GB637714A - Improvements in and relating to the production of metal powders - Google Patents

Abstract

637,714. Electrolytic production of metal powders. JOHANSSON, E. H. E., and TRUEDSSON, C. M. Dec. 14, 1945, No. 33953. [Class 41] In the production of powder from heavy metals or alloys such as iron, nickel, chromium and copper, using anodes of the required metal, the electrolysis is carried out in a non- oxidizing atmosphere with an electrolyte comprising a melt of a salt of an alkali or alkaline earth metal or a radical which is more electropositive than the required metal, which melt does not attack the anode metal except when current is passed and which is kept at a temperature below the melting point of the metal, the required metal being present in the melt in an ionized state in a low concentration, kept constant by avoiding any oxidation and introduction of non-anodic substances which might cause an increase of the anion concentration. The melt is preferably a chloride or other halogen salt of an alkali metal, and is preferably free from oxides or other compounds of the anode metal, with the exception of the salt formed at the anode during the electrolysis. Preferably the cathode also consists of the metal or alloy to be produced in powdered form. To remove oxidizing compounds, the melt, apparatus and electrodes may be heated to redness in an atmosphere of hydrogen. During electrolysis there may be added to the electrolyte alkali or alkaline earth metals which vaporize and thus prevent oxidation ; alternatively, mixtures which liberate these metals may be added. To prevent short-circuiting by liquid metal floating on the electrolyte, these added metals may be contained in tubes having openings controlled in such a way that only vapour can escape to the region above the electrolyte. The vapour may be expelled from the tubes by an inert gas. To prevent sintering of the powder produced, the temperature in the space below the electrodes where the powder collects may be kept low by extending the vessel downwards and by using a low-melting point melt. A coarser powder is produced if halogen salts, preferably fluorides of the anode metal or metals, preferably mixed with alkali metal fluorides, are added to the melt. For the production of iron powder the electrolyser consists of outer and inner vessels 1, 2, the space between them being filled by a non-oxidizing gas such as hydrogen led in at 4 and out at 4<1>. In an annular lid 3, tubes 6 are provided for introducing gases or vapours to drive out the air and prevent oxidation. A cylindrical skirt 3<1> depending from the lid 3 is closed by a circular lid 5, provided with further pipes 6<1>. The vessel, including the skirt 3<1>, is made the cathode, and scrapers 7 are provided for removing the powder from the vertical surfaces as it is formed. A scraper 9 is provided. There may be a plurality of cylindrical extensions 3<1> serving as cathodes. The electrolysis may be carried out with a diaphragm between the cathode and anodes 8.