▎ 摘　　要

NOVELTY - A graphene composite film comprises reduced graphene oxide film and graphene film set on side surface of reduced graphene oxide film. USE - The graphene composite film is used for acoustic diaphragm or battery or water purifying diaphragm or nanoelectromechanical system (all claimed). ADVANTAGE - The film is easy to prepare, flat and non-wrinkle, and has low cost, high quality and high mechanical property and electrical performance. The method is simple and easy to operate. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a method for preparing graphene composite film comprising placing graphene film on side surface of reduced graphene oxide film, and heating to combine reduced graphene oxide film and graphene film. The graphene film is prepared by depositing graphene layer on surface of preset substrate by vapor deposition for 3.5-4.5 hours. The gas used in vapor deposition comprises mixed gas comprising methane and inert gas and hydrogen. The mixed gas has methane content of 180-220 ppm, flowrate of 1.8-2.2 sccm and hydrogen flow rate of 18-22 sccm. The method further involves before depositing graphene layer, annealing preset substrate to 900-1100 degrees C under inert gas flow of 450-550 sccm and hydrogen flowrate of 80-120 sccm. The reduced graphene oxide is prepared by spin coating dispersion liquid of graphene oxide at speed of 500-3000 revolutions/minute (rpm), and reducing by reducing agent. The concentration of graphene oxide in dispersion is 1-10 wt.%. The reducing agent comprises hydroiodic acid, hydrazine hydrate or sodium citrate.