Phase-change characteristics and thermal performance of form-stable n-alkanes/silica composite phase change materials fabricated by sodium silicate precursor

• The n-alkanes/silica composites were synthesized using sodium silicate precursor.
• The composites have a good shape stability with variation of ambient temperature.
• The phase change behaviors of the composites depend on carbon number of n-alkanes.
• The thermal conductivity, working reliability, and thermal stability were enhanced.

A series of n-alkanes/silica composites as form-stable phase change materials (PCMs) were synthesized in a sol–gel process using sodium silicate precursor. The chemical compositions and structures of the synthesized composites were characterized by Fourier transform infrared spectroscopy. Scanning electric micrographs show an irregularly spherical morphology of the n-alkanes/silica composites, and transmission electric micrographs confirm that the n-alkanes have been well encapsulated by silica. These n-alkanes/silica composites keep a good sharp stability due to the support of silica wall even if the n-alkanes are in molten state. The differential scanning calorimetric analysis indicates that the phase change behaviors and characteristics of the n-alkanes/silica composites strongly depend on the carbon atom number in n-alkanes, and meanwhile, the encapsulated n-alkanes have a high thermal storage capability. The investigation on thermal performance demonstrated that the n-alkanes/silica composites achieved a high thermal conductivity, low supercooling, and good work reliability as a result of the encapsulation of n-alkanes with highly thermal conductive inorganic silica. Moreover, the thermal stability of the composites was also improved due to the protection of silica wall toward the encapsulated n-alkanes. It is anticipative that, owing to the easy availability and low cost of sodium silicate, the synthetic technology developed by this work has a high feasibility in the industrial manufacture of the form-stable PCMs.

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