High thermal conductive paraffin/calcium carbonate phase change microcapsules based composites with different carbon network

Novel microcapsules based phase change composites (PCC) with improved thermal conductivity and thermal stability are developed. Different mass fractions (1%, 5%, 10% and 20%) of flake graphite (FG), expanded graphite (EG) and graphite nanosheets (GNS) acted as heat transfer promoters are employed to enhance thermal properties of PCC. The influences of carbon additives on forming network structure and promoting thermal conductivity are analyzed, the mechanism of heat transfer enhancement is further studied. The results showed that distinct carbon network structure in PCC was observed with 20%, 20%, 10% mass fraction of FG, EG and GNS, respectively. The corresponding thermal conductivity was increased up to 70.0 times of the pristine paraffin when PCC contains 20 wt% GNS. Negligible change in thermal properties of the PCC-GNS was confirmed after 500 times thermal cycling tests. Therefore, such enhancement in thermal properties of PCC can result in an improvement of heat storage efficiency, which will be more suitable for numerous thermal applications.