Gas permeability of graphite foil prepared from exfoliated graphite with different microstructures

Graphite foil (GF) is widely used as a sealing material in different industries. Different methods of GF preparation result in differences of its crystalline and pore structure, which in turn influences its ability to pass through gases and provide the required level of sealability. The influence of the preparation temperature of exfoliated graphite (EG) on the microstructure and gas permeability of EG-based graphite foil was investigated. The preparation of graphite foil consisted of the synthesis of stage-1 graphite bisulfate, followed by washing with water, rapid heating of obtained expandable graphite at temperatures of 600, 800, 1000 °C with the formation of exfoliated graphite and the subsequent compression of EG into graphite foil. The structure of the materials was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The correlation between EG preparation conditions, the presence of amorphous and turbostratic carbon, which influence the GF porous structure and GF gas permeance, was found. Graphite foil based on EG obtained at 600 °C had the minimal nitrogen and hydrogen permeances of 0.11·10 –10 and 0.44·10 –10 mol m −2 s −1 Pa −1 , while the increase in EG preparation temperature up to 1000 °C raises GF gas permeance. Graphical abstract