Fig. 3

Thermal conductivities of various as-prepared composite TIMs with increasing mass fractions of the graphene fillers. The thermal conductivities of the resulting TIMs samples are shown in the figure, and the obtained thermal properties are closely related to the adopted RGO sample. Compared with those samples of adopting the RGO(OH) and RGO(O), the RGO(OOH)-assisted composite displays the better performances. The thermal conductivity (5.5 Wm⁻¹ K⁻¹) of the latter is about ~ 12% higher than that of the former (the mass fraction of the filler is 20 wt%), proving that the types of surface functional groups of the RGO exert a significant influence on the resulting thermal performance of the composite TIMs. Thermal conductivity of the as-prepared RGO(OOH)-3DGNs-ER is compared with that of the previous reported graphene-assisted ER (inset of the figure), implying adopting the RGO(OOH) is significant to achieve the high performance [6, 7, 10, 14, 20,21,22,23]. The thermal conductivity further increases after adding the 3DGNs (6.1 Wm⁻¹ K⁻¹), indicating adding the 3DGNs and a selective retention of functional groups of the RGO are both the determinants for the resulting thermal conductivities