【作者】 杨春利；

【导师】 刘卫；

【作者基本信息】 中国科学技术大学 ， 材料学， 2010， 博士

【摘要】 当今世界,能源和环保已成为全世界共同关心的问题。由于在化工、冶金、能源、环保等领域具有巨大潜在应用价值,陶瓷膜材料的研究在最近几十年受到了学术界和工业界的关注。陶瓷中空纤维膜由于具有管径小、管壁薄、单位体积有效膜面积大等特点,近年来更是受到人们广泛研究。本论文主要对陶瓷中空纤维氧渗透和氢渗透膜的分离性能以及中空纤维管固体氧化物燃料电池的电学性能进行了研究。第一章是论文综述,首先简要介绍了膜的定义和分类；然后较全面阐述了陶瓷中空纤维膜的制备工艺和应用前景；最后着重论述了陶瓷中空纤维膜的研究现状和存在的问题。第二章制备出了Bi1.5Y0.3Sm0.2O3(BYS)-La0.8Sr0.2MnO3-δ(LSM)双相复合陶瓷中空纤维透氧膜并研究了其氧渗透性能。利用相转化／烧结技术制备的中空纤维膜具有非对称结构,靠近膜管内表面部分是指状孔结构,而靠近膜管外表面则是非常致密的结构。氧渗透测量给出膜管在中低温具有较高的氧渗透速率,在air／He梯度下,850℃时的氧渗透速率为3.9×10-7mol cm-2 s-1。研究表明中空纤维膜的氧渗透总流量随着膜管内吹扫气流量、纤维膜的长度和膜管外侧氧气来源气的氧分压的增加而增大。采用柱塞式流动模型和Wagner氧渗透理论我们还对双相复合中空纤维膜的氧渗透过程进行了模拟,模拟结果和实测的相符合。第三章研究了Ni-BaZr0.1Ce0.7Y0.2O3-δ金属陶瓷中空纤维膜的氢分离性能。NiO-BZCY复合粉体采用柠檬酸法一步制备,制备的NiO-BZCY纤维膜生坯在还原气氛中直接烧结形成Ni-BZCY金属陶瓷膜。所得的中空纤维膜具有“三明治”结构,靠近内外表面是指状孔结构而中间部分是致密层。中空纤维膜的氢渗透率随着管外H2和管内吹扫气流量的增加而增加。由于膜管内有BaCO3的形成,中空纤维膜的氢渗透率与较厚的片状膜相当,为了增加纤维膜的氢分离性能,必须抑制BaCO3的产生。第四章采用相转化法制备出了管径小于0.2 cm的中空纤维膜阳极支撑体,在靠近膜的内外表面具有指状孔结构,为气体传输提供了通道。通过真空辅助浸渍技术制备了约为12μm厚的电解质薄膜。烧结后的NiO-YSZ/YSZ中空纤维管的三点弯曲强度是118.3 MPa,但是氢气还原后机械强度要降低一半左右。当采用H2(～3%H2O)作为燃料气体时,微管电池在600℃,700℃和800℃的最大输出功率密度分别是124,287,377 mW cm-2,且开路电压都在1.01 V以上。由于具有很高的堆积密度,这种中空纤维管固体氧化物燃料电池具有很大的实际应用潜力。第五章以YSZ中空纤维膜为电解质,在膜管内表面沉积催化剂Ni作为阳极层并在外层涂阴极制备了电解质支撑的微管SOFC。通过降低YSZ纤维膜的预烧温度,可以抑制指状孔烧结成闭气孔,能更有效的在孔内沉积Ni。这样制备的阳极膜与电解质层结合非常紧密,可以大大降低离子界面电阻并防止了阳极在运行过程中的剥落。制备的电解质支撑的微管SOFC,在600℃,700℃和800℃时的最大功率密度分别是28,78,146 mW cm-2。电池的机械强度在测试过程中一直保持很高,这一特点使电解质支撑的中空纤维管SOFC在未来的实际应用中具有很大的优势。第六章对La2Cu1-xNixO4+δ(0≤x≤1)体系的低频内耗进行了研究。体系具有正交的K2NiF4结构,随着Ni含量的增加,晶胞参数中a,b轴伸长,c轴收缩,且额外氧含量δ呈线形增加。低频内耗研究表明,x≤0.005时,样品在200 K和250 K左右存在两个弛豫内耗峰,分别是由单个间隙氧和氧对跳跃引起的。0.015≤x≤1时,体系的低温内耗峰消失,只存在一个高温内耗峰；并且x＜0.2时,峰高随着x的增加慢慢升高,而当x＞0.2时,峰高随着x的继续增加急剧下降,说明此时间隙氧发生了从一维有序向三位有序的转变,并随着x的增加,三维有序化能力增强。此外,样品从正交向四方相的转变温度随着Ni的增加向低温移动。第七章对本论文的工作进行了总结,并对陶瓷中空纤维膜今后的研究工作进行了展望。更多还原

【Abstract】 Today, energy and environmental protection have become issues of common concern around the world. Oxide ceramic membrane materials have attracted much attention for their great potential applications in the chemical, metallurgy, energy, environmental protection and other areas. As the ceramic hollow fiber membrane has a small diameter, a thin wall and very large effective membrane area per unit volume, it has been studied extensively in recent years. This thesis mainly investigates the permeation performance of the ceramic hollow fiber membranes for oxygen or hydrogen separation, and the electrochemical properties of hollow fiber solid oxide fuel cells.Chapter 1 is the literature review. It briefly describes the definition and classification of membranes, as well as the preparation and applications of ceramic hollow fiber membranes. The research progress and problems of ceramic hollow fiber membranes are also intensively discussed.In Chapter 2, dense dual phase composite Bi1.5Y0.3Sm0.2O3-La0.8Sr0.2MnO3-δhollow fiber membrane was fabricated by the combined phase inversion/sintering technique. The hollow fiber membrane possessed an asymmetric structure. A finger-like porous structure was present on the inner side and a denser structure on the outer side of the hollow fiber membrane. An oxygen permeation flux 3.9×10-7 mol cm-2 s-1 was obtained at 850℃under a gradient of air/helium. The oxygen permeation flux increases with the helium sweeping rate, the length of the hollow fiber and the oxygen partial pressure on the feed side increasing. The oxygen permeation process was simulated by a plug flow model in combination with the Wagner theory. The simulation results were in fair agreement with the measured permeation data.In Chapter 3, the hydrogen permeation performance of Ni-BaZr0.1Ce0.7Y0.2O3-δdual phase composite metal-ceramic hollow fiber membrane was investigated. NiO-BZCY composite powders were prepared by the nitrate-citric method with one step. The as-prepared NiO-BZCY hollow fiber precursors were sintered in reducing atmosphere to get Ni-BZCY metal ceramic membrane. The hollow fiber membrane has a "sandwich" structure:finger-like structures were formed near both the inner and outer walls, but a sponge-like layer occured at the center of the fiber. The hydrogen permeation flux of the hollow fiber membrane increases with the hydrogen flow rate on the feed side and the argon sweeping rate increasing. As formation of BaCO3 in the membrane, the hydrogen permeation flux of the hollow fiber membrane is not larger than that of disc-shaped membrane with relative high thickness. Therefore, in order to increase the fiber membrane separation performance, the formation of BaCO3 must be inhibited.In Chapter 4, an anode hollow fiber of diameter 1.7 mm has been successfully fabricated using the phase inversion technique. The Ni-YSZ anode layer possesses large finger-like pores on both sides of the hollow-fiber membrane, which provides a convenient channel for transporting the fuel gas to the electrolyte. A 12-μm-thick dense YSZ electrolyte membrane was successfully coated on the anode hollow-fiber by vacuum assisted coating and co-sintering method. The three-point bending strength of sintered NiO-YSZ/YSZ hollow fiber may reach up to 118.3 MPa. However, after reduction by hydrogen gas, the mechanical strength of the resulted Ni-YSZ/YSZ hollow fiber would be reduced noticeably. The open circuit voltage (OCV) values are greater than 1.01 V and the maximum power densities reach 124, 287,377 mW cm-2 at 600,700 and 800℃, respectively, using wet H2 (～3%H2O) as fuel and static air as oxidant gas. As a result of high packing densities, this kind of anode-supported hollow-fiber SOFCs has a high potential for practical applications.In Chapter 5, an YSZ hollow fiber used for electrolyte membrane of SOFC has been prepared by the phase inversion and sintering method. The nickel anode was deposited into the YSZ electrolyte membrane from nickel nitrate solution. Appropriate sintering temperature can make nickel deposited into the finger-like pores near inner surface of the YSZ electrolyte membrane more effectively. The anode adheres very well to the electrolyte membrane, which can significantly reduce the ionic resistance. The maximum power densities of 28,78, and 146 mW cm-2 are achieved at 600,700 and 800℃, respectively. With further optimization of the electrolyte and anode layers, more improvements on output power of SOFC may be expected. In addition, the YSZ electrolyte-supported hollow fiber SOFC shows a high mechanical strength throughout the measurement process, which is beneficial for practical applications in the future.In Chapter 6, the low-frequency internal friction Q-1 and relative shear modulus M of La2Cu1-xNixO4+δ(0≤x≤1) compounds were measured. La2Cu1-xNixO4+δcompounds have an orthorhombic K2NiF4 structure. The unit cell parameters a and b slightly increase, whereas it is contrary for c with the nickel content increasing and the excess oxygenδincreases from 0.0132 to 0.1250. For x<0.005, there are two relaxation internal friction peaks around 200 and 250 K, which is due to the hopping of single interstitial O atoms and O pairs, respectively. The peak at low temperature is invisible for 0.015≤x≤1 and the peak height at high temperature decreases suddenly with the nickel content increasing at x≈0.2 (δ≈0.046), indicating the existence 3D ordering of interstitial oxygen. Moreover, the temperatures of O-T phase transition for La2Cu1-xNixO4+δdecrease with increasing the nickel content.In Chapter 7, the researches presented in this dissertation are evaluated and future work concerning the development of ceramic hollow fiber membranes is discussed.更多还原