A new silica-microencapsulation technology toward n-alkane PCMs was developed through sol–gel synthesis using sodium silicate as a silica precursor, and the effect of carbon number on the synthetic condition, morphology, and performance of microencapsulated n-alkanes were intensively investigated. The carbon number of n-alkanes not only influences the phase change enthalpies but also determines the phase change temperatures. The even and odd carbon numbers of n-alkanes show a significant effect on the synthetic temperatures and acidities for the microencapsulation of the n-alkane PCMs. The pH value and temperature of reaction solution determines the silica condensation rate and thus influences the balance between the self-assembly and polycondensation of silica precursors on the surface of n-alkane droplets, and thus, the appropriate conditions can result in a perfect spherical morphology and a well-defined core-shell microstructure. Fourier transform infrared spectra confirm the chemical composition of the synthesized microcapsules, and wide-angle X-ray scattering patterns indicate good crystallinity for these n-alkanes inside microcapsules. The microencapsulated n-alkanes alsoexhibited good phase change performance andachieveda high encapsulation rate and high encapsulation efficiency when synthesized in appropriate conditions. The encapsulation of n-alkanes with compact and thick silica wall can impart a high thermal conductivity and a good anti-osmosis property to the microcapsules, and can also improve the thermal stability of the microcapsules by preventing inside n-alkanes from thermally evaporating. Owing to the easy availability and low cost of sodium silicate, this synthetic technology indicates a high feasibility in industrial manufacture for microencapsulated PCMs with inorganic walls.
