▎ 摘　　要

NOVELTY - An electrolytic solution containing potassium sulfate is added to reaction vessel and natural graphite powder is added to reaction vessel and tungsten wire as positive electrode and platinum wire as negative electrode are inserted into vessel. Voltage is applied between electrodes, graphite flakes are swollen, and graphite is oxidized and then reduced. Process is repeated continuously and graphite is rapidly dissociated into bilayered graphene flakes. Solution is vacuum-filtered, large graphite particles are removed, washed and centrifuged, to obtain high-quality graphene. USE - Preparation of high-quality graphene (claimed). ADVANTAGE - The method efficiently and economically provides high-quality graphene with honeycomb crystal lattice having membrane resistance of 1-70 K( Omega )/square and light transmittance of less than 80%. DETAILED DESCRIPTION - An electrolytic solution containing potassium sulfate is added to a reaction vessel made of glass, plastic or ceramic. Natural graphite powder is added to the reaction vessel and tungsten wire as positive electrode and platinum wire as negative electrode are inserted into the vessel. Voltage of 8-12 V is applied between electrode, graphite flakes are swollen, graphite is oxidized and then reduced. The process is repeated continuously and graphite is rapidly dissociated into bilayered graphene flakes having thickness of 1-3 nm floating on the surface of the electrolyte. The solution is vacuum-filtered using a filter membrane and large graphite particles are removed, washed with water, and residual acid is removed. The obtained powder is dispersed in dimethylformamide solution, ultrasonically processed in water bath and centrifuged, to obtain graphene having size of 1.5 nm.