▎ 摘　　要

NOVELTY - Production of few-layer graphene powders involves (a) mixing graphite with sodium nitrate, (b) adding and reacting sulfuric acid and potassium permanganate in the mixture, (c) adding deionized water to the mixture, (d) preparing the oxidized graphite by adding hydrogen peroxide and deionized water, (e) preparing the pure oxidized graphite solution (S2), (g) adding hydrazine hydrate to the graphene solution, (h) adding aqueous ammonia, (i) producing a graphene colloidal solution, (j) mixing the graphene colloidal solution with coagulating floating agent. USE - Production of few-layer graphene powders used in transparent conductive film, transistors, transistor circuit interconnected memory semiconductor, conductive inks, solar cells, lithium batteries, super conductor, sensors and biomedicine. ADVANTAGE - The method economically produces graphene powder in mass-scale with reduced low-concentrated solution of oxidized graphene and waste material with reduced amount of ions, and prevents graphene from coacervation by formation of graphene colloidal solution using hydrazine hydrate and rapid washing of graphene, and is simple and environmentally-friendly. DETAILED DESCRIPTION - Production of few-layer graphene powders involves (a) mixing natural graphite with sodium nitrate under an ice-cooling conditions to form a mixture, (b) adding and reacting high-concentrated sulfuric acid and potassium permanganate in the mixture, (c) adding deionized water in the mixture after reacting, (d) preparing the oxidized graphite solution having a bright yellow color by adding hydrogen peroxide and deionized water in the mixture after reacting, (e) preparing the pure oxidized graphite solution (S2) having a pH of 5-6 by alternately carrying out centrifugal washing, acid-washing and water-washing of the graphite solution, (f) ultrasonically processing the graphite solution (S2) to form an oxide of graphene solution, (g) adding hydrazine hydrate to the graphene solution while stirring, (h) adding aqueous ammonia until the pH is 9-10, (i) producing a graphene colloidal solution by incubating the oxide of graphene solution, (j) mixing the graphene colloidal solution with an electrolytic solution as coagulating floating agent, (k) washing graphene colloidal solution with water and (l) producing graphene powder (G1) by freeze-drying the mixed solution. The electrolytic solution is water-based solution of sulfuric acid, hydrochloric acid, sodium hydroxide, potassium hydroxide, sodium nitrate, sodium sulfate, sodium chloride and sodium carbonate or ammonium carbonate.