Influence of tin content on spectral selectivity and thermal conductivity of Sn\u2013Al2O3 solar selective absorber

Abstract

The tin-pigmented aluminium oxide film (Sn–Al2O3) based solar selective absorber was successfully prepared with three different contents of tin by an anodization process. The phase and morphology of the Sn–Al2O3 were measured by X-ray diffractometer and a scanning electron microscope equipped with an energy dispersive X-ray analyser. The reflectance (R) of the coating was determined by Ultraviolet–visible-near infrared spectrophotometer in the wavelength interval of 300–2500 nm and the Fourier transform infrared spectrophotometer in the wavelength of infrared region (2500–25,000 nm). As a result, aluminium and tin phases were detected at the coating surface. The Al2O3 films were formed and compacted as a barrier on the Al substrate. The compositions of the oxide film composed of tin (Sn), aluminium (Al) and oxygen (O) elements. With increasing Sn content, the solar absorptance (αsol) gradually increased, but it has little effect on the thermal emittance (εtherm). The thermal conductivity of Sn–Al2O3 samples decreased with increasing Sn content as a result of the increasing thickness of the Sn layer at the interface leading to obstruct the free electrons and phonon contributions. The present result suggests that the increasing Sn content in the Sn–Al2O3 coating can enhance the solar selectivity properties and a good solar absorber material.