Efficient Preconstruction of Three-Dimensional Graphene Networks for Thermally Conductive Polymer Composites

Abstract

Electronic devices generate heat during operation and require efficient thermal management to extend the lifetime and prevent performance degradation. Featured by its exceptional thermal conductivity, graphene is an ideal functional filler for fabricating thermally conductive polymer composites to provide efficient thermal management. Extensive studies have been focusing on constructing graphene networks in polymer composites to achieve high thermal conductivities. Compared with conventional composite fabrications by directly mixing graphene with polymers, preconstruction of three-dimensional graphene networks followed by backfilling polymers represents a promising way to produce composites with higher performances, enabling high manufacturing flexibility and controllability. In this review, we first summarize the factors that affect thermal conductivity of graphene composites and strategies for fabricating highly thermally conductive graphene/polymer composites. Subsequently, we give the reasoning behind using preconstructed three-dimensional graphene networks for fabricating thermally conductive polymer composites and highlight their potential applications. Finally, our insight into the existing bottlenecks and opportunities is provided for developing preconstructed porous architectures of graphene and their thermally conductive composites.

Keywords: Anisotropic aerogels; Graphene networks; Phase change composites; Thermal conductivity; Thermal interface materials.

Fig. 1

Factors affecting thermal conductivity of polymer composites functionalized by graphene 3D networks [–29]

Fig. 2

Schematic illustrations of phonon scattering in crystalline materials caused by defects [37]

Fig. 3

Schematic illustrations showing the heat transfer in epoxy composites containing fillers with different sizes [37]

Fig. 4

a Schematic illustrating the thermal conduction mechanism at the interface between the crystal filler and the polymer [37]. b, c Enhancement of thermal conductivity of graphene/polymer composites by graphene surface modification [23, 54]

Fig. 5

a Schematic illustration of GNs/GF/NR composites with compact network [75]. b Comparison of freeze-drying and air-drying [79]

Fig. 6

Schematic illustrating the graphene dispersion in polymer composites fabricated by different compounding methods

Fig. 7

a Schematic of formation of networks during hydrothermal reduction in microscale, optical photographs of GO suspension and GHs formed by hydrothermal reduction and the scanning electron microscope (SEM) image of the graphene network [123]. b Optical photographs of GO suspension and GHs formed by chemical reduction and the SEM image of the graphene network [124]. c–e Schematics of the microscopic mechanism of the formation of graphene 3D networks induced by adding multivalent metal ions and water-soluble polymers and optical photographs of the graphene foams formed after post-treatment [–127]

Fig. 8

Schematic of synthesis of GF and the GF/PDMS composite by isotropic template-assisted assembly method [147]

Fig. 9

a Schematics of the phase transition of GO liquid crystal with the increase in concentration [171]. b Microscopic schematics of the formation of the anisotropic graphene 3D network by the orientation of GO liquid crystal [175]. c Polarized-light optical microscope and SEM images of the anisotropic graphene 3D network formed by the orientation of GO liquid crystal [175]

Fig. 10

a Schematic of the microscopic principle of directional freezing [189]. b Schematic of directional freezing of GO suspension and GA structure [192]. c Top-view SEM images of vertically aligned graphene networks fabricated with freeze-casting at different freezing rate and subsequent freeze-drying [40]

Fig. 11

Schemes of bidirectional freezing techniques and resulting scaffolds [198, 199]

Fig. 12

Scheme of the fabrication process of radiating GA [200]

Fig. 13

Effect of freezing rate on GA layer spacing [207]

Fig. 14

Schematic illustrations of anisotropic graphene 3D networks prepared by template method and their polymer composites [212, 213]

Fig. 15

The application of a compaction [116] and b rolling [115] processing in the fabrication of anisotropic graphene networks and their composites

Fig. 16

a Schematic illustrating the fabrication of conductive epoxy composite with vertically aligned RGO/GNP hybrid foam. b Through-plane conductivity (red column) and in-plane conductivity (blue column) of the epoxy composite containing the vertically aligned RGO/GNP hybrid foam annealed at different temperatures (inset: Raman I_D/I_G mapping) [41]

Fig. 17

a, b Schematic illustrations of synergies of GNPs and CNTs on thermal conduction [62, 251]. c Schematic illustrations of synergies of GNPs (blue slices) and BN (red spheres) [65]. d Schematic illustrating the preparation of graphene/MF foam and the derived graphene/carbon foam [149]

Fig. 18

Situations where efficient thermal management of excessive heat is needed and thermally conductive polymer composites containing 3D graphene networks for various applications: TIMs [6, 45], PCMs [287, 288], energy conversion materials [283, 289] and thermal switches [269]