Multifunctional graphene nanoplatelets/cellulose nanocrystals composite paper

We demonstrate a water-based method to fabricate strong, electrically and thermally conductive hybrid thin films (papers) made from the combination of graphene nanoplatelets (GnP) and cellulose nanocrystals (CNC). Unpressed and hot-pressed GnP papers containing CNC ranging from 0 wt% to 25 wt% were prepared. It is found that the GnP is well aligned within the hybrid paper, and a higher degree of alignment is induced by the hot-pressing process. The mechanical properties of the resulting papers increased with increasing content of CNC. The hot-pressed 25 wt% CNC hybrid paper showed the best mechanical properties among all the papers studied and improved the tensile strength by 33% and the modulus by 57% compared to neat GnP paper. Both the highest in-plane and though-plane thermal conductivity of 41 W/m K and 1.2 W/m K were measured respectively for the hot-pressed 15 wt% CNC hybrid paper. The electrical conductivity decreased continuously with increasing content of CNC but the thin film was still conductive at the highest CNC content in this study. The low-cost, environmental-friendly, thermally and electrically conductive flexible GnP/CNC hybrid papers have a set of properties making them suitable for many potential applications.