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niobium, English name: niobium, element symbol: Nb, atomic number 41, is VB group metal. Niobium has a density of 8.57g/cm³, a melting point of 2477°C and a boiling point of 4744°C. Niobium is a silver-gray, soft and malleable rare high melting point metal. At room temperature, niobium does not react with air and will not be completely oxidized when red hot in oxygen. Niobium can combine directly with sulfur, nitrogen and carbon at high temperature. Niobium does not react with inorganic acids or bases and is insoluble in aqua regia, but soluble in . The content of niobium in the crust is 20 ppm, and the distribution of niobium resources is relatively concentrated. Because of its good superconductivity, high melting point, corrosion resistance, wear resistance and other characteristics, niobium is widely used in steel, superconducting materials, aerospace, atomic energy and other fields.
About 85% ~ 90% of the world's niobium is used in iron and steel production in the form of niobium. Adding only 0.03% ~ 0.05% niobium to steel can increase the yield strength of steel by more than 30%. Niobium can also achieve the dispersion distribution of precipitates by inducing precipitation and controlling the cooling rate, and adjust the toughness level of steel in a wide range. Therefore, adding niobium to steel can not only improve the strength of steel, but also improve the toughness, high temperature oxidation resistance and corrosion resistance of steel, reduce the brittleness transition temperature of steel, so that steel has good welding performance and forming performance.
Superconducting materials industry
Some compounds and alloys of niobium have high superconducting transition temperature, so it is widely used in the manufacture of various industrial superconductors, such as superconducting generators, accelerator high-power magnets, superconducting magnetic accumulators, nuclear magnetic resonance imaging equipment, etc. At present, the most important superconductors are niobium-titanium and niobium-tin, which are widely used in magnetic resonance imaging apparatus for medical diagnosis and nuclear magnetic resonance apparatus for spectral line analysis.
Aerospace industry
The aerospace industry is the main application field of high purity niobium, mainly used in the production of rockets, spacecraft engines and heat-resistant components. Niobium and tantalum alloys have good thermal strength, thermal resistance and processing properties, and are widely used in the manufacture of aircraft engine parts and gas turbine blades. In the United States almost all jet fighters engine thermal components are made of niobium alloy.
Atomic energy industry
Niobium is a very suitable material for nuclear reactors because of its good thermal conductivity, high melting point, good corrosion resistance and low neutron capture cross section. The main uses of niobium in the atomic energy industry include: cladding material for nuclear fuel, alloy for nuclear fuel, structural material for heat exchangers in nuclear reactors.
Electronics industry
Niobate ceramics can be used to make capacitors, lithium niobate, potassium niobate and other compound single crystal is a new type of optoelectronics and electronics crystals, with good piezoelectric, thermoelectric and optical properties, is widely used in infrared, laser technology and electronics industry. In addition, niobium has a high melting point, strong ability to emit electrons, and has the ability to inhale, which can be used to make vacuum tubes and other electric vacuum devices.
Medical field
Niobium has good resistance to physiological corrosion and biocompatibility, will not occur with a variety of liquid substances in the human body, and almost will not damage biological tissue, for any sterilization method can adapt, so often used in the manufacture of bone plate, skull plate bone screw, implant root, surgical equipment, etc.
Other applications
In the chemical industry, niobium is a high quality acid resistant and liquid metal corrosion resistant material, can be used to make digesters, heaters, coolers and so on. In addition, niobic acid is also an important catalyst.
Niobium is also used in the foundry industry, its main role is to form hard carbide (good for wear) and change the shape and size of graphite sheet, so it is often used in the manufacture of automobile cylinder caps, piston rings and brake pads. In addition, niobium is sometimes used in commemorative coins along with gold and silver.
Niobium is also used in the manufacture of lenses in the optical industry because it helps to increase the transmittivity of lenses.
Niobium can also be applied to the lighting industry. For example, the alloy of niobium and 1% zirconium can be used to make the precision support of high efficiency and high strength sodium vapor street lamps, so that these small parts have high thermal strength, excellent formability and corrosion resistance of sodium vapor.
Niobium preparation method
The main production methods of niobium metal include the production of niobium by carbothermal reduction, the production of niobium by thermite reduction and the production of niobium powder by sodium thermal reduction, followed by the production of niobium powder by molten salt electrolysis and the production of niobium halide reduction.
Vacuum carbon reduction process
Vacuum carbon reduction is one of the main methods of niobium production at home and abroad. Carbon reduction is generally carried out in vacuum carbon tube furnace. The affinity of carbon to oxygen is greater than that of niobium to oxygen, and carbon is used as reducing agent to reduce Nb2O5 to produce niobium strips. Its advantages are high yield (> 96%), cheap reducing agent, low production cost, no sodium reduction method of by-products need wet treatment, can obtain high purity niobium strip and metal powder.
There are direct carbon reduction and indirect carbon reduction processes in industry. The niobium produced by direct carbon reduction is sponge-like, with large surface area, low content of metal impurities and nitrogen, which is conducive to the specific capacity of niobium powder. Therefore, the process is suitable for the production of capacitor grade niobium powder. Indirect reduction is characterized by large production capacity of equipment, stable process, the metal niobium strips are compact, the shape size is more regular, suitable for making niobium strips, niobium ingot and niobium processing materials.
Production of niobium by vacuum carbon reduction
Thermite reduction process
Thermite reduction is usually done outside the furnace. The reduction smelting reaction is carried out in a vessel without external heating. After the reaction is completed, the vessel is removed, the product is taken out, and the metal and slag are separated outside the furnace. The metal niobium produced by thermite reduction contains more aluminum, aluminum and other impurities can be removed by vacuum heat treatment (1800ºC), electrolytic refining and electron beam furnace melting. After two electron beam furnace melting, niobium can reach high purity. Thermite reduction does not need vacuum conditions, the equipment is simple, but the product purity is low, niobium aluminum content is high, need to be further purified through electron beam melting to remove impurities.
Production of niobium by thermite reduction
Sodium thermal reduction method
Niobium is rarely used in the manufacture of capacitors, so the sodium reduction method is rarely used.
electrolysis
The electrolysis method of niobium has two methods: molten salt electrolysis and water solution electrolysis. The equipment used for producing niobium powder by molten salt electrolysis is simple and the production cost is low.
Nitriding process
In addition to the above methods, niobium has been produced by nitride process in recent years. This method takes niobium oxide or ferric niobium as raw material and reacts with ammonia, nitrogen and carbon to produce niobium nitride. Niobium nitride is then decomposed into niobium metal under vacuum and temperature of 2103 ~ 2373K.
Niobium refining
Niobium powder, sponge niobium or brittle niobium strips can be prepared by reducing niobium compounds, but these niobium products also contain a certain amount of impurities, among which hydrogen, oxygen, nitrogen and other impurities are especially easy to make niobium brittle, so it needs to be further removed. The main purposes of niobium refining are purification and densification, and these two processes are generally completed simultaneously in industrial production.
Because of the strong affinity of niobium to oxygen and carbon, it is not possible to use containers made of oxygen and carbon materials, and must be carried out under high temperature and high vacuum conditions, which not only complicates the refining process, but also requires high equipment. The main refining methods for niobium are vacuum sintering method, such as niobium vacuum sintering method refining, arc melting method, such as niobium vacuum arc melting, electron beam melting, such as niobium electron beam melting. Electron beam melting has the best purification effect and is widely used. In order to obtain the best refining effect, several refining methods are often used, such as sintered niobium strips, and then electron beam melting.
Niobium industry standard
The latest price of niobium the latest market of niobium buyers of niobium sellers of niobium
GB/T 6896-2007 National standard for niobium strips
GB/T 7737-2007 iron niobium
GB/T 27688-2011 National standard for niobium and niobium alloy scrap
GB/T 24485-2009 National standard for niobium carbide powder
GB/T 7737-2007 National Standard for iron niobium
YS/T 548-2007 National Standard for high purity niobium pentoxide
XB/T 617.5-2014 NdFeb chemical analysis methods Part 5: Determination of zirconium, niobium, molybdenum, tungsten and titanium amount inductively coupled plasma atomic emission spectrometry method to be implemented
GB/T 14842-2007 Niobium and niobium alloy bars
GB/T 3630-2006 Niobium sheet, strip and foil
YS/T 258-2011 niobium powder for metallurgical use
YS/T 428-2012 Niobium pentoxide
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