Niobium, chemical symbol Nb, atomic number 41, is a transition metal element. Niobium is a shiny gray metal. High-purity niobium metal has high ductility, but it becomes harder as the impurity content increases. Niobium has a low capture cross section for thermal neutrons, so it is quite useful in the nuclear industry.

Physical Properties

Niobium is a gray-white metal with a melting point of 2468℃, a boiling point of 4742℃, and a density of 8.57g/cm3. Niobium is a shiny gray metal with paramagnetism. High-purity niobium metal has high ductility, but it becomes harder as the impurity content increases. Its outermost electron layer arrangement is very different from other group 5 elements. The same phenomenon also occurs in the elements before and after ruthenium (44), rhodium (45) and palladium (46).

Niobium exhibits superconducting properties at low temperatures. At standard atmospheric pressure, the superconducting critical transition temperature Tc of niobium is 9.25K, the highest among all metals with superconducting properties. Its magnetic penetration depth is also the highest of all elements. Niobium is one of the three elemental type II superconductors, the other two being vanadium and technetium. The purity of niobium metal greatly affects its superconducting properties.

Niobium has a very low capture cross section for thermal neutrons, so it is quite useful in the nuclear industry.

Chemical properties

Niobium is stable in air at room temperature, and is not completely oxidized when red-hot in oxygen. It directly combines with sulfur, nitrogen, and carbon at high temperatures, and can form alloys with titanium, zirconium, hafnium, and tungsten. It does not react with inorganic acids or bases, nor does it dissolve in aqua regia, but is soluble in hydrofluoric acid.

Niobium metal is extremely stable in air at room temperature and does not react with air. Although it has a high melting point in its elemental state (2468°C), its density is lower than that of other refractory metals. Niobium can also resist various corrosion and can form a dielectric oxide layer.

Niobium is less electropositive than zirconium, which is located to its left. Its atomic size is almost the same as that of tantalum, which is located below it, which is caused by the lanthanide contraction effect. This makes the chemical properties of niobium very similar to those of tantalum. Although its corrosion resistance is not as high as tantalum, it is cheaper and more common, so it is often used to replace tantalum in situations with lower requirements, such as as a coating material in chemical tanks in chemical plants.

PRODUCT USES

Medical Applications

Niobium also plays an important role in surgical medicine. It can not only be used to manufacture medical devices, but also is a good "bioadaptive material".

Steel Applications

Among the various microalloying elements in steel, waste niobium is the most effective microalloying element. The effect of niobium is so great that the rich niobium atoms in iron atoms can achieve the purpose of improving the performance of steel. For example: the yield strength of ordinary medium carbon steel is generally 250MPa, and the addition of trace niobium can increase the strength to 350-800MPa.

Niobium as a microalloying element added to steel does not change the structure of iron, but combines with carbon, nitrogen and sulfur in steel to change the microstructure of steel. The strengthening effect of niobium on steel is mainly fine grain strengthening and dispersion strengthening. Niobium can generate stable carbides and carbonitrides with carbon and nitrogen in steel. It can also disperse carbides and form steel with refined grains.