Measurement of the Thermal Diffusivity of Solids with an Improved Accuracy (original) (raw)
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Analytical Sciences/Supplements Proceedings of 11th International Conference of Photoacoustic and Photothermal Phenomena, 2002
An experimental setup was developed at the NPL with the goal of improving the accuracy of photothermal measurements. The principle is to perform accurate measurements of the experimental boundary conditions during a photothermal radiometry experiment. A numerical 3D heat diffusion model based on thermal transfer functions has been developed to use the measured boundary conditions. To prove the validity of this methodology, the thermal diffusivities of pure metal samples were estimated from experimental thermal radiance data by a least-squares fitting to the model. Experiments carried out at about 900K demonstrate good agreement between the theoretical and experimental data and accuracies of about 1.5% for thermal diffusivity measurements.
Thermal Diffusivity Measurements by Photothermal and Thermographic Techniques
International Journal of Thermophysics, 2000
In this work, fruit of the collaboration between two laboratories, we present different techniques to measure thermal diffusivity. At first a brief description of every technique both in the experimental layout and in the processing algorithms is given. After that, results obtained on samples cut from the same block of stainless steel AISI 304, are reported. Uncertainties evaluation of any measurement is reported together with a discussion on the pros and cons of the related technique.
International Journal of Thermal Sciences, 2015
This work demonstrates that in photothermal experiments performed in frequency domain the heat losses due to convection and radiation should be taken into account at low frequencies for poor heat conductors. From a model-solution of the heat diffusion equation a dimensionless frequency dependent parameter M ¼ ZH, with sample's thermal impedance Z and H the convection-radiation heat transfer coefficient, turns out to adequately quantify the importance of the effect of those heat losses. A straightforward photothermal infrared radiometry setup was designed to demonstrate the above hypothesis. Disc shaped samples of different test materials were heated by square wave modulated illumination at one of their surfaces at different frequencies using an amplitude modulated laser beam, and the temperature at the rear surfaces was monitored as a function of time using an infrared sensor. The frequency dependence of peak-to-peak values of the temperature signals was found to be consistent with the amplitude spectrum obtained by Fourier transforming the data. The frequency dependence of the peak-to-peak amplitude was compared with a theoretical model with and without taking convection and radiation induced heat losses (CRHL) into consideration. It is found that for poor heat conductors at low modulation frequencies the conventional model without CRHL does not fit well the experimental data, while the extended model leads to good agreement, resulting in reliable values for the thermal diffusivity. For the investigated samples, the contribution to the signal of thermal wave reflection at the back side of the sample turn out to have a minor effect on the signal spectrum.
Journal of Physics: Conference Series, 2010
The aim of this work is to approach in an experimental way, the possibilities of diffusivity thermal measurement, under less energy constraints, offered by front face random photothermal radiometry associated to a parametric analysis. First, we present the principle of the random method. Then, we present the experimental device SAMMIR used in our study. In a third stage, we present the studied sample, the experimental conditions selected and the model developed for the study. We show finally, using the experimental study of a sample of nylon 6.6 that the photothermal method allows, in a particular case, a good approximation of the thermal diffusivity parameter.
International Journal of Thermophysics, 1997
The thermal diffusivity of various types of aluminunl has been measured, using a completely noncontact experimental configuration based on infrared photothermal radiometry. Photothcrmal response transients, conventional frequency scans, and pulse duration-or repetition rate-scanned rate windows have been investigated. It has been shown that the conventional fi'equency scan is not suitable for measurements of ah,ninum with a short thermal transport time such as foils, due to an extremely degraded signal-to-noise ratio (SNR I. Also, it has been found that the conventional frequency scan method is less sensitive to the actual value of thermal diffusivity than the rate-window scan. The ratewindow method, furthermore, gives superior SNR especially tbr thin metals and yields excellent agreement between the theory and the data. An advantage of the paise duration-scanned rate window mode is that it does not reqt, ire knowledge of the instrumental transfer function as an input. The transient response gives the worst SNR but is best for the physical interpretation of the photothermal signals. In addition, it has been shown that the infrared photothermal radiometric transmission mode is less sensitive to surface roughness than the reflection mode and, therefore, is preferable for thermal diffusivity measurements of alt, minum and of good thermal conductors, in general.
2011
In this paper we propose a new procedure of simultaneous estimation of the effective infrared optical absorption coefficient and the thermal diffusivity of solid state samples using the photothermal infrared radiometry method in the transmission configuration. The proposed procedure relies on the analysis of the frequency dependent signal obtained from the samples covered with thin aluminum foil. This method can be applied for both optically opaque and transparent samples. The proposed method is illustrated with the results of the thermal diffusivity and the effective IR absorption coefficient obtained for several Cd 1Àx Mg x Se crystals.
Review of Scientific Instruments, 2003
A self-normalized photothermal method for measuring thermal diffusivity of thin metal layers has been implemented using two experimental configurations based on photothermal radiometry and gas-cell photoacoustic detection. The corresponding measurement procedures involve linear fits in the photothermally thin and/or thick limits. As part of this method, simple experimental criteria have been developed to ascertain that a purely thermal-diffusion-wave mechanism is dominant throughout the selected frequency range, thus validating the accuracy of the thermal diffusivity measurements. Thermal-diffusivity values measured using the intrinsic reliability of this self-normalized photothermal measurement scheme are reported for two commercial samples of aluminum and steel thin layers.
Measurement of thermal diffusivity of solids using infrared thermography
Materials Letters, 2008
We report measurement of thermal diffusivity of solid samples by using a continuous heat source and infrared thermal imaging. In this technique, a continuous heat source is used for heating the front surface of solid specimen and a thermal camera for detecting the time dependent temperature variations at the rear surface. The advantage of this technique is that it does not require an expensive thermal camera with high acquisition rate or transient heat sources like laser or flash lamp. The time dependent heat equation is solved analytically for the given experimental boundary conditions. The incorporation of heat loss correction in the solution of heat equation provides the values of thermal diffusivity for aluminum, copper and brass, in good agreement with the literature values.
Cross-comparison of thermal diffusivity measurements by thermal methods
Infrared Physics & Technology, 2002
Thermal diffusivity is measured applying three techniques: (a) thermal wave generation by thermoelectric device; (b) non-adiabatic flash method with correction for non-ideal Dirac pulse by deconvolution; (c) photothermal deflection. They are applied on a sample of AISI 304. Results are compared with those obtained by the standard laser flash method. Ó 2002 Published by Elsevier Science B.V.
Determination of thermal diffusivity of opaque materials using the photothermal mirror method
Optical Engineering, 2014
A pump-probe photothermal mirror (PTM) method has been developed to determine the thermal diffusivity of opaque solid samples. The method involves the detection of the distortion of a probe beam whose reflection profile is affected by the photoelastic deformation of a polished material surface induced by the absorption of a focused pump field. We have measured the time dependence of the PTM signal of Ti, Al, Cu, Sn, Ag, and Ni samples. We show theoretically and experimentally that the time derivative of the signal in the first microseconds is proportional to the square root of the thermal diffusivity coefficient. The method affords a simple calibration and efficient interpretation of experimental data for a sensitive determination of the thermal diffusivity coefficient for materials. We demonstrate the applicability of the technique by measuring the thermal diffusivities of wadsleyite (β-Mg 2 SiO 4) and diopside (MgCaSi 2 O 6), two important minerals relevant to geophysical studies.