Synthesis and Characterization of Exfoliated Graphite (EG) and to Use it as a Reinforcement in Zn-based Metal Matrix Composites

Abstract

Here H2SO4 was used as an intercalant and H2O2 as an oxidant. Expandable graphite was prepared at room temperature by mixing 16 ml of sulfuric acid (98%) and 1.5 ml hydrogen peroxide(30%) with 6 gm of natural flake graphite (60 mesh) having 98% purity. The mixture was placed for 1 h 30 min in a magnetic stirrer. The mixture which was prepared after stirring was washed with water to achieve pH in the range of 5-7. The prepared mixture was then dried at 60oC for 30 h before further heat treatment. Heat treatment was performed by inserting a silica crucible containing the prepared mixture inside a muffle furnace. Finally the resulting graphite preparation procedure of expanded graphite compound was subjected to thermal shock at 1000oC for about 30 sec in a muffle furnace in air, resulting in the formation of expanded graphite.  At such a high temperature the intercalates trapped between the graphite layers decompose and force the layers to separate. The expansion process cause an enormous increase in volume (240 cc/g) and also causes an expansion in the thickness in the c direction of about 80–100 times. 100 ml acetone was then mixed with 1 gm of the expanded graphite and sonicated in an ultrasonicator followed by simultaneous heating at 80oC and magnetic stirring. The expanded graphite was treated in an ultrasonicator in order to achieve better exfoliation of graphite having high aspect ratio. It has been found that the sonication exfoliation method aids the preparation for graphene sheets remarkably.