Preparation and characterization of hydrated salts/silica composite as shape-stabilized phase change material via sol–gel process

• A mixture of hydrated salts were adopted as phase change materials.
• Phase segregation of the hydrated salts was inhibited.
• Subcooling was slightly mitigated.
• Thermal cycling performance was greatly improved after PVP coating.

A novel shape-stabilized phase change material composite was prepared by impregnating the mixture of hydrated salts (Na2SO4·10H2O–Na2HPO4·12H2O) into porous silica matrix obtained by sol–gel process and further coated with polyvinylpyrrolidone (PVP) to improve the thermal cycling performance. The chemical compatibility, morphology and phase change properties were investigated by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), hot-stage polarizing optical microscope (HS-POM) and differential scanning calorimetry (DSC). Confined in the silica matrix, phase segregation of the hydrated salts was inhibited and subcooling was slightly mitigated. No leakage was observed during the solid–liquid phase transition even when the mass ratio of hydrated salts to silica was as high as 70:30. Results showed that the melting enthalpy of the composite can reach 106.2 kJ/kg with the melting temperature at 30.13 °C and there was no significant enthalpy loss after 30 thermal cycles.