Doubly Coated, Organic–Inorganic Paraffin Phase Change Materials: Zinc Oxide Coating of Hermetically Encapsulated Paraffins

A way to benefit from the favorable attributes of both organic microencapsulation, including the hermetic sealing of the organic phase change material (PCM) core, and inorganic microencapsulation, including dispersibility in aqueous and polar solvents and improved thermal conductivity, is outlined. The approach is demonstrated by uniformly coating organic polymer encapsulated PCMs with zinc oxide, which allows thermal percolation through the interconnected inorganic shells. It is demonstrated that hydrogen peroxide sol–gel processing can be used to form such uniform zinc peroxide coatings which are then converted by chemical treatment to zinc oxide shells. The way to overcome different challenges associated with the synthesis of thin film coatings of organic PCMs by zinc oxide are addressed, and the favorable attributes of the new doubly coated PCM capsules are demonstrated.