title: A travelling photothermal technique employing pyroelectric detection to measure thermal diffusivity of films and coatings.
abstract: A travelling thermal wave technique employing optical excitation and pyroelectric detection of thermal waves propagating along a material film/coating on a substrate is described. The method enables direct measurement of thermal diffusivity. The technique involves measurement of the phase lag undergone by an optically excited thermal wave as it propagates along the coating. The set up has been automated for convenient and fast data acquisition and analysis. The technique has been adapted to measurement of thermal diffusivity of a commercial paint sample coated on glass and copper substrates. It is found that thermal diffusivity of the coating is independent of the thermal conductivity of the substrate. Dependence of thermal diffusivity on coating thickness shows exponential increase, with value reaching a constant at a characteristic high thickness. Measurements have been carried out on a few other samples with wide variations in thermal diffusivity, and the results compared with available reports or results obtained following other techniques. Analyses of the results show that the technique allows measurement of thermal diffusivity of coatings and films with uncertainties better than ±2.5%.
authors: Department of Instrumentation and STIC, Cochin University of Science and Technology, Cochin 682 022, India. jp@cusat.ac.in
authors: J
authors: J
authors: Philip
authors: M V
authors: MV
authors: Manjusha
authors: H
authors: H
authors: Soumya