Effective thermal management enabled by encapsulation of phase change myristic acid in silica shells for coatings: Experimental and molecular dynamics studies

In order to alleviate the energy crisis and improve energy savings while ensuring the thermal reliability of the material, a commonly used method is the preparation of silica phase change nanocapsules. However, most of the current studies are more concerned with enhancing the thermal conductivity of silica phase change nanocapsules. On the contrary, few studies have been reported on decreasing the thermal conductivity of silica phase change nanocapsules. In general, silica phase change nanocapsules with reduced thermal conductivity have great potential for application in building materials. Therefore, we prepare three different MA/SiO2 nanocapsule samples by sol-gel method using myristic acid (MA) as the phase change core and silica (SiO2) as the shell layer. MA/SiO2 has a well-defined spherical morphology and MA is successfully encapsulated by SiO2. MA improves the thermal storage capacity of silica nanocapsules, with the highest melting enthalpy of 144.6 J/g, corresponding to an encapsulation ratio of 74.8 % and a minimum thermal conductivity of 0.219 W/(m•K). Silica phase change nanocapsules have good thermal stability, and the maximum temperature difference between the upper surface of the uncoated and coated substrates is about 10.2 °C, which can play an important role in preventing heat exchange, demonstrating excellent thermal insulation and temperature control capabilities. In addition, the thermal mechanism of silica phase change nanocapsules is affected by the interfacial nanolayers, and we perform molecular dynamics simulations from an atomic point of view to further analyze the thermal mechanism. Simulation results show that the thermal conductivity of silica phase change nanocapsules is affected by the silica phonon diffusion channel, the resonance of the carbon backbone with the acid root in myristic acid, and the thermal resistance at the interface between SiO2 and MA.