Newswise — Imagine having a device that acts as an insulator when it's cool and can also be a great heat sink when it gets hot — a smart material that knows how to change its behavior at different temperatures.
Researchers at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, have achieved a major breakthrough in the development of advanced materials technology that can effectively manage thermal conditions, particularly in buildings and data centers, offering a promising solution for mitigation. Impact of energy consumption on climate change.
The research, described in “High emissivity contrast in adaptive, thin-film, tungsten-doped VO2 composites,” was published Aug. 15 in Applied Physics Letters. It focuses on adaptive, thin-film, tungsten-doped vanadium dioxide (VO2) composites that exhibit high emission contrast and tunable metal-insulator transition temperatures. The principal investigator for the technical project is Joe Miragliotta, who works with APL's Office of Technical Transfer to transfer advanced materials technology to industry.
More than half of the energy used in the American housing industry is used to heat and cool homes. And data centers—buildings used to house critical computer systems and related components, such as telecommunications and storage systems—spend more than 40% of their energy on thermal regulation of electronics.
“Current thermal management solutions, such as radiant roofs, reflective window films and warm water cooling systems, often result in excessive energy consumption or are limited in their efficiency,” explained David Schreckenhammer, assistant program manager of the Physics, Electronic Materials and Devices Program at APL and co-author of the paper. . “Developing passive and adaptive thermal management systems with high radiative efficiency at high temperatures and effective insulation at low temperatures has been a critical goal of the researchers.”
Performance of tungsten-doped VO2 composites
VO2 has emerged as a candidate material for adaptive thermal management due to its unique ability to switch from a low-temperature reflective state to a high-temperature emissive state at a specific temperature threshold (around 154°F, or 68°C). However, researchers have found that by “doping” VO2 with high-valence tungsten (W6+), the transition temperature can be lowered to near room temperature (about 71°F, or 22°C), making it highly suitable for a variety of thermals. management applications.
Lead author Gabriela Hunt and her co-authors, who include employees of Plasmonics Inc., describe how they designed and demonstrated the multilayer film. They used computational tools to optimize layer thickness and doping concentration to achieve high emissivity contrast—the difference in radiation efficiency between a low- and high-temperature state—while lowering the transition temperature.
Through a controlled fabrication process, the team deposited films with different thermally adaptive layer thicknesses and doping levels. By adjusting the dopant concentration and layer thickness, the team was able to achieve a tunable metal-insulator transition temperature that would allow the material to work efficiently in a variety of thermal management applications.
“With this smart material, we could have more efficient heating and cooling systems,” explained Schreckenhammer. “When it's cold outside, the material acts as an insulator and helps keep the heat inside. But once it gets hot, the material moves to the radiator, allowing it to release excess heat and keep it cool.”
Effective thermal management potential
The research results show great promise in revolutionizing thermal management technology and represent an important step in ongoing efforts to reduce energy consumption and combat climate change, Schreckenhammer said.
“Our research shows that we can use a dielectric material in our device that would normally cause some power loss without significantly reducing the efficiency of our device,” noted Hunt, Ph.D. student in the Materials Science and Engineering program at the Johns Hopkins Whiting School of Engineering. “We also provide information on the best design choices to optimize the performance of these devices over a range of temperatures. These findings are important for the realization of commercial production of VO2-based devices that can be used in industries for various applications.
The team plans to continue exploring other refinements to the process. “By continuing to enhance the operational optical contrast of these multilayer composites, we hope to further demonstrate a wide range of applications for this innovative thermal management technology,” Schreckenhammer said.
“The ability to integrate advanced materials science, fabrication and optics and develop state-of-the-art thermal management coatings is a tribute to the lab's incredible collection of scientists and engineers,” Miragliotta added.