Graphite was intercalated with 100% HNO3 by chem. method and by sweep voltametry (electrochem. method). The intercalated graphite was heated to produce an exfoliated graphite. Whole process was repeated to prep. re-intercalated compd. and re-exfoliated graphite. Thermal treatment of the graphites resulted in an increase in their vol. accompanied by the deformation and sepn. of graphene layers within the graphitic matrix. Some changes within the chem. compn. of the prepd. graphitic materials were also obsd.