US 12,092,595 B2
Steady-state thermo-reflectance method and system to measure thermal conductivity
Jeffrey L. Braun, Charlottesville, VA (US); David H. Olson, Charlottesville, VA (US); John T. Gaskins, Charlottesville, VA (US); and Patrick E. Hopkins, Charlottesville, VA (US)
Assigned to UNIVERSITY OF VIRGINIA PATENT FOUNDATION, Charlottesville, VA (US)
Appl. No. 17/272,011
Filed by UNIVERSITY OF VIRGINIA PATENT FOUNDATION, Charlottesville, VA (US)
PCT Filed Aug. 28, 2019, PCT No. PCT/US2019/048505
§ 371(c)(1), (2) Date Feb. 26, 2021,
PCT Pub. No. WO2020/047054, PCT Pub. Date Mar. 5, 2020.
Claims priority of provisional application 62/860,949, filed on Jun. 13, 2019.
Claims priority of provisional application 62/723,750, filed on Aug. 28, 2018.
Prior Publication US 2022/0146443 A1, May 12, 2022
Int. Cl. G01N 25/18 (2006.01); G01N 21/17 (2006.01); G01N 21/55 (2014.01); G01N 25/20 (2006.01)
CPC G01N 25/18 (2013.01) [G01N 21/1717 (2013.01); G01N 21/55 (2013.01); G01N 25/20 (2013.01); G01N 2021/1731 (2013.01)] 15 Claims
OG exemplary drawing
 
1. A method of measuring a thermal conductivity of a material, the method comprising:
focusing a pump beam having pump beam a diameter and a power at a spot on a surface of the material of a size of the pump beam diameter, the pump beam having a modulation frequency that induces a cyclical steady-state temperature rise in the spot of the material, the pump beam providing a radial heat flux to the material, the cyclical steady-state temperature rise being related to the radial heat flux by a thermal model, the thermal model being a function of the thermal conductivity of the material;
focusing a probe beam having a probe beam diameter at the spot of the material and generating a reflected probe beam reflected from the spot of the material, the reflected probe beam having a reflectance signal, a magnitude of the reflectance signal being a function of the temperature of the material, and the magnitude of the reflectance signal being periodic corresponding to the cyclical steady-state temperature rise;
measuring the magnitude of the reflectance signal of the reflected probe beam with a photodetector, the measured magnitude of the reflectance signal and the power of the pump beam being related to the cyclical steady-state temperature rise and the radial heat flux by a proportionality constant;
calibrating the proportionality constant with a transducer made of a material having a known thermal conductivity; and
determining the thermal conductivity of the material by fitting the power of the pump beam and the measured magnitude of the reflectance signal to the thermal model by the calibrated proportionality constant, the thermal model being a function of the modulation frequency and the pump and probe beam diameters.