Tang, Wei-Renn

The heat generated by the components of high-tech products is a problem of increasing importance. Therefore, improving the thermal conductivity of the heat dissipation material becomes very important. The planar thermal conductivity of graphene, a typical C-base materials is 5000 W/mK or more. However, this high thermal conductivity is limited to the two-dimensional plane of graphene. Thus, graphene is not suitable for application isotropic in thermal interface materials which require isotropic thermal conductivity. Therefore, the two-dimensional plane of graphene is converted into a three-dimensional crumpled structure to improve the thermal conductivity.
In this study, three-dimensional wrinkled spheres were synthesized from graphene by a cold method. X-ray diffraction analysis shows no 2D stacking signal for the sample of crumpled graphene. Then, the microstructure of the sample was confirmed to be crumpled spheres by scanning electron microscope. It was further confirmed that the addition of only 1.5 wt% crumpled spherical graphene improves the thermal conductivity of pure epoxy resin by a factor of 1.40. It was observed that the high surface area features of crumpled graphene composite would form clay-like features if just stirred by hand. After mixing by planet stirrer for 8 hours it can be uniformly mixed then improves the thermal conductivity of composite by 0.16 times. Such an enhancement was also observe in thermal grease, crumpled graphene can reduce the heat source temperature from 124.6\uc2\ub0C to 96.4\uc2\ub0C. At the same time, mixing crumpled graphene and one-dimensional carbon nanotubes can effectively increase the vertical thermal conductivity to 1.74 times. Research can contribute to the development of heat-dissipating fillers material in the future. It has been found that in this study that the thermal conductivity properties are not directly related to the dispersion of crumpled graphene, and that there may be other mechanisms that needs to be understood torationalize the enhancement in the thermal conductivity 

Effect of Crumpled Graphene on the Thermal Conductivity of Composite Paste

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