Study Of Flexible And Electrically, Thermally Conductive Graphene Paper And Cu@Graphitic-carbon Nanocables

The main challenges of increasing the power density and shrinking the size of electronic devices are the electrical conductivity and heat-diffusing of microelectronics. As a two-dimensional material, graphene has broad application prospects as lateral heat spreaders and conductor due to its unique electrical, thermal and mechanical property exceeding the limit of bulk graphite.In this study, fewer layers even monolayer graphene oxide and graphene were produced through a chemistry method. Ultra-flexible graphene oxide papers were produced via a vacuum filtration method, in which graphene oxide sheets assembled into a paper-like material under a directional flow. Thermally reduced graphene papers were prepared by annealing the filtrated GO films. Conductivity measurements revealed that the obtained graphene papers are flexible and possess ultra-high electrical conductivity but low thermal conductivity. In-plane sheet resistance of graphene paper could be as low as 1.008 ?/?, the resistance could be as low as 3.699 m?·cm, and the electric conductivity could be up to 27034 S/m. The electrical conductivity is 38 % higher than that of others graphene paper, 3.87 times higher than that of graphene-carbon fiber paper. In addition, with increasing of the paper thickness, sheet resistance reduced, electric resistivity increased and electric conductivity decreased. This predicts a broad application as conductive thin films.Copper nanowires have been thoroughly investigated due to their unique applications as interconnects in nanoelectronics or flexible transparent conductors. However, when the diameter of Cu nanowires shrinks to nanoscale, inelastic electronic scattering and oxidization become very serious,increasing the electrical resistivity of copper nanowires and restricting their scopes of application. So, it is important to curb the rising resistivity of Cu nanowires.Nanocables of metallic copper nanowire cores coated with amorphous carbon(Cu@C NCs) were mass produced by the hydrothermal method and nanocables of metallic copper nanowire cores coated with graphitic carbon(Cu@G NCs) were also produced after carbonization. TEM and other results demonstrated that the copper nanowires were well crystallized along the [110] direction and uniformly encapsulated by 15 nm thick graphitic carbon. Electrical measurements revealed that Cu@C NCs are insulating while Cu@G NCs are conductive. Furthermore, the electrical resistivity of a single Cu@G NC is 1.61×10-5 ?·cm at room temperature lower than that of copper nanowires, and no significant different after several months at room temperature, meaning that the graphitic carbon sheaths improved the stability of the Cu nanowires and dramatically reduced their electrical resistivity. We predict that the electrical conductivity and air stability of many other metal nanowires will be enhanced by graphitic carbon encapsulation. This will have broad applications in nanoelectronics.