GOALI: Understanding and Controlling Heat Transport Mechanisms in Nano-Layered Materials for Energy Harvesting Thermal Barrier Coatings in Jet Engines

随着人口的爆炸性增长和电力消费技术的快速进步，我们的社会在持续进步和未来可持续发展方面面临着关键的障碍。材料、工艺和系统的重大进步必须彻底提高能源生产效率，同时减少净废热，这不仅将增加用作工作的能源，还将减少不可再生资源的消耗。因此，在这场世界性的能源危机中，一条潜在的理想道路是提高发电效率，同时收集被丢弃的能量，否则就会被浪费掉。这一概念依赖于提高现有技术的效率，同时回收能源以提高净发电量；即利用能源的副产品进行回收和再利用。飞机发动机就是通过对系统的材料部件进行“热优先”设计来提高能效的一个例子，在这种发动机中，热障涂层材料的导热系数的降低使涡轮机的运行温度更高。这些较高的工作温度直接转化为功率输出的改善。为了解决这一关键问题，该项目将侧重于在理解由高温稳定的热电纳米材料系统组成的热障涂层的纳米和微尺度热性能方面的进展，因为它与燃气轮机发动机技术有关。更具体地说，这个项目将发展基本的热输运理解，即声子散射过程如何受到空间变化的缺陷的影响，这些缺陷是具有超低导热系数的新型纳米层状氧化物热障涂层材料。这将导致热障涂层的材料解决方案显示出卓越的热化学保护，同时不依赖昂贵的稀土元素，而这些元素在当前最先进的热障涂层中是典型的。此外，这类材料产生热电响应的能力将使在发动机环境中产生的温度梯度能够发电，从而允许回收原本撞击涡轮叶片的废热。这项拟议的工作对提高发动机效率和通过氧化物纳米材料推进高温废热回收领域具有深远的社会意义。此外，将我们提议的行业和学术合作整合到课程、外展和会议组织中，将通过弗吉尼亚州各地K-12课堂中代表不足的群体的参与，最大限度地发挥这种更广泛的影响。与罗尔斯-罗伊斯公司合作，该项目将通过系统的实验，展示晶体边界散射、相纯度、空位和掺杂散射之间的相互作用，在一系列长度尺度和温度范围内，促进对纳米级分层结构中声子散射和热传输的基础性理解。关于结构缺陷如何影响具有超低导热系数的自然分层、各向异性原子结构中的导热系数的知识基础是缺乏的，特别是在与发动机环境相关的高温下，其中声子缺陷散射可能变得更加明显。因此，这一学术价值的一部分在于了解在高温下表现出热电响应的纳米层钙钛矿氧化物类中的声子传输过程，同时评估当前晶体中声子缺陷和界面散射理论应用于这些类热电材料的适用性。因此，这项拟议工作的其他智力价值将是开发和实施一种程序，将时间域热反射测量扩展到与燃气轮机发动机运行相关的环境中。这些拟议的进展，加上劳斯莱斯进一步的材料集成和发动机特定指导，将导致评估一种潜在的破坏性材料解决方案，即基于氧化物纳米材料的新型热电热障涂层。

With an exploding population and rapid advances in power consuming technologies, our society faces a critical roadblock in continued advancement and future sustainability. Major advances in materials, processes and systems must cleanly increase energy generation efficiency, while decreasing the net wasted heat, which will not only increase the energy used as work but also decrease the consumption of nonrenewable resources. Therefore, a potential ideal path forward in this world-wide energy crisis is to improve power production efficiency while also harvesting the energy that is rejected as otherwise wasted heat. This concept relies on improving the efficiency of existing technologies while recycling energy to improve the net power production; that is, using byproducts of energy sources to recycle and reuse. An example of advancements in energy efficiency through "thermal first" engineering of material components of a system is an aircraft engine, in which reductions in the thermal conductivities of thermal barrier coating materials enable higher temperature operation of turbines. These high operating temperatures translate directly to improvements in power output. To address this critical issue, this project will focus on advances in understanding of nano- and microscale thermal properties of thermal barrier coatings comprised of high-temperature stable thermoelectric nanomaterial systems as it relates to gas-turbine engine technologies. More specifically, this project will develop the fundamental thermal transport understanding of how phonon scattering processes are impacted by spatially varying defects in novel nanoscale-layered oxide thermal barrier coatings materials with ultralow thermal conductivities. This will result in material solutions for thermal barrier coatings that exhibit superior thermochemical protection while not relying on expensive rare earth elements that are typical in current state-of-the-art thermal barrier coatings. Furthermore, the ability of this class to materials to generate a thermoelectric response will enable power generation from the temperature gradients produced in the engine environments, thus allowing for recycling the otherwise wasted heat impinging on the turbine blades. This proposed work has far-reaching societal implications by both improving engine efficiency and advancing the field of high temperature waste heat recovery via oxide nanomaterials. Furthermore, the integration of our proposed industry and academic collaboration into curricula, outreach, and conference organization will maximize this broader impact through involvement from underrepresented groups in K-12 classrooms around Virginia. In partnership with Rolls-Royce, this project will advance the foundational understanding of phonon scattering and thermal transport in nanoscale layered structures with systematic experiments that demonstrate the interplay between crystal boundary scattering, phase purity, and vacancy and dopant scattering over a range of length scales and temperatures. The knowledge-base of how structural imperfections affect the thermal conductivity in naturally layered, anisotropic atomic structures with ultra-low thermal conductivities is lacking, especially at elevated temperatures relevant to engine environments where phonon-defect scattering can become more pronounced. Thus, part of this intellectual merit lies in understanding phonon transport processes in classes of nano-layered perovskite oxides that can exhibit thermoelectric responses at elevated temperatures, while assessing the applicability of current theories of phonon-defect and interface scattering in crystals as applied to these classes of thermoelectric materials. Therefore, additional intellectual merit of this proposed work will be the development and implementation of a procedure to extend time-domain thermoreflectance measurements to environments relevant to gas-turbine engine operation. These proposed advances, with further material integration and engine specific guidance from Rolls-Royce, will lead to the assessment of a potentially disruptive material solution in the form of a novel thermoelectric thermal barrier coating based on oxide nanomaterials.