ИСТИНА

Nowadays, expanded graphite (EG), a light-weight carbon material is widely used in the sealing materials production. EG sorption, gas separating and several other properties make it an interesting object for various investigations. For examples, there were efforts to apply it as a sorbent, membrane material, electrode in electric capacitors, etc. The essential disadvantage of EG is its poor-developed porous structure in comparison with other carbon adsorbents, for example, activated carbon. Therefore activation of porous structure of the EG is rather actual problem. Herein we report a technique for developing of EG porous structure. Two types of expanded graphite were subjected to steam activation: the chemically prepared (EG-C) and electrochemically prepared (EG-E) ones. EG-C was obtained by graphite nitrate of II stage hydrolysis followed by exfoliation at 900 oC. EG-E was prepared by graphite anodic polarization in diluted nitric acid and exfoliation at 400 and 900 oC. Porous structure activation was carried out by steam passing trough the samples at a temperature of 600 and 800 oC for 1 to 8 hours. Activated EG morphology was studied by XRD, Raman spectroscopy and low-temperature nitrogen adsorption. Steam activation at a temperature of 800 oC results in partial combustion of samples whereas porous structure activation is not observed. The possibility to activate porous structure of expanded graphite at 600 oC was shown only for electrochemically prepared samples. Surface area of samples increase for 20 %: from 80 m2/g to 101 m2/g. According to SEM, numerous small caverns are observed on the samples surface. Activation process promotes the appearance of additional amount of imperfect carbon. Thus, the technique of expanded graphite activation was proposed and porous structure of activated samples was studied.