| 摘要 |
521,827. Asymmetrically-conducting resistances ; electrolytic reduction of copper oxide- WESTINGHOUSE BRAKE & SIGNAL CO., Ltd. Nov. 29, 1938, No. 34788. Convention date, Aug. 17. [Classes 37 and 41] The outer surface of the copper oxide layer of a rectifier is reduced electrolytically to form a copper contact surface in a bath comprising , ammonium hydroxide preferably in weak aqueous solution, e.g. 0.2 per cent. by volume of concentrated NH4OH (s.g. 0.880). Current of density of 12 amps. per sq. ft. is passed for 3-5 minutes, the bath being at room temperature and mechanically agitated. 0.05 per cent by volume of a saturated solution of ammoniun sulphate may be added tc the solution whereby the voltage required is reduced. In preparing the oxide surface annular, copper blanks are mounted in pairs on a support and heated in an oxidizing atmosphere, whereby they are coated with an inner layer of cuprous oxide and an outer layer of cupric oxide, the layers being thinner on the facing surfaces. They are then quenched and'treated with an aqueous solution of 2 per cent. by volume of sulphuric acid and 0.1 per cent. by volume of hydrochloric acid whereby both layers are removed on the thinly coated side and the cupric oxide layer only on the other side. In the electrolytic treatment two blanks A are mounted with their oxide coatings outwards on either side of a metal washer 3 to which are cemented rubber washers 4 extending beyond the periphery of the blanks A. Rubber washers 6 masking the outer edge of the oxide coatings are then applied and the assembly clamped between washers 7. Nickel or other metal may be plated on to the reduced surface. A suitable nickel bath contains NiSO4.7H2O 27 oz., NiCl2.6H2O 4 oz., boric acid 6 oz. per U.S.A. gallon.
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