Hydrophobic composite phase change coating: Preparation, performance and application

The utilization of composite phase change materials in energy storage and solar thermal applications is significantly restrained by their inherent non-hydrophobic surfaces and susceptibility to contamination. This study presents a novel synthesis of modified paraffin (Pa) @ silica (SiO 2 ) nanocapsules through an efficient in situ hydrolysis and polycondensation reaction utilizing tetraethyl orthosilicate (TEOS) as the silicon source, paraffin as the phase change material, and hexamethyldisilazane (HMDS) as the surface modifier. These nanocapsules were then employed to formulate a composite phase change coating (PSC-1) by spraying onto a substrate of lithium silicate (Li 2 SiO 3 ), a green inorganic binder. This coating combines self-cleaning and energy storage functionalities. The thermal characterization of PSC-1 revealed an enthalpy of phase transition of 92.95 J/g at a core-shell ratio of 1.5:1 and an HMDS to TEOS volume ratio of 1:1. Additionally, the thermal conductivity of PSC-1 was measured at 0.505 W/m∙K, which is approximately 53 % higher than that of pure paraffin. PSC-1 also demonstrated superior hydrophobicity, with a static water contact angle of 132.6°. Enhancing its practicality, the coating was subsequently dyed black and assessed for photothermal conversion efficiency, which was determined to be around 68 %. The integration of robust self-cleaning properties and high-efficiency thermal characteristics renders PSC-1 a highly promising material for broad applications in solar energy conversion and storage. • Pa@SiO 2 nanocapsules with hydrophobic surface were synthesised using a simple method. • PSC-1 has good self-cleaning properties and maintains a high latent heat. • The improved thermal conductivity of PSC-1 benefits the thermal management. • The blackened coating can be used for solar energy storage.