▎ 摘　　要

NOVELTY - Natural graphite flake is added into a reactor, 50-98% sulfuric acid solution is added, and mixed. The resulted product is maintained at 10-60 degrees C, oxidizing agent is added, stirred, water is added, maintained at 95 degrees C or less, cooled to room temperature, and separated, to obtain graphite intercalation compound. The resulted product is dried in microwave oven, to obtain expanded graphite intermediate. The expanded graphite intermediate is added into sand mill or ball mill with solvent, ground, and dried, to obtain graphene powder material. USE - Preparation of graphene powder material (claimed) used as electroconductive material and thermally conductive material. ADVANTAGE - The method enables preparation of graphene powder material having high electroconductivity and thermal conductivity. DETAILED DESCRIPTION - Natural graphite flake is added into a reactor, 50-98% sulfuric acid solution is added, and mixed. The resulted product is maintained at 10-60 degrees C, oxidizing agent is added, stirred for 20-120 minutes, water is added, maintained at 95 degrees C or less, cooled to room temperature, and separated, to obtain graphite intercalation compound. The resulted product is dried in microwave oven, to obtain expanded graphite intermediate. The expanded graphite intermediate is added into sand mill or ball mill with solvent, and ground for 0.5-12 hours, to obtain graphene slurry. The obtained graphene slurry is dried, to obtain graphene powder material.