Properties of form-stable paraffin/silicon dioxide/expanded graphite phase change composites prepared by sol–gel method

A form-stable paraffin/silicon dioxide (SiO2)/expanded graphite (EG) composite phase change material (PCM) was prepared by sol–gel method. Silica gel acts as the supporting material and EG is used to increase the thermal conductivity. The mass fractions of silicon oxide and graphite are 20.8% and 7.2%, respectively. The composite PCM was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transformation infrared spectroscopy (FTIR) method. Thermal properties and thermal stability of the composite PCM were studied using differential scanning calorimetry (DSC). The result shows that paraffin was well dispersed in the network of silica gel and there is no chemical reaction between them. The phase change temperature of the paraffin/SiO2 composite and the paraffin/SiO2/EG composite are 27.53 °C and 27.72 °C, respectively. The latent heat of the paraffin/SiO2 composite and the paraffin/SiO2/EG composite are 112.8 J/g and 104.4 J/g, respectively. The thermal conductivity of the SiO2/paraffin composite and the SiO2/paraffin/EG composite are 28.2% and 94.7% higher than that of paraffin.