Enhancing buckypaper conductivity through co-deposition with copper nanowires

Buckypapers, the thin sheets made from an aggregate of carbon nanotubes (CNTs), have demonstrated promising electrical and thermal conductivities. However, the high in-plane to perpendicular anisotropy makes its application as thermal interface materials difficult. In order to increase the perpendicular electrical and thermal conductivities, copper nanowires (Cu NWs) were introduced into buckypapers. The Cu NWs stuck into the empty spaces between CNTs, connected them perpendicularly, and even induced a certain perpendicular CNT alignment. The electrical conductivity increased continuously with increasing the Cu content, while the smallest anisotropy was observed at the 50 wt.% Cu filling because an in-plane Cu network formed and improved much more the in-plane conductivity above this filling. On the contrary, as CNTs are more thermally conducting than Cu, the loading of Cu NWs over 50 wt.% decreased the thermal conductivity. Our measurement showed a high perpendicular conductivity of 10.1 W/m K at the 50 wt.% loading, more than quadruple and double as compared with the ones for a pure buckypaper and the one filled with 67-75 wt.% Cu NWs.