Thermal Conductivity and Grain Boundary Energy of Interfaces in Multiphase Ceramics

非技术描述：通过制造含有多种材料的复合材料，可以改善许多部件的性能。例如，更坚固的陶瓷可以通过使用三种不同类型的陶瓷的混合物而不是仅仅一种来制造。在技术应用中，热量通过材料的传递是很重要的，不同类型的陶瓷接触的边界（界面）可能会阻挡热量的流动。本研究研究了不同类型陶瓷之间的界面如何改变热流。该项目的目标是帮助设计更好的隔热和冷却系统，以提高能源效率和降低成本。研究生和本科生将参与这项研究，来自低收入背景的高中学生将在每年夏天与工程专业的学生和教师一起在实验室度过，作为“突破工程”计划的一部分。技术细节：该项目的目标是了解不同陶瓷之间的界面如何影响多相氧化物材料的导热性。虽然添加离散的第二相和第三相可以提高陶瓷的机械强度，增强导热性，并增加抗热震性，但最近的报告表明，声子散射引起的晶界固有热阻（Kapitza电阻）可能会限制小晶粒尺寸下的导热性。本研究研究了与单相氧化物相比，多相氧化物陶瓷的热导率显著降低的晶粒尺寸范围，并评估了界面能量，表征了相之间的化学/结构紊乱，以确定与多晶材料和双晶的Kapitza电阻的相关性。本研究基于晶界和界面的结构、化学和相对能量的影响，为多相氧化物的热输运提供了新的见解。包括晶界特性在内的计算模型被用于更好地预测多相氧化物材料的导热性。这项研究的结果为导热性至关重要的陶瓷应用提供了改进的设计策略。学生们还接受了新的热表征方法的培训，如3-omega技术，以及新的原子分辨率先进的透射电子显微镜技术。

NON-TECHNICAL DESCRIPTION: The properties of many components can be improved by making composites containing more than one type of material. For example, stronger ceramics can be made by using a mixture of three different types of ceramics rather than just one. For technical applications where the transport of heat through a material is important, boundaries (interfaces), where the different types of ceramics touch, may block the flow of heat. This research studies how the interfaces between different types of ceramics change the flow of heat. The goal of this project is to help design better thermal insulation and better cooling systems, for improved energy efficiency and reduced cost. Graduate students and undergraduates will participate in this research, and high school students from low-income underrepresented backgrounds will spend each summer in the lab with engineering students and faculty as part of the pipeline program "Breakthrough to Engineering". TECHNICAL DETAILS: The goal of this project is to understand how interfaces between dissimilar ceramics affect the thermal conductivity of multiphase oxide materials. While the addition of discrete second and third phases can improve mechanical strength, enhance thermal conductivity, and increase thermal shock resistance in ceramics, recent reports suggest that the intrinsic thermal resistance (Kapitza resistance) of grain boundaries due to phonon scattering may limit thermal conductivity at small grain sizes. This research studies the grain size range below which the thermal conductivity is significantly decreased for multiphase oxide ceramics compared to single phase oxides, and evaluates the energy of interfaces and characterizes the chemical/structural disorder between phases to determine correlation with Kapitza resistances using polycrystalline materials and bicrystals. This research provides new insights into thermal transport in multiphase oxides based on the influence of the structure, chemistry, and relative energy of grain boundaries and interfaces. Computational modeling that includes grain boundary specific properties is used to better predict the thermal conductivity of multiphase oxide materials. The results of this research offer improved design strategies for applications of ceramics where thermal conductivity is paramount. Students are also trained on new thermal characterization methods such as the 3-omega technique, and new atomic resolution advanced transmission electron microscopy techniques.