History of Columbium / Niobium
Niobium, discovered in 1801 by C. Hatchett, an English Chemist in an ore called columbite, is a metal that is closely related to tantalum. It was originally thought that the material was chromium but upon analysis it was determined it was not chromium but an oxide of an unknown element. The element was named columbium but many scientists believed that it was actually tantalum and the element was not universally accepted. Fifty years later European scientists determined the element niobium came from tantalum and that columbium was the same element. The effort to change the name back failed however so we are left with the niobium designation used today. It offers similar corrosion resistance to tantalum but is formable, weldable, and easier to machine. However, neither niobium nor tantalum are considered to be easy to machine.
Applications of Niobium
Niobium’s combination of strength, melting point, resistance to chemical attack, and low neutron absorption cross-section promotes its use in the nuclear industry. It has been identified as the preferred construction material for the first reactors in the space power systems programs. As C-103 alloy, it has been used for rocket nozzles and exhaust nozzles for jet engines and rockets because of its high strength and oxidation resistance at a low weight. Recently, it has been gaining favor in its pure form for semiconductor equipment components and corrosion resistant parts. Niobium mill products are used in the fabrication of corrosion resistant process equipment including:
- reaction vessels, columns, bayonet heaters,
- shell and tube heat exchangers, U-tubes, thermowells
- spargers, rupture diaphragms, and orifices
- also, frequently used in pacemakers, artificial joints, dental implants and jewelry
Niobium is very similar to tantalum and several alloys are available in the arc-cast and wrought condition. It has the lowest melting point of all the refractory metals covered, the lowest modulus of elasticity and thermal conductivity, and the highest thermal expansion. It also has the lowest strength and lowest density of the refractory metals. This metal also has the low thermal neutron capture cross-section required for nuclear applications. Its high melting point warrants its use at temperatures above the maximum service temperatures of the iron, nickel and cobalt base metals. It has excellent ductility and fabricatibility. Pure niobium has a re-crystallization temperature range of 1800 to 2000°F (982° to 1093°C). Niobium offers nearly the corrosion resistance of tantalum and nearly the melting temperature of molybdenum. Yet its cost is about 1/6th that of tantalum and 25% more than molybdenum. Niobium was used as an alloy for many years. Nb/1% Zr was and still is used in nuclear reactors as the tubing for the fuel pellets because of its resistance to neutron bombardment. Niobium can be rolled, drawn, deep-drawn and formed at room temperature up to its maximum work hardening.
This metal is an ideal candidate as a lower cost alternative where tantalum is being considered. H. Cross Company supplies niobium in strip, ribbon, foil, sheet, rod, and wire forms.