Vertically Aligned High-Quality Graphene Foams for Anisotropically Conductive Polymer Composites with Ultrahigh Through-Plane Thermal Conductivities

Abstract

Although graphene-based thermal interface materials (TIMs) have great potentials in removing excess heat generated during highly efficient running of electronic devices, their practical applications are usually limited by their unsatisfactory thermal conductions, which are mainly caused by unsatisfactory dispersion and distribution, low loading, and low quality of graphene sheets, as well as the thermal interfacial resistance between graphene sheets and polymer matrix. Herein, we develop vertically aligned graphene hybrid foams (GHFs) with high densities by hydrothermal reduction of graphene oxide in the presence of high-quality graphene nanoplatelets (GNPs) followed by air-drying. The reduced graphene oxide sheets play an important role in constructing a vertically aligned interconnection network for accommodating GNPs during the hydrothermal reduction process, while the incorporated GNPs not only make the thermal conductance network denser but also prevent excessive shrinkage of the foams during air-drying. More critically, graphitization of GHF at 2800 °C removes the residual oxygen-containing groups and heals the defects of their reduced graphene oxide component, leading to high-quality graphene foams. The resultant vertically aligned high-quality graphene porous architecture with high density as an ideal thermal conductance network of TIMs is highly efficient in improving the thermal conductivity of its epoxy composite, which exhibits an ultrahigh through-plane thermal conductivity of 35.5 W m K at a graphene loading of 19.0 vol %. The excellent thermally conductive performance makes the annealed GHF/epoxy composites suitable for the thermal management.

Allotrope carbon materials in thermal interface materials and fuel cell applications: A review

“…However, the cost is high due to the complicated structure that requires few processes. Meanwhile, the graphene framework and dispersed polymer have gained much attention due to their moderate cost and good adaptability . Although the cost of fabricating graphene framework is high, its thermal conductivity is much higher than that of dispersed polymer .…”

“…Meanwhile, the graphene framework and dispersed polymer have gained much attention due to their moderate cost and good adaptability. [116][117][118][119][120][121] Although the cost of fabricating graphene framework is high, its thermal conductivity is much higher than that of dispersed polymer. 122 Table 2 presents current works on graphene-based TIMs.…”

3D Thermally Cross‐Linked Graphene Aerogel–Enhanced Silicone Rubber Elastomer as Thermal Interface Material

“…Previous studies have also studied the effects of high temperatures. Such as An et al, they applied this treatment method to prepare vertically aligned graphene hybrid foams/epoxy composites with an out‐of‐plane TC up to 35.5 W m −1 K −1 . The effects of graphitization on the TC of composites were all discussed in these two papers, but it was only attributed to the removal of oxygen‐containing functional groups and the repair of defects on the graphene sheet.…”

“…After high temperature treatment at 2800 °C, the carbon content of gGA increases to 99.89 wt% while the oxygen content declines to 0.01 wt%. In addition, C/O atomic ratio of gGA reaches 13 318.17, which means the oxygen‐containing group is negligible and the graphitization degree has been greatly improved …”

Free-standing graphene films embedded in epoxy resin with enhanced thermal properties

“…At a low graphene loading of 5.5 wt%, graphene/epoxy inand through-plane thermal conductivities of 10.0 and 5.4 W/ mK, respectively, were reported. The An F. group [19] described a thermal conductivity of 35.5 W/mK throughthickness while in-plane is 17.2 W/mK at 19 vol% for epoxy containing a densely packed and vertically aligned graphene film. Solutions based on vertically aligned graphene are reporting high through-thickness thermal conductivity of epoxy composites; Zhang et al present values up to 384.9 W/ mK in through-thickness and 0.18 W/mK in-plane at 44 vol% graphene [20].…”