Recently, researchers at the NOMAD Laboratory discovered fundamental microscopic mechanisms that can assist in customizing heat insulation materials. This development contributes to the ongoing efforts to improve sustainability and energy efficiency.
Catalysis, turbine technologies, and thermoelectric heat converters that convert waste heat into electricity all rely heavily on heat transport for their operations.
Especially with regards to energy preservation and the improvement of reasonable innovations, materials with high heat protection abilities are of extreme significance. These materials make it conceivable to hold and use heat that would otherwise go to waste. As a result, increasing energy efficiency in applications necessitates advancing the design of highly insulating materials.
Even though the fundamental physical laws that underlie them have been known for nearly a century, designing heat-resistant materials is far from simple. The collective oscillation of the atoms around their equilibrium positions in the crystal lattice was used to explain heat transport at the microscopic level in semiconductors and insulators. These motions, called “phonons” in the field, include countless particles in strong materials and thus cover huge, practically plainly visible length and time scales.
“Such effects are typically ignored in thermal-conductivity simulations because these defects are so short-lived and microscopically localized compared to typical heat-transport scales that they are assumed to be irrelevant. However, simulations revealed that they cause poorer thermal conductivities.”
Dr. Christian Carbogno, a senior author of the studies.
Researchers from the Fritz Haber Institute’s NOMAD Laboratory have improved the computational capabilities to compute thermal conductivities with unprecedented accuracy without experimental input in a joint publication in Physical Review B and Physical Review Letters. They demonstrated that the aforementioned phonon picture is inappropriate for strong heat insulators.
They scanned over 465 crystalline materials for which the thermal conductivity had not been measured yet using large-scale calculations on supercomputers at the Max Planck Society, the North-German Supercomputing Alliance, and the Jülich Supercomputing Centre. Other than finding major areas of strength for 28 covers, six of which include a super low warm conductivity practically identical to wood, this study shed light on an until now commonly directed instrument that permits one to bring down the warm conductivity efficiently.
Dr. Florian Knoop, who is now at Linköping University and is the first author of both publications, states, “We observed the temporary formation of defect structures that massively influence the atomic motion for an extremely short period of time.”
“Since these defects are so brief-lived and so microscopically localized in comparison to typical heat-transport scales, such effects are typically ignored in thermal-conductivity simulations.” In any case, the performed estimations showed that they trigger lower warm conductivities,” adds Dr. Christian Carbogno, a senior creator of the examinations.
These experiences might offer new chances to tweak and plan warm separators on a nanoscale level through imperfection design, possibly propelling energy-proficient innovation.
More information: Florian Knoop et al, Anharmonicity in Thermal Insulators: An Analysis from First Principles, Physical Review Letters (2023). DOI: 10.1103/PhysRevLett.130.236301
Florian Knoop et al, Ab initio Green-Kubo simulations of heat transport in solids: Method and implementation, Physical Review B (2023). DOI: 10.1103/PhysRevB.107.224304
