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: An anode for the electrowinning of aluminium by the electrolysis of alumina dissolved in a molten fluoride electrolyte comprises a porous combustion synthesis product of nickel, aluminium, iron, copper and optional doping elements in the amounts 60-90 wt % nickel, 3-10 wt % aluminium, 5-20 wt % iron, 0-15 wt % copper and 0-5 wt % of one or more of chromium, manganese, titanium, molybdenum, cobalt, zirconium, niobium, yttrium, cerium, oxygen, boron and nitrogen. The combustion synthesis product contains metallic and intermetallic phases. A composite oxide surface is produced in-situ by anodic polarization of the porous combustion synthesis product in a molten fluoride electrolyte containing dissolved alumina. The in-situ formed composite oxide surface comprises an iron-rich relatively dense outer portion, and an aluminate-rich relatively porous inner portion.

Abstract: A cell component for use in particular as anodes, cathodes and cell linings of cells for the electrolysis of alumina for the production of aluminum, comprising a solidified carbon containing paste consisting essentially of a compact mixture of one or more particulate carbonaceous material(s) with a non-carbonaceous binder and optionally with one or more fillers to form a fluid paste, the binder being a suspension of one or more colloids or being derived from one or more colloid precursors or colloid reagents optionally with chelating agents. A method of producing the cell component is also included.

Abstract: Electrical heating elements and related articles having oxidation resistance at high temperatures, produced by a method involving micropyretic synthesis. A composition subjected to micropyretic synthesis comprises a filler material, a reactive system capable of undergoing micropyretic synthesis, and (optionally) a plasticizer or extrusion agent. The method of preparation of articles includes slurry techniques, plastic extrusion, slip casting, or coating.

Abstract: A slurry for joining metallic or ceramic surfaces or for coating metallic or ceramic and refractory surfaces, comprising a liquid suspending medium and at least two constituents in particulate form suspended in the medium, the constituents being so selected and proportioned as to undergo combustion synthesis when ignited. A method for coating or joining metallic or ceramic surfaces comprises applying such a slurry to a surface to be coated or to surfaces to be joined, and igniting the slurry to cause combustion synthesis.

Abstract: A heating element assembly for a radiant heating device with a metallic heating element in series with non-metallic heating elements, with a plurality of ceramic or metal-ceramic coolers which are used to connect the heating elements to each other. The heating elements and the coolers are formed by micropyretic synthesis.

Abstract: A method for joining a ceramic or metal ceramic electrical heating element to a electrical terminal is disclosed, the heating element having been manufactured using micropyretic synthesis, the method for joining comprising the steps of preparing the electrical terminal by blending a combustible mixture and fashioning the mixture into a desired wet and uncombusted shape for the terminal, attaching the terminal to the element, drying the terminal portion of the terminal-element attachment and combusting the terminal portion of said terminal-element attachment by ignition at a temperature between about 150.degree. C. and 1800.degree. C. An electrical terminal is disclosed, the terminal having been formed by micropyretic synthesis of a specific combustible composition.

Abstract: Electrical heating elements and related articles having oxidation resistance at high temperatures, produced by a method involving micropyretic synthesis. A composition subjected to micropyretic synthesis includes a filler material, a reactive system capable of undergoing micropyretic synthesis, and (optionally) a plasticizer or extrusion agent. The method of preparation of articles includes slurry techniques, plastic extrusion, slip casting, or coating.

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 slurry for joining metallic or ceramic surfaces or for coating metallic or ceramic and refractory surfaces, comprising a liquid suspending medium and at least two constituents in particulate form suspended in the medium, the constituents being so selected and proportioned as to undergo combustion synthesis when ignited. A method for coating or joining metallic or ceramic surfaces comprises applying such a slurry to a surface to be coated or to surfaces to be joined, and igniting the slurry to cause combustion synthesis.

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 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: A slurry for joining metallic or ceramic surfaces or for coating metallic or ceramic and refractory surfaces, comprising a liquid suspending medium and at least two constituents in particulate form suspended in the medium, the constituents being so selected and proportioned as to undergo combustion synthesis when ignited. A method for coating or joining metallic or ceramic surfaces comprises applying such a slurry to a surface to be coated or to surfaces to be joined, and igniting the slurry to cause combustion synthesis.

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.

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: 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 40% 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.