NIR reflective pigments to mitigate the urban heat islands effect (UHIE)

For building applications, coatings are needed in order to obtain an attractive appearance and protection against the outdoor environments. Buildings are responsible for consumption of cooling energy. Cool coatings applied over buildings surface provide an effective solution for passive cooling of building indoors and influencing local outdoor microclimate, mitigating urban heat islands effect (UHIE). Cool coatings have to resistant to weathering and ageing. For this reason, we developed near infrared (NIR) reflective pigments with the aim to add in binder and obtaining a cool coating. A series of pigments displaying YIn0.9Mn0.1O3-ZnO stoichiometry was synthesized by sol-gel route. The dried gel precursor was calcined at different temperatures for 2h (650 degrees C, 800 degrees C and 850 degrees C) to observe the formation of a light brown pigment and two different blue shades. Precursors and calcined final pigments were characterized by using physicochemical analyses. The colour of pigments was studied using CIE-2004 L*a*b* colorimetric method. The cooling effect of pigments and their thermal stability were confirmed by NIR reflectance measurements and TGA respectively.