Abstract: Process for the production of tantalum-niobium concentrates from low-tantalum, high-niobium raw materials with an Nb.sub.2 O.sub.5 /Ta.sub.2 O.sub.5 ratio of 5 to 15 in a pyrometallurgical concentration process by smelting with carbon-containing reducing agents, reductions and resmelting.

Abstract: Improved solvent extraction recovery of tantalum and niobium oxides from an acid solution of raw materials containing such oxides wherein the charged organic solvent [e.g., MIBK] is washed out (a) with 8-16N sulfuric acid and then (b) with water or dilute HF. This avoids the use of a second mineral acid addition after digestion by HF of raw materials (and avoids problems attendant to use a second mineral acid).

Abstract: A highly pure tantalum pentoxide powder and a process for its preparation are disclosed. The powder is substantially free of impurities and is further characterized by improved flow characteristics.

Abstract: A method of recovering molybdenum oxide as in U.S. Pat. No. 4,379,127 wherein, however, the temperature in the autoclave and the pressure therein are controlled within narrow ranges by increasing the suspension density of the molybdenum sulfide suspension fed to the autoclave upon a fall in temperature and by adding water to the slurry of molybdenum sulfide concentrate formed before introduction into the autoclave upon an increase in temperature.

Abstract: A method of recovering molybdenum oxide by oxidation of a molybdenum sulfide concentrate contaminated with impurities wherein the concentrate in an average particle size in the range of 20 to 90 microns is suspended to form an aqueous suspension which is oxidized at elevated temperature and an elevated oxygen partial pressure in an autoclave. The suspension withdrawn from the autoclave is subjected to filtration to remove the molybdenum oxide from the primary filtrate containing sulfuric acid and this filtrate is neutralized with lime to form calcium sulfate which is then removed from the suspension to provide a second filtrate. According to the invention, only this second filtrate is recirculated at a rate such that the suspension density in the oxidation stage is between 100 to 150 g of solids per liter and this suspension density is maintained in the oxidation stage by the recirculation.

Abstract: A turbine type synchronous motor capable of starting directly and asynchronously when coupled to a work-performing machine is constructed with a drum rotor of high mass, made of solid magnetic material containing iron, and having no damper winding. The field windings, short-circuited or closed through a resistance during starting, are radially disposed in insulated slots which are closed by insulated wedges wherein the insulation is of highly temperature resistant material.

Abstract: The present invention relates to a housing for a solar cell driven motor suitable for use in model toys. The housing typically has an inclined surface to which the solar cells may be applied. The housing may be used to energize a toy mill, radar tower, conveyor, or lever conductor.

Abstract: In an asynchronous machine including a rotor of solid iron and a squirrel cage winding, the rotor is further provided with closed slots of any cross sectional shape which receive the bars of the squirrel cage winding whose upper edge is spaced from the outer surface of the rotor by a distance which is equal to the depth of penetration a of the eddy currents generated for a given starting voltage and for a slip s.gtoreq.0.8.