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Rhenium is a real rare and dispersed element in rare metals

Rare and scattered means the rhenium content is rare and dispersed in the crust; refractory means high melting point of rhenium metal, up to 3180°C, second only to tungsten, ranking second in all metals.

Due to its excellent compound properties of catalytic activity, high temperature and corrosion resistance and so like, it is mainly used in the fields of oil refining catalysts, thermoelectric superalloy, electronic valve structures, special aerospace alloy and environmental protection and so on.

Rhenium, as a member of manganese subgroup, was predicted its existence earlier when Mendeleev established the periodic system of elements, and called dwi-manganese, and another member of this group that was also not found at that time was called eka-manganese. Moseley later identified the atomic number of those two elements as 75 and 43 respectively. An unknown element can often be found from the minerals of elements that are similar to it, so scientists had been dedicated to finding those two elements from manganese ore, platinum ore and niobium iron ore (tantalum and niobium minerals). Until 1925, W. Noddack, I. Noddack-Tucker and OC Berg of German found the element rhenium when analyzing niobium manganese iron ore with spectrometry and named it, which comes from the Latin word Rhenus, meaning Rhine River. Noddack discovered later rhenium existed mainly in molybdenite, and extracted the metal rhenium from molybdenite. Because Rhenium resource is rare and expensive, there are fewer studies on it for long time. After 1950, rhenium began to be applied in modern technology, showing a growing production output. China has begun to extract rhenium from the molybdenum concentrate roasting dust and put in industrial production since 1960s, and now has been one of rhenium production and application powers.

Rhenium is 0.001 × 10-4% of content in the crust, and one of the few non-ferrous metal reserves on Earth. The world's known economic reserves in places is about 2500t, and the resource quantity is 10000t, mostly in Chile, the former Soviet Union, and Canada and other regions. The current available reserves of rhenium is 237t in China. The rhenium yield is less, only 30-50t of the world's annual output in recent years, while the consumption of rhenium has steadily increased with the rapid development of advanced materials technology.

Properties of rhenium

Physical properties of rhenium
Rhenium is a very hard, silver-white metal, looks just like platinum, but pure rhenium powder is generally gray. The physical properties of rhenium are very similar to that of refractory metal molybdenum and tungsten in VII group of the periodic table, and sort of similar to platinum group metals, especially platinum, ruthenium and osmium. Rhenium is a refractory metal, with melting point of 3180°C, second only to tungsten, and same to molybdenum and tungsten that are good refractory metals. Rhenium has a big specific gravity, but the relative density is 21.03g/cm3, only lower than platinum, iridium and osmium. This property makes rhenium the densest metal other than platinum group metals, with great hardness, wear resistance and corrosion resistance. Rhenium has a very high mechanical strength. Rhenium alloy wire thinner than a human hair is able to withstand more than seven kilograms of gravity. In addition, rhenium has other electrical properties such as high resistance, with resistivity 3.84 times to tungsten. Its modulus of elasticity and mechanical properties are similar to iron. Natural rhenium consists of two isotopes Re187 and Re185. Re187 is radioisotope, accounting for 62.6% in natural rhenium; Re185 is non-radioactive isotope, accounting for 37.2%. The half-life of Re187 is 43 million a, emitting very weak radiation that can not wear through the skin or harm to the human body.

Chemical properties of rhenium
Rhenium is stable in chemical properties, highly corrosion-resistant, free of being oxidized in air, and strongly resistant to the corrosive effect of acids and bases. Rhenium is stable at room temperature, and begins to be oxidized from 300°C. At high temperature, rhenium can generate rhenium disulfide with sulfur vapor, and generate halides with fluorine, chlorine and bromine. Rhenium is insoluble in hydrochloric acid, and soluble in nitric acid and hot sulfuric acid to generate high rhenium acid (HReO4). Rhenium has a strong affinity to oxygen. Its oxidation state are + 1, + 2, + 3, + 4, + 5, + 6, + 7, and its oxides are Re2O, Re2O3, ReO2, ReO3, Re2O7. High valence oxide of rhenium (Re2O7) is soluble in water, usually processed into stable salts such as ammonium perrhenate (NH4ReO4) and rhenium potassium (KReO4). Rhenium does not react with carbon, and is the only refractory metal element that does not generate carbide with carbon. The most prominent chemical property of rhenium is the high volatility of Re2O7, and easy to dissolve in water and oxygenated solvents. These two properties are used extensively in rhenium recove. Rhenium aqueous solution is acidic, and its electromotive force is between copper and thallium, therefore, iron and zinc can precipitate rhenium in aqueous solution.

Since rhenium having various excellent properties described above, it has become an important material in many fields of use. In the metallurgical industry, rhenium as an alloy additive elements can be improved to improve the properties of the alloy. For example, pure tungsten, pure molybdenum and at lower temperatures the situation will become brittle as glass, difficult processing technology, and thus use is limited. But adding the right amount of tungsten or molybdenum rhenium-rhenium alloy made of tungsten or molybdenum-rhenium alloy, it has a good plasticity, it can be processed into a variety of structural materials, but also to maintain high hardness, high strength and high temperature and other characteristics. Many parts of the US manned spacecraft is to use this type of rhenium alloy. Add a small amount of chromium-nickel alloys rhenium, melting point and can greatly improve the strength of the alloy, this alloy made parts, its life may be extended several times to several times.

Rhenium is used as the main catalyst for the oil industry, and high-temperature alloys and superalloys additive elements, pure rhenium products for high temperature components under particularly harsh working atmosphere. Rhenium metal plating (such as space technology for tungsten surface plating rhenium) can increase wear and corrosion resistance. Rhenium wire plated or rhenium tungsten filament and the cathode tubes used in argon or nitrogen containing traces of moisture are more durable than tungsten. Rhenium has high temperature stability and strong anti-electrical erosion ability in electric arc, so rhenium-tungsten alloy can be used in work of electrical contact points, its performance can be compared with platinum, ruthenium products.

Rhenium has a high electron emission performance, widely used in radio, television and vacuum technology. Rhenium has a very high melting point, is a major instrument of high temperature materials, tungsten-rhenium thermocouples at 3100 ℃ do not soften. Rhenium, tungsten or molybdenum is added to form an alloy increases the ductility. Rhenium and rhenium alloys can be made tube elements and ultra-high temperature heater to vaporize the metal. Rhenium is used in rockets, missiles, high temperature coating, instruments and spacecraft with high temperature components such as heat shields, arc discharge, electrical contacts and so need rhenium.

Effects of rhenium - rhenium alloy
Rhenium is added a substantial increase in tungsten, molybdenum, chromium strength and plasticity, people called this "rhenium effect." Add a small amount (3% to 5%) of the tungsten rhenium enables the recrystallization starting temperature 300 ℃ ~ 500 ℃. Tungsten, rhenium and molybdenum-rhenium alloy has good high temperature strength and plasticity, can be processed into plates, sheets, wire, wire, rod, used in aerospace high temperature structural member (orifice, nozzle, heat shield, etc.), an elastic element, electronic components, etc., can also be used to make heating elements, parts, light bulbs, X-ray equipment and medical devices. W-Re-ThO2 alloy can be used as high-temperature heating of the workpiece, tungsten, rhenium and molybdenum-rhenium alloy contacts with high thermal conductivity and high-temperature corrosion, can improve the service life and reliability of power supply equipment. Such as: platinum-rhenium alloy; platinum-tungsten-rhenium alloy; tungsten-rhenium alloy; molybdenum rhenium alloy.
Rhenium expensive in the application use of rhenium-containing alloy, the most widely tungsten-rhenium and molybdenum-rhenium alloy use. Rhenium tungsten-rhenium alloy containing 1% to 26%, molybdenum-rhenium alloy containing rhenium content of 11% to 50%. There is also W-33.3Mo-33.3Re, Mo-Re-Hf-Zr, Mo-Re-Hf-V alloys, tungsten, rhenium and nickel radical pluralism superalloys, etc., after several alloys with high strength and high temperature performance, the key components used in aerospace equipment.

Whose electronic structure of rhenium unsaturated 4d layer 5 is easy to emit electrons, and the two layers 6s and ease of electrons involved in the action of forming a covalent bond, with its larger lattice parameters and other characteristics, the rhenium and compounds having excellent catalytic activity, as a catalyst for the petrochemical industry is one of its main uses conventional. Such as for oil reforming Pt-Re / Al2O3 catalyst, but with other inexpensive alternatives such as platinum - tin catalyst occurs, although its performance a bit weak, but rhenium application in this field is still reduced. In addition, the production of unleaded petrol and rhenium can be used as automobile exhaust purification catalyst; rhenium sulfide as cresol and lignin and other hydrogenation catalysts; NH4ReO4 / C is used as dehydrogenation of cyclohexane and ethanol dehydrogenation catalyst; KReO4 , / SiO2 is a series of hydrogenation catalyst; Re2O7 is to make the conversion of SO2 to SO3, and to make a good catalyst HNO2 conversion of HNO3.

Defense, aerospace industry
Rhenium is one of the hardest melting metal having a melting point up to 3180 ℃ ,, after the tungsten 3410 ℃. The rhenium and other metals can be prepared by a series of high temperature, corrosion, wear-resistant alloys, such as Re25-W was a space station nuclear reactor materials, was developed to better performance Re30-W-Mo30 alloy; Re-Pt with structural materials for nuclear reactors, high temperature resistant hot body download corrosion 1000 ℃, can also be radiation shield; Re-Mo alloy to 3000 ℃ still have high mechanical strength, can be used to manufacture supersonic aircraft and missile parts of high temperature and high strength and as a heat shield. Particularly for jet engine turbine blades and turbine thermal power machine material nickel-base superalloys containing rhenium successful development (rhenium 3% -7%, the melting point up to 3180 ℃ above) and used in fighter aircraft and firepower generators, the US, Western Europe, increase the amount of rhenium, rhenium also makes the sharp increase in world consumption. In recent years, the amount of rhenium alloys in terms of the amount of the catalyst has exceeded its terms, superalloys has become their most important applications.

Temperature, heating components and temperature measurement
Re3-W and Re25-W alloy wire thermocouple produced good linear relationship between temperature and thermal electromotive force, accurate temperature measurement, wide measuring range (0-2485 ℃). Thermal electromotive force reaches 1012mV, much higher than Pt-Rh / Pt (at 1900 ℃ when only 30mV) is high, use in a vacuum or inert gas medium can be temperature to 2700 ℃, and the price is cheaper than the Pt-Rh / Pt thermocouple . Re28-W / W thermocouple temperature to 2760 ℃, Mo-Re thermocouple temperature to 3000 ℃.
Heating element rhenium alloy production base than tungsten or molybdenum of 5-10 times longer life; working life under high temperature Re8-12-Ni-Cr than the Ni-Cr alloy heating element 9 times higher, and has a high temperature and normal outstanding advantages to work under pressure; Tim rhenium Rh-Ir Rh-Ir representing both increased strength and improved mechanical properties, used in aerospace and missiles. Rhenium based alloys can also be produced at high temperatures without deformation both sensitive spring for high temperature measurement instruments are necessary. Rhenium as the absorption of solar energy in the photosensitizing dye solar cells has broad application prospects.

electronic industry
Rhenium alloy or coating material with tungsten, molybdenum, or platinum group consisting of, because of its high melting point, resistance, good magnetic intensity and environmental stability and is widely used in the electronics industry. 3% -20% Re-doped tungsten or tungsten wire coating H4ReO4, neither as brittle as tungsten, but also improve their elongation and resistance, with high shock and vibration performance, so in vacuum technology and electronics or filament vibration-prone places shows its important uses such as X- ray target, flash, sonographer, high vacuum quick start measuring voltage parts, aircraft rhenium tungsten filament bulbs, color TV with heaters. Re-Pt, Re-Ag, Re-Cu, Re-Cu-Zr, etc. have been substituted for platinum in Electrical switches, key, and an arc current cut-discharge shielding member or the contact elements, having the advantage of reliable and durable. Molybdenum and Rhenium cermet anode practical application. In recent years, one kind of rhenium-based composite material as a base material is applied to the emitter of ultra-high temperature, the thermal electron discharge effect increased by 20%, the current density increases, improving the heat discharge performance.

Coating and welding materials
The use of a high melting point and rhenium Premium corrosion wear characteristics as coatings, such as rhenium-coated metal wire, sheet or tube, the compound can achieve anti-acid, alkali, seawater or sulfur etching purposes, it is used for Re-NiRe-Mo or R-W is used as instrument components, engines and rocket warheads coating; marine and chemical sectors.
Adding to Re W or Mo alloy, both to increase its strength, but also to improve its plasticity and weldability, can be used as electrode welding device with a W or Mo.

Other uses
Medical radioactive rhenium - amino acid compounds to treat cancer, KReO4 can be used for preparing color photographic film sensitizing agent.

Rhenium minerals are rare, only ReS2 and CuReS4. Rhenium is mainly accompanied with molybdenum, copper, lead, zinc, platinum and niobium minerals. Molybdenite that contains rhenium mineral and has economic value contains rhenium generally from 0.001% to 0.031%. However, the molybdenum concentrate processed from porphyry copper contains rhenium up to 0.16%. The main raw materials to produce rhenium are by-products in molybdenum smelting process. Rhenium can be recovered from some copper ore, platinum group ore and niobium ore, even sphalerite smelting slag, dust and processing low-grade molybdenite waste.

Rhenium is 0.001 × 10-4% of content in the crust, and one of the few non-ferrous metal reserves on Earth. The world's known economic reserves in places is about 2500t, and the resource quantity is 10000t, mostly in Chile, the former Soviet Union, and Canada and other regions. The current available reserves of rhenium is 237t in China. The rhenium yield is less, only 30-50t of the world's annual output in recent years, while the consumption of rhenium has steadily increased with the rapid development of advanced materials technology.

Rhenium is closely related to the development of market demand and high-tech industries. As a strategic material, rhenium major consuming countries is the United States, Western Europe, Japan and other developed countries and the military power of Russia. In recent years, total annual world consumption reached 40t, and increasing year by year. Wherein due to the better economic situation in Europe, consumption increased rapidly, and its annual consumption by the 2-3t to almost 10t. US annual consumption of rhenium is maintained at 20-25t. Rhenium consumption in Japan, but also with the recovery of economic growth of about 2-3t / a scale, mainly for electronic materials such as automotive exhaust gas sensor Re-W wire, thin film electrodes and other integrated circuits. Russia's annual demand of about rhenium 5t.

Chile is the world's largest supplier of rhenium, which accounted for more than 60% of US imports of rhenium raw materials market; rhenium production in other countries are the United States, Russia, Germany, Kazakhstan, China and so on.

Due to the recent rapid increase in resource utilization technology, the amount of rhenium is recovered from spent catalysts showed steady growth, while the native production of rhenium also has expanded each year, although it is the world's yearly consumption of rhenium, rhenium but the price is still relatively stable.