Molybdenum disulfide as a lubricant
Like most mineral salts, MoS2 has a very high melting point but starts to sublime at a relatively low 450°C. This property is useful for purifying compounds. Due to its layered structure, the hexagonal MoS2 is like graphite and is an excellent dry lubricant. It and its cousin tungsten disulfide can be used as a surface coating in mechanical parts (for example, the aerospace industry), two-stroke engines (the type used in motorcycles), and barrels (to reduce friction between bullets and ammunition) ).
Unlike graphite, the lubricating properties of MoS2 do not depend on adsorbed water or other vapors. Its maximum temperature in an oxidizing environment is 350°C, and its maximum temperature in a non-oxidizing environment is 1100°C. Its stability allows it to be used in high-temperature applications where grease is not practical.
It is understood that molybdenum disulfide powder is recognized as the best solid lubricant in the world, but in the application of lubricating oil, because molybdenum is only soluble in aqua regia and boiling concentrated sulfuric acid, and the physical diameter of molybdenum particles is large, it will form in the oil Sediment layering can not be uniformly integrated with the engine oil, so it can only be added to the grease. This makes the manufacture of molybdenum disulfide lubricants a global problem. At present, only a few companies in Germany and the United States have mastered this technology.
Molybdenum disulfide is the main component of molybdenite—solid black powder with a metallic luster. The chemical formula is MoS2, the melting point is 1185°C, the density is 4.80g/cm (14°C), and the Mohs hardness is 1.0-1.5.
Analysis of the advantages and disadvantages of molybdenum disulfide as a lubricant
(1) Thoroughly prevent oil leakage, clean and clean, which significantly promotes civilized production.
(2) A large amount of grease can be saved.
(3) Improve the technical operating conditions, extend the maintenance cycle, reduce the labor intensity of maintenance workers, and save labor.
(4) Due to the low friction coefficient of molybdenum disulfide, the frictional resistance between the friction devices is small, which can save electricity. According to the measurement of the brother unit, the power can be held by 12%.
(5) It can reduce mechanical wear, extend the service life of friction equipment, reduce the loss of equipment parts, and improve the attendance rate of the equipment.
(6) The application of molybdenum disulfide lubrication solves critical technology and improves work efficiency and accuracy.
(7) Molybdenum disulfide has the functions of filling and filling, which can restore the geometric dimensions of individual parts and extend the service life.
(8) Molybdenum disulfide has the characteristics of moisture-proof, waterproof, alkali-proof, and acid-proof.
(9) The use of molybdenum disulfide plastic or powder smelted molded parts can save many non-ferrous metals.
(10) After using molybdenum disulfide lubrication in some equipment, the complicated oil supply system can be omitted, which significantly simplifies the structure of the equipment, relatively improves the effective area utilization, and will also cause significant reforms.
(11) Molybdenum disulfide also has shortcomings, such as poor thermal conductivity, low friction coefficient, and low permeability (compared to thin oil). These shortcomings are the main obstacles to expand the scope of use further. On the contrary, industrialized countries attach great importance to the research of solid lubricants and have also held international lubrication conferences to exchange relevant information and discuss new technologies.
Molybdenum disulfide as a superconductor
In addition to its lubricity, MoS2 is also a semiconductor. It is also known that when doped with an electrostatic field, it and other semiconductor transition metal chalcogenides become superconductors on its surface.
Until 2018, the mechanism of superconductivity was uncertain when Andrea C.Ferrari of the University of Cambridge (UK) and his colleagues and the Turin Polytechnic Institute (Italy), reported on Duogufei. The surface of the meter is related to the superconducting state in MoS2. The author believes that this Fermi surface topology will serve as a guide for seeking new superconductors.
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