Solid State Chemistry of Low and Negative Thermal Expansion Materials

点击翻译按钮获取中文摘要

Non-technical Abstract Most materials change their shape or size as temperature is varied. These changes are often unwanted, as they can lead to objects breaking when they are subjected to abrupt temperature changes (thermal shock), or malfunctioning if optical components, including ones found in fiber optic communications systems. To avoid problems of this type, it is necessary to use materials that show very small or no change in size/shape as the temperature varies. The current project focuses on developing materials that display negative (material shrinks on heating) and low (almost no change in size/shape on heating) thermal expansion, and enhancing our understanding of what controls their properties. Negative thermal expansion materials are of technological interest because they can be mixed with metals and other substances that show normal (positive) thermal expansion to produce composites (intimate mixtures) that do not change shape or size on heating. Undergraduates, graduate students and postdoctoral workers will be trained in a variety of materials preparation and testing methods as part of the project. A significant part of the work involves experiments at major national facilities, or is collaborative with other universities, providing opportunities for professional growth through interactions between researchers at different institutions.Technical abstract This project focuses on the preparation of new materials showing low or negative thermal expansion (NTE), and developing a deeper understanding of the factors that control their properties. This understanding will be of value in the search for new engineering materials. Undergraduates, graduate students and postdoctoral workers will be trained in a wide variety of synthetic and materials characterization techniques. Thermal expansion plays a very important role in determining if a material will be suitable for a particular application. Low or zero thermal expansion is necessary when dimensional stability is important, such as in the fabrication of precision optical devices. It is also highly beneficial in ceramics that are exposed to thermal shock, such as those used in cookware and in some engine and aerospace applications. Negative thermal expansion can be very valuable in niche applications, such as compensating for positive thermal expansion in another component. A significant part of the project either involves experiments at major national facilities or is collaborative with other universities. This provides opportunities for professional growth through interactions between researchers at different institutions.