Preparation of low density monolithic expanded graphite from flexible graphite

Low density monolithic expanded graphites were prepared from flexible graphite sheet or plate by soaking the sheet or plate in concentrated sulfuric acid or nitric acid for intercalation and then expanding them at temperatures from 200 ℃ to 750 ℃.The effects of the type of intercalating agent,intercalating time and temperature for expansion on bulk density and integrity of the monoliths were investigated.Results show that the higher the expansion temperature,the lower the bulk density,and the more difficult to obtain a monolithic expanded graphite with structural integrity.Monolithic expanded graphites with structural integrity can be obtained using concentrated sulfuric acid or nitric acid as intercalating agent for over 3 h at an expansion temperatures of less than 550 ℃ for the former or less than 650 ℃ for the latter.Both uniform and non-uniform expansions were found in the monolithic products.