Identification of the spectral complex refractive indices of micrometric phases within a semi-transparent medium up to elevated temperatures

Complex refractive indices of micrometric aluminosilicate fibers and of silica aerogel, components of a biphasic and semi-transparent material, were identified in the mid-infrared range from 295 to 1350 K. The identification was carried out by successive applications of a methodology combining infrared spectroscopy (FTIR), X-ray microtomography and Monte Carlo Ray Tracing. This identification technique proves to be an interesting tool for material design since it is now possible to forecast the radiative properties of heterogeneous and semi-transparent materials composed of identical microphases but involving different proportions and spatial distributions. With this approach, it is no longer necessary to identify effective indices or perform systematic FTIR spectroscopy measurements to get a first overview of the radiative properties of a new spatial layout of the microphases.