Abstract
We report the laser-induced pressure-wave and the barocaloric effect captured by an infrared detector during thermal diffusivity measurements. Very fast (<1 ms) and negative transients during laser flash measurements were captured using the infrared detector on thin, high thermal conductivity samples. The standard thermal diffusivity analysis only focuses on the longer time scale thermal transient measured from the back-surface due to heat conduction. Previously, these negative transients or spikes were filtered out and ignored as noise or anomaly from the instrument. This study confirmed that the initial negative signal was indeed a temperature drop induced by the laser pulse. The laser pulse induced instantaneous volume expansion and the associated cooling in the specimen can be explained by the barocaloric effect. The initial cooling (<100 μs) is also known as the thermoelastic effect in which a negative temperature change is generated when the material is elastically deformed by volume expansion. A subsequent temperature oscillation in the sample was observed and only lasted about 1 ms. The pressure-wave induced thermal signal was systematically studied and analyzed. The underlying physics of photon-mechanical-thermal energy conversions and the potential of using this signal to study barocaloric effects in solids are discussed.
| Original language | English |
|---|---|
| Article number | 051901 |
| Journal | Applied Physics Letters |
| Volume | 111 |
| Issue number | 5 |
| DOIs | |
| State | Published - Jul 31 2017 |
Funding
This research was sponsored by the U.S. Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, as part of the Propulsion Materials Program and Oak Ridge National Laboratory managed by the UT-Battelle LLC, for the Department of Energy under Contract No. DE-AC05000OR22725.