ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Comparison of structure and solar-selective absorbance properties of Al₂O₃ thin films with Al and Ni reflector interlayers

Aliaa Abdelfatah, Lamiaa Z. Mohamed, Iman Elmahallawi, and Hanan Abd El-Fattah

Mining, Petroleum, and Metallurgical Engineering Department, Faculty of Engineering, Cairo University, Giza, Egypt

E-mail: lamiaa.zaky@cu.edu.eg

Received: 2 March 2023  Accepted: 20 April 2023

Abstract:

This work aims at evaluating the selective solar absorbance (SSA) of Al₂O₃ thin films deposited by physical vapor deposition (PVD) with two different metallic reflector interlayers. Al₂O₃ thin films are deposited on the same substrate stainless steel (SS) 304L, with two different interlayers between the thin film and the substrate, namely, nickel (Ni) and aluminum (Al) are used as the reflector interlayer SS304L/Al/Al₂O₃ and SS304L/Ni/Al₂O₃. A scanning electron microscope (SEM) was utilized to characterize the chemical composition by energy dispersive X-ray analysis (EDX) and surface morphology of the deposited thin films. The phases of the thin films were analyzed and identified by X-ray diffraction (XRD) to detect the present phases. The surface topography and the thickness of the deposited thin films were investigated using an atomic force microscope (AFM). The optical properties of the substrate and the deposited thin films (absorbance & emittance) in two conditions were identified by Fourier transform infrared spectroscopy (FTIR) and spectrophotometer. The obtained results demonstrate that both SS304L/Al/Al₂O₃ and SS304L/Ni/Al₂O₃ show good performance, such as high solar absorbance and low thermal emittance. However, the Al/Al₂O₃ thin film provides high selectivity (absorbance/emittance (α/ε)) of 0.916/0.05, compared to 0.913/0.15 for the Ni/Al₂O₃ coating. The effect of different properties and microstructure on the efficiency of deposited thin films showed that the SS304L/Al/Al₂O₃ has higher absorbance (92%) in visible and ultraviolet (UV) regions; and lower emittance (5%) than the SS304L/Ni/Al₂O₃. This work shows that the intermediate IR layer has a more pronounced effect on the emittance properties rather than the absorbance properties of the Al/Al₂O₃ layer.

Keywords: Selective solar absorber; Solar thermal energy; Magnetron sputtering; SS304L substrate; Optical properties; Microstructure

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-023-02842-z

Chemical Papers 77 (9) 5047–5057 (2023)