Solid State Chemistry of Low and Negative Thermal Expansion Materials

非技术摘要大多数材料随着温度的变化而改变它们的形状或尺寸。这些变化通常是不需要的，因为它们可能导致物体在受到突然的温度变化（热冲击）时破裂，或者如果光学组件（包括光纤通信系统中的光学组件）发生故障。为了避免这种类型的问题，有必要使用在温度变化时尺寸/形状变化非常小或没有变化的材料。当前项目的重点是开发显示负（材料在加热时收缩）和低（加热时尺寸/形状几乎没有变化）热膨胀的材料，并提高我们对控制其性能的因素的理解。负热膨胀材料具有技术意义，因为它们可以与显示正常（正）热膨胀的金属和其他物质混合，以产生在加热时不改变形状或尺寸的复合材料（紧密混合物）。作为该项目的一部分，本科生、研究生和博士后工作人员将接受各种材料制备和测试方法的培训。该项目的主要工作是在国家重点实验室进行实验，或与其他大学合作，通过不同机构的研究人员之间的互动，提供专业发展的机会。技术摘要本项目的重点是制备具有低或负热膨胀（NTE）的新材料，并对控制其性能的因素进行更深入的了解。这种理解将在寻找新的工程材料方面具有价值。本科生，研究生和博士后工作人员将接受各种合成和材料表征技术的培训。热膨胀在确定材料是否适用于特定应用方面起着非常重要的作用。当尺寸稳定性很重要时，例如在精密光学器件的制造中，低或零热膨胀是必要的。它对暴露于热冲击的陶瓷也非常有益，例如用于炊具以及一些发动机和航空航天应用的陶瓷。负热膨胀在利基应用中可能非常有价值，例如补偿另一个组件中的正热膨胀。该项目的一个重要部分是在主要的国家设施进行实验，或与其他大学合作。这通过不同机构的研究人员之间的互动提供了专业成长的机会。

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.