Preparation and thermal properties of palmitic acid @ZnO/Expanded graphite composite phase change material for heat storage

A novel palmitic acid @ZnO/Expanded graphite composite phase change material (PCM) was prepared. Palmitic acid (PA) was selected as phase change material and ZnO/Expanded Graphite as supporting material. Expanded graphite (EG), which was used to improve the thermal conductivity of PCM, was chemically modified using ZnO derived from ZIF-8. ZnO derived from ZIF-8 has abundant pore structure and large specific surface area. The structure of ZnO/EG additive was characterized by SEM analyzing method. The prepared ZnO/EG has a three-dimensional coupled network and hierarchical porous structure. Meanwhile, EG can effectively prevent the structural collapse and aggregation of Metal-Organic Framework (MOF) derivatives. The morphology and thermal properties of composite PCMs were analyzed with SEM, XRD, FTIR, DSC, TG, and DTG. The melting/solidifying temperatures and corresponding latent heats of composite PCM PA@ZnO/EG-6% are 60.38 °C and 58.46 °C, and 203.35 kJ/kg and 207.87 kJ/kg. Thermal conductivity of the composite PCM PA@ZnO/EG-6% increases by 137.5% than that of PA. The DTG results indicated the composite PCM has superior thermal stability. All test results suggested that this composite is a good PCM and has excellent potential in heat storage due to its excellent thermal properties, good thermal stability, and reliability. • The expanded graphite was modified by ZnO in situ precipitation method. • The prepared ZnO/EG has the three-dimensional coupled network. • The melting phase change enthalpy of the composite PCMs could attain 203.35 kJ/kg. • The thermal conductivity of PCM with 6 wt% ZnO/EG increases by 137.5% than that of PA.