Apparent emissivity measurement of semi-transparent materials part 2: Theoretical concept

Semi-transparent materials are increasingly applied in various industrial and scientific applications. Because there is a strong coupling between optical and thermal properties of these materials, they pose unique challenges for their modelling and experimental characterization. At PTB, the facilities for spectral emissivity measurement of opaque materials have been expanded for the characterization of semitransparent materials in the near-, mid- and far-IR region and for temperatures between 20 degrees C and 90 degrees C by using a new sample holder. The experimental realization and validation of the new facility for emissivity measurement of semi-transparent materials is presented in part 1 of this publication. Here the evaluation procedure of the measurement data obtained with the new sample-holder is discussed in detail. A model of radiative transport within semi-transparent samples considering emission, absorption, scattering and multiple reflections was formulated and solved over a wide spectral range. The model was inverted using a least squares approach and an extensive sensitivity analysis was performed. (C) 2020 The Authors. Published by Elsevier Ltd.

Automated summary

Semi-transparent materials pose unique challenges due to the strong coupling between their optical and thermal properties; spectral emissivity measurement of these materials using a new facility; evaluation, inversion, and sensitivity analysis of measurement data based on a radiative transport model formulated for semi-transparent materials.