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Nitride Intermediates in the Preparation of Columbium, Vanadium, and Tantalum Metals (In Two Parts). 1. Nitride Preparation.
Guidotti-RA; Atkinson-GB; Kesterke-DG
NTIS: PB 248 108 :25 pages
The federal Bureau of Mines has studied the reaction of oxides of columbium, vanadium, and tantalum with ammonia in vertical, gas- solids reactors at temperatures ranging from 300 deg to 1,300 deg c with the goal of preparing nitride intermediates for subsequent preparation of the metals by a thermal-decomposition step. The best nitride conversions were obtained in nonmetal reactors. With cb2o5, v2o3, and v2o5, low-temperature maxima in reaction rates occurred at 800 deg, 800 deg, and 450 deg c, respectively, during oxynitride formation (in al2o3) in 1 atm of pure ammonia. Conversion of the oxynitride, in a second step, to the mononitride was optimum at 1,200 deg c for columbium and 1,050 deg c for vanadium. In the case of ta2o5, the rate of reaction to form ta3n5 (in a single step) was highest at 900 deg c, where the presence of up to 5 percent methane was found to be beneficial; improved results were obtained by conducting the nitriding in a rotary kiln. Optimum space velocities (in the vertical al2o3 reactor) ranged from 5,280 hr-1 for cb2o5 to 7,950 hr-1 for v2o3. Oxide particle size had little effect upon reaction rates. Under fully optimized conditions, products containing less than 1 percent oxygen were readily obtained in under 6 hours.
IH; Report of Investigation;
NTIS Accession No.
NTIS: PB 248 108
Page last reviewed: April 12, 2019
Content source: National Institute for Occupational Safety and Health Education and Information Division