Fig. 5
From: A review on solar water heating technology: Impacts of parameters and techno-economic studies
a “Photograph of the three FPCs: PVD Ti—sputter-deposited nitrogen-doped titanium dioxide; E BN—electrodeposited bright nickel/black; CuO—copper oxide. b The appearance of the copper fin is enclosed with the electrodeposited black nickel selective glazing, with SEM photos shot from planar divisions of the fin as shown with alphabets A, B, and C” (Lizama-Tzec et al. 2019)