Chemical Expansion of Mixed Conducting Ceramics

混合导电陶瓷的化学膨胀

• 批准号: 0222001
• 负责人: Stuart Adler
• 金额: $ 16.66万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-01-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0222001&HistoricalAwards=false
• 关键词: Chemical; Expansion; Mixed; Conducting; Ceramics

0074539AdlerCeramics used in high-temperature applications must match closely in coefficient of thermal expansion (CTE) to avoid excessive stress associated with strain differences over large changes in temperature. Electrochemical ceramics (used as ion-transport membranes or in solid oxide fuel cells) present yet an additional challenge. These materials not only expand with temperature, but also with changes in chemical oxidation state. The majority of expansion at high temperatures in these materials may result from chemical rather than thermal effects. Yet today there is little knowledge or understanding of chemical expansion, or its consequences and technological applications. This project will enlarge our understanding of expansion in ceramics to include these chemical effects. A new continuum theory that defines expansion thermodynamically in terms of temperature and oxygen content will be presented and then an experimental study of expansion in several mixed conducting oxides as a function of cation stoichiometry, temperature, and oxygen partial pressure will be performed. By examining this data in the framework of the theory, a more complete and general understanding of expansion in ceramics will be gained, as well as into how expansion relates to electronic and defect structure. As a secondary goal, new experimental techniques will be developed involving non-equilibrium expansion for directly measuring oxygen surface exchange kinetics and chemical diffusion. The material systems under study include lanthanum-strontium-cobalt-iron-oxide (LSCF) and strontium-iron-cobalt-oxide (SFC). LSCF is of direct relevance to solid-oxide fuel cells and electrically driven air separation, while SFC is of particular interest to workers developing dense membranes for partial oxidation of methane to syngas. LSCF is also a good model material system because its defect thermodynamics are well understood, and its cation composition covers an enormous range of defect and electronic structure (both ionic and electronic). Electrochemical ceramics are of importance in a broad spectrum of applications, including fuels processing, electricity production, and air separation. A full understanding of expansion in is critical to advancing knowledge and application of electrochemical ceramics. This project will also provide a framework for approaching chemical expansion in all solids, thus extending the impact of it much further.

0074539高温应用中使用的AdlerCeramics必须在热膨胀系数（CTE）方面紧密匹配，以避免与温度大幅变化时的应变差相关的过大应力。 电化学陶瓷（用作离子传输膜或固体氧化物燃料电池）还提出了另一个挑战。 这些材料不仅随着温度而膨胀，而且还随着化学氧化态的变化而膨胀。 这些材料在高温下的大部分膨胀可能是由化学效应而不是热效应引起的。 然而，今天人们对化学膨胀或其后果和技术应用知之甚少。该项目将扩大我们对陶瓷膨胀的理解，包括这些化学效应。 将提出一种新的连续介质理论，该理论根据温度和氧含量从热力学角度定义膨胀，然后对几种混合导电氧化物的膨胀作为阳离子化学计量、温度和氧分压的函数进行实验研究。 通过在理论框架内检查这些数据，将获得对陶瓷膨胀以及膨胀与电子和缺陷结构的关系的更完整和普遍的理解。 作为次要目标，将开发新的实验技术，涉及非平衡膨胀，用于直接测量氧表面交换动力学和化学扩散。 正在研究的材料系统包括镧锶钴铁氧化物（LSCF）和锶铁钴氧化物（SFC）。 LSCF 与固体氧化物燃料电池和电驱动空气分离直接相关，而 SFC 对于开发用于将甲烷部分氧化为合成气的致密膜的工作人员特别感兴趣。 LSCF也是一个很好的模型材料系统，因为它的缺陷热力学很好理解，并且它的阳离子组成涵盖了广泛的缺陷和电子结构（离子和电子）。电化学陶瓷在广泛的应用中具有重要意义，包括燃料加工、电力生产和空气分离。充分理解膨胀对于推进电化学陶瓷的知识和应用至关重要。该项目还将提供一个框架来实现所有固体的化学膨胀，从而进一步扩大其影响。