GB1093185A - Improvements in or relating to electrolytic cells and cathodic structures therefor - Google Patents

Abstract

An electrolytic cell for producing aluminium comprises a shell 18 defining a receptacle, at least one anode 36 e.g. of carbon and a catholic structure 30 disposed within the receptacle e.g. on a carbon bottom 26 and intended to be exposed to molten cell constituents 33, e.g. molten cryolite with dissolved alumina and other materials such as fluorspar, the structure including at least one drained molten-constituent contacting surface 27 formed from a mixture wettable by molten aluminium, having a cathodic expansion <PICT:1093185/C6-C7/1> of less than 3% and comprising at least 5% "free" carbon with a refractory hard substance selected from the carbides, borides, silicides and nitrides of the transition metals in the 4th to 6th Groups of the Periodic System of elements (excluding Cr), particularly the borides and/or carbides of Ti and/or Zr e.g. 70% TiB2 and 30% TiC, with or without one or more of aluminium borides, nitrides and carbides, and compounds of rare earth metals and Cr. The "free" carbon may be provided by petroleum coke or other carbonaceous material calcined at least 1500 DEG C. The above mixture, to which may be added oxides such as TiO2, ZrO2 and 10-20% carbonaceous binder, may be baked e.g. at 900-1800 DEG C. either in situ in the cell or after shaping to provide a sloping surface and prior to disposing in the cell. A molten aluminium collecting well 32 may be included in the receptacle.