The in-plane thermal diffusivity of several kinds of metal foils was measured by
the converging thermal-wave technique. This is a typical technique which can
obtain the thermal diffusivity by taking the temperature evolution at the center of
pulsed an...
The in-plane thermal diffusivity of several kinds of metal foils was measured by
the converging thermal-wave technique. This is a typical technique which can
obtain the thermal diffusivity by taking the temperature evolution at the center of
pulsed annular laser beam when the beam irradiates the surface of the samples.
The thermal diffusivity is normally calculated using the half-maximum time
$t_{1/2}$ or maximum time $t_m$ when the temperature evolution is half and
maximum, respectively, however the rapid temperature increase and the nonlinearity
of the infrared detector in the earlier part, convection heat loss from the sample
surface, and some times the low signal to noise ratio can produce errors. In this
study, a nonlinear least-square regression was performed to estimate the optimal
values of several separate parameters by fitting the data to the theoretical
equation. The thermal diffusivity of the samples obtained from the optimal values
of the estimated parameters was compared with the values from $t_{1/2}$ and
$t_m$, and the reference values, and it shows that the thermal diffusivity obtained
by this parameter estimation technique agrees quite well with the reference data
within 3.4 \% at maximum and the same materials have nearly the same values
within 4.4 \% for different thicknesses.