Niobium (Nb)
Niobium (Nb), also known as columbium (Cb), is a hard, lustrous metal with an atomic number of 41. It is primarily found in the mineral niobite, with significant deposits located in countries such as Brazil, Australia, Canada, and the United States. This element has various industrial applications, notably in the manufacturing of steel where it is used to enhance toughness and strength. Approximately 78% of niobium's end use in the U.S. is in steel production, while the remaining 22% is utilized in superalloys and superconductors.
Niobium is characterized by its high melting point of 2,468° Celsius and its ability to resist tarnish, making it suitable for high-temperature applications. It plays a critical role in the production of vacuum tubes and superconducting magnets, which are essential in technologies such as maglev trains and experimental nuclear reactors. Discovered in 1801, niobium is named after Niobe, the daughter of Tantalus from Greek mythology, reflecting its historical connection to another element, tantalum, with which it is often found.
Niobium (Nb)
Where Found
Niobium is most often found as niobium pentoxide in the mineral niobite (also called columbite or tantalite), which in the United States is found in Colorado, Connecticut, Maine, North Carolina, South Dakota, and Virginia. This mineral is also found in Australia, Brazil, Canada, Madagascar, South Africa, the Democratic Republic of the Congo, Nigeria, Norway, and Russia.
Primary Uses
Niobium is used to toughen and harden steel. It is also used to make low- and high-temperature superconductors. In its Mineral Commodity Summaries (January, 2009), the U.S. Geological Survey reported that approximately 78 percent of U.S. end use of niobium is in manufacturing of steels, with the remaining 22 percent devoted to production of superalloys.
Technical Definition
Niobium (symbol Nb), or columbium (symbol Cb), has an atomic number of 41, an atomic weight of 92.9064, and sixteen isotopes. It is a hard, lustrous metal, gray or silver-white in color, malleable (capable of being bent or flattened), and ductile (capable of being stretched). It has a melting point of 2,468° Celsius, a boiling point of 4,742° Celsius, and a specific gravity of 8.4.
Description, Distribution, and Forms
Niobium is named for Niobe, the mythical daughter of the Greek god Tantalus. The designation niobium was officially adopted by the International Union of Pure and Applied Chemistry in 1949. However, an alternative name, columbium, is still used by many metallurgists in the United States and, to a lesser degree, England.
History
Niobium was discovered by the English chemist Charles Hatchett in 1801, and it was first prepared in 1864 when Christian Wilhelm Blomstrand of Sweden isolated it from niobium chloride by reduction in a stream of hydrogen. Niobium is easily welded and resists tarnish. It exhibits a variable valency of +2, +3, +5, and possibly +4. At high temperatures, it reacts with oxygen, carbon, nitrogen, sulfur, chlorine, fluorine, bromine, iodine, and other nonmetals.
Obtaining Niobium
Niobite forms in pegmatite (exceptionally coarse-grained igneous rocks typically made of granite), often with tin and tungsten minerals. Ores of niobium are also sometimes found in placer deposits. Niobium is rarely found without a similar element called tantalum. Eighty-five percent of all niobium reserves are located in Brazil. The element niobium is extracted from niobite by reducing the complex alkali fluoride with sodium, or the oxide with calcium, aluminum, or hydrogen.
Uses of Niobium
Because niobium has excellent gas-absorbing qualities and a high melting point, it is used in the manufacture of vacuum tubes. Niobium is used as an alloying agent in carbon and alloy steels. In the preparation of stainless steel, it is used to prevent corrosion at high temperatures and to permit fabrication without added heat treatment. Niobium adds strength, toughness, and ductility to chrome steel. Niobium alloys are used in jet and rocket engines. In the form of a carbide, niobium is used in making cutting tools. Combined with selenium and hydrogen, it forms a low-temperature superconductor (a material that can conduct electricity without any resistance), which is used in the construction of superconducting magnets. Applications include monorail trains, where the tracks are made of superconductor material and the trains are magnetized and glide along without any resistance. It is also combined with other elements to form high-temperature superconductors. Since niobium allows neutrons to pass through it without interference, it is used in nuclear reactors, particularly in the walls of experimental fusion reactors.
Bibliography
Natural Resources Canada.
U.S. Geological Survey.