(591e) Effective Thermal Conductivity of Graphene Sheet COMPOSITES and Comparison to Carbon Nanotube COMPOSITES

By incorporating Carbon nanotubes (CNTs) into a polymer matrix, the effective thermal conductivity of the resulting composites can be increased. For example, it can increase by 27% over pure polymer for the case of epoxy composites [1], or by a factor of almost 4 for the case of high volume fraction single-walled carbon nanotubes in polystyrene [2]. Based, however, on the properties of pure CNTs, one would expect a much higher increase of the effective thermal conductivity of such composite materials, more than an order of magnitude. The presence of resistance to the transfer of heat at the CNT-polymer interface, known as the Kapitza resistance, is the reason for this difference [3]. A lot of research has been done in order to investigate the nature of the Kapitza resistance, but there are not many reports of successfully eliminating or minimizing this effect in CNT composites.

Recently, Balandin et al. [4] reported extremely high values for the thermal conductivity of single-layer graphene sheets (GS) that outperform carbon nanotubes in heat conduction. This result gives rise to the expectation that GS composites could be able to make the unfulfilled promise of CNT composites a reality. In this work, we investigate the effective conductivity of GS composites by means of off-lattice Monte-Carlo algorithms [5]. This method is more efficient than conventional random walk algorithms and faster than molecular dynamics algorithms. We will present the methodology and the validation of the method, which is used to study the effects of GS orientation, dispersion and volume fraction on the effective thermal conductivity of the GS composites. The discussion will include a comparison between theoretical predictions of the value of the thermal resistance at the GS-polymer interface relative to the CNT-polymer interface based on the acoustic mismatch theory and the diffuse mismatch theory, and a comparison between CNT composites and GS composites with similar volume fraction and similar dispersion pattern of the nano-inclusions in the composite matrix.

References

[1] Bryning M. B.; Milkie D. E.; Kikkawa J. M. and Yodh A. G., Appl. Phys. Lett. 2005, 87, 161909.

[2] Peters J. E.; Papavassiliou D.V. and Grady, B. P., Macromolecules, 2008, 41, 7274-7277.

[3] Swartz E. T.; Pohl R. O., Rev. Mod. Phys. 1989, 61, 605.

[4] Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I. ; Teweldebrhan, D.; Miao F.; Lau, C. N., Nano Lett. 2008, 7, 902.

[5] Duong H. M.; Papavassiliou D.V.; Mullen K.J.; Maruyama S. Nanotechnology, 2008, 19(6), 065702.