High temperature optical and thermal properties of radiation barrier coatings
Abstract
The fundamental thermal transport processes that contribute to heat transfer in intensely heated coatings that operate at temperatures above 1000 degrees Celsius are driven by carrier and phonon conduction processes along with radiative thermal transport, the latter of which becomes a rapidly increasing driving factor as temperature increases. An ideal protective coating would thus possess ultralow thermal conductivity by maximizing phonon scattering processes while blocking heat carrying blackbody radiation by appearingIR opaque in the window of peak blackbody emission around more than 1000 Celsius degree. Recently, the realization of rare earth (RE) doping to enhance the IR opacity of traditionally employed environmental and thermal barrier coating material phases has led to the development of the #radiative barrier coating# (RBC), in which traditionally used E/TBCs can be doped to independently engineer the optical properties in the spectral range of interest to add this radiative functionality to existing E/TBC coatings. The overarching objective of this proposed work is to develop measurements of the optical properties from the visible through the mid-IR (i.e., broad spectrum dielectric function measurements), thermal conductivity, and phase transition temperatures of existing and novel RBCs up through their melting temperatures. We will use these measurements to assess the performance of RE-doped RBCs that are developed to maximize the broadband opacity. Specifically, our hypothesis is that through point defect engineering of RE dopants and additional metal inclusions, broadband gray-body opaque coatings can be developed by increased absorption by both the electronic and vibrational states in high temperature stable, ultralow thermal conductivity RBCs. The experimental development of these properties will build off of Hopkins# existing facility and will lead to the world#s only facility for these optical, thermal and thermodynamic measurements on both bulk materials and coatings, offering a unique competitive advantage for the DoD given this unique facility thatwill only exists domestically in the USA. These #Radiation Barrier Coatings#, which will be developed in close collaboration with Professor David Clarke (Harvard), Professor Prasanna Balachandran (UVA) and Professor Haydn Wadley (UVA), will be designed for use and integration into high temperature engine environments, and thus have additional physical property characteristics that will ensure the survivability of these materials in the harsh atmospheres of jet turbine engines. A constant feedback loop between experimental measurements, experimental development and coating design and fabrication will be enabled through theory and computation from first principles atomistic to continuum scales. This will lead to collaborations between our team and other universities, prime contractors, DoD labs, and other stakeholders to conduct measurements of materials for propulsion applications and technologies in the interest of National Security and Defense. The proposed effort to measure and optimize the conduction and radiation thermal transport in high temperature coatings is directly relevant to Navy propulsion needs for reliably and performance of thermal/environmental barrier coatings in hot section components of turbine engines. The coating used in gas turbine engines are utilized by the Navy for both its aircraft and ship propulsion platforms. These coatings ensure high temperature operation, thus improving engine efficiency leading to lower fuel burn and reducing costs, and our novel radiation barrier coatings will provide a disruptive solution to improveefficiency in turbine engines for the Navy and other stakeholders in the DoD.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Apr 10, 2025
- Source ID
- N000142512286
Entities
People
- Patrick Hopkins
Organizations
- Office of Naval Research
- United States Navy
- University of Virginia