Optical modeling of multilayered coatings based on SiC(N)H materials for their potential use as high-temperature solar selective absorbers

Abstract

SiCH thin films grown from Ar/tetramethylsilane plasmas (PECVD) were evaluated as absorber layers in selective coatings for high-temperature solar receivers. SiCH coatings are used in thermomechanical applications because of their good thermal stability. A SiCH film with an absorption index k(430nm)=0.11 was taken as a reference for optical simulations of refractory metal–SiCH multilayer stacks and cermets. The transfer matrix method and Maxwell–Garnett effective medium approximation were used to calculate the spectral reflectance and transmittance of the selective absorbers. Their solar absorptance and thermal emittance were also deduced. A seven-layer stack with alternating metal and SiCH layers was found to present a simulated solar absorptance of 0.92 and thermal emittance of 0.08 at 500°C.