The numerical mirage method for photothermal characterization of materials

Abstract

Noncontact thermal measurement techniques offer rapid thermal characterization without modification or destruction of the sample being studied. A simple and versatile method has been developed, termed the "numerical mirage method," that utilizes the transient photothermal deflection of a laser beam traversing a modulated temperature gradient. This method expands the range and simplifies the experimental procedure of traditional mirage methods. A numerical solver is used to create accurate deflection profile models and a linear curve fitting routine is developed, from which the thermal diffusivity of a material may be determined. This method allows for rapid modification of sample and heating configurations. Verification of the method is performed on bismuth and fused quartz reference samples, and good agreement with literature is obtained.

Application of the thermal flash technique for low thermal diffusivity micro/nanofibers

“…Note that even potential inaccuracies associated with the length measurement of the microfiber of Ϯ10% still resulted in a thermal diffusivity within the error bars given. As a comparison, a bulk form of the glass sample was measured using the numerical mirage method, 19 giving a It should be noted that the 271 nm fibers are not expected to exhibit significant effects of enhanced thermal boundary scattering or other nanoscale mechanisms that might be present in sub-100 nm fibers, and therefore their thermal diffusivity should be comparable to that of the 570 nm diameter fibers. A bulk form of the polyimide was measured using the dynamic plane source technique, 20 resulting in a thermal diffusivity of ͑6.53Ϯ 0.22͒ ϫ 10 −8 m 2 / s, which compares well with the measurements obtained using the thermal flash method.…”

Detection limit of chemical gases in ambient air with co-linear photo-thermal deflection spectroscopy

“…[1][2][3][4][5][6][7][8] A slightly different form of photo-thermal deflection has been performed using resonant absorption of IR on explosives on a cantilever device. The gas or liquid heats up due to absorption of long wavelength IR radiation.…”

A 3-dimensional time-resolved photothermal deflection “Mirage” method

“…5 The method and its theoretical basis were first introduced by Boccara et al 5,6 The technique has been applied to investigate solid and fluid interfaces. [7][8][9][10][11][12][13][14][15][16] Several methods have been developed to quantitate the thermal properties of solid materials. For instance, the "zero crossing" method 9 and the "phase method" 10 are used to quantitate thermal diffusivity of materials.…”

“…This introduces errors in the determination of thermal diffusivity. 14 As an alternative approach, Demko et al 14 proposed a "numerical mirage method" considering accurate boundary conditions, but only numerical solutions to the probe beam deflection can be obtained. For these reasons, it is highly desirable to have a simple analytical solution describing the mirage effect for real experimental geometries.…”