Optical property and thermal stability of Mo/Mo–SiO₂/SiO₂ solar‐selective coating prepared by magnetron sputtering

Abstract

Mo/Mo–SiO2/SiO2 solar‐selective coating for high‐temperature solar thermal application is prepared on quartz glass by direct‐current (DC) and radio‐frequency (RF) co‐sputtering. The normal solar absorptance αn = 0.95 and thermal emittance εn = 0.097 (353 K) are obtained through process optimization. The normal reflectance Rn(λ) before and after 1073 K vacuum annealing, are measured by ultraviolet–visible–infrared (UV–VIS–IR) and Fourier transform infrared (FT‐IR) spectroscopy. There is only a slight increase in Rn(λ) in IR region after annealing, which results in a lower εn = 0.075 (353 K). The crystallized grain of Mo in the coating, obtained from XRD pattern, increased from 23 to 60 nm after vacuum annealing. These phenomena are mainly caused by the change of crystal state and reflectance of Mo IR layer according to the comparison of Rn(λ) and XRD patterns of Mo/SiO2 and Mo–SiO2/SiO2 tandem films. The near‐normal reflectance of Mo/Mo–SiO2/SiO2 solar‐selective coating before and after 1073 K vacuum annealing.

CrAlSiN barrier layer to improve the thermal stability of W/CrAlSiNx/CrAlSiOyNx/SiAlOx solar thermal absorber

“…With the absorption layers and the antireflection layer, FTIR analyses would integrate the signals from the three layers. Changes in the first annealing steps followed by steps without significant changes, with very good thermal stability, were reported in our previous studies [9] and by other authors in coatings based on W-Al 2 O 3 [25], Mo-SiO 2 [26] and W-SiO 2 [27] cermet composites. The changes were not similar in all cases: in most cases a small increase in reflectance in IR range was observed, but also a small decrease in the reflectance occurred in other cases.…”

Structural, morphological, and optical characterizations of Mo, CrN and Mo:CrN sputtered coatings for potential solar selective applications

“…Mo/Mo-SiO 2 /SiO 2 spectral selective absorbers deposited onto quartz substrate via cosputtering method for high temperature applications showed high absorptance in the visible range and low thermal emittance in the infra-red range of the solar spectra [14]. After annealing at 800 °C, the thermal emittance of such absorber coatings was significantly reduced from 9.7% to 7.5%.…”

Optical and structural analysis of solar selective absorbing coatings based on AlSiOx:W cermets

“…These ceramic materials have been chosen due to its inherent high chemical and thermal stability, together with metals inclusions, such as W, Mo, Ag, Ni, Pt, Nb, and V, bearing some of these metals a relatively good oxidation resistance. Those combinations are, for example, Mo-Al 2 O 3 (Zhang et al, 1996;Teixeira et al, 2001;Cheng et al, 2013), W-Al 2 O 3 (Antonaia et al, 2010;Cao et al, 2015), Ni-Al 2 O 3 (Boström et al, 2011;Craighead and Buhrman, 1977), Pt-Al 2 O 3 (Lafait et al, 1986;Craighead et al, 1979), V-Al 2 O 3 (Farooq and Hutchins, 2002), Mo-SiO 2 (Esposito et al, 2009;Zheng et al, 2013;Wang et al, 2011), W-SiO 2 (Wäckelgård et al, 2015), Ag-SiO 2 (Granqvist and Hunderi, 1978), Ni-SiO 2 (Farooq et al, 1998), Nb-TiO 2 (Wäckelgård et al, 2015), W-AlN (Zhang and Shen, 2004) and Mo-Si 3 N 4 (Céspedes et al, 2014). This paper presents the development of solar absorber coatings for high operation temperatures (>400°C), based on AlSiO x :W cermets.…”