【作者】 李喜宝；

【导师】 邵刚勤；

【作者基本信息】 武汉理工大学 ， 材料学， 2010， 博士

【摘要】 固体氧化物燃料电池(SOFC)因其零排放、高效率、燃料适应性广而成为一种举世公认的绿色能源,得到了世界范围内的广泛关注。但在走向实用化和商业化进程中,还有一些问题没有解决。其中一个主要问题是SOFC的工作温度过高,从而带来种种技术和材料困难。解决的主要措施是减小工作温度下固体电解质隔膜的电阻、提高电极的催化活性及机械强度。研究中温下具有高离子电导率的固体电解质材料,以及采用匹配性好和机械性能优良的阳极支撑的薄膜电解质,是近年来国际上的热点。本论文工作采用环保的醋酸盐为原料,以喷雾热分解技术制备氧化衫掺杂二氧化铈(SDC)粉末,研究实验配方及喷雾热分解工艺对SDC粉末性能的影响,并采用差热-热重分析及热力学计算研究了SDC的形成机制。系统研究了水基流延SDC浆料的制备、分散剂及其分散机理、流变学特性、浆料干燥及成膜机理,结果表明：当固相含量大于50wt.%时浆料显示出较明显的假塑性行为。三乙醇胺的分散机理主要为静电稳定机理。以20-25℃干燥16-24后,得到了表面平整光滑、显微结构均匀、强度和柔韧性高的SDC、NiO-SDC和NiO-YSZ：氧化钇稳定氧化锆)单膜生坯,生坯厚度与刮刀第2道刀口间隙的高度之间满足1/2.5-1/3的关系。研究了不同的脱脂和烧结制度对流延成型的SDC电解质性能的影响,结果表明：高温烧成后SDC的相结构没有发生改变,而晶粒尺寸增大。1400℃烧结2小时后得到了相对密度为97%的SDC电解质。烧结过程的动力学模型指出升高温度、细化粉末粒径可以促进烧结过程的进行。SDC电解质的离子电导率表现出Arrhenius行为。1300℃,1400℃和1500℃烧结2小时的SDC电解质的电导活化能分别为1.24 eV,0.90 eV和1.08 eV。1400℃烧结2小时的SDC在600℃时得到最大的离子电导率为9.5×10-3S·cm-1。系统研究了电解质厚度、叠层层数、叠层温度、叠层压力、共烧制度等因素对叠层法制备NiO-SDC和NiO-YSZ阳极,以及NiO-SDC阳极或NiO-YSZ阳极支撑的SDC薄膜电解质性能的影响。结果表明：在较低的温度和压力下制备出了平整无裂纹的叠层片。经1400℃共烧2h后,NiO-YSZ阳极达到了较高的机械性能并达到实用要求。采用叠层法成功制备出了直径为25mm,厚度为1.2mm的NiO-YSZ阳极支撑SDC薄膜电解质半电池。从理论上推导了单电池电动势与温度的关系及电流与氢气用量间的关系,并首次提出了氢气用量的阈值。研究了温度和氢气用量对单电池Ni-YSZ//SDC//LSCF-SDC电学性能的影响。结果表明：单电池于500℃,600℃,700℃,800℃时的最大功率密度分别为26.60 mW/cm2,42.30 mW/cm2,66.78 mW/cm2,93.03 mW/cm2,开路电压分别为0.978V,0.921V,0.861V,0.803V。各个温度下单电池的浓差极化较大,较低温时欧姆极化较大。单电池中Ni-YSZ阳极和SDC电解质界面间发生反应形成了低电导率的中间层。在未达到氢气用量阈值之前,单电池产生的电流I和其氢气用量v之间满足v=1.25×10-71I的定量关系：阈值之后,电流不随氢气用量的增大而增大。本文最后对流延-叠层法制备阳极支撑平板型中温固体氧化物燃料电池的发展方向进行了展望,指出采用双层流延制备Ni-SDC//SDC//LSCF-SDC单电池,从而得到电极与电解质间无界面反应、匹配性好的单电池是进一步提高其性能的关键。更多还原

【Abstract】 Due to the zero emission, high efficiency, good fuel flexibility and being a clean energy conversion device, the Solid Oxide Fuel Cell (SOFC) has now got a lot of attention in the world. To provide commercial and practical applications, some problems should be resolved. Among them, one is that the operating temperature of SOFC is too high, which leads to some technical and materials problems. The main method of reducing operating temperature of SOFC is decreasing the resistance of electrolyte, increasing the catalytic activity and mechanical properties of electrodes. Developing electrolyte materials with high ionic conductivity at intermediate temperature, and using the anode-supported film electrolyte with good matching and mechanical properties have become hotspots in recent years.Using the environment-friendly acetate as raw materials, Sm2O3 doped CeO2 (SDC) powder was prepared by spray paralysis. The effect of composition and processing technics of spray paralysis on the properties of SDC powder was investigated. The formation mechanics of SDC was studied by TG-TDA analysis and thermodynamics.This paper focuses systematically on the preparation of aqueous tape casting SDC slurry, dispersant and dispersing mechanism, the film forming mechanism and the rheological behaviors of suspensions. Results showed that the pseudoplastic behavior was appeared when the solid content was above 50 wt.%. The dispersing mechanism of triethanolamine was electrostatic stabilization. After dried at 20～25℃for 16～24 h, SDC, NiO-SDC and NiO-YSZ green tapes with smooth face, good microstructure and high strength were obtained. The thickness of green tapes was 1/2.5～1/3 of the gap height of the second doctor blade.The effect of binder burnout and sintering process on the properties of SDC electrolyte prepared by tape casting was investigated. Results showed that the phase structure of SDC was not changed besides grain sized was increased. The relative density of SDC reached 97% of the theory density after sintered at 1400℃for 2 h. The dynamics model indicated that increasing the sintering temperature and reducing the particle size could improve the sintering process. The ionic conductivity of SDC showed itself an Arrhenius behavior. The activation energy for conduction of SDC electrolyte sintered at 1300℃,1400℃and 1500℃for 2 h was 1.24 eV,0.90 eV and 1.08 eV, respectively. The ionic conductivity of SDC electrolyte sintered at 1400℃ for 2 h reached a maximum value of 9.5×10-3 S·cm-1 (tested at 600℃).The effect of electrolyte thickness, laminating number of sheets, laminating temperature amd press, and co-sintering process on the properties of NiO-SDC anode, NiO-YSZ anode, NiO-SDC anode-supported or NiO-YSZ anode-supported SDC film electrolytes prepared by tape casting were studied. Results showed that the laminated green tapes with smooth face were prepared at low temperature and pressure. NiO-YSZ anode reached good mechanical properties and practical utility after co-sintered at 1400℃for 2 h. The half cell with NiO-YSZ anode-supported SDC film electrolyte and with a diameter of 25 mm and a thickness of 1.2 mm was successfully prepared by laminating process.The relationships between electromotive force and temperature, current and hydrogen consumption were deduced theoretically. The threshold value of hydrogen consumption was firstly demonstrated. The effect of temperature and hydrogen consumption on the electrical properties of Ni-YSZ//SDC//LSCF-SDC single cell was studied. Results showed that the maximum power density of single cell reached 26.60 mW/cm2,42.30 mW/cm2,66.78 mW/cm2,93.03 mW/cm2 at 500℃,600℃,700℃, 800℃, respectively. And the open circuit voltage was 0.978 V,0.921 V,0.861 V, 0.803 V, respectively. The concentration polarization kept high at various temperatures, and the ohmic polarization was high only at relatively lower temperature. A boundary layer with low conductivity was formed between Ni-YSZ anode and SDC electrolyte. Before reaching the threshold value, the current (I) of single cell and hydrogen consumption (v) had a relationship of v=1.25×10-7I. After reaching the threshold value, the current did not change with the increasing of hydrogen consumption.Lastly, the developing perspective of anode-supported planar ITSOFC prepared by tape casting and laminating was described. It was pointed out that the Ni-SDC//SDC//LSCF-SDC single cell with good match, no interface reaction and better performance could be prepared by double layer tape casting.更多还原