Optical Properties of AlxOy/Ni/AlxOy Multilayered Absorber Coatings Prepared by Reactive DC Magnetron Sputtering

Abstract

Al (x) O (y) /Ni/Al (x) O (y) multilayered absorber coatings were deposited on stainless-steel substrates using reactive direct-current (DC) magnetron sputtering. Al (x) O (y) films with different morphologies, structures, and optical transmittances were obtained by varying the DC power and oxygen flux. The Al (x) O (y) films were characterized using field-emission scanning electron microscopy, transmission electron microscopy, energy-dispersive x-ray spectrometry, grazing-incidence x-ray diffraction, and ultraviolet/visible/near-infrared spectrophotometry. The effect of the thickness of the Al (x) O (y) films on the optical properties of Al (x) O (y) /Ni/Al (x) O (y) coatings was also investigated. Experimental results show that the thermal emittance of the Al (x) O (y) /Ni/Al (x) O (y) multilayered absorber coatings decreases as the thickness of the Al (x) O (y) top layer is decreased. The Al (x) O (y) /Ni/Al (x) O (y) multilayered absorber coating with 70-nm-thick Al (x) O (y) top and bottom layers showed the best optical properties. The thermal stability of the Al (x) O (y) /Ni/Al (x) O (y) multilayered absorber coating in which the Al (x) O (y) films were deposited at conditions of 150 W and 8 sccm O-2 was at least 12 h when the multilayered absorber was annealed at 400A degrees C in air.