Activated carbon/expanded graphite hybrid structure for development of nonadecane based composite PCM with excellent shape stability, enhanced thermal conductivity and heat charging-discharging performance

Activated carbon (AC) has been promoted as one of the most effective carrier materials for adsorbing large amounts of PCMs due to its high surface area and porous structure. Although AC can also have a favourable impact on improving the low thermal conductivity of PCMs, a more obvious impact on this issue can only be achieved by doping AC with high conductive carbon-based materials to form hybrid structures. In this context, the current study focused on low-cost and environmentally friendly AC-hybrids made of wood-derived AC and expanded graphite to handle the leakage problem and low thermal conductivity issue of Nonadecane (ND) chosen as a PCM. AC-EG hybrids exhibited high ND adsorption rates of up to 75% by weight, while AC alone had an ND loading rate of 50% by weight. The characterization analysis results designated that the chemical and crystal structure of ND was not affected after compositing, revealing that chemical reactions did not occur among AC-EG-ND throughout the impregnation. Devised AC90-EG10/ND composite with 75% load of ND possessed a melting point of 29.84 °C and the enthalpy fusion of 173.11 J/g. The thermal conductivity of AC90-EG10/ND was up to 2.47 and 3.81 times that of AC/ND and ND, respectively. In conclusion, the strategy of developing AC-EG hybrids as carrier matrices and thermal conductivity enhancers for ND and preparing different leak-proof composite PCMs from them can be very beneficial for low-temperature thermal management systems such as building envelopes, electronic device/equipment, food transportation and textile products.