Development, Analysis of Tungsten-Aluminium oxide based solar thermal multilayer Coating

Abstract

Development of magnetron sputtered tungsten based thin film coatings are considered as enhanced solar selective multilayer coatings for solar thermal applications. Tungsten thin film coatings deposited using magnetron sputtering process on stainless steel substrate acts as an infrared reflective layer and solar absorber layer. Aluminum oxide layer used has a ceramic and antireflective layer in a stacking sequence to match the phase and amplitude of the light wave propagated in the material. Solar absorptance and thermal emittance were simulated for different thickness and stacking of multilayer coatings and optimized using CODE software. The number and stacking sequence of alternate tungsten and aluminum oxide layer thin film coating is optimised using magnetron sputtering process. Coating adhesion was improved by adding a binding layer above the polished stainless steel substrate.Influence of mechanical thickness and varying sputtering parameters on optical property were analysed using UV-Vis-NIR spectrophotometer, 410-Solar and ET-100 reflectometer for absorptance (α) and thermal emittance (ε) values.Tungsten thin film deposited on stainless steel substrate yields a value of Solar absorptance of 0.94 in UV-Visible-NIR (0.3µm to 2.5µm) and thermal emittance of 0.07 (2.5µm-25µm) at room temperature. Enhanced Tungsten-Aluminum oxide based solar selective multilayer coating on stainless steel substrate is exhibited with high thermal stability at 400’C.