Permeation of hydrogen through MPG-8 graphite

Hydrogen gas driven permeation through fine-grain graphite MPG-8 has been investigated in the range of thickness from 0.55 to 4.38 mm and pressures from 10−2 to 1 Pa. The permeation rate is proportional to the gas pressure and inversely proportional to the thickness. It has been concluded that GDP through fine-grain graphite is due to gas flow through the internal porosity network in the molecular regime. The specific bulk conductivity of the graphite is measured to be of about (5–7.3) × 1015 molecules s−1 m−1 Pa−1. Surface treatment influences the permeation through membranes thinner than 1 mm. Surface polishing, washing in the ultrasonic bath, hydrogen and argon plasma irradiation, methane plasma treatment, argon ion irradiation, and annealing at 1000 K have 0–10% influence on the permeation rate.