

Two types of Y₂O₃ partially stabilized ZrO₂(YSZ)-based agglomerated powders with and without SiC whiskers were prepared by spray granulation, and the flow ability, apparent density and particle size distribution of them were investigated. The thermal cycling performance and failure mechanism of conventional high temperature sealing coating and modified one with additional layer with whiskers, which were sprayed by air plasma spraying (APS), were comparatively analyzed. The results showed that, compared to the powder without whiskers, the flow ability of that with whiskers reduced by 2.32%, and the apparent density and the proportion of 45–150 μm agglomerated powder increased by 1.53% and 2.29%, respectively. The thermal cycling failure mode of conventional high temperature sealing coating was the overall spalling of ceramic coating, and the spalling position originated from the interface of thermally grown oxide (TGO)/ceramic coating. Microstructure observation indicated that the structure integrity of SiC whiskers in the additional layer sprayed by APS was still retained. The whiskers were uniformly distributed and theinterface between bonding coating and ceramic coating exhibited excellent bonding. With the additional layer containing whiskers, the thermal cycling life of the coating was increased by 102.53%. In the thermal cycling process, the “bridging” and “pulling-out” effects of whiskers located at the additional layer consumed considerable energy, which could reduce the driving force of crack growth. Besides, a porous structure of the additional layer after thermal cycling was formed due to “bridging” and “pulling-out” of whiskers, further improving the thermal cycling life of coating with the additional layer.     

Enhanced power cycling performance of IGBT modules with a reinforced emitter contact

A typical emitter contact of an IGBT consists of a front metallization and bond wires. In this study, the power cycling performance of a special emitter contact design is experimentally verified. The emitter contact includes a metal plate, which is Ag-sintered to the metallization and wire bonded on the top surface. Either Cu or Al bond wires were implemented. Power cycling tests were performed to investigate the performance of such IGBT modules. The results were very promising and a cycling lifetime was achieved, which is about 20 times higher than the lifetime of typical IGBT modules. For a better understanding of the experimental results, the electrical and thermal response of the IGBT modules were simulated by FEM. The results of this study, provide a key for high-reliability designs of the emitter contact of IGBT modules with superior power cycling capability.     

Diffusion of Bike Sharing as an Innovation Vector in the City: The Case of BiciMAD (Madrid)

Bike sharing nowadays is a must-have element of the urban transport system that is changing mobility patterns in cities worldwide. BiciMAD, a fleet of bicycles with electric pedal-assistance (pedelecs)—introduced in the center of Madrid (Spain) in 2014—is an example of the latest generation. In this article, Innovation Diffusion Theory (IDT) is adapted and applied as a framework to study data from a series of surveys among BiciMAD subscribers to describe adopter profiles and analyze attributes that influence the time of adoption, including an additional one: cycling familiarity. Empirical results are presented to show how an innovation (in terms of technology and service configuration on the level of a city) is dispersed. Conclusions show that smart bike sharing is an innovation vector in urban mobility, an attractive new travel mode for the identified adopter categories, namely (1) lifestyle cyclists, the venturesome and technology enthusiast Earliest Adopters, (2) dedicated cyclists, the rational and deliberate Early Majority, (3) leisure cyclists, the skeptical and peer-dependent Late Majority, and (4) fair-weather cyclists, the prudent Laggards.     

Mg2SiO4 as a novel thermal barrier coating material for gas turbine applications

Forsterite-type Mg₂SiO₄ was investigated systematically for thermal barrier coating (TBC) applications. Results showed that Mg₂SiO₄ synthesized by solid-state reaction possessed the good phase stability up to 1573 K. The thermal conductivity of Mg₂SiO₄ at 1273 K was lower ˜20% than that of yttria stabilized zirconia (8YSZ). Mg₂SiO₄ also presented moderate thermal expansion coefficients, which increased from 8.6 × 10⁻⁶ K⁻¹ to 11.3 × 10⁻⁶ K⁻¹ (473˜1623 K). Mechanical properties including hardness, fracture toughness, and Young’s modulus of Mg₂SiO₄ were comparable to those of 8YSZ. The sintering results indicated a promising low-sintering activity of Mg₂SiO₄. Mg₂SiO₄ samples were subjected to water quenching test at 1573 K and showed a superior thermal shock resistance compared to 8YSZ. Mg₂SiO₄ coating with stoichiometric composition was produced by atmospheric plasma spraying. The thermal cycling test result showed that Mg₂SiO₄ coating had a lifetime more than 830 cycles at 1273 K, which is desirable for TBC applications.     

Synaesthesia and cycling data art: towards cross-modal representations of self-tacking cycling data

This paper develops ideas around cycling as art practice. The questions at the heart of it revolve around how new data technologies enable us to represent such experiences as artworks. Recent research in neuroscience has begun to establish the ways in which modes of perception are processed in the brain. Related research suggests that Synaesthesia may be caused by a genetic mutation that results in a ‘cross wiring’ of these modes of perception. Within the arts there is a long history of exploration around synaesthesia, ideas that are becoming relevant again particularly in relation to the growth in personal data. Representing sensations and transferring them from one mode to another offers a way to handle some of this data and potentially say new things about our experiences. The author explores these ideas through artworks made using data from cycling to investigate the visualization of this experience.