Size Effect of Expanded Graphite

Expanded graphite (EG) was prepared by using natural flaky graphite as raw material which was from different producing area and with different particle sizes,and by using sulfuric acid,nitric acid, potassium permanganate mixture of certain compounding ratio as oxidant.The results show that the expansion ratio of EG decreases from 750mL/g when the particle size is larger than 420#m to ll0mL/g when the particle size is 95-85#m.Observing and determining the pore structures in EG by using SEM and mercury porosimetry,it is found that the size of macrostructures and sub-microstructures decreases along with the decrease in particle sizes.The size effect mainly results from the difference in the crystallization degree of graphite,and it is reflected in the ash content,sulfur content,adsorptivity of EG,tensile strength of compressed EG sheet.