Abstract: High purity silicon nitride particles are disclosed which are essentially alpha crystalline and which have a surface area of greater than about 25 m.sup.2 /g.

Abstract: A process is disclosed for producing high purity high surface area silicon nitride. The process involves contacting silicon tetrachloride with water to form a two phase system consisting essentially of a solid phase which is essentially silica gel and a liquid phase, heating the two phase system at a sufficient temperature for a sufficient time to partially dehydrate the silica gel followed by removing the solid phase from the liquid phase. A slurry is then formed of the solid phase in an aqueous solution of a water soluble organic carbon source. A dispersing agent is added to the slurry to disperse the silica gel, and the pH of the slurry is adjusted to greater than about 7, followed by heating the slurry at a sufficient temperature for a sufficient time to remove essentially all of the water and to decompose the carbon source.

Abstract: A process is disclosed for removing chromium from cobalt. The process involves first contacting an acidic cobalt chloride solution with an oxidizing agent, followed by adjusting the pH to from about 3.2 to about 5.5 with a base at a sufficient temperature to form a first solid containing essentially all of the chromium and a portion of the cobalt and a first liquor containing the balance of the cobalt, and then separating the first solid from the first liquor. The first solid is then heated at a sufficient temperature to remove essentially all of the water and form a second solid which is contacted with sufficient water and ammonium hydroxide to form a slurry which is at a pH of greater than about 3.8.

Abstract: A process is disclosed for producing high purity tantalum oxide from impure tantalum oxide. The starting tantalum oxide is dissolved in a hydrofluoric acid solution and insolubles are removed. The hydrofluoric acid solution containing the tantalum values is adjusted to a pH of from about 6.0 to about 8.0 with a base to precipitate tantalum which is separated from the mother liquor. The tantalum precipitate is then dissolved in an oxalic acid solution, the pH adjusted to from about 5.1 to about 5.5, and the resulting solution digested to precipitate a high purity tantalum compound which is separated. The high purity tantalum compound is then digested in hydrochloric acid to dissolve the compound and then precipitate pure optical grade tantalum oxide which is then separated from its mother liquor.

Abstract: Tantalum is recovered from an impure source containing niobium, tungsten, titanium, iron, and other impurities by a process comprising mixing the impure source with an alkali metal carbonate, drying the resulting mixture, heating the dried mixture to convert the tungsten to a soluble form, leaching to solubilize the tungsten, digesting the resulting leached solids containing tantalum in hydrochloric acid to solubilize iron values and a portion of the titanium values, dissolving the leached solids containing tantalum values in hydrofluoric acid, adjusting the pH of the resulting solution to form a first tantalum precipitate, dissolving the first tantalum precipitate in oxalic acid adjusting the pH to form a second tantalum precipitate, dissolving and digesting the second tantalum precipitate in hydrochloric acid solution to form a third tantalum precipitate of high purity.

Abstract: A process is disclosed for producing a high purity tantalum precipitate from an impure source by dissolving in a first hydrofluoric acid solution and digested to form a first precipitate of tantalum which dissolved in hydrochloric acid. The resulting solution is heated to form a second precipitate of tantalum which is dissolved in another hydrofluoric acid solution and digested to form a third precipitate of tantalum. The third precipitate of tantalum is then dissolved in an oxalic acid solution with the pH being adjusted to form another tantalum precipitate which is converted to tantalum oxide.

Abstract: Tungsten and molybdenum are recovered from sulfur bearing material such as sulfide sludges by a pollution free process in which the sulfur bearing material is heated with agitation in an aqueous solution of sodium carbonate to form water soluble molybdenum and tungsten compounds without forming any appreciable amount of water soluble sulfur compounds. The reaction mixture is oxidized to convert partially reduced tungsten values or molybdenum values to sodium tungstate and sodium molybdate respectively. The liquid phase containing tungsten and molybdenum is separated from the solid phase containing free sulfur.

Abstract: In a process for recovering tungsten from cemented tungsten carbide, the tungsten carbide is oxidized to form an oxidized product and the oxidized product is digested in an aqueous solution of alkali metal hydroxide to form a soluble portion containing tungsten values and an insoluble residue portion. According to the improved process of the present invention, tungsten values are recovered from the insoluble residue portion by mixing the insoluble portion with an alkali metal carbonate to form a resulting mixture, roasting the resulting mixture in an atmosphere containing oxygen to oxidize the insoluble portion and form another product which is leached with water to recover soluble tungsten values.

Abstract: Cobalt is recovered from by-product streams from a basic process by heating the by-product streams containing ammonia for a sufficient period of time at a pH of about 8 to about 10 to produce an ammonia enriched vapor and an aqueous mixture comprising a solution substantially free of ammonia and another cobalt containing precipitate. The basic process is the type wherein cobalt ions in solution are complexed with ammonia in the presence of halide ions to form an ammine halide solution which is digested to form a cobalt containing precipitate. The precipitate is subsequently reduced to form a cobalt metal powder.

Abstract: A method for producing extra fine cobalt metal powder (up to 1.7 FSSS) by the digestion of cobalt pentammine chloride in a dilute ammonium hydroxide solution to form a cobalt-containing precipitate, followed by reducing the precipitate in a hydrogen atmosphere to cobalt metal powder, is improved by: (a) treating the mother liquor with an ion exchange resin to remove cobalt species; (b) stripping the resin with an HCl solution; (c) recovering solid cobalt hexammine chloride from the stripping solution; (d) forming a solution of the solid in water; (e) adding NaOH to the solution to form a cobalt-containing precipitate; and (f) either heating the precipitate in hydrogen to reduce it to cobalt metal powder or recycling the precipitate as a cobalt source for the formation of cobalt pentammine chloride. The final cobalt metal powder is useful, for example, as a starting material in the manufacture of cemented carbides.

Abstract: Extra fine cobalt metal powder (up to about 0.8 microns) having less than 100 parts per million cation impurities is produced by a process in which cobalt pentammine chloride is digested in a dilute ammonium hydroxide solution to form a black precipitate, which is separated and heated in a hydrogen atmosphere to reduce the precipitate directly to cobalt metal powder. The cobalt pentammine chloride may be obtained by digesting a cobalt source in hydrochloric acid, adding ammonium hydroxide, oxidizing the cobaltous ion to cobaltic ion, and reducing the pH with hydrochloric acid to less than 1.0 in order to precipitate cobalt pentammine chloride. The final cobalt metal powder is useful, for example, as a starting material in the manufacture of cemented carbides.