Nanostructured zinc aluminates: A promising material for cool roof coating

Abstract

Nanostructured zinc aluminate pigments were synthesized using a citrate sol–gel method. All the samples were annealed at 600 °C, 700 °C, 800 °C, and 1100 °C for 6 h, respectively. The as-synthesized samples were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), UV–Vis–NIR spectroscopy and CIE L*a*b* color analysis. The phase purity and structural analysis of the zinc aluminates were confirmed using X-ray diffraction and Rietveld refinement. The morphological and microchemical analysis was done using FE-SEM, TEM and EDX. The particle size and reflectance properties are found to be sensitive to the annealing temperature. The samples exhibited a total solar reflectance of about 85%. An attempt was also made to compare the total solar reflectance of the synthesized zinc aluminates with that of commercially available TiO2 by applying over a concrete cement surface. Keywords: Zinc aluminate, Nanocrystalline materials, Citrate-sol gel method, NIR reflectance, Cool coating