Nb - Niobium (Columbium)
|Chemical Element||Niobium (Columbium)||Melting Point °C||2468|
|Chemical Symbol||Nb||Boiling Point °C||4742|
|Atomic Number||41||Density g/cm3||8.6|
Niobium is a shiny, steel-grey metal, which is soft when pure. It is a member of Group 5 of the Periodic Table and is the 33rd most abundant element within the Earth’s crust. It reacts with the air to form a tough niobium oxide layer that makes the remaining metal resistant to corrosion. The metal is inert to acids at room temperature. However, it is attacked by hot, concentrated acids, and especially by alkalis and oxidising agents. Niobium has very similar chemical properties to that of the element directly below it in the Periodic Table, tantalum. These two elements are always found together, their chemical similarities make it difficult to isolate pure niobium without contamination by tantalum.
Niobium was discovered by English chemist Charles Hatchett in 1801, whilst he was working with a sample of columbite owned by the British Museum in London. Hatchett was able to deduce that this mineral contained a new element, despite the confusion caused by the similarity that this new element has to tantalum and the resultant difficulty in differentiating the two. Hatchett named the element columbium, the poetic name for America. It was in 1844 when a German chemist, Heinrich Rose, renamed the metal to nobium, in honour of the Greek goddess of grief. He did this after proving that the mineral columbite contained both niobium and tantalum. It was not until 1864 that a sample of pure niobium was produced by the Swedish chemist Christian Wilhlem Blomstrand, but by this time Hatchett had already died, and never got to witness his discovery in its pure form.
Niobium and tantalum are mined together and mainly found in the mineral columbite, also known as niobite, the composition of which is approximately (Fe,Mn)(Nb,Ta)2O6, which can vary according to the proportions of the four metals that are present. Another mined mineral is pyrochlore, (Na,Ca)2Nb2O6(OH,F). Niobium and tantalum are separated by chemical means, such as solvent extraction. Brazil and Canada are the main locations of niobium mining and produce over 85% of niobium products, as well as Australia, with small amounts also produced as a by-product of tin smelting. Niobium is normally traded in the form of ferro-niobium with a nominal 60% niobium oxide content, for making high-strength, low-alloy steel.
Niobium consumption is dominated by high-strength, low-alloy steels used in automobiles, aircraft and pipelines. Other uses for niobium include heat-resistant and stainless steels for the petrochemical industry, together with cutting and machining tools, well casings and drill pipes. Small amounts of niobium are also added to super-alloys for jet and rocket engines and industrial gas turbines. Although in the future the demand for niobium is likely to increase, at present supply shortages seem highly unlikely.