Highly Solar-Reflective Litchis-Like Core-Shell HGM/TiO2 Microspheres Synthesized by Controllable Heterogeneous Precipitation Method

Abstract

Hollow glass microsphere (HGM)/TiO2 core-shell structural composites have promising applications in the field of energy efficient solar-reflective paints. In this work, after pretreated with saturated Ca(OH)2 solutions, litchis-like TiO2 shells have been successfully synthesized on HGMs via a controllably heterogeneous precipitation method with Titanium (IV) sulfate (Ti(SO[Formula: see text] and urea as reaction precursors. It is emphasized that the use of urea as the precipitating agent is essential for the heterogeneous nucleation and growth of Ti(OH)4 on HGMs, while the Ca(OH)2 pretreatment provides the heterogeneous nucleation sites on HGMs which promotes the nucleation and growth of Ti(OH)4, and gives rise to large secondary Ti(OH)4 particles, leading to the formation of litchis-like TiO2 shells. The resulted core-shell structural HGM/TiO2 microspheres exhibited highest solar reflectance of [Formula: see text]83%.