The compounds of Niobium
1. Niobium Oxide: the most valuable applications of Niobium Oxide is Nb2O5. Niobium Pentoxide is a kind of white powder, it is odorless and tasteless, the specific gravity of it is 4.55 g/cm3, and the melting point of it is 1512 ℃. With obvious acidic, it is insoluble in water and also insoluble in most of the acids and alkali. But it can be slowly dissolved in hot hydrofluoric acid and peracetic acid, with alkali fusion, can generate Niobate.
Niobium suboxide has NbO2, NbO and Nb2O. Nb2O is a kind of black powder, insoluble in acid or oxidizer at a cold state. When it is heated, Nb2O is a kind of strong reducing agent, such as the reduction of NO at 210 ℃, the reduction of SO2 at 320 ℃ and the reduction of CO2 at 900 ℃.
2. Niobium Halide: NaCl5 is a kind of yellow powder, the melting point of it is 209.5 ℃, the boiling point of it is 2540 ℃, and the specific gravity of it is 2.77 g/cm3, it is volatile, has strong moisture absorption, and easy to parse out the white water hydroxide precipitation. In addition to high-priced NbCl5, Niobium low chloride has NbCl4 and NbCl3 and so on, they are all volatiles.
3. Niobium Carbide: the mainly Niobium Carbide are Nb2C, NbC and Nb4C3. NbC is a kind of brown powder, the melting point of it is 3500 ℃, the boiling point of it is 4300 ℃, and the density of it is 7.82 g/cm3. It has good chemical stability, can only be dissolved in a mixed solution of nitric acid and hydrofluoric acid. When the temperature is below 1000 to 1100 ℃, it is not easily oxidized in the air. In the effect of nitrogen or ammonia, it is easy for it to generate Nitride. Niobium Carbide is a kind of hard refractory compound, it is widely used in the cemented carbide.
4. Niobium Hydride: the Niobium Hydride is very stable when it at a room temperature in air. When it is in a high vacuum and heated to 1000 to 1200 ℃, decomposition of hydrogen evolution.
5. Niobium Nitride: there are three kinds of Niobium Nitride: NbN, Nb2N, Nb4N3. NbN is a kind of light gray powder with yellow luster, the melting point of it is 2050 to 2320 ℃, and the density of it is 8.4 g/cm3. It is insoluble in nitric acid, hydrofluoric acid and sulfuric acid, but is soluble in hot alkaline solution and release the ammonia or nitrogen.
6. Niobium Boride: there are NbB and NbB2 of Niobium Boride. The melting point of NbB is 2000 ℃, and the density of it is 6.9 g/cm3. And the melting point of NbB2 is 3050 ℃, and the density of it is 6.4 g/cm3, it cannot be eroded by hydrochloric acid and aqua regia, but can be slowly decomposed by hot sulfuric acid and hydrofluoric acid.
7. Niobium Selenate: Niobium Diselenide ( the chemical formular of it is NbSe2) is a kind of dark gray powder with metallic luster, the density of it is 6.28 g/cm3. It has high chemical stability, in addition to concentrated nitric acid, it has a good stability on the other acids, alkali and organic solvents, does not absorb moisture in the air, has good abrasion resistance.
8. Niobium Silicone: the main silicide of Niobium is NbSi2, there are also some other compounds such as Nb4Si and Nb5Si3. The melting point of NbSi2 is 1930 to 1950 ℃,and the density of it is 5.29 g/cm3.
9. Niobate: the most important salts of Niobate are Niobate Potassium and Sodium.
10. Niobium intermetallic compound: most Niobium intermetallic compounds are superconducting compounds, such as a binary compound Nb3Sn, Nb3Al, Nb3Ga, Nb3Ge and ternary compound Nb3(Al, Ge) and so on.
11. Niobium organic complex compound: Niobium organic complex mainly are Niobium Oxalate and Tannic Acid complexes.
12. Niobium Organic Alkoxide: Niobium Alkoxide pentavalent is highly volatile, these alkoxide can be distilled without decompose under the pressure of 6.67 to 1333Pa.