Preparation of sulfur-free expanded graphite with 320 μm mesh of flake graphite

The sulfur-free expanded graphite was a kind of graphite intercalation compound, which was prepared by the method of chemical oxidation. Glacial acetic acid and perchloric acid were used as inserting reagent, and a mixture of perchloric acid and potassium dichromate was used as an oxidizing agent. The optimum weight ratio was as follows: m, (flake graphite):m(2) (perchloric acid):m(3) (glacial acetic acid):m(4) (potassium dichromate) = 1:1.4:0.8:0.4;the reaction time was 60 min and the temperature was 45 degrees C. X-ray diffraction patterns showed the intercalation product was a stage 2 compound. High-pressure liquid chromatography proved that the molecules of acetic acid and perchloric acid had entered into the graphite layers. The largest expanded volume was 400 ml/g at 1000 degrees C. (c) 2006 Elsevier B.V. All rights reserved.