Abstract
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°C, 800°C and 850°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.
Highlights
The expansion of urban agglomerations is responsible of a lot of energy consumption
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)
We developed near infrared (NIR) reflective pigments with the aim to add in binder and obtaining a cool coating
Summary
Buildings consume the 40% of primary energy [1] This is because in urban environments temperatures increase for concrete and paved surfaces that adsorb solar energy. The use of cool materials for roofs and envelopes of buildings (Figure 1.) can achieve the retention of the UHIE. This kind of materials is characterized by high solar reflectance (ability to reflect sunlight, spectrum 0.3-2.5 μm) and high thermal emittance (ability to emit thermal radiation, spectrum 4-80 μm) [2]. Three different pigments were achieved maintaining exactly the same formulation tuned by Jose et al [9], acting only on the heat treatment which will give the final colour. The final colour was evaluated according to CIE-2004 L*a*b* colorimetric method [10] with the aim to have a standard identification of each colour
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