Enhanced thermal properties of SiO2 nanocomposite for solar thermal energy storage applications

In this study the thermo-physical properties of a solid nano-composite material was measured and compared with the undoped solid material. SiO2 nanoparticles were dispersed in eutectic of lithium carbonate and potassium carbonate (62:38 molar ratio) to obtain a high temperature nanocomposite. Specific heat measurement was performed using a differential scanning calorimeter (DSC). A laser flash apparatus (LFA) was used to measure thermal diffusivity. The thermal conductivity was computed based on the specific heat and the thermal diffusivity. On mixing (doping) with the nanoparticles at 1% concentration by weight the specific heat was enhanced by 5–15% and the thermal diffusivity was enhanced by 25–28%, respectively. The corresponding effective thermal conductivity of the nanocomposite was calculated to be enhanced by 35–45% compared with that of the undoped (pure) material. On performing scanning electron microscopy (SEM) of the nanocomposite a percolation network (interconnected substructure) of a dense material was observed. Such substructures were not observed in the undoped (pure) material. It is assumed that this percolation network of higher density phase that is observed to form around the nanoparticles is responsible for the enhancement of the thermal properties of the nanocomposite.