Abstract: A method for improving the separation properties of semi-permeable membranes having penetrating defects due to the manufacturing process or subsequent handling and membranes accordingly improved. During a certain time one side of the membrane is exposed to a first chemical reaction partner and the other side of the membrane is exposed to a second chemical reaction partner so that in the penetrating membrane defects a chemical reaction will take place in a boundary region between the two reaction partners forming occlusions blocking said defects.

Abstract: A porous support material is selected having a relatively narrow pore size distribution. During a certain time one side of said support material is then exposed to a first chemical reaction partner. The other side of the support material is at the same time exposed to a second chemical reaction partner. In the penetrating pores or channels a chemical reaction takes place in a boundary region between the two reaction partners forming selectively occlusions blocking said pores and channels.

Abstract: In the electrolytic production of aluminum by electrowinning or electrorefining processes, cell components such as cathode current feeders which in use are normally covered with molten aluminum are made of a composite material of aluminum or an aluminum alloy or intermetallic compound with an aluminum oxycompound, usually alumina, and possibly containing minor amounts of additives such as borides carbides, nitrides or oxides. The composite material, which remains mechanically stable and electrically conductive at 1000.degree. C., may be prepared by hot pressing powders at 1000.degree.-1700.degree. C. possibly after surface treating the alumina to improve wettability by molten Al. The components are optionally coated, e.g. with TiB.sub.2. The composite materials are also useful as non-current carrying components, including separator walls, weirs, packing elements and baffles.

Abstract: A semi-conducting, stable polychelate coating is manufactured in situ on a conducting substrate providing metal coordination centers, by carrying out a controlled chelating reaction and thermal treatment on the substrate surface with a predetermined specific amount (X.sub.o) of tetranitrile compound per unit substrate area. The temperature and duration as well as this specific amount (X.sub.o) are selected from given ranges to form a uniform polychelate coatingbonded to the substrate surface.Titanium electrodes are provided with such polychelate coatings for different purposes. Electrodes with other metal substrates are further provided with such polychelate coatings.

Abstract: An electrode with an outer coating for effecting an electrolytic process is provided with a protective intermediate coating consisting of a conducting insoluble polymer network formed in situ on a titanium base and containing a small amount of finely dispersed platinum group metal catalyst.A method of manufacturing the electrode comprises applying to the titanium base several layers of a solution containing a polymer precursor and a platinum metal compound which are thermally converted to the protective polymer coating, on which the outer coating is formed, more particularly by electrodepositing manganese dioxide or lead dioxide.The polymeric intermediate coating serves to protect the titanium base from oxidation, and to more particularly provide stable electrode performance with economical use of precious metal.

Abstract: A catalytic electrode has an electrically conductive substrate such as titanium with a coating comprising a platinum-group metal catalyst finely dispersed in a matrix consisting of a semi-conducting polymer formed in situ on the substrate. The catalyst may be a platinum-group metal oxide such as iridium oxide formed in situ together with the semi-conducting polymer by the application of a uniform liquid mixture followed by a controlled heat treatment.The semi-conducting polymer is preferably formed from polyacrylonitrile, polybenzimidazo-pyrrolone or an adamantane based polybenzoxazole.