Design and construction of mesoporous silica/n-eicosane phase-change nanocomposites for supercooling depression and heat transfer enhancement

Traditional micro- or nanoencapsulation of phase change materials (PCMs) generally results in high supercooling and slow thermal response. Hereby, we designed and synthesized two types of meso-silica/n-eicosane phase-change nanocomposites in the forms of uniform nanospheres and core-shell structured nanocapsules through self-templating strategy. The meso-silica/n-eicosane nanospheres have a disordered worm-like mesopore nanostructure, whereas the meso-silica/n-eicosane nanocapsules show a 3D cubic cage-like mesoporous structure for the core and a solid silica layer for the shell. These two types of phase-change nanocomposites achieved superior thermal performance including a good thermal storage capability, high thermal stability, good shape stability and satisfactory phase-change reliability. Most of all, owing to the formation of specific hierarchical nanostructures, both of them achieved a significant enhancement in thermal conductivity and effective depression in supercooling. Compared to the conventional silica/n-eicosane microcapsules, these two types of phase-change nanocomposites exhibited a shorter heat-charging period due to good thermal conduction by their interconnecting mesopores silica matrix, but a longer heat-discharging period because of the internal narrow mesopores resulting in crystallization confinement of encapsulated n-eicosane. With low supercooling and rapid thermal response, the phase-change nanocomposites developed by this work exhibit a great potential for hi-tech applications in fast temperature regulation and precise thermal management.