Fig. 4

a Relationship between the thermal performances and the RGO morphology with increased mass fraction of the filler b thermal conductivity stability of the resulting TIMs with various mass fractions of the RGO filler under 50 °C for a long time. According to Balandin’s equation, the resulting thermal conductivity is also influenced from the morphology parameters of the graphene filler. Fu’s group optimized the morphology of the adopted RGO (nanoplatelets), which brings about a high thermal performance (4.01 Wm⁻¹ K⁻¹) [7]. Furthermore, our group discussed the detailed influence from the average size and thickness of the adopted RGO [10]. An average size (> 100 nm) and thickness (~ 2 nm) are recommended, and the thermal conductivity of the resulting TIM enhances to 6.7 Wm⁻¹ K⁻¹ (which is 25% higher than the previously reported values) [7, 10]. According to the obtained data (a), the influence on the resulting thermal conductivities from the average size of the RGO is more remarkable than the influence from the thickness of the filler, implying the contact area between the graphene basal plane and ER is the determinant for the obtained performance. Lastly, the mass proportions between the 3DGNs and RGO are optimized (10 wt% for the 3DGNs and 20 wt% for the RGO; although the thermal conductivity of the resulting TIMs almost increases linearly with the increased mass fraction of the graphene filler, a higher mass fraction of the filler will lead to a poor adhesiveness of the resulting TIMs) to achieve the synergy between them. A high stability of the thermal performances under a high temperature is vital to the TIMs to insure the electron devices working in the normal status. The thermal conductivities of the as-prepared TIMs with various mass fractions of the RGO(OOH) under 50 °C are listed in b, and no remarkable degradation can be seen after 7 days, indicating the promising prospect for the practical application