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.

高温应用中使用的0074539Adlerceramics必须与热膨胀系数（CTE）紧密匹配，以避免在温度大变化中与应变差异相关的过度压力。 电化学陶瓷（用作离子传输膜或固体氧化物燃料电池）提出了额外的挑战。 这些材料不仅随温度而膨胀，而且随着化学氧化状态的变化而膨胀。 这些材料中高温下的大部分膨胀可能是由于化学而不是热效应引起的。 然而，今天对化学扩展或其后果和技术应用的了解或了解很少。该项目将扩大我们对陶瓷扩张的理解，以包括这些化学作用。 将提出一种新的连续理论，该理论在温度和氧含量方面定义了热力学的膨胀理论，然后将对几种混合导电氧化物的扩展进行实验研究，这是阳离学化学测定法，温度和氧气部分压力的函数。 通过在理论框架中检查这些数据，将获得对陶瓷扩展的更完整和一般的了解，以及扩展与电子和缺陷结构的关系。 作为次要目标，将开发新的实验技术，涉及直接测量氧表面交换动力学和化学扩散的非平衡膨胀。 所研究的材料系统包括灯笼甲状腺果果皮铁氧化物（LSCF）和锶 - 铁 - 果胶氧化物（SFC）。 LSCF与固体氧化物燃料电池和电动空气分离直接相关，而SFC对于开发致密膜的工人特别感兴趣，以部分氧化甲烷向同性气氧化。 LSCF也是一个良好的模型材料系统，因为它的缺陷热力学已被充分了解，并且其阳离子组成涵盖了巨大的缺陷和电子结构（离子和电子结构）。电化学陶瓷在广泛的应用中非常重要，包括燃料加工，电力生产和空气分离。对扩展的充分理解对于促进电化学陶瓷的知识和应用至关重要。该项目还将为在所有固体中接近化学膨胀的框架提供一个框架，从而进一步扩展其影响。