Introduction of the metal molybdenum
Basic introduction of molybdenum metal
Molybdenum is a member of the VIB group of elements in the periodic table, with atomic number 42 and atomic weight 95.94. Density 10.2 g/cm3.Melting point is 2610 ℃. The boiling point of 5560 ℃.The valence is +2, +4, and +6, and the stable valence is +6.Molybdenum is a transition element, which easily changes its oxidation state and plays a role of electron transfer in the REDOX reaction in vivo. In the oxidized form, molybdenum is probably in the plus 6 state. Other oxidation states of molybdenum have been found in the reduced enzyme, although it is also likely that it was first reduced to a +5 valence state during electron transfer. Molybdenum is a component of xanthine oxidase/dehydrogenase, aldehyde oxidase and sulfite oxidase, so it is identified as an essential trace element for human body, plants and animals.
The distribution of molybdenum
The discovered rare metal resources in China are abundant and large in scale. Molybdenum, rare earth, titanium and tungsten rank first in the world. According to the United States Geological Survey, in 2007 China buried about 27 million tons of rare earths, 1.8 million tons of tungsten, 3.3 million tons of molybdenum and 200 million tons of titanium.
Molybdenum deposits are found in Jindui Town of Huaxian County in Shaanxi Province, Huludao City in Liaoning Province, Jilin Province, Shanxi Province, Henan Province, Fujian Province, Guangdong Province, Hunan Province, Sichuan Province, Jiangxi Province, Gansu Province and other provinces with large reserves and good development conditions, and the output occupies an important position in the country. The majority of molybdenum ore of industrial value is molybdenite, and about 99% of molybdenum ore is mined as molybdenite.
Physical properties of molybdenum metal
High melting point and high boiling point is one of the remarkable characteristics of molybdenum, its melting point is 2620℃, second only to carbon, tungsten, rhenium, tantalum and osmium, boiling point is 5560℃. At 20℃, the density of molybdenum is 10.22 g/cm, which is only about 1/2 of that of tungsten. The linear expansion coefficient of molybdenum is (5.8-6.2)×10, which is only 1/3-1/2 of that of ordinary steel, and close to that of silicon dioxide. The low linear expansion coefficient makes molybdenum material stable in size at high temperature and reduces the risk of rupture. The thermal conductivity of molybdenum is several times that of many superalloys and is about 1/2 that of copper. The conductivity of molybdenum is relatively high, about 1/3 that of copper, and decreases with increasing temperature. Molybdenum has a very high modulus of elasticity, one of the highest in the industry, and is less affected by temperature, even at 800℃ is still higher than the value of ordinary steel at room temperature. The small thermal neutron capture surface is also an important property of molybdenum, which allows molybdenum to be used as a structural material in the core of a nuclear reactor. Molybdenum has better elongation than tungsten and can be processed into very thin foil and fine wire.
