Publication

Abstract :

In an attempt to study the expansion characteristics of natural graphite in presence of two different oxidizing agents in concentrated acid medium, potassium permanganate and potassium dichromate have been chosen. Under identical reaction conditions, for the same concentrations of oxidizing agents, the expansion of natural graphite in presence of potassium permanganate - con. sulphuric acid mixture has been found to be higher when the heat treatment temperature is varied from 400°C to 1030°C. The expanded volume of natural graphite is observed to be four times greater in presence of potassium permanganate/con.sulfuric acid mixture when compared to potassium dichromate in presence of con. sulfuric acid. Also, at 400°C, potassium permanganate in con. sulfuric acid treated natural graphite resulted in appreciable expansion which has not been observed in the case of potassium dichromate added graphite in presence of con. sulfuric acid. The XRD analysis clearly proved that the crystallite size of natural graphite after intercalation of sulfuric acid decreases and upon further heat treatment, the decrease in crystallite size is appreciable. The full width at half maximum (FWHM) of the most prominent (002) peak of graphite increases with heat treatment temperature even at 500°C. The optical microscope images very clearly prove the formation of more fluffy structure after intercalation of acid followed by heat treatment at 700°C. The formation of graphite nanosheets has been proved through FESEM images when the synthesized expanded graphite is sonicated in acetone for few minutes. The present study clearly reveals the possibility of optimizing reagents concentrations and reaction time so that maximum expansion can be obtained. © 2017 Elsevier Ltd.