Abstract: An electrolytic cell for electrolysis of alumina for the production of aluminum, comprising at least two cell components joined by a ramming paste consisting essentially of a compact mixture of one or more particulate carbonaceous material(s) with a non-carbonaceous non-polluting colloidal binder and optionally with one or more non-carbonaceous fillers, the binder being a suspension of one or more colloids, or being derived from one or more colloid precursors or colloid reagents optionally with one or more chelating agents.

Abstract: Carbon-containing components (1, 2, 5) of cells for the production of aluminium (8) by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte (7) are protected from attack by liquid and/or gaseous components of the electrolyte (7) in the form of elements, ions or compounds, by a refractory boride coating (9, 10, 11) applied from a slurry composed of preformed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: A cell for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride-based electrolyte comprises a cathode composed of a carbon body having an aluminium resistant aluminium-wettable surface layer containing particulate titanium or other refractory hard metal boride and a bonding material providing a porous layer which contains cathodic molten aluminium. Molten cathodic aluminium external to the aluminium-resistant and aluminium-wettable surface contains refractory hard metal and boron in a total concentration sufficient or just below that sufficient to inhibit dissolution into the molten aluminium of the refractory hard metal boride. Alumina is fed to the cell whereby the required amount of titanium in the aluminium results from the alumina feed while, when boron is not present in a sufficient amount, boron is added to bring the total titanium and boron content to or just below the equilibrium solubility product.

Abstract: Components of electrolytic cells for the production of aluminum in particular by the electrolysis of alumina in a molten fluoride electrolyte, made of carbon or other microporous material which remains stable or may be consumed in the cell operating conditions, are conditioned to better resist in the cell operating conditions by impregnating them with colloidal ceria, cerium acetate, silica, alumina, lithia, yttria, thoria, zirconia, magnesia or monoaluminum phosphate containing ionic species of sodium, lithium, potassium, aluminum, calcium or ammonium, followed by drying and heat treatment.

Abstract: Carbon-containing components of cells for the production of aluminum by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte are protected from attack by liquid and/or gaseous components of the electrolyte in the form of elements, ions or compounds, by a treatment composition which consists essentially of a solution of one or more phosphates of aluminum. The treatment composition may alternatively consist essentially of one or more phosphates of aluminum, and one on more colloidal carriers.

Abstract: A carbonaceous, refractory or metal alloy substrate material coated with a refractory material, the refractory material including at least one of borides, silicides, nitrides, aluminides, carbides, phosphides, oxides, metal alloys, inter-metallic compounds and mixtures of one of titanium, chromium, zirconium, hafnium, vanadium, silicon, niobium, tantalum, nickel, molybdenum and iron and at least one refractory oxide of rare earth metals. An aluminum production cell including a component made up of a material coated with the coating described above is also disclosed.

Abstract: A body of carbonaceous or other material for use in corrosive environments such as oxidising media or gaseous or liquid corrosive agents at elevated temperatures, in particular in molten salts such as cryolite, is coated with a protective surface coating which improves the resistance of the body to oxidation or corrosion and which may also enhance the bodies electrical conductivity and/or its electrochemical activity. The protective coating is applied in one or more layers from a colloidal slurry containing reactant or non-reactant substances, or a mixture of reactant and non-reactant substances, in particular mixtures containing silicon carbide and molybdenum silicide or silicon carbide and silicon nitride, which when the body is heated to a sufficient elevated temperature reaction sinter as a result of micropyretic reaction and/or sinter without reaction to form the protective coating.

Abstract: A prebaked carbon-based anode of an electrolytic cell for the production of aluminium, in particular by the electrolysis of alumina in a molten fluoride electrolyte, is treated over its sides and top to improve the resistance thereof to erosion during operation of the cell by oxidising gases released at the anode, by immersing the anode in a boron-containing solution containing 5-60 weight % of H.sub.3 BO.sub.3 or B.sub.2 O.sub.3 in methanol, ethylene glycol, glycerin or water with a surface-active agent, e.g. at 80.degree. to 120.degree. C. After 2-60 minutes immersion, the boron-containing solution is impregnated to a depth of 1-10 cm, usually about 2-4 cm over the top and side surfaces of the anode to be protected, producing a concentration of boron in the impregnated surface from 200 ppm to 0.35%. The same treatment can be applied to cell sidewalls.

Abstract: A cell for the production of aluminium by the electrolysis of a molten electrolyte, in particular the electrolysis of alumina dissolved in a molten halide electrolyte such as cryolite, comprises anodes immersed in the molten electrolyte above a cell bottom whereon molten product aluminium is collected in a pool containing bodies of aluminium-resistant material. Under the anodes is at least one grid (10) of side-by-side upright or inclined walls (11,12) of aluminium-resistant material whose bottom ends stand on a ceramic-coated carbon cell bottom covered by the pool of molten aluminium. The bottom ends of the grid walls form a base which is large compared to the height of the walls, each grid (10) standing on the cell bottom and being removable from the cell. These grids reduce movements in the aluminium pool and their top parts may act as a drained cathode.

Abstract: A carbon containing paste for use in particular as components of electrolytic cells as such or compacted to form anodes, cathodes and cell linings of cells for the electrolysis of alumina for the production of aluminium, consists of a compact mixture of one or more particulate carbonaceous material(s) with a non-carbonaceous non-polluting binder and optionally with one or more fillers, the binder being a suspension of one or more colloids such as colloidal silica, alumina, yttria, ceria, thoria, zirconia, magnesia, lithia or being derived from one or more colloid precursors or colloid reagents optionally with one or more chelating agents. Cell components are produced by forming the paste to a desired shape and size, for instance in a mold, an injection die or in a cell bottom, compacting and drying before use, or the paste can be used as such like in a Soderberg type anode, or for bonding together carbon blocks like a ramming paste.

Abstract: A method of producing a component of an aluminium production cell made of a carbon-based composite material containing a refractory hard metal boride, carbide, oxide, nitride or combinations or mixtures thereof and aluminium as metal, alloy or as an aluminium compound, comprises firstly providing a reaction mixture of aluminium and precursors which react to form the refractory hard metal compound, and optional fillers and additives. The reaction mixture is mixed with particulate carbon in an amount of from 1 to 20 parts by weight of carbon for 1 part by weight of the reaction mixture; and with a colloidal binder containing at least one of colloidal silica, alumina, yttria, ceria, thoria, zirconia, magnesia, lithia, in an amount to fully wet the carbon particles. The resulting mixture is compacted and dried and heated to initiate reaction of the reaction mixture by self-propagating micropyretic reaction.

Abstract: A carbon containing material for use in particular as an anode of electrolytic cells for the production of aluminum by the electrolysis of alumina in a cryolite-based electrolyte, consists substantially of a mixture of one or more particulate carbonaceous material(s) with a binder based on compounds of aluminum with carbon, oxygen and/or nitrogen, such as aluminum carbide or aluminum oxycarbide, or such compounds mixed with aluminum. This binder is obtained by mixing the particulate carbonaceous material(s) with particulate aluminum and with at least one lithium compound and/or with at least one aluminum compound in a liquid carrier, and heat treating to form the binder. The liquid carrier may comprise a binding agent selected from methyl cellulose, polyvinyl alcohol and colloidal suspensions, in particular colloidal alumina.

Abstract: To improve its resistance to penetration and degradation by sodium, a carbon cathode for use in aluminium production by the electrolysis of alumina dissolved in a cryolite-based molten electrolyte is pre-treated with a solution, suspension or melt of a compound of lithium, sodium and/or potassium. This pre-treatment takes place prior to, during or after forming the cathode but before use thereof. The entire carbon cathode, or only that part of the carbon which is nearest to the active cathode surface is treated, making it more resistant to penetration by components of the molten electrolyte of aluminium.

Abstract: A method of producing a component of an aluminium production cell made of a carbon-based composite material containing a refractory hard metal boride, carbide, oxide, nitride or combinations or mixtures thereof and aluminium as metal, alloy or as an aluminium compound, comprises firstly providing a reaction mixture of aluminium and precursors which react to form the refractory hard metal compound, and optional fillers and additives. The reaction mixture is mixed with particulate carbon in an amount of from 1 to 20 parts by weight of carbon for 1 part by weight of the reaction mixture; and with a colloidal binder containing at least one of colloidal silica, alumina, yttria, ceria, thoria, zirconia, magnesia, lithia, in an amount to fully wet the carbon particles. The resulting mixture is compacted and dried and heated to initiate reaction of the reaction mixture by self-propagating micropyretic reaction.

Abstract: A multimonopolar cell for electrowinning aluminium by the electrolysis of alumina dissolved in a molten salt electrolyte, comprises electrode assemblies each having a non-consumable anode and a non-consumable cathode both resistant to attack by the electrolyte and by the respective product of electrolysis. The anode (2) is preferably of tubular form with an active anode surface (7) inside, and the cathode is made of one or more rods (1) or tubes placed in the middle of the tubular anode or between plate anodes, the cathode extending beyond the bottom of the anode. The active anode surface area is bigger than the facing active cathode surface area. In use, the electrode assembly is partly immersed vertically or at a slope in the electrolyte (3) with the cathode dipping in a layer (4) of aluminum on the cell bottom.

Abstract: A body of carbonaceous or other material for use in corrosive environments such as oxidizing media or gaseous or liquid corrosive agents at elevated temperatures, in particular in molten salts such as cryolite, is coated with a protective surface coating which improves the resistance of the body to oxidation or corrosion and which may also enhance the bodies electrical conductivity and/or its electrochemical activity. The protective coating is applied in one or more layers from a colloidal slurry containing reactant or non-reactant substances, or a mixture of reactant and non-reactant substances, in particular mixtures containing silicon carbide and molybdenum silicide or silicon carbide and silicon nitride, which when the body is heated to a sufficient elevated temperature reaction sinter as a result of micropyretic reaction and/or sinter without reaction to form the protective coating.

Abstract: A composite electrode for electrochemical processing having improved high temperature properties, and a process for making the electrode by combustion synthesis. A composition from which the electrode is made by combustion synthesis comprises from about 4% to about 90% by weight of a particulate or fibrous combustible mixture which, when ignited, is capable of forming an interconnected network of a ceramic or metal-ceramic composite, and from about 10% to about 60% by weight of a particulate or fibrous filler material capable of providing the electrode with improved oxidation resistance and maintenance of adequate electrical conductivity at temperatures above 1000.degree. C. The filler material is molybdenum silicide, silicon carbide, titanium carbide, boron carbide, boron nitride, zirconium boride, cerium oxide, cerium oxyfluoride, or mixtures thereof.

Abstract: A novel anode-cathode arrangement for the electrowinning of aluminum from alumina dissolved in molten sales, consisting of an anode-cathode double-polar electrode assembly unit or a continuous double polar assembly in which the anode and cathode are bound together and their interelectrode gap is maintained substantially constant by connections made of materials of high electrical, chemical, and mechanical resistance. Novel, multi-double-polar cells for the electrowinning of aluminum contain two or more of such anode-cathode double-polar electrode assembly units. This arrangement permits the removal of reimmersion into any of the anode-cathode double-polar electrode assembly units during operation of the multi-double-polar cell whenever the anode and or the cathode or any part of the electrode unit needs reconditioning for efficient cell operation.

Abstract: Bodies (3) such as tiles, plates, slabs or bricks of Refractory Hard Material (RHM) or other refractory composites are bonded to the cathodes or to other components, in particular to a carbon cell bottom (1), of a cell for the production of aluminium by electrolysis of a cryolite-based molten electrolyte, made of carbonaceous or other electrically conductive refractory material, by a non-reactive colloidal slurry (4) comprising particulate preformed RHM in a colloidal carrier selected from colloidal alumina, colloidal yttria and colloidal ceria. The slurry usually comprises preformed particulate TiB.sub.2 in colloidal alumina. The bodies (3) are usually TiB.sub.2 --Al.sub.2 O.sub.3 composites. The bonding is achieved simply by applying the slurry and allowing it to dry.

Abstract: An adherent protective coating of a refractory material is produced on the surface of carbonaceous, refractory, ceramic, metallic or other materials serving as components of electrolytic cells operating at high temperature, by applying to such surfaces a well chosen micropyretic reaction layer from a slurry, which when dried is ignited to initiate a self-sustaining micropyretic reaction, along a combustion front, to produce condensed matter forming such refractory protective adherent coating. The slurry is preferably applied in several layers, the first layer(s) to facilitate adherence and the last layer(s) to provide protection and may contain some preformed non-reactant materials. The electrolytic cells whose components require such coatings are especially those operating at high temperature with a molten salt electrolyte, particularly those for the production of metals, aluminum being the most important.