▎ 摘　　要

NOVELTY - The preparation of microcrystalline graphene involves (1) mixing sodium nitrate, potassium permanganate and concentrated sulfuric acid to obtain oxidized microcrystalline graphite, (2) calcining oxidized microcrystalline graphite in presence of hydrogen, where weight ratio of sodium nitrate and potassium permanganate is 1:0.5-1:20, amount of concentrated sulfuric acid is 2-40 times of the sum of amount of sodium nitrate and potassium permanganate, and the amount of microcrystalline graphite is 0.01-5 wt.% by amount of the mixture. USE - Preparation method of microcrystalline graphene for lubricant composition of mechanical device such as vehicle drive system and internal combustion engine (all claimed). ADVANTAGE - The method enables preparation of microcrystalline graphene with excellent dispersibility, compatibility in lubricating oil, and improved lubrication performance. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) lubricant composition which comprises lubricant and 0.001-10 wt.% microcrystalline graphene; and (2) lubricating method of mechanical device, which involves feeding lubricant composition.