The State Key Lab of
High Performance Ceramics and Superfine Microstructure
Shanghai Institute of Ceramics, Chinese Academy of Sciences
中 国 科 学 院 上 海 硅 酸 盐 研 究 所 高 性 能 陶 瓷和 超 微 结 构 国 家 重 点 实 验 室
Laser-Induced Pressure-Wave and BarocAloric effect During flash diffusivity measurements
Oak Ridge National Laboratory, Oak Ridge, TN USA
Laser-induced pressure-wave and barocaloric effect was captured by an infrared detector during thermal diffusivity measurements. Very fast (< 1 millisecond) and negative transients during laser flash measurements were captured by the infrared detector on thin, high thermal conductivity samples. 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 microsecond) is also known as 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 one millisecond. 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.
Dr. Hsin Wang is a distinguished R&D staff member from the Materials Science and Technology Division at ORNL. He received his bachelor’s degree in solid state physics from Tsinghua University in 1989, MS and Ph.D. in ceramic science from New York State College of Ceramics at Alfred University. He has been working at ORNL since 1995 focusing on transport properties measurements, energy conversion materials including thermoelectrics and thermal management and safety of Li-ion batteries.