碱金属热电转换器的电极材料

碱金属热电转换器的电极材料对碱金属热电转换器的热电转换特征及其影响很大,选用何种材料作为碱金属热电转换器的电极材料一直是该领域众多科研人员的研究课题,该文主要从化学稳定性的角度对碱金属热电转换器的电极材料的选择进行了分析。     

碱金属热电转换器（AMTEC）的新技术

介绍了采用熔融合金电极的碱金属热电转换器和采用钾循环工质,以钾－β氧化铝材料作为固体电解质的碱金属热电转换器两种碱金属热电转换器新技术,并与钠工质碱金属热电转换器进行了比较。     

钠钾工质碱金属热电转换器发电组件制备关键技术的研究

提出了钠钾工质碱金属热电转换器的概念,论证了开展钠钾工质碱金属热电转换器基础研究的意义,介绍了NaK-BASE管的制备方法,开展了NaK-BASE管—α-Al_2O_3绝缘过渡件—金属法兰之间的活性焊接和NaK-BASE管外表面电极多孔薄膜的制备等关键技术的探索性试验研究。试验结果表明,NaK-BASE管与α-Al_2O_3管以及α- Al_2O_3管与钛合金件之间的钎缝的漏率均达到10~(10)Pa·m~3/s级以上。采用反应性磁控溅射技术,在NaK-BASE管外表面制备了TiN电极多孔薄膜。     

碱金属热电直接发电装置的热辐射损失

寄生热辐射损失，特别是BASE管外表面的热辐射是影响碱金属热电转换器(AMTEC)高效运行的主要因素之一。为了量化BASE管外表面的热辐射对碱金属热电转换器热电转换效率的影响程度，文章用一简化模型，计算了采用不同层数遮热屏的碱金属热电转换器中的BASE管外表面的净热辐射量。结果表明，恰当设计AMTEC装置的结构，并在BASE管外加数层遮热屏，可使BASE管外单位电极表面的净热辐射损失在其工作温度范围内控制在1W／cm^2以下。     

碱金属热电转换器的循环工质和固体电解质的选择

对碱金属热电转换器所用的循环工质和β″氧化铝固体电解质的选择进行了探讨,对Na-AMTEC、K-AMTEC、NaK-AMTEC3种形式的碱金属热电转换器的热电转换特性进行了比较,认为K-AMTEC和NaK-AMTEC将是两种很有发展前途的碱金属热电转换器形式。     

碱金属热电转换器实用化的两个关键问题

文章提出了提高AMTEC热电转换效率的可能途径，分析了AMTEC的电输出特性在运行过程中发生退化的原因。认为AMTEC电特性随运行时间的退化现象主要是由于在运行过程中电极多孔薄膜和BASE材料特性的退化所引起的。     

碱金属热电转换器的电极效率

该文计算了碱金属热电转换器在不同的工作温度和不同BASE面电阻下当输入最大电极功率密度时的电极效率，推导出了在给定工作温度和BASE面电阻时取得最大电极效率的条件，并计算了最大电极效率点和最大电极效率，对在给定了工作温度下BASE面电阻和单位面积电极表面的热辐射量对最大电极效率及其工作点位置的影响从理论上进行了推导。     

碱金属热电转换器（AMTEC）理论分析

从理论上分析了碱金属热电转换器的输出电压与电极电流密度之间的关系,最大电极功率密度与工作温度,电极电流密度和BASE面电阻之间的关系,电极效率与工作温度,电极电流密度和BASE面电阻之间的关系。     

千瓦级空间堆热离子—碱金属混合式热电转换系统设计及性能

针对空间核电转换系统静态热电转换发电效率低的问题，设计开发了一种新型的热离子-碱金属混合发电系统，即利用热离子转换系统的余热作为碱金属转换器的热源，利用余热进行二次发电以提高转换系统效率，通过建立热离子-碱金属混合发电系统数理模型，研究了热离子热电转换系统接收极功函数和系统电流密度对混合发电系统功率效率的影响，得到了两个参数的最优区间，计算结果表明热离子-碱金属混合发电系统相比于热离子热电转换系统效率约6％~10％，为静态热电转换系统的效率优化提供了理论依据。     

表面特性对含水多孔介质的气体扩散特性的影响

为研究多孔介质材料的表面特性即亲水性和疏水性对其含水状态下的扩散特性的影响,基于材料的气孔分布特性,利用材料表面特性不同其液态水充填方式的差异,分析了不同接触角对多孔材料在含水状态下扩散特性的影响。结果表明,不同表面性质的多孔材料其扩散特性差异很大,疏水性多孔介质的渗透性能和扩散性能均低于亲水性多孔介质。     

Temperature effect on lifetimes of AMTEC electrodes

The alkali metal thermal to electric converter (AMTEC) is perhaps one of the most desirable devices for directly converting heat into electrical energy, particularly for deep space exploration, where time can be prolonged from a decade to a score of years. Its stability is expected to last for a long time, 15 years or more. The two major components responsible for power output of AMTEC are the electrolyte and the electrode. In this work, we describe research on the AMTEC electrodes, which might function without much power degradation as a function of time.     

The role of electrodes in power degradation of AMTEC: analysis and simulation

During the testing of the alkali metal thermal to electric converter (AMTEC) in laboratory, maximum power output of the AMTEC was found to be decreasing from 2.48 to 1.27 W after 18,000 h of operation with the hot side temperature of 1023 K and the condenser side temperature of 600 K. Electrode is one of the components in AMTEC which has effective lifetime. In this study, the role of the electrode on the overall power degradation has been investigated and reasons of the degradation are established qualitatively and quantitatively. The electrode is found 17% on average responsible for the overall degradation of power output.     

Modeling of hydrogen alkaline membrane fuel cell with interfacial effect and water management optimization

In this study, a whole-cell 3D multiphase non-isothermal model is developed for hydrogen alkaline anion exchange membrane (AAEM) fuel cell, and the interfacial effect on the two-phase transport in porous electrode is also considered in the model. The results show that the insertion of anode MPL, slight anode pressurization and reduction of membrane thickness generally improve the cell performance because the water transport from anode to cathode is enhanced, which favors both the mass transport and membrane hydration. The effect of cathode MPL is generally insignificant because liquid water rarely presents in cathode. It is demonstrated that slight pressurization of anode, which might not lead to apparent damage to the membrane, can effectively solve the anode flooding and cathode dryout issues.     

On the mesoporous TiN catalyst support for proton exchange membrane fuel cell

A mesoporous TiN structure with high surface area and excellent electrical conductivity was fabricated for application as a catalyst support in proton exchange membrane fuel cell (PEMFC). Pt nanoparticles were then uniformly deposited on the TiN porous support by wet chemical reduction. The performances of PEMFC using Pt@TiN electrodes were evaluated by a single cell test station. The membrane electrode assembly using Pt@TiN for both anode and cathode exhibited 70%–120% higher specific power densities than that of commercial E-Tek due to higher electrical conductivity and porosity of the catalyst support and higher Pt utilization efficiency.     

Characteristics of electrodes materials and their lifetime modeling for AMTEC

One major problem in the power output of alkali metal thermal to electric converter (AMTEC) is its decay with time. From the 18,000 h of laboratory testing on AMTEC, it was found that power output decreased from 2.48 to 1.27 W. One of the major causes of this decay is the grain growth of the electrodes. In this study, three electrodes have been studied in terms of their grain growth and a comparison of their performance has been made. Materials for those three electrodes, namely, RhW, Rh₂W, and TiN have been tried. From this analysis, RhW was found to be the best electrode, whereas Rh₂W was found to be the better electrode over TiN electrode. It was observed that power degradation of RhW electrode is 3.63% from grain growth effect. Power degradation by Rh₂W and TiN electrodes were calculated to be 6.45 and 10.89%, respectively, due to grain growth.     

质子交换膜燃料电池内部传热传质三维模拟

针对常规流场质子交换膜燃料电池提出了三维非等温数学模型。模型考虑了电化学反应动力学以及反应气体在流道和多孔介质内的流动和传递过程,详细研究了水在质子膜内的电渗和扩散作用。计算结果表明,反应气体传质的限制和质子膜内的水含量直接决定了电极局部电流密度的分布和电池输出性能;在电流密度大于0.3~0.4A/cm2时开始出现水从阳极到阴极侧的净迁移;高电流密度时膜厚度方向存在很大的温度梯度,这对膜内传递过程有较大影响。     

Numerical investigations of effect of membrane electrode assembly structure on water crossover in a liquid-feed direct methanol fuel cell

A two-phase mass-transport model is employed to investigate the water transport behaviour through the membrane electrode assembly (MEA) of a liquid-feed direct methanol fuel cell (DMFC). Emphasis is placed on examining the effects of each constituent component design of the MEA, including catalyst layers, microporous layers and membranes, on each of the three water crossover mechanisms: electro-osmotic drag, diffusion, and convection. The results show that lowering the diffusion flux of water or enhancing the convection flux of water (termed as the back-flow flux) through the membrane are both feasible to suppress water crossover in DMFCs. It is found that the reduction in the diffusion flux of water can be mainly achieved through optimum design of the anode porous layers, as the effect of the cathode porous region on water crossover by diffusion is relatively smaller. On the other hand, the design of the cathode porous layers plays a more important role in increasing the back-flow flux of water from the cathode to anode.