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

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 microm. 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.