Nanosized Natural Minerals as Sustainable Fillers for Near-Infrared Shielding Coatings: Comparative Study of Rutile, Leucoxene, Ilmenite, and Hydroilmenite

Abstract

This study investigates nanosized Thai natural minerals rutile, leucoxene, ilmenite, and hydroilmenite as sustainable fillers for near-infrared (NIR) shielding coatings. The minerals, mainly composed of TiO₂, were processed by high-energy ball milling without chemical additives. The resulting natural mineral nanopowders were subsequently dispersed into a polyvinyl alcohol (PVA) matrix and applied as thin film coatings. and incorporated into polyvinyl alcohol (PVA) coatings. The optical and thermal performance was found to be highly dependent on the resulting particle size and elemental composition. Specifically, the TiO₂-rich rutile and leucoxene coatings primarily enhanced IR reflection, whereas the iron-rich of ilmenite and hydroilmenite coatings significantly improved NIR absorption. Critically, the ilmenite coating achieved optimal thermal performance, resulting in a maximum reduction of the model house interior temperature by 3 °C compared to the unmodified PVA film. These findings confirm the feasibility of utilizing locally sourced, processed natural minerals as cost-effective and environmentally friendly alternatives to synthetic nanomaterials, demonstrating a promising pathway for developing high-performance, energy-saving coatings.