SINTERING OF COLUMBIUM POWDER

Journal Article · Thu Feb 01 04:00:00 EST 1962 · Tsvetnye Metally

OSTI ID:4786313

Amosov, V M

Vacuum sintering of niobium powder with an increased content of impurities was investigated in a vacuum of 10/sup -3/ mm Hg and at 15 deg C/min to 2350 deg C. The investigation showed that under the combined effect of high temperature and a vacuum a series of physical and chemical processes takes place resulting in the simultaneous sintering and refining of the metal. The refining begins at 1600 deg C, when removal of Fe and Ni and intensive evolution of gas eous CO and SiO are initiated. The Nb and Ta content in the compact increases proportionally to the extent of vaporization of the lower Nb oxides, whose appreciable volatilization begins at 1700 deg C. Within the temperature range 1800 to 2200 deg C the major part of the Fe, Ni, and Nb/sub m/O/sub n/, is eliminated. This range is critical, a rapid temperature increase in this range resulting in the formation of blisters and blowholes. At temperatures above 1800 to 2000 deg C a noticeable removal of nitrogen is observed as the result of decomposition of Nb nitride; the most intensive removal occurs at 2250 deg C. Although at temperatures above 2000 to 2300 deg C the amount of Nb/sub 2/C and NbO/sub 2/ decreases considerably, additional holding at higher temperatures is required to remove the remainder of O, Ni, and Fe. Thus, up to ~ 1750 deg C the temperature can be raised rather rapidly; between 1750 and 2000 deg C it must be raised much more slowly, and still more slowly between 2000 and 2300 deg C. At 2000 deg C the compacts should be held for 0.25 to 2 hrs, depending on their dianmeter, and at 2300 deg C for 4 to 5 hrs. The total time of temperature increase to 2300 deg C for small specimens (5 x 5x 120 mm) is 2 to 2.5 hrs and for large ones (20 x 20 x 600 mm), 10 to 11 hrs. The latter period can be decreased to 6 to 8 hrs when a purer powder is used. Under optimunm conditions ductile metal is obtained in spite of an increased content of impurities. (OTS)

• Research Organization: Originating Research Org. not identified
• NSA Number: NSA-16-013557
• OSTI ID: 4786313
• Journal Information: Tsvetnye Metally, Journal Name: Tsvetnye Metally Vol. Vol: 35: No. 2
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

CARBON MONOXIDE
CHEMICAL REACTIONS
DECOMPOSITION
DEFECTS
DUCTILITY
HIGH TEMPERATURE
IMPURITIES
IRON
METALS, CERAMICS, AND OTHER MATERIALS
NICKEL
NIOBIUM
NIOBIUM CARBIDES
NIOBIUM NITRIDES
NIOBIUM OXIDES
POWDERS
QUANTITY RATIO
REFINING
SILICON OXIDES
SINTERED MATERIALS
SINTERING
TANTALUM
TEMPERATURE
VACUUM
VAPORS