Mixed‐Conducting Perovskites as Cathode Materials for Protonic Ceramic Fuel Cells: Understanding the Trends in Proton Uptake

The proton uptake of 18 compositions in the perovskite family (Ba,Sr,La)(Fe,Co,Zn,Y)O_3‐δ, perovskites, which are potential cathode materials for protonic ceramic fuel cells (PCFCs), is investigated by thermogravimetry. Hydration enthalpies and entropies are derived, and the doping trends are explored. The uptake is found to be largely determined by the basicity of the oxide ions. Partial substitution of Zn on the B‐site strongly enhances proton uptake, while Co substitution has the opposite effect. The proton concentration in Ba_0.95La_0.05Fe_0.8Zn_0.2O_3‐δ is found to be 10% per formula unit at 250 °C, 5.5% at 400 °C, and 2.3% at 500 °C, which are the highest values reported so far for a mixed‐conducting perovskite exhibiting hole, proton, and oxygen vacancy transport. A comprehensive set of thermodynamic data for proton uptake in (Ba,Sr,La)(Fe,Co,Zn,Y)O_3‐δ is determined. Defect interactions between protons and holes partially delocalized from the B‐site transition metal to the adjacent oxide ions decrease the proton uptake. From these results, guidelines for the optimization of PCFC cathode materials are derived.     

一种基于Z源逆变器的燃料电池汽车变换器

在燃料电池汽车中,电能转换是一个核心问题。结合燃料电池的特性,简要说明了燃料电池汽车中现有变换器的不足。同时,为了克服传统燃料电池汽车电能变换器两级结构固有的不足,进一步提高其稳定性,提出了一种性能较高的Z源逆变器,分析了该结构的工作原理,采用了一种新型的具有直通零矢量的三相电压空间矢量调制方法,介绍了其工作特点以及直通零矢量的产生方法,进行了相关的仿真实验。仿真结果表明,该电路结构能够达到较高的性能要求,适合在燃料电池汽车上应用。     

湿法清洗制程优化对焊盘表面再结晶缺陷抑制

芯片焊盘上的再结晶缺陷是引起半导体后段封测工艺中键合失效的主要原因之一.国际上已经对这一缺陷的形成有了一定的理论分析,也提出了可以通过湿法清洗来去除此缺陷.在此基础上,通过对湿法清洗这一制程的优化,可在抑制焊盘表面再结晶缺陷的同时,有效地避免随之产生的焊盘腐蚀的问题,并且通过更换晶盒的步骤进一步降低了再结晶缺陷出现的可能性.同时提出了氟浓度对再结晶缺陷的影响以及对此的监测方法,对于大生产过程中抑制焊盘表面再结晶缺陷形成有一定的参考价值.     

免清洗焊接工艺与在线测试的兼容性

介绍了电路板组装免清洗工艺及其与在线测试的兼容性问题 ,并提出了相应的对策     

探讨单侧下回风局部百级洁净区的影响因素

本文运用CFD技术以疫苗车间接毒无菌室为例,探讨了干扰采用FFU单侧下回风形式的局部百级洁净区流场的各种因素和影响程度,这对类似局部百级洁净区的优化设计具有较重要的理论意义与工程应用价值。     

Development and Simulation of Sulfur‐doped Graphene Supported Platinum with Exemplary Stability and Activity Towards Oxygen Reduction

Sulfur‐doped graphene (SG) is prepared by a thermal shock/quench anneal process and investigated as a unique Pt nanoparticle support (Pt/SG) for the oxygen reduction reaction (ORR). Particularly, SG is found to induce highly favorable catalyst‐support interactions, resulting in excellent half‐cell based ORR activity of 139 mA mg_Pt ^?1 at 0.9 V vs RHE, significant improvements over commercial Pt/C (121 mA mg_Pt ^?1) and Pt‐graphene (Pt/G, 101 mA mg_Pt ^?1). Pt/SG also demonstrates unprecedented stability, maintaining 87% of its electrochemically active surface area following accelerated degradation testing. Furthermore, a majority of ORR activity is maintained, providing 108 mA mg_Pt ^?1, a remarkable 171% improvement over Pt/C (39.8 mA mg_Pt ^?1) and an 89% improvement over Pt/G (57.0 mA mg_Pt ^?1). Computational simulations highlight that the interactions between Pt and graphene are enhanced significantly by sulfur doping, leading to a tethering effect that can explain the outstanding electrochemical stability. Furthermore, sulfur dopants result in a downshift of the platinum d‐band center, explaining the excellent ORR activity and rendering SG as a new and highly promising class of catalyst supports for electrochemical energy technologies such as fuel cells.     

电磁铆接工艺在机翼整体油箱上的应用

针对锤铆、压铆工艺存在的不足,通过干涉量分布、疲劳寿命和气密耐久性等试验对几种典型铆接工艺进行对比,表明电磁铆接工艺不仅保证了较高的疲劳寿命,改善了劳动条件,提高了生产效率,而且能较好地满足气密性要求。在此基础上,制作了油箱试验件,测得实际检漏条件下的各漏源的漏率不大于10 -6 Pa．m3/s.该研究对于提高机翼整体油箱的制造质量具有重要应用价值。     

硅片纳米微粒清洗洁净新技术

随着半导体技术的不断发展,集成电路的线宽正在不断减小,对硅片表面质量处理的要求也就越来越高.传统的湿法清洗已经不能满足要求,故必须研发新的微粒清洗方法.简述了硅片表面污染物杂质的类型、传统的微粒湿法清洗法和干法清洗法,然后在此基础上分析了几种硅片制备工艺中纳米微粒的去除新技术,包括低温冷凝喷雾清洗工艺,N2O电子回旋加速共振等离子系统清洗技术,以及超细晶圆质量无危险的清洗方法等.     

High‐Performance Micro‐Solid Oxide Fuel Cells Fabricated on Nanoporous Anodic Aluminum Oxide Templates

Micro‐solid oxide fuel cells (μ‐SOFCs) are fabricated on nanoporous anodic aluminum oxide (AAO) templates with a cell structure composed of a 600‐nm‐thick AAO free‐standing membrane embedded on a Si substrate, sputter‐deposited Pt electrodes (cathode and anode) and an yttria‐stabilized zirconia (YSZ) electrolyte deposited by pulsed laser deposition (PLD). Initially, the open circuit voltages (OCVs) of the AAO‐supported μ‐SOFCs are in the range of 0.05 V to 0.78 V, which is much lower than the ideal value, depending on the average pore size of the AAO template and the thickness of the YSZ electrolyte. Transmission electron microscopy (TEM) analysis reveals the formation of pinholes in the electrolyte layer that originate from the porous nature of the underlying AAO membrane. In order to clog these pinholes, a 20‐nm thick Al₂O₃ layer is deposited by atomic layer deposition (ALD) on top of the 300‐nm thick YSZ layer and another 600‐nm thick YSZ layer is deposited after removing the top intermittent Al₂O₃ layer. Fuel cell devices fabricated in this way manifest OCVs of 1.02 V, and a maximum power density of 350 mW cm^?2 at 500 °C.     

Performance of a mesoscale liquid fuel‐film combustion‐driven TPV power system

Combustion‐driven thermophotovoltaic (TPV) systems have obtained increasing attention in recent decades, but most studies have focused on developing narrowband photovoltaic cells and selective emitters. In terms of the heat source, conventional combustion configurations and light gaseous fuels are extensively utilized in macro‐ or meso‐scale TPV power systems to simplify thermal management and mechanical fabrication. As far as miniaturization is concerned, however, fuelling these systems with liquid hydrocarbons would provide inherent advantages of high energy density and low volatility. Liquid fuels also promise easy and safe fuel recharging for small‐scale power systems. In this paper, a central porous‐medium combustor was employed in a small scale TPV power system. The combustor incorporated an emitting chamber wall and a heat recuperator. The radiant efficiency and overall efficiency were compared using different liquid hydrocarbon fuels in the system. The electric output characteristics of the combustion driven TPV system have been investigated to demonstrate the feasibility of a GaSb cell‐based TPV power system and to provide design guidance for mesoscale liquid‐burning TPV systems. Copyright © 2008 John Wiley & Sons, Ltd.