基于MEMS技术的微型DMFC阳极流场结构的设计与研究

流场结构对微型直接甲醇燃料电池(μDMFC)的性能有着重要的影响,尤其表现在影响燃料供应和温度分布上.本文运用计算流体动力学(CFD)的方法,分析和比较了双蛇形和平行流场结构中流速、温度等分布情况.模拟结果表明双蛇形流场结构比平行流场结构显示出更优的流速分布和更均匀的温度分布.采用微机电系统(MEMS)技术,在N型单晶...     

紫外固化技术在微型直接甲醇燃料电池封装中的应用

为了提高燃料电池的有效面积比并减少封装用时,采用紫外固化技术成功封装了微型直接甲醇燃料电池.首先基于非硅MEMS工艺制作了带有封装孔的燃料电池集流板,然后组装燃料电池并在封装孔和两集流板间缝隙中注入紫外固化胶,最后用紫外灯照射30s完成封装.实验结果显示,电池在室温、全被动、3mol/L甲醇的条件下,峰值功率密度为2.1mW/cm^2,内阻为800mΩ.cm^2.这说明紫外固化封装技术对微型直接甲醇燃料电池来说是一种有效的方法,并有望应用于其他MEMS器件的封装.     

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.     

微型直接甲醇燃料电池阳极流场结构

针对微型直接甲醇燃料电池(DMFC)阳极传质效率低和性能差等问题,对DMFC阳极流场结构进行了研究.利用MEMS技术实现了具有点形、平行和蛇形等阳极流场结构的硅基自呼吸式DMFC,测试对比结果表明单蛇形流场结构性能要优于其他几种流场;另外,对单蛇形流场结构参数进行了优化,结果表明当流道宽度∶脊的宽度∶流道长度为2∶3∶254时,电池性能达到最佳.在此基础上,为了改善反应物到催化层的传质效率和提高性能,提出了一种渐缩式单蛇形流场结构,其电池最大输出功率密度达到15.41 mW/cm2,比传统等宽式单蛇形流场提高了将近35%,为便携式微能源系统的应用开发奠定了基础.     

自呼吸式微型直接甲醇燃料电池的设计与性能分析

为了提高燃料电池的机械强度并降低加工成本,设计了一种基于不锈钢材料的空气自呼吸式微型直接甲醇燃料电池(DMFC).采用高温微型冲压技术制作电池的极板,并在其表面溅射Au和TiN来防止电化学腐蚀和减少接触电阻.在不同运行参数条件下对电池进行性能和稳定性的测试,结果表明阳极流速、甲醇浓度以及工作温度等均对电池性能有较明显的影响.该自呼吸式微型直接甲醇燃料电池在室温(20℃)条件下最高功率密度达到23.38 mW/cm2,并在温度40℃时可稳定地长时间工作,具有一定的应用价值.     

高温质子交换膜燃料电池用Nafion／SiO2复合膜研究进展

传统的质子交换膜燃料电池在高温下工作时，质子膜会因温度升高而发生脱水和膜电阻升高的现象，这对提高燃料电池的工作性能是一个致命的阻碍．由于Nafion／SiO2复合膜具有较好的吸水和保水性能和较好的阻止甲醇渗透的能力，人们通过溶胶一凝胶法或重铸法合成了Nafion／SiO2复合膜，并于高温(80～140℃)下应用在质子交换膜燃料电池和直接甲醇燃料电池中．简单介绍了Nafion／SiO2复合膜的制备方法、结构性能及研究情况，并分析了存在的问题和其广阔的应用前景．     

微型直接甲醇燃料电池的热传导

根据各种传热机理建立了微型直接甲醇燃料电池的热传导模型,通过分析热量主要散失途径,对甲醇流速和封装材料对热传导的影响进行研究与优化.研究表明,减小甲醇流速有利于减小甲醇溶液流出带走的热量,热导系数小、厚度大的封装材料有利于减小对流和辐射散热.     

燃料电池实现商业化应用的大门正在打开--2005年全球燃料电池应用调查报告

燃料电池是一个将化学能直接转化为电能的电化学系统。依据所用电解质的不同，燃料电池可分为碱性燃料电池（AFC）、质子交换膜燃料电池（PEMFC）、磷酸型燃料电池（PAFC）、熔融碳酸盐燃料电池（MCFC）和固体氧化物燃料电池（SOFC）五类。近年来，由于PEMFC中的直接甲醇燃料电池（Direct Methanol Fuel Cell，DMFC）具有激活速度快，使用的燃料为甲醇，具有储运方便且成本低等优势而倍受青睐，在全球国际大厂积极投入研发推波助澜下，技术进展迅速。     

直接甲醇燃料电池高阻醇质子交换膜的研究进展

为降低甲醇的渗透,提高直接甲醇燃料电池的性能,许多研究者致力于低甲醇渗透质子交换膜的研究.每种膜都有优缺点,综述了改性Nation膜及其替代膜的研究现状,指出它们在直接甲醇燃料电池中的应用前景.     

叶栅内非定常不可压流动的数值模拟

基于SMAC(SimplifiedMarkerandCell)方法推导出直接求解二维非定常、不可压N-S方程的隐式数值方法。求解的基本方程是任意曲线坐标系中以逆变速度为变量的N-S方程和椭圆型的压力Poisson方程。采用该方法,对二维叶栅非定常分离流场进行了数值模拟,叶栅表面压力的计算结果与试验结果相比比较吻合,从而验证了这种方法的可靠性。同时对叶栅非定常流场的流场结构和流动机理做了初步的探讨。在均匀来流和定常边界条件下,叶栅内部流动表现出强烈的非定常性;在小冲角和高雷诺数时,叶栅尾部产生类似卡门涡街的周期性流动。     

Novel Flow Field with Superhydrophobic Gas Channels Prepared by One-step Solvent-induced Crystallization for Micro Direct Methanol Fuel Cell

Nano-Micro Letters - The CO2-induced capillary blocking in anode flow field is one of the key adverse factors to reduce the performance of a micro-direct methanol fuel cell (μDMFC). In order...     

聚乙烯醇膜的阻醇及导电性能研究(Ⅰ)热处理聚乙烯醇膜

直接甲醇质子交换膜燃料电池（DMFC）中甲醇的穿透问题是阻碍其发展的瓶颈，为提高膜的阻醇性能，采用在渗透蒸发领域广泛使用且具有良好分离效果的聚乙烯醇（PVA）为原料，制备了热处理PVA膜，对其阻醇及质子导电能力进行了研究。PVA膜的阻醇效果较目前在DMFC中广泛使用的Nafion全氟磺酸膜的有明显提高。但其自身不具有质子导电能力。需外加电解质溶液以提高其电导率。     

Flexible All-Solid-State Direct Methanol Fuel Cells with High Specific Power Density

It is vital to create flexible batteries as power sources to suit the needs of flexible electronic devices because they are widely employed in wearable and portable electronics. The direct methanol fuel cell (DMFC) is a desirable alternative portable energy source since it is a clean, safe, and high energy density cell. The traditional DMFC in mechanical assembly and its unbending property, however, prevent it from being employed in flexible electrical devices. In this study, the flexible membrane electrode assembly (MEA) with superior electrical conductivity and nanoscale TiC-modified carbon cloth (TiC/CC) is used as supporting layer. Additionally, solid methanol fuels used in the manufacturing of flexible all-solid-state DMFC have the advantages of being tiny, light, and having high energy density. Furthermore, the DMFC's placement and bending angle have little effect on its performance, suggesting that DMFC is appropriate for flexible portable energy. The flexible all-solid-state DMFC's power density can reach 14.06 mW cm⁻², and after 50 bends at 60°, its voltage loss can be disregarded. The flexible all-solid DMFC has an energy density that is 777.78 Wh Kg⁻¹ higher than flexible lithium-ion batteries, which is advantageous for the commercialization of flexible electronic products.     

Microtubular Fuel Cell with Ultrahigh Power Output per Footprint

A novel realization of microtubular direct methanol fuel cells (µ DMFC) with ultrahigh power output is reported by using “rolled‐up” nanotechnology. The microtube (Pt‐RuO₂‐RUMT) is prepared by rolling up Ru₂O layers coated with magnetron‐sputtered Pt nanoparticles (cat‐NPs). The µ DMFC is fabricated by embedding the tube in a fluidic cell. The footprint of per tube is as small as 1.5 × 10^?4 cm². A power density of ≈257 mW cm^?2 is obtained, which is three orders of magnitude higher than the present microsized DFMCs. Atomic layer deposition technique is applied to alleviate the methanol crossover as well as improve stability of the tube, sustaining electrolyte flow for days. A laminar flow driven mechanism is proposed, and the kinetics of the fuel oxidation depends on a linear‐diffusion‐controlled process. The electrocatalytic performance on anode and cathode is studied by scanning both sides of the tube wall as an ex situ working electrode, respectively. This prototype µ DFMC is extremely interesting for integration with micro‐ and nanoelectronics systems.     

Electrical enhancement of DMFC by Pt-M/C catalyst-assisted PVD

Direct methanol fuel cells (DMFC) are studied extensively owing to their simple cell configuration, high volume energy density, short start-up time and operation reliability. However, the major drawbacks include high production cost, catalyst and methanol crossover poisoning. This study presents a simple method for Pt-M/C catalyst preparation using a magnetron sputtering (MS) and metal-plasma ion implantation (MPII) technique. The Pt catalysts were sputtered onto a gas diffusion layer (GDL), followed by implanting Cr, Fe, Ni, and Mo catalysts using MPII (accelerating voltage is 20 kV and implantation fluence is 1 × 10¹⁶ ions/cm²). The crystallinity and microstructure of the catalyst films were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM). The cell performance was tested using potential stat/galvano station. The results indicate that the membrane electrode assembly for Pt-Ni/C, Pt-Fe/C and Pt-Cr/C catalysts can enhance DMFC cell performance, compared with traditional Pt/C and Pt-Ru/C. The maximum Pt-Ni/C power density is 2.4 mW/cm² with an open circuit voltage (OCV) 0.334 V when tested at a methanol concentration of 1 M.     

Silicon rice-straw array emitters and their superior electron field emission

Free standing and vertically aligned silicon rice-straw- like array emitters were fabricated by modified electroless metal deposition (EMD), using HF-H(2)O(2) as an etching solution to reduce the emitter density and to make the emitter end of the formed silicon rice-straw arrays shaper than those formed by conventional EMD. These silicon rice-straw array emitters can be turned on at E(0) = 4.7 V/μm, yielding an EFE (electron field emission) current density of J(e) = 139 μA/cm(2) in an applied field of 12.8 V/μm. According to a simple simulation, the excellent EFE performance of the silicon rice-straw array emitters originates in not only the favorable distribution of emitter arrays, but also the shape of the emitter apexes. The modified-EMD method is easily scaled up without expensive equipment, so silicon rice-straw array emitters are a promising alternative to silicon-based field emitters.     

硅基电泳芯片非接触电导检测器

研制了一种集成于硅基电泳芯片分离沟道末端侧壁的新型二电极非接触电导检测器.讨论了影响电导检测响应灵敏度的相关因素;采用MEMS分析软件及等效电路模拟仿真,确定了检测器的相关参数,电极长度为550μm,宽度为15μm,间距为80μm,绝缘层厚度为1μm,电导检测工作频率为300 kHz.在加工技术中,选用SOI(sili-con on insulator)基片制作十字形微沟道及集成电导检测电极,采用深刻蚀和隔离技术使检测电极被完全隔离成孤岛,利用硼掺杂技术在分离沟道末端侧壁形成立体电极,获得了集成非接触电导检测电极的硅基电泳芯片.在外加Vpp为10 V、工作频率为300 kHz的正弦波激励下,进行了Na+无机阳离子浓度梯度实验以及Na+和Li+混合无机阳离子的电泳分离检测.结果表明,Na+浓度在1×10-9～1×10-4 mol/L范围内,电导响应信号随着离子浓度的增加而增大,检出限达到1×10-9 mol/L;Na+和Li+混合无机阳离子的分离度达到2.0,实现基线分离.