Charging analysis and characterizations of COOH group functionalized graphene combined with paraffin wax as phase change material for thermal energy storage applications

In this work to increase the thermal capacity and performance of pristine paraffin wax (phase change material), it is mixed with COOH group functionalized graphene. The various concentrations of graphene mixed with paraffin wax are 0.25 volume percent to 1 volume percent at an increment of 0.25 volume% at three different volumetric flow rates of 6.25 mL s⁻¹, 12.5 mL s⁻¹, and 25 mL s⁻¹. The charging performance is analyzed, and Fourier transform infrared spectroscopy (FTIR), X ray diffraction (XRD), differential scanning calorimetric (DSC) analysis, Thermo gravimetric analysis (TGA), field effective scanning electron microscopy, with energy dispersive spectroscopy are done for characterizing chemical structure, crystal structure, enthalpy, thermal stability, and microstructure, along with elemental composition, respectively. The results indicated that with increasing percentages of COOH group functionalized graphene the charging time decreases by 6.25–25% for the HTF flow rate 6.25 mL s⁻¹, 6.67–26.67% for HTF flow rate 12.5 mL s⁻¹, and 15.38–38% for HTF flow rate 25 mL s⁻¹ over pure paraffin wax owing to increasing percentage and thermal conductivity of COOH group functionalized graphene in paraffin wax. This advanced material with the help of XRD and FTIR also showed that the functionalized COOH graphene was chemically inert and did not lead to any new product being formed. Through TGA the advanced functional materials manifested that they were thermally very stable and by DSC it showed that it was having very high enthalpy of melting.