Copper-coated phase change nanocapsules with improved thermal properties synthesized by a green method

This study aims to develop an eco-friendly method for synthesizing phase change nanocapsules with improved thermal properties. It focuses on coating nanocapsules with highly thermal conductive Cu, using a non-toxic reducing agent. The morphology, microstructure, crystal structure, element compositions, and thermal stability of the Cu-coated nanocapsules were analyzed to ensure successful nanoencapsulation and coating. Melting-solidifying cycling experiments were conducted to assess the thermal reliability of the nanocapsules and the thermal conductivity of their suspensions was measured. The results indicated that the nanocapsules were continuously coated with Cu under appropriate reaction conditions. The optimal preparation conditions were determined, resulting in a phase change enthalpy of 77.42 kJ/kg. The SiO2 shell and Cu coating increased the thermal stability of the nanocapsules, with a mere 7.59 kJ/kg reduction in melting enthalpy after 250 melting-solidifying cycles. The thermal conductivity of the Cu-coated nanocapsule suspension increased by 26.67 % compared to that of the uncoated nanocapsules.