Synthesis and characterization of geometrically tunable nano-size hollow silicate particles and their dip-coating prepared films for thermal management applications

The synthesis of geometrically tunable nano-size hollow silicate particles (NHSPs) using water-based poly_(methacrylic acid) sodium salt (NaPMA) colloidal nano size-aggregate particles as soft-templates, tetraethyl orthosilicate (TEOS) as a silica precursor and ammonia hydroxide (NH4OH) as a catalyst by simple sol-gel reaction was carried out. Tuning the nano-size diameter of NHSPs between 60 nm and 200 nm and decreasing the shell thickness from 40 nm down to 18 nm were achieved by only varying the concentrations of alternative-NaPMA and the amount of TEOS, respectively. The thermal insulating feature of NHSPs was demonstrated by coating the glass substrate with NHSPs, a reduction of approximately 29.9% in thermal conductivity was observed after coating the glass substrate, which was evaluated by contactless approach using the xenon flash lamp set-up. The coated-glass with NHSPs was prepared by simple sequential adsorption of poly_(allylamine hydroxide) (PAH) followed by deposition of NHSPs on the cleaned glass substrate surfaces using an automated dip coater. The dip coated samples showed good thermal insulating properties as well as good transparency in the visible light range.