【作者】 易建新；

【导师】 陈初升；

【作者基本信息】 中国科学技术大学 ， 材料学， 2006， 博士

【摘要】 致密陶瓷透氧膜在纯氧制备及许多涉氧过程如钢铁冶炼、富氧燃烧、甲烷部分氧化制合成气等中具有广泛的应用前景。其氧渗透能力来自于在中高温条件下材料中的氧离子和电子混合电导。在实际应用中，透氧膜必须具有高的氧渗透能力同时又能在操作条件下保持结构完整。但目前绝大多数透氧膜材料都无法满足这个条件。本论文针对这个问题，对单相钙钛矿型（第二、三章）和双相复合的（第四-六章）透氧膜在不同条件下的稳定性以及氧输运性能展开了一系列研究。 第一章简要介绍了混合导体透氧膜的氧渗透基本原理、研究概况以及本论文的研究目的。 第二章对具有高氧渗透能力的钙钛矿氧化物SrCo_1-xFe_xO_3-δ（x=0，0.05，0.1，0.2）中铁掺杂对相结构、电导和氧渗透性能的影响进行了研究。结果表明，随铁掺杂量的增加SrCo_1-xFe_xO_3-δ的室温钙钛矿结构发生了六方→Brownmillerite→立方+Brownmillerite→立方的变化，而相应的电子电导率和氧渗透能力也逐渐增大。我们认为，这是由于随着晶体结构逐步趋向立方钙钛矿结构，晶格畸变程度逐渐降低、Co／Fe-O-Co／Fe键角逐渐增大、Co／Fe的3d轨道和O的2p轨道的重叠程度逐渐提高，氧空位从高度有序排列逐渐无序化所导致的。结果还表明，SrCo_1-xFe_xO_3-δ的高温立方相的电子电导率和氧渗透能力反而随x的增大而下降，这可能是由Co-O和Fe-O键之间的差别引起的。 钙钛矿混合导体中大多含有碱性的碱土金属和稀土元素，容易在工作条件下与气氛中的CO₂和水蒸气发生反应，导致材料结构分解或性能的下降。在第三章中以钙钛矿氧化物Sr_0.95Co_0.8Fe_0.2O_3-δ为模型体系，研究了它在含CO₂和H₂O的空气气氛中的氧渗透性能和结构稳定性。结果表明，与这两种气体在空气中单独存在时相比，5vol.％CO₂和4vol.％H₂O共存时对Sr_0.95Co_0.8Fe_0.2O_3-δ透氧膜的相组成、表面形貌和氧渗透能力的破坏作用要大得多，这种不利影响在较低的温度更多还原

【Abstract】 Oxygen-permeable dense ceramic membranes hold promise of finding applications in separation of oxygen from air and upgrading of oxygen-involved processes such as production of syngas through the partial oxidation of methane and combustion of fossil fuels. The oxygen permeability of this type of membrane arises from its mixed oxygen ionic and electronic conductivity at elevated temperatures. For practical applications, the membrane is required to possess high oxygen permeability and retain its integrity under operation conditions. This thesis presents a number of studies on the stability and oxygen transport properties of single-phase perovskite-type （Chapters 2 & 3） and dual-phase ceramic membranes （Chapters 4-6）.Chapter 1 introduces the concepts and theories of oxygen permeation for dense ceramic membranes, presents a brief overview of membrane materials, and describes the scope of this thesis.In Chapter 2, the effects of iron doping on the structure, electric and oxygen transport properties of SrCo_1-xFe_xO_3-δ （x=0, 0.05, 0.1, 0.2） are investigated. The perovskite structure of the as-prepared SrCo_1-xFe_xO_3-δ is shown to change in the sequence of hexagonal→Brownmillerite→cubic+Brownrnillerite→cubic as iron content x increases. Along with this structural evolution is the increase in the electric conductivity and oxygen permeability. This is explained as a result of reduced structural distortion, increased Co/Fe-O-Co/Fe bond angle, improved overlapping of the Co/Fe’s 3d orbital and oxygen’s 2p orbital and gradual disordering of oxygen vacancies with increasing x. It is also found that both the high-temperature electric conductivity and oxygen permeability of the cubic-perovskite SrCo_1-xFe_xO_3-δ decrease as x increases, which is attributed to the difference between the Co-O and Fe-O bond.In Chapter 3, the oxygen transport and stability of perovskite-structured membranes are investigated in atmosphere containing CO₂ and H₂O. It is known that most of perovskite oxides contain basic alkaline earth metals and rare earth elements, and may react with CO₂ and H₂O in the atmosphere, leading to degradation of the更多还原