The mysterious strategic metal - molybdenum
In nature, molybdenum mainly exists in the form of molybdenite (MoS2).Natural molybdenite is a soft black mineral, and while molybdenite has been used since ancient times, it is indistinguishable from lead, galena and graphite.The word "molybdos" means lead in Greek.Until the late 18th century, both were sold as molybadenite in European markets.
In 1779, scheele noted that lead or graphite were two distinct substances from molybadenite.He found that nitric acid had no effect on the graphite and reacted with molybadenite to obtain a white powder.It is boiled with an alkali solution and crystallized to form a salt.He thinks the white powder is a metal oxide (actually molybdenum oxide);It was mixed with charcoal and heated at high temperature to obtain no metal, but the original molybadenite was obtained after co-heating with sulfur.
In 1782, a close friend of scheele's, a Swedish mine owner named elmore, burned a mixture of charcoal and molybdic acid mixed with flaxseed oil in an airtight process to separate the metal from molybadenite and named it molybdenum, with the element symbol Mo.China translates it as "molybdenum."It was recognized by bezirius, a famous Swedish chemist who had discovered cerium, selenium, silicon, tantalum and thorium.
Molybdenum burns in the air, giving off a golden glow;Molybdenum ions with different oxidation states have different colors.It was not until 1893, more than 100 years after the discovery of molybdenum, that m. moisson smelted a mixture of carbon and molybdenum trioxide in an electric furnace and obtained for the first time a cast metal containing 92 to 96 percent molybdenum.
Although the discovery of molybdenum has a history of more than 200 years, the large-scale exploitation and utilization of molybdenum is still a matter of this century especially in recent decades.
Molybdenum and molybdenum alloys are widely used because of their many properties, such as high strength, low thermal expansion coefficient, excellent thermal and electrical conductivity, high corrosion resistance to molten glass, molten salt and molten metal, as well as the abrasion resistance of thin coatings.
Alloy steel, stainless steel, tool steel and cast iron are the main application fields of molybdenum.Adding molybdenum to stainless steel can improve its corrosion resistance.Adding molybdenum into cast iron can improve the strength and wear resistance of iron.Nickel base superalloy containing 18% molybdenum has the characteristics of high melting point, low density and small thermal expansion coefficient, etc.Molybdenum is widely used in electronic devices such as electron tubes, transistors and rectifiers.Pure molybdenum wire is used in high temperature electric furnace, edm and wire cutting.Molybdenum sheets are used to make radio and X-ray equipment.Molybdenum has been widely used in other alloys and chemical industry.Adding molybdenum to alloy steel can improve its elastic limit, corrosion resistance and permanent magnetism.Molybdenum oxide and molybdate are excellent catalysts in the chemical and petroleum industries.
Molybdenum disulfide is an important lubricant used in aerospace and mechanical industries.In addition, molybdenum disulfide, because of its unique sulfur-resistant properties, can catalyze the hydrogenation of carbon monoxide to produce alcohols under certain conditions, and is a promising chemical catalyst.
Molybdenum has also been gradually applied to nuclear power, new energy and other fields.
Molybdenum is also one of the essential trace elements for plants. Without it, plants cannot live.Molybdenum can be used as microelement fertilizer in agriculture.
All sorts of human body organization contain molybdenum, the gross of copper inside adult body is 9 milligram, in order to liver, kidney content is highest.Molybdenum-99 is one of the radioactive isotopes of molybdenum used in hospitals to prepare technetium-99.Technetium-99 is a radioactive isotope that can be used for imaging of the internal organs of patients.Molybdenum-99 used for this purpose is usually absorbed in alumina powder and stored in relatively small containers, where technetium-99 is formed when molybdenum-99 decays.
