Abstract: In a method for reducing a solid feedstock (110), such as a solid metal compound, feedstock is arranged on upper surfaces of elements (60, 80, 81) in a bipolar cell stack contained within a housing (25). A molten salt electrolyte is circulated through the housing so that it contacts the elements of the bipolar stack and the feedstock. A potential is applied to terminal electrodes (50, 60) of the bipolar stack such that the upper surfaces of the elements become cathodic and the lower surfaces of the elements become anodic. The applied potential is sufficient to cause reduction of the feedstock. The invention also provides an apparatus for implementing the method.

Abstract: A bipolar multi-purpose electrolytic cell for high current loads has a frame, two electrode edge plates with metal electrode sheet, and power supply and of bipolar plates. Each includes a plastic electrode base body with electrode rear spaces and/or with coolings spaces that are incorporated on one or both sides: incorporated supply and discharge lines for the electrolyte solutions and the cooling medium, metal electrode sheets which are applied to both sides of the base body and are solid and/or perforated in the electrochemically active area: electrolyte sealing frames, which rest on the solid metal electrode sheets and which are made of flexible plastic, and: ion exchanger membranes, which rest on the perforated metal electrode sheets and/or on the electrolyte sheets and/or on the electrolyte sealing frames and which are provided for separating the electrode spaces.

Abstract: A cell for the electrowinning of aluminium comprising one or more anodes (10), each having a metal-based anode substrate, for instance comprising a metal core (11) covered with an metal layer 12, an oxygen barrier layer (13), one or more intermediate layers (14, 14A, 14B) and an iron layer (15). The anode substrate is covered with an electrochemically active iron oxide-based outside layer (16), in particular a hematite-based layer, which remains dimensionally stable during operation in a cell by maintaining in the electrolyte a sufficient concentration of iron species. The cell operating temperature is sufficiently low so that the required concentration of iron species in the electrolyte (5) is limited by the reduced solubility of iron species in the electrolyte at the operating temperature, which consequently limits the contamination of the product aluminium by iron to an acceptable level.

Abstract: A refractory boride body or coating made of a boride of titanium, chromium, vanadium, ziconium, hafnium, niobium, tantalum, molybednum and cerium is produced from a slurry of the refractory boride or a precursor in a collidal carrier preferably composed of two more different grades of the same colloidal carrier selected from colloidal alumina, yttria, ceria, thoria, zirconia, magnesia, lithia, monoaluminum phosphate and cerium acetate. The slurry can also comprise an organic additive selected from polyvinyl alcohol; polyacrylic acid; hydroxyy propyl methyl cellulose; polythylene glycol; ethylene glycol, butyl benzyl phthalate; ammonium polymethacrylate and mixtures thereof. The retractory boride body or coated body is useful as a component of aluminum electrowinning cells.

Abstract: In this cathode, which is a single block, the electrical resistivity is heterogeneous along its longitudinal axis, this resistivity being higher in the end regions of the cathode (3) than in the central region of the latter.

Abstract: A refractory boride body or coating made of a boride of titanium, chromium, vanadium, ziconium, hafnium, niobium, tantalum, molybednum and cerium is produced from a slurry of the refractory boride or a precursor in a collidal carrier preferably composed of two more different grades of the same colloidal carrier selected from colloidal alumina, yttria, ceria, thoria, zirconia, magnesia, lithia, monoaluminum phosphate and cerium acetate. The slurry can also comprise an organic additive selected from polyvinyl alcohol; polyacrylic acid; hydroxyy propyl methyl cellulose; polythylene glycol; ethylene glycol, butyl benzyl phthalate; ammonium polymethacrylate and mixtures thereof. The retractory boride body or coated body is useful as a component of aluminum electrowinning cells.

Abstract: A cell for the electrowinning of aluminium comprising one or more anodes (10), each having a metal-based anode substrate, for instance comprising a metal core (11) covered with an metal layer 12, an oxygen barrier layer (13), one or more intermediate layers (14; 14A, 14B) and an iron layer (15). The anode substrate is covered with an electrochemically active transition metal oxide layer, in particular an iron oxide-based outside layer (16) such as a hematite-based layer, which remains dimensionally stable during operation in a cell by maintaining in the electrolyte a sufficient concentration of iron species and dissolved alumina. The cell operating temperature is sufficiently low so that the required concentration of iron species in the electrolyte (5) is limited by the reduced solubility of iron species in the electrolyte at the operating temperature, which consequently limits the contamination of the product aluminium by iron to an acceptable level.

Abstract: A non-carbon, metal-based slow-consumable anode of a cell for the electrowinning of aluminium self-forms during normal electrolysis an electrochemically-active oxide-based surface layer (20). The rate of formation (35) of the layer (20) is substantially equal to its rate of dissolution (30) at the surface layer/electrolyte interface (25) thereby maintaining its thickness substantially constant, forming a limited barrier controlling the oxidation rate (35). The anode (10) usually comprises an alloy of iron with at least one of nickel, copper, cobalt or zinc which during use forms an oxide surface layer (20) mainly containing ferrite.

Abstract: A cell for the electrowinning of aluminium comprising one or more anodes (10), each having a metal-based anode substrate, for instance comprising a metal core (11) covered with an metal layer 12, an oxygen barrier layer (13), one or more intermediate layers (14; 14A, 14B) and an iron layer (15). The anode substrate is covered with an electrochemically active transition metal oxide layer, in particular an iron oxide-based outside layer (16) such as a hematite-based layer, which remains dimensionally stable during operation in a cell by maintaining in the electrolyte a sufficient concentration of iron species and dissolved alumina. The cell operating temperature is sufficiently low so species and dissolved alumina.

Abstract: Carbon-containing components of cells for the production of aluminium 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 refractory boride coating applied from a slurry composed of pre-formed particulate refractory boride in a colloidal carrier which is dried and heated to consolidate the coating.

Abstract: A bipolar cell for the electrowinning of aluminum has bipolar electrodes each comprising a carbon cathode body having on one side an active surface on which aluminum is produced and connected on the other side through an oxygen impermeable barrier layer to an electrochemically active anode layer having an oxygen evolving iron oxide-based outer surface. The anode layer may comprise a metal-based anode substrate and a transition metal oxide-based outside layer, in particular an iron oxide-based outside layer, which either is an applied layer or is obtainable by oxidising the surface of the anode substrate which contains iron. During operation, the anode layer can be kept dimensionally stable by maintaining in the electrolyte a concentration of transition metal species which are present as one or more corresponding transition metal oxides in the electrochemically-active layer.

Abstract: A non-carbon, metal based slow-consumable anode of a cell for the electrowinning of aluminum self-forms during normal electrolysis an electrochemically-active oxide-based surface layer (20). The rate of formation (35) of the layer (20) is substantially equal to its rate of dissolution (30) at the surface layer/electrolyte interface (25) thereby maintaining its thickness substantially constant, forming a limited barrier controlling the oxidation rate (35). The anode (10) usually comprises an alloy or iron at least one of nickel, copper, cobalt or zinc which during use forms an oxide surface layer (20) mainly containing ferrite.

Abstract: A non-carbon, metal-based slow-consumable anode of a cell for the electrowinning of aluminium self-forms during normal electrolysis an electrochemically-active oxide-based surface layer (20). The rate of formation (35) of the layer (20) is substantially equal to its rate of dissolution (30) at the surface layer/electrolyte interface (25) thereby maintaining its thickness substantially constant, forming a limited barrier controlling the oxidation rate (35). The anode (10) usually comprises an alloy of iron with at least one of nickel, copper, cobalt or zinc which during use forms an oxide surface layer (20) mainly containing ferrite.