Silica encapsulation of n-octadecane via sol–gel process: A novel microencapsulated phase-change material with enhanced thermal conductivity and performance

Abstract

A novel microencapsulated phase-change material (PCM) based on an n-octadecane core and an inorganic silica shell was designed to enhance thermal conductivity and phase-change performance. These silica microcapsules were synthesized by using TEOS as an inorganic source through a sol–gel process. Fourier transform infrared spectra confirm that the silica shell material was successfully fabricated onto the surface of the n-octadecane core. Scanning electronic microscopy images suggest that the silica microcapsules exhibit a spherical morphology with a well-defined core–shell microstructure. Furthermore, the silica microcapsules synthesized at pH 2.45 display a smooth and compact surface. These microcapsules also present a large particle size range of 7–16 μm. Wide-angle X-ray scattering patterns indicate that the n-octadecane inside the silica microcapsules still retains a good crystallinity. Thermogravimetric analysis shows that these silica microcapsules are degraded in two distinct steps, and have good thermal stability. The silica-microencapsulated n-octadecane can achieve good phase-change performance, high encapsulation efficiency, and good antiosmosis property by controlling the loading of core material and acidity of the reaction solution during the sol–gel process. The thermal conductivity of the microencapsulated n-octadecane is also significantly enhanced due to the presence of the high thermal conductive silica shell.