An ultrathin coating developed by University of Wisconsin-Madison engineers upends a ubiquitous physics phenomenon of materials related to thermal radiation: The hotter an object gets, the brighter it glows.
The new coating -- engineered from samarium nickel oxide, a unique tunable material -- employs a bit of temperature trickery.
"This is the first time temperature and thermal light emission have been decoupled in a solid object. We built a coating that 'breaks' the relationship between temperature and thermal radiation in a very particular way," says Mikhail Kats, a UW-Madison professor of electrical and computer engineering. "Essentially, there is a temperature range within which the power of the thermal radiation emitted by our coating stays the same."
Currently, that temperature range is fairly small, between approximately 105 and 135 degrees Celsius. With further development, however, Kats says the coating could have applications in heat transfer, camouflage and, as infrared cameras become widely available to consumers, even in clothing to protect people's personal privacy.
Kats, his group members, and their collaborators at UW-Madison, Purdue University, Harvard University, Massachusetts Institute of Technology and Brookhaven National Laboratory published details of the advance this week in the Proceedings of the National Academy of Sciences.
The coating itself emits a fixed amount of thermal radiation regardless of its temperature. That's because its emissivity -- the degree to which a given material will emit light at a given temperature -- actually goes down with temperature and cancels out its intrinsic radiation, says Alireza Shahsafi, a doctoral student in Kats' lab and one of the lead authors of the study.
"We can imagine a future where infrared imaging is much more common, negatively impacting personal privacy," Shahsafi says. "If we could cover the outside of clothing or even a vehicle with a coating of this type, an infrared camera would have a harder time distinguishing what is underneath. View it as an infrared privacy shield.
The effect relies on changes in the optical properties of our coating due to a change in temperature. Thus, the thermal radiation of the surface is dramatically changed and can confuse an infrared camera."
In the lab, Shahsafi and fellow members of Kats' group demonstrated the coating's efficacy. They suspended two samples -- a coated piece of sapphire and a reference piece with no coating -- from a heater so that part of each sample was touching the heater and the rest was suspended in much cooler air.
When they viewed each sample with an infrared camera, they saw a distinct temperature gradient on the reference sapphire, from deep blue to pink, red, orange and almost white, while the coated sapphire's thermal image remained largely uniform.
A team effort was critical to the project's success. Purdue collaborator Shriram Ramanathan's group synthesized the samarium nickel oxide and performed detailed materials characterization. Colleagues at MIT and at Brookhaven National Laboratory used the bright light of a particle-accelerating synchrotron to study the coating's atomic-level behavior.
Shahsafi and Patrick Roney (whose employer, Sandia National Laboratory, funded his master's degree under Kats) led the experimental work, which also led Kats' postdoctoral researcher Yuzhe Xiao to author additional papers describing their very precise measurement techniques. Several other students in Kats' group characterized the coating through microscopy and other methods.
Kats is the Dugald C. Jackson Faculty Scholar in Electrical and Computer Engineering at UW-Madison. Other authors on the PNAS paper include Yuzhe Xiao, Chenghao Wan, Raymond Wambold, Jad Salman and Zhaoning Yu of UW-Madison, You Zhou of Harvard, Zhen Zhang of Purdue, Jiarui Li and Riccardo Comin of MIT, and Jerzy Sadowski of Brookhaven National Laboratory.
This research was supported by grants from the Office of Naval Research (N00014-16-1-2556) and the National Science Foundation (ECCS-1750341).
Renee Meiller, 608-262-2481, email@example.com
DOWNLOAD IMAGES: https:/
Mikhail Kats | EurekAlert!
Ultrafast camera takes 1 trillion frames per second of transparent objects and phenomena
22.01.2020 | California Institute of Technology
EU-project SONAR: Better batteries for electricity from renewable energy sources
17.01.2020 | Fraunhofer-Institut für Algorithmen und Wissenschaftliches Rechnen SCAI
A Duke University research team has identified a new function of a gene called huntingtin, a mutation of which underlies the progressive neurodegenerative...
For years, a new synthesis method has been developed at TU Wien (Vienna) to unlock the secrets of "strange metals". Now a breakthrough has been achieved. The results have been published in "Science".
Superconductors allow electrical current to flow without any resistance - but only below a certain critical temperature. Many materials have to be cooled down...
KIT researchers develop novel composites of DNA, silica particles, and carbon nanotubes -- Properties can be tailored to various applications
Using DNA, smallest silica particles, and carbon nanotubes, researchers of Karlsruhe Institute of Technology (KIT) developed novel programmable materials....
Styrofoam or copper - both materials have very different properties with regard to their ability to conduct heat. Scientists at the Max Planck Institute for Polymer Research (MPI-P) in Mainz and the University of Bayreuth have now jointly developed and characterized a novel, extremely thin and transparent material that has different thermal conduction properties depending on the direction. While it can conduct heat extremely well in one direction, it shows good thermal insulation in the other direction.
Thermal insulation and thermal conduction play a crucial role in our everyday lives - from computer processors, where it is important to dissipate heat as...
In order to advance the transfer of research developments from the field of quantum sensor technology into industrial applications, an application laboratory is being established at Fraunhofer IAF. This will enable interested companies and especially regional SMEs and start-ups to evaluate the innovation potential of quantum sensors for their specific requirements. Both the state of Baden-Württemberg and the Fraunhofer-Gesellschaft are supporting the four-year project with one million euros each.
The application laboratory is being set up as part of the Fraunhofer lighthouse project »QMag«, short for quantum magnetometry. In this project, researchers...
16.01.2020 | Event News
15.01.2020 | Event News
07.01.2020 | Event News
22.01.2020 | Life Sciences
22.01.2020 | Power and Electrical Engineering
22.01.2020 | Life Sciences