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.
