Title: MELTING POINTS AND OTHER PARAMETERS OF THE LOWER OXIDES OF NIOBIUM
Abstract: The melting point, microstructure, electric conductivity, and oxidation of lower oxides of niobium were studied with prepared specimens containing O.O4to 0.06 wt.% C and 0.03 wt.% N and composition of NbO/sub 0.9//sub 5/, NbO/sub 1.0// sub 1/, and NbO/sub 1.0//sub 2/ in a homogeneous niobium oxide. The melting point for niobium monoxide was found at 1935 deg C and for niobium dioxide at 20S0 deg C. Evaporation of niobium monoxide and dioxide begins at 1700 deg C. All monoxides evaporated after 4 hours at 1850 deg C, and 45 wt.% of dioxide evaporated. After 8 hours all dioxide evaporated. Microhardness of niobium monoxide with in homogeneous oxide limits is 1930 kg/mm/sup 2/; the eu tectic microhardness is 794 kg/mm/sup 2/ at 50 g load. The microhardness of niobium dioxide is 1720 kg/mm/sup 2/; however, the latter is not accurate as cracks were observed later. The niobium monoxide exhibits metal-type electric conductivity, while niobium dioxide is a semiconductor. After 6 hours heating at 100, 150, 200, 225, 250, and 275 deg C, the content of oxygen was not changed, while in niobium dioxide it slightly increased at 275 deg C, and at 150 deg C the surface of the monoxide andmore » dioxide dust particles became yellow. At 200 deg C they acquired a bronze color. After 6 hours at 300 deg C both the monoxide and dioxide of niobium oxidized into niobium pentoxide. (R.V.J.)« less
Publication Year: 1961
Publication Date: 1961-02-01
Language: en
Type: article
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