Niobium is a rare high melting point metal. The melting point is 2467 degrees, the density is 8.6g/cm3, and the lattice type is body-centered cubic. The coefficient of linear expansion (0~100 C) is 7.1 x 10-6. Adding a small amount of niobium into a steel can greatly improve the strength of steel, improve the mechanical and welding properties of steel, and improve its corrosion resistance. Niobium can be used as a capacitor and niobium based superalloy. FS - 85 alloy is a structural material for the orbiting engine on the shuttle. C - 103 alloy can be used as a rocket nozzle material. Other niobium alloys, such as Nb - Zr, Nb-Ti, Nb-Ti - Ta, can be used as superconducting materials, and are widely used in magnetic resonance medical human images. Niobium-based compounds and complexes can be used as catalysts to remove pollution, selective oxidation and hydrogenation.
Niobium oxide
The most valuable application of niobium oxide is Nb 2O 5. Nb 2O 5 is a white powder, tasteless, odorless, specific gravity 4.55g/cm3, melting point 1512 degrees. It has obvious acidity, insoluble in water and insoluble in most acids and bases, but it can be dissolved slowly in hydrofluoric acid and peroxy acid.
Nb2O5 has three varieties of alpha, beta, and gamma, producing low temperature variant alpha -Nb 2O 5 at 800-900 C, producing medium temperature variant beta -Nb 2O 5 at 1000-1150, and producing high-temperature variant gamma -Nb 2O 5 at 1200-1250 C. The lattice constants, density and other properties of oxides with different variants are distinctly different.
Low valence oxides of Nb have NbO 2, NbO and Nb 2O. Nb2O is a black powder, which is insoluble in acid or oxidant in cold state. When heated, Nb 2O is a strong reducing agent, such as reducing NO at 210 C, reducing SO 2 at 320 C and reducing CO 2 at 900 C.
Niobium halide
NbCl 5 is a yellow powder with a melting point of 209.5, a boiling point of 2540 degrees C, a specific gravity of 2.77g/cm3, easy to volatilize, and a strong hygroscopicity. It is very easy for water to analyze white hydroxide precipitates. Besides high NbCl 5, the low valence chlorides of niobium are NbCl 4, NbCl 3 and so on. They are all volatile compounds. NbF 5 is a white crystal with a melting point of 78.9-80 C, a boiling point of 234.9 C, a specific gravity of 3.29g/cm3, and a strong hygroscopicity. In a weak acid solution (when the concentration of HF is below 7%), after the dissolution of NbF 5, NbOF 3 and H 2NbOF 5 are formed.
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