Thermal conductivity enhancement of silica fume based composite thermal energy storage material using different carbon nanomaterials

In the present study, raw silica fume (RSF) was evaluated as carrier matrix to create PEG-included form-stable latent heat storage materials (FS-LHSMs), and carbon nanofiber (CNF), carbon nanotube (CNT) and graphene nanoplatelet (GNP) were used for enhancing thermal conductivity of the developed FS-LHSMs. The obtained novel RSF/PEG, RSF/PEG/CNF, RSF/PEG/CNT and RSF/PEG/GNP form-stable (FS-LHSMs) displayed significantly thermal conductivity and well resistance against the leakage of PEG during their heating periods. The techniques of differential scanning calorimetry (DSC), thermal gravimetric analyzer (TGA), thermal conductivity meter, fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) were employed in the characterizations. The form-stable loading of PEG in the fabricated FS-LHSMs was found to be 40 wt%. The FS-LHSMs are fundamentally physical mixes according to interactions revealed in the FTIR analysis. The melting temperature of synthesized FS-LHSMs was in the range of about 14–15 °C while their LH of fusion was in the range of about 55–56 J/g. The FS-LHSMs exhibited admirable thermal cycling reliability and thermal durability properties. The thermal conductivity of RSF/PEG composite was significantly improved by the CNF-CNT-GNP additives, and such improvements were also affirmed by the heat charging-discharging rate test. All the results exposed that the prepared FS-LHSMs can be utilized for engineering different building materials or elements with solar TES capability.