Abstract: The invention relates to a method of manufacturing permeable mineral membranes.The method of the invention is characterized in that a thin layer of gel of peptised hydroxide of at least aluminum is deposited on a permeable perous substrate and the resulting membrane is dried and fired at a temperature between 500.degree. and 1100.degree. C.The resulting membranes can be used for isotopic separation of gases or for filtration and ultrafiltration.

Abstract: An apparatus and process are disclosed for separation of isotopes by gaseous diffusion. The apparatus comprises at least one assembly of microporous capillary tubes having a hydraulic diameter below 0.5 cm, an average pore radius below 200 .ANG., a thickness between 20 and 500 microns, a length of at least 25 cm, a porosity between 10 and 60% and a permeability to air between 10.10.sup.-7 and 100.10.sup.-7 mole/cm/.sup.2 /min/cm of mercury. The tubes are made from an inorganic material and have a circular, square or rectangualr cross-section.

Abstract: The invention relates to a support for a ceramic porous barrier of the kind used for obtaining a concentration of uranium 235 in uranium hexafluoride by ultrafiltration. The support is formed by superposing a number of layers in the form of pastes, the particle size being homogeneous and constant in each layer and decreasing from the outer towards the inner layers. The pastes are prepared from powdered materials such as metals, oxides, silicates, borides, nitrides and halides to which mineral binders are added. The pastes are simultaneously extruded or co-extruded after which the resulting support is baked.

Abstract: A gas which is the most readily condensable of the gases of a mixture is separated by passing the mixture in contact with at least one microporous barrier having a permeability of 100.times.10.sup.-7 to 1000.times.10.sup.-7 moles of air/cm.sup.2 /min./cmHg, a pore thickness of 10 to 100 A, by adjusting the partial pressure of the most readily condensable gas and/or the temperature of the gas mixture as a function of the mean pore radius of the barrier in order to ensure capillary condensation of the condensable gas at the pore inlets of the barrier and to induce a flow of condensed gas along the pores and across the barrier, the gas which has thus condensed being then collected.

Abstract: A method of processing porous metal filters used for separating isotopes of uranium hexafluoride, so as to improve the mechanical strength and resistance to corrosion of the fiters.The filters are placed in the presence of an aluminum-based cement in a closed heat-resistant and oxidation-resistant vessel, the interior of the vessel is disposed in a inert gas atmosphere and the vessel is heated to between 800.degree. and 1,000.degree. C in a furnace for about 1 hour.The filters are used for separating uranium isotopes.