β Scribed by A.I. Livshitz
No coin nor oath required. For personal study only.
Solid membrane permeable for a substantial part of the incident gas flow in one direction and impermeable in the inverse direction might be used as an ideal vacuum pump. In the case where gas is absorbed without dissociation and the gas temperature is equal to that of the membrane, only an infinitesimal part of the incident gas flow can penetrate through the membrane. If, however, the gas is "hotter" than the membrane (on account of excitation, dissociation, heating, etc.) the membrane permeability may become comparable to that of the opening in a thin wall (superpermeability). The condition indispensable for this to take place is the inlet boundary special state hindering the thermal desorption of the absorbed gas. After special boundary processing the membrane becomes superpermeable for non-equilibrium gas while ordinary permeability, small as it is, becomes practically negligible. So when non-equilibrium is maintained only at one side of the membrane, gas would flow only in one direction as is required for pumping, compression and recuperation. In the case where the absorption is accompanied by dissociation (as in the H2-Me systems) superpermeability in principle may be achieved with equal temperatures of gas and the membrane. However, in the temperature and pressure ranges of practical interest this can be achieved only in the H2-Pd system and with a clean membrane surface. Under the non-equilibrium condition superpermeability is possible for various gas-solid combinations over a wide range of the gas pressures, membrane temperatures (low temperatures included) and boundary conditions.
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