Thermal properties of sodium nitrate-expanded vermiculite form-stable composite phase change materials

• The composite materials were prepared by direct impregnation method.
• The thermo physical properties of composites were investigated.
• Silicon carbide can improve the thermal conductivity of composites.
• The composites have good thermal stability.

This paper focused on the preparation and characterization of a novel thermal storage material applied in thermal storage. Sodium nitrate-Expanded vermiculite (EV) composite phase change materials were prepared by direct impregnation method. The chemical composition is investigated by X-ray diffraction (XRD). Scanning electron microscope (SEM) revealed that EV is porous structures, and sodium nitrate was stably adsorbed in the pores of EV. Further, the adsorptive capacity of EV to sodium nitrate is 734.6%. Meanwhile the thermal conductivity of composites is higher than single component, and the silicon carbide can improve the thermal conductivity of composites obvious. After 200 h heat treatment, differential scanning calorimeter (DSC) result indicated that the melting temperature changes are < 3.9 °C and thermal enthalpy changes are < 5.0%. All the results indicated that the composite materials can be as a good candidate to be applied in thermal energy storage fields.

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