The measure of expanded volume (EV) A certain amount of sulfur-free expandable graphite was weighed, and the EV was measured using a 150 mL graduated cylinder after expansion. The EV of the EG was calculated by the following equation: EV = V/M (mL/g). The higher expansion volume indicate that the more expanded graphite is obtained. Under the same conditions, three groups of parallel experiments were carried out. The average value and standard deviation of the data are calculated. The optimal preparation conditions were obtained by data analysis. (The influence of NaClO4 dosage; The influence of C2H2O4 dosage ; The influence of current density; The influence of reaction time)