Event
MSE Seminar: Dr. Patrick E. Hopkins, UVA
Wednesday, December 10, 2025
3:30 p.m.
Kay Boardrooms 1107 Jeong H. Kim Engineering Building
Sherri Tatum
301-405-5240
statum12@umd.edu
Coupled Heat Transfer in Materials: from Ultrasmall Length Scales (Nanoscale Interfaces) to Ultrahigh Temperatures (> 3,000 °C)
Abstract: The heat transfer processes in materials play a critical role in the performance and efficacy in a wide range of materials and technologies, from nano-to-macro scales. Be it a wide bandgap nanomaterial used in power and RF devices for radar, or a carbon composite used as a protecting coating in a hypersonic vehicle, the complex chemistries and heterogeneous interfaces lead to additional thermal resistances that make dissipation of these aforementioned extreme heat fluxes challenging. In this talk, I will discuss our recent research directions that focus on the ability to measure heat transfer processes across interfaces by understanding how thermal carriers (electrons, phonons and photons) interface and couple across material boundaries and surfaces. Specifically, I will discuss our recent research efforts in developing experimental metrologies to measure the heat transfer processes of materials and across interfaces when subjected to thermal and environmental fluxes typical in extreme environments, from nanoscales to macroscales and up to temperature as high as 4000 °C. I will focus on the following directions:
-Measuring thermal conductivity of materials: Using laser-based techniques, I will discuss the power and limitations of optical based thermal properties measurements to measure thermal conductivity of materials from nano-to-macroscales. I will discuss advances in thermoreflectance techniques and laser-based radiometry methods to measure heat transfer across interfaces and spectral emissivity across a range of length scales and temperatures.1,2
-Creating “crystals of interfaces” to manipulate the thermal conductivity of materials: The unique vibrational modes that can occur at, and due to interface can lead to unique trends in the thermal conductivity of materials with high interface densities, such as superlattices and layered phases of crystals. 3,4,5,6
-The transient thermal diode for directionally control of interfacial heat transfer in devices: Harnessing electron-phonon nonequilibrium at interfaces for remote thermal control of mid-IR plasmonics and polaritonics. By relying on the coupling of photons, electrons and phonons across interfaces, we can begin to realize ballistic heat flow control that can not be predicted by the 2nd Law of Thermodynamics.7 These measurements are realized through advances in pump-probe techniques using sub-picosecond infrared probes. We will then extend this to demonstrate novel mechanisms of interfacial heat transfer via phonon polaritons in hexagonal boron nitride.8
-Thermal conductivity and spectral emissivity of ultrahigh temperature materials up to 4000 °C: Here we present the measurements of the spectral absorptivity/emissivity and emittance of a series of rare-earth doped oxides, zirconates and metal carbides at temperatures up to their melting point through a combination of infrared variable angle spectroscopic ellipsometry to measure the intrinsic optical properties of the ceramics,9 and laser heating-based radiometry for emittance measurements.10 In the oxides, we show blackbody like emissivity in the mid-infrared due to phonon mode absorption, which broaden the near-perfect-like emissivity into the near-IR at increased temperature. In the visible and near-IR, we observe a nearly universal increase in graybody-like emittance of the rare earth oxides up to their melting points. In the metal carbides, we show that the temperature dependent emissivity of metal carbides either increases or decreases up to their melting point depending on the electronic configuration and surface roughness, with all measured values for emittance converging close to melt.
1. Annual Review of Materials Research 55, 37-70 (2025); 2. Nature Reviews Methods Primers 5, 55 (2025); 3. Nature Materials 13 168 (2014); 4. Nature 601 556 (2022); 5. Advanced Materials 35 2208920 (2023); 6. Nature Communications 16 6104 (2025); 7. Nature Nanotechnology 16, 47-51 (2021); 8. Nature Materials 24, 698-706 (2025); 9. Nature Communications 16, 3333 (2025); 10. Physical Review Letters 132, 146303 (2024).
Bio: Patrick E. Hopkins is a Professor in the Department of Mechanical and Aerospace Engineering at the University of Virginia, with courtesy appointments in the Department of Materials Science and Engineering and the Department of Physics. Patrick received his Ph.D. in Mechanical and Aerospace Engineering at the University of Virginia in 2008 under the mentorship of Professor Pamela Norris. After his Ph.D., Patrick was one of two researchers in the nation to receive a Truman Fellowship from Sandia National Laboratories in 2008, working under the mentorship of Dr. Leslie Phinney. In 2011, Patrick returned to the University of Virginia and joined the faculty. Patrick’s current research interests are in energy transport, charge flow, laser-chemical processes and photonic interactions with condensed matter, soft materials, liquids, vapors and their interfaces. Patrick’s group at the University of Virginia uses various optical thermometry-based experiments to measure the thermal conductivity, thermal boundary conductance, emissivity, thermal accommodation, strain propagation and sound speed, and coupled electron, phonon, and photon mechanisms in a wide array of bulk materials and nanosystems. In 2021, Patrick co-founded Laser Thermal, Inc., a company based in Charlottesville Virginia that is commercializing thermal conductivity measurement systems that provide non-contact, automated metrologies for thermal properties of thin films, coatings and bulk materials.
In the general fields of nanoscale heat transfer, laser interactions with matter, and energy transport, storage and capture, Patrick has authored or co-authored over 340 technical papers (peer reviewed) and been awarded 6 patents focused on materials, energy and laser metrology for measuring thermal properties. Patrick has been recognized for his accomplishments in these fields via AFOSR and ONR Young Investigator Awards, the ASME Bergles-Rohsenhow Young Investigator Award in Heat Transfer, and a Presidential Early Career Award for Scientists and Engineering (PECASE). Patrick is a fellow of AAAS and ASME, was awarded the ASME Gustus L. Larson Memorial Award and is a 3 time National Finalist for the Blavatnik Award for Young Scientists. During 2021-2022, Patrick was awarded a Humboldt Fellowship to work on laser thermometry of materials in extreme environments at the Joint Research Center in Karlsruhe, Germany. Patrick is currently a member of the Defense Science Study Group (2022 – 2024).
