Characterization of Exfoliated Graphite Prepared with the Method of Secondary Intervening

Exfoliated graphite was prepared with the method of secondary intervening. The results showed that the optimum conditions for the procedure were as follows: mass ratio of nature flake graphite: sulfuric acid: nitric acid: potassium permanganate =1:9:3:0.44 and immersing time in formic acid was 150 minutes. Exfoliated graphite with 300 mL/g exfoliation volume at 900 C was obtained. The prepared sample in the best process condition was characterized by means of scanning electron microscopy (SEM), thermogravimetry and differential thermal analysis (TGA-DTA), infrared ray spectrum (IR) and X-ray diffraction (XRD). After secondary intervening, the layer distance of expandable graphite was enlarged and the boundary layers were broken. Exfoliated graphite was worm-like and graphite layers were held together at their edges, and the expanded domain had a multilayer structure with many diamond-shaped pores. Sulfuric acid, nitric acid and formic acid were intercalated into graphite, and the decomposition of exfoliated graphite at 900 C was mostly derived from graphite intercalation. Crystalline of graphite was damaged because of oxidation intercalation, but the C-C bond was not undermined. Furthermore, oxidation intercalation process and mechanism were discussed.