Elektrodensystem unsymmetrischer Leitfähigkeit.

摘要

471,390. Asymmetrically conducting resistances. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN. June 6, 1936, Nos. 15916 and 15917. Convention dates, June 7, 1935 and Dec. 19, 1935. [Class 37] A dry contact rectifier, in which a selenium layer is used as one electrode and is separated from the counter electrode by a blocking layer, is formed by applying the selenium in a liquid state to a carbon support. The carbon support may be in the form of a block to which a lead may be attached or may be a layer of carbon applied to a roughened brass or other metal plate by rubbing or from a carbon suspension in a binding agent ; in the latter case, the dispersion medium may be removed by heat. A selenium layer of suitable thickness is applied to the carbon layer and is heated to transform it into the conductive crystalline state. The blocking layer may consist of polystyrene which is applied to the selenium layer and the counter electrode which can be applied by spraying to the blocking layer may be of Wood's metal or other readily fusible allov. In a modification, barium tungstate in finely divided condition may be mixed with the liquid selenium before this is applied to the carbon support. Upon heating, the selenium vaporizes superficially leaving a film of barium tungstate as the insulating blocking layer. Cadmium may be used as the counter electrode. In order to prevent the formation of undesirable films when the carbon layer is carried by a metal support, the latter is provided with an anticorrosion layer. The support 13, which may be of copper or of aluminium when a number of series-connected rectifying units are used as a high-tension rectifier, is given electrolytic coatings 14, 15 of nickel and chromium, serving as anti-corrosion layers. The selenium layer 17 is applied over the carbon layer 16 and a polystyrene layer 18 is provided which may be applied from a solution in benzene. The counter-electrode 19 is of Wood's metal. Chromium, nickel, platinum or gold may be used for the anti-corrosion coating.