Solid State Chemistry of Low and Negative Thermal Expansion Frameworks

低热膨胀框架和负热膨胀框架的固态化学

• 批准号: 0203342
• 负责人: Angus Wilkinson
• 金额: $ 42.5万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0203342&HistoricalAwards=false
• 关键词: Solid; State; Chemistry; Low; Negative

This project will investigate the thermal expansion characteristics of materials that determine suitability for various applications. For example, frameworks that display low or negative thermal expansion at high temperatures often undergo a phase transition on cooling to a denser form with a higher coefficient of thermal expansion. The phase transition of quartz can be suppressed by "stuffing", that is replacing some silicon with lithium or aluminium to produce materials such as the commercially useful beta-eucrytpite. The "stuffing" of phases with the zirconium phosphatre structure will be explored as a means of producing new materials with interesting thermal expansion characteristics. Additionally, the replacement of zirconium plus four with mixtures of metal plus three and plus five ions will be examined as a means of suppressing this unwanted phase transition. Many negative thermal expansion materials become amorphous at modest pressures and this limits their application. The mechanism of this amorphization will be investigated using techniques that include x-ray absorption fine structure determinations at high pressure.The proposed work will provide several graduate and undergraduate students with experience of a wide variety of methods that are of general utility in the field of materials science/chemistry.%%%The thermal expansion characteristics of a material play a very important role in determining if it will be suitable for a particular application. Low or zero thermal expansion is necessary in areas where dimensional stability is a major issue, such as in the fabrication of precision optical devices. Low or zero thermal expansion is also necessary in ceramics that are exposed to thermal shock, such as those used in cookware and in some internal combustion engine and aerospace applications. Negative thermal expansion can be very valuable in niche applications, such as compensating for the positive thermal expansion of another component in microelectronics. This project focuses on the preparation of new materials displaying low or negative thermal expansion and extending our understanding of both their preparation and physical properties. The knowledge gained will be of value in the search for new engineering materials. The project provides several graduate and undergraduate students with experience in a wide variety of synthetic and characterization methods that are of great and general utility in the fields of materials chemistry and materials science.***

该项目将研究材料的热膨胀特性，以确定其是否适用于各种应用。例如，在高温下表现出低或负热膨胀的骨架通常在冷却到具有较高热膨胀系数的致密形式时经历相变。石英的相变可以通过“填充”来抑制，即用锂或铝取代一些硅，以生产商业上有用的贝塔榴辉石等材料。具有磷酸锆相结构的相的“填充”将被探索为一种生产具有有趣的热膨胀特性的新材料的方法。此外，还将研究用金属+3和+5离子的混合物取代+4的锆离子，以此作为抑制这种不必要的相变的手段。许多负热膨胀材料在中等压力下变得无定形，这限制了它们的应用。我们将利用高压X射线吸收精细结构测定等技术来研究这种非晶化的机理。所提出的工作将为几名研究生和本科生提供在材料科学/化学领域具有普遍实用价值的各种方法的经验。材料的热膨胀特性在决定其是否适用于特定应用方面起着非常重要的作用。在尺寸稳定性是主要问题的领域，例如在制造精密光学设备中，低或零热膨胀是必要的。低或零热膨胀对于暴露在热冲击下的陶瓷也是必要的，例如用于厨具以及一些内燃机和航空航天应用的陶瓷。负热膨胀在特殊应用中可能非常有价值，例如补偿微电子中另一个元件的正热膨胀。本项目致力于低膨胀或负热膨胀的新材料的制备，并扩大了我们对其制备和物理性能的理解。所获得的知识对寻找新的工程材料将是有价值的。该项目为几名研究生和本科生提供了各种合成和表征方法的经验，这些方法在材料化学和材料科学领域具有巨大和普遍的实用价值。