ИСТИНА

Graphite foil (GF), a material obtained by binderless compaction of expanded graphite (EG), is widely used as sealing material in various industries such as metallurgy, oil refining, etc. Gas permeability of GF is a key characteristic to estimate the degree of sealing and effectiveness of GF as a sealing material. The aim of this research is to investigate the influence of two factors, the stage number of initial GIC and the exfoliation temperature, on the structure of obtained GF and its gas permeation properties. GF samples were prepared as follows. Graphite bisulfate of I, II, III, IV stages was washed by water and dried, and then exfoliated at the temperatures of 600, 800 and 1000oC. The obtained EG was pressed in the form of the disc with a height of 0.6 mm, a diameter of 74 mm and a density of 1 g/cm3. The samples were studied by means of XRD, SEM, Raman spectroscopy. Nitrogen and hydrogen permeances of GF samples were measured by a differential method. The change of both the exfoliation temperature and the stage number influences on the change of EG particle volume and distance between graphite layer packs and on both the outer form and inner structure of EG particle. The nitrogen and hydrogen permeances of GF decrease with the increase of the exfoliation temperature and reach the minimum for the samples obtained at 800 °C, and then increase again. The dependence of GF gas permeance on stage number for each exfoliation temperatures was studied.