Abstract: A method for forming a polycrystalline ceramic fiber which comprises blending about 5 to about 25 weight percent polymer, about 70 to about 95 weight percent silicon carbide powder and greater than 1 weight percent sintering aid; forming a fiber from the blend; and sintering the formed fiber. Preferably, the sintering aid is boron carbide. In addition, the fiber is preferably pre-sintered at a first temperature of from about 1700.degree. C. to 2300.degree. C. and then subsequently sintered at a second temperature of approximately 2000.degree. C. to about 2300.degree. C.

Abstract: A method of producing near net shape fusion cast refractories. The method includes the steps of continuously introducing refractory particles into a melting furnace, rapidly heating the particles, depositing the heated particles into a melt pool, continuously introducing the molten material into a mold, and continuously withdrawing a solidified body from the mold as the molten material continually solidifies. The above stated method produces a fusion cast refractory having a generally random, fine, uniform microstructure; uniform chemistry; and generally evenly distributed closed pores.

Abstract: A process for the manufacture of high purity, ultra-fine aluminum nitride powder by the carbo-nitridization of alumina. Agglomerates uniform in both size, chemical composition and porosity are formed containing a stoichiometric mixture of alumina and carbon with the addition of a small amount of catalyst. The agglomerates are furnaced in a controlled manner in a well-mixed reaction vessel to achieve a uniform and consistent level of conversion. Milling of the as-reacted agglomerates under a controlled atmosphere will produce high purity, micron sized aluminum nitride powder.

Abstract: A process and apparatus for the manufacture of high purity, ultra-fine aluminum nitride powder by the carbo-nitridization of alumina. In the method, agglomerates uniform in both size, chemical composition and porosity are formed containing a stoichiometric mixture of alumina and carbon, and a small amount of catalyst, and furnaced in a controlled manner in a well-mixed two chamber reaction vessel having optional top or bottom fluidizing gas feed to achieve a uniform and consistent level of conversion. Milling of the as-reacted agglomerates under a controlled atmosphere will produce high purity, micron sized aluminum nitride powder. The reactor is an automatically controlled fluid bed reactor for treatment of refractory materials with a hot fluidizing gas having a two chamber design in which the lower furnace chamber and reactor bed are removable from the bottom of the reactor. With unique reactor, unusually high reaction temperatures of up to 2000.degree. C. are obtainable.

Abstract: Fused cast refractory moldings having a random microstructure, which are near in size and configuration to the desired final shape, and process and apparatus used in their manufacture are described. The process includes rapid melting of the refractory material followed by controlled rapid cooling. Laminated composite fused cast refractories may be produced.

Abstract: An anode for plasma torch that has a primary section and a secondary section with a gradual transition between the sections. The diameter of the hollow primary section tapers down toward a transition zone, at which point the anode formed by the sections makes a gradual transition to the secondary section. The secondary section is cylindrical and has a diameter larger than that of the primary section from which the plasma exists the anode. The transition zone will describe a generally conical surface and may include a convex radius on the neck where the primary and transition sections meet.

Abstract: A fluid bed reactor for treatment of refractory materials with a hot fluidizing gas and a method to use same. Both the refractory materials and the fluidizing gas are introduced from the top of the reactor. Unusually high reaction temperatures of up to 2000.degree. C. are maintained in the reaction chamber due to the presence of heating elements within the reactor and due to countercurrent heat transfer.

Abstract: Fused cast refractory moldings having a random microstructure, which are near in size and configuration to the desired final shape, and process and apparatus used in their manufacture are described. The process includes rapid melting of the refractory material followed by controlled rapid cooling. Laminated composite fused cast refractories may be produced.

Abstract: A furnace for the sintering of refractory or ceramic materials using plasma heated gases. The furnace comprises a sintering chamber with strategic positioning of the plasma torch inlets and exhaust outlet, a furnace temperature controlling device during sintering so that the article being sintered does not decompose. The devices which can be used for controlling the temperature of the furnace during sintering include: (1) Tangential injection of a secondary colder gas stream into the hot primary plasma gas stream; (2) Utilization of a plasma torch or torches which can be temperature controlled to achieve stable and lower plasma gas temperatures; and (3) Introduction of a secondary cooler gas directly into the furnace sintering chamber.

Abstract: A system to prevent, retard or reverse the decomposition of silicon carbide articles during high temperature plasma sintering. Preferably, the system comprises sintering a silicon carbide refractory or ceramic green body in a closed sintering environment, such as a closed tube, with strategic placement of the plasma torch or torches, exhaust outlet and tube. As sintering proceeds, a silicon vapor pressure builds up within the tube, retarding the decomposition of the silicon carbide body. The plasma torch, exhaust outlet, and tubes are positioned so that buoyant convective flow is maximized to increase the heat transfer and energy efficiency. In another embodiment, a "sacrificial" source of silicon carbide is placed into the sintering furnace. The silicon carbide in the sacrificial source starts to decompose before the silicon carbide refractory or ceramic article, creating a supersaturated atmosphere of silicon vapor species in the furnace.

Abstract: A process for the sintering of silicon carbide refractory or ceramic articles using plasma arc gases. In the process of the invention, a formed silicon carbide article is heated in a plasma fired furnace to a sintering temperature of between 2000.degree. C.-2500.degree. C. at a heating rate of 300.degree. C./hr-2000.degree. C./hr, and held at the sintering temperature for 0.1-2 hours. The enthalpy of the plasma gas is 2000 BTU/lb-4000 BTU/lb, when nitrogen is used as the plasma gas. The total cycle time for the process of the invention, including cooling and loading, is 1.5-20 hours. Silicon carbide articles, produced in accordance with the invention, have high strength, high density, high corrosion resistance and high dimensional stability.

Abstract: An improved process for sintering extruded powder shapes comprising drying or calcining an extruded shape in a microwave furnace and rapid sintering the shape in a plasma fired furnace. Alternatively, calcining or drying may take place within a furnace heated by the plasma furnace's exhaust. The process of the invention is especially useful for silicon carbide extruded materials and for tubular shapes. This process significantly reduces sintering times and costs. Use of the process yields a high strength sintered product.

Abstract: A system to prevent, retard or reverse the decomposition of silicon carbide articles during high temperature plasma sintering. Preferably, the system comprises sintering a silicon carbide refractory or ceramic green body in a closed sintering environment, such as a covered crucible, with strategic placement of the plasma torch or torches, exhaust outlet and crucibles. As sintering proceeds, a silicon vapor pressure builds up within the crucible, retarding the decomposition of the silicon carbide body. The plasma torch, exhaust outlet, and crucibles are positioned so that buoyant convective flow is maximized to increase the heat transfer and energy efficiency. In another embodiment, a "sacrificial" source of silicon carbide is placed into the sintering furnace. The silicon carbide in the sacrificial source starts to decompose before the silicon carbide refractory or ceramic article, creating a supersaturated atmosphere of silicon vapor species in the furnace.

Abstract: A process for sintering or reaction sintering ceramic or refractory materials with hot plasma gases. The hot plasma gases are produced by injecting a combined primary plasma arc with a secondary gas stream directly into a reaction furnace. The secondary gas stream is tangentially injected into the primary plasma arc gas stream to mix the gases for the required sintering temperature at the highest energy efficiency. The plasma torches are positioned in the furnace ports so that the plasma gas flow is perpendicular to the furnace process gas flow. This process is inexpensive and efficient and results in a superior quality sintered product. It may be adapted to continuous or periodic kilns to achieve a high furnace productivity.

Abstract: Molten molybdenum-copper-iron-sulfur mattes or alloys, obtained, for example, by reacting slags or other copper-molybdenum containing oxide residues or waste materials witn an iron and/or sulfide reductant, are enriched in molybdenum and copper by a pyrometallurgical process. The molten matte or alloy material is first carburized whereupon a copper-rich matte phase separates from the alloy phase and is removed. The molten alloy phase is next treated one or more times by the addition of sulfur or pyrite resulting in the formation of additional copper-rich matte as a separate phase which is separated after each treatment, leaving an alloy of molybdenum and iron of reduced Cu content. Finally the alloy is desulfurized to provide a commercial product.

Abstract: Molten molybdenum-(copper)-iron-sulfur mattes or alloys, obtained for example, by reacting slags or other molybdenum containing oxide residues or waste materials with an iron and/or sulfide reductant, are enriched in molybdenum and copper (if present) by a pyrometallurgical process. The molten matte or alloy material is oxidized to remove sulfur, as sulfur oxides, while varying amounts of iron are converted to iron oxides which separate from the metallics. The oxidation thus enriches the molybdenum and copper content of the remaining alloy. Silica flux may be added during the reaction process to form a fluid slag with the iron oxide which separates from the remaining molybdenum-iron-(copper) material which constitutes the product.

Abstract: Waste materials containing significant quantities of zinc oxide are mixed with carbon and a sufficient amount of copper to set the overall Zn/Cu weight ratio to a selected value below 0.66. The mixture is loaded into the top of a shaft furnace having a lower region which is heated. Hot gas rising from lower regions of the shaft furnace preheats the mixture as it descends. Rising zinc vapor is prevented from escaping the furnace because it condenses in the relatively cool preheated mixture descending down the furnace. As the mixture descends, it enters a brass production zone where zinc vapor alloys with the copper in the mixture. Further descent brings the mixture to a zinc reduction zone where the temperature is above 950.degree. C and where ZnO is reduced by carbon or carbon monoxide to produce a zinc vapor which rises coutercurrently to the charge. Molten brass and some slag is removed from a brass reservoir which forms in the bottom of the furnace.

Abstract: The present specification discloses a pyrometallurgical system for maintaining a material in a molten state, the system comprising a vessel for molten material, the vessel conceptually dividable into a number of substantially uniform cells. A mechanical stirrer is provided for each such cell and is centered within the cell. The stirrers are sized and driven at a rate so as to promote a uniform temperature and composition of the molten material and improved heat transfer between, and blending of, various constituents of molten material, while producing minimal erosion of the conventional refractory lining of the vessel. Preferably, adjacent pairs of stirrers are driven with opposite rotational senses, thereby assuring reinforcing flow patterns at the cell boundaries. Heating means (e.g., power electrodes) are provided at locations which do not substantially interfere with the flow patterns generated by the array of mechanical stirrers.

Abstract: Process for recovering nickel and nickel-copper from molten smelter-type slags or other highly oxidized sources of nickel and nickel-copper containing 7 to 30 percent by weight of magnetite (Fe.sub.3 O.sub.4). The magnetite in the slag is reduced with carbonaceous materials or other solid reductants such as sulfides, metals or carbides. While the slag is mixed with a fluid cooled, metal-bladed mechanical stirrer, the reductant is reacted with the slag. As a result of stirring the reductant into the slag, the rate of magnetite reduction is highly accelerated. With the reduction, the nickel or nickel-copper (as well as cobalt, if present) separates into a phase as either immiscible metal, a sulfide, or a nickel-copper-iron-sulfide matte, depending upon the initial composition of the slag.

Abstract: A process for recovering iron from preliminarily decopperized molten copper smelter slags having an initial composition which includes iron oxide, silica, and aluminum oxide as the major constituents. These constituents are initially present in the range of 40-70 percent FeO, 25-40 percent SiO.sub.2 and 5-10 percent Al.sub.2 O.sub.3. The slag is maintained in a molten state and a solid reductant is mixed into the slag using an internally cooled, metal bladed, rotating stirrer, which rotates at a rate sufficient to pump the reductant into the slag to enhance the reduction of the iron oxide. An important aspect of this invention is to reduce slag to recover iron when the slag contains the following constituents, 40-60 percent SiO.sub.2, 15-35 percent CaO, less than 20 percent FeO and 5-10 percent Al.sub.2 O.sub.3. Although the above constituents can vary within the range set forth, it is important to maintain the SiO.sub.2 to CaO ratio in the range of about 2.0 - 3.3.