Molybdenum disulfide
IUPAC name	Molybdenum disulfide Molybdenum(IV) sulfide molybdenum sulfide
Other names	Molybdenite
Identifiers
CAS number	[1317-33-5]
RTECS number	QA4697000
Properties
Molecular formula	MoS2
Molar mass	160.07 g/mol
Appearance	black solid
Density	5.06 g/cm³, ?
Melting point	1185 °C decomp. IUPAC nomenclature is a system of naming chemical compounds and of describing the science of chemistry in general. ... Molybdenite is a mineral of molybdenum disulfide, MoS2. ... CAS registry numbers are unique numerical identifiers for chemical compounds, polymers, biological sequences, mixtures and alloys. ... RTECS, also known as Registry of Toxic Effects of Chemical Substances, is a database of toxicity information compiled from the open scientific literature that is available for charge. ... A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound. ... Molar mass is the mass of one mole of a chemical element or chemical compound. ... For other uses, see Density (disambiguation). ... The melting point of a solid is the temperature range at which it changes state from solid to liquid. ...
Structure
Crystal structure	see text
Coordination geometry	Trigonal prismatic at Mo, pyramidal at S Enargite crystals In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ... The coordination geometry of an atom is the geometrical pattern formed by its neighbors in a molecule or a crystal. ...
Hazards
EU classification	not listed
Flash point	n.a.
Related compounds
Other anions	Molybdenum(IV) oxide Molybdenum trioxide
Other cations	Tungsten disulfide
Related lubricants	Graphite
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Molybdenum disulfide, commonly abbreviated as moly, is the inorganic compound with the formula MoS₂. This black crystalline sulfide of molybdenum occurs as the mineral molybdenite. More so than other transition metal chalcogenides, MoS₂ is unreactive, being unaffected by dilute acids. In terms of its appearance and feel, molybdenum disulfide is similar to graphite and indeed it is widely used as a solid lubricant^[1][2] due to its low friction properties, sometimes to relatively high temperatures. Council Directive 67/548/EEC of 27 June 1967 on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances (as amended) is the main European Union law concerning chemical safety. ... For other uses, see Flash point (disambiguation). ... This article is about the electrically charged particle. ... Molybdenum trioxide is an oxide of molybdenum, chemical formula MoO3. ... This article is about the electrically charged particle. ... Tungsten(IV) sulfide is the chemical compound with the formula WS2. ... A lubricant (colloquially, lube) is a substance (often a liquid) introduced between two moving surfaces to reduce the friction and wear between them. ... For other uses, see Graphite (disambiguation). ... The plimsoll symbol as used in shipping In chemistry, the standard state of a material is its state at 1 bar (100 kilopascals exactly). ... Inorganic chemistry is the branch of chemistry concerned with the properties and reactions of inorganic compounds. ... A chemical formula is an easy way of expressing information about the atoms that constitute a particular chemical compound. ... Formally, sulfide is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2S. Sulfide is exceptionally basic and, with a pKa > 14, it does not exist in appreciable concentrations even in highly alkaline water. ... General Name, Symbol, Number molybdenum, Mo, 42 Chemical series transition metals Group, Period, Block 6, 5, d Appearance gray metallic Standard atomic weight 95. ... Molybdenite is a mineral of molybdenum disulfide, MoS2. ... In chemistry, the term transition metal (sometimes also called a transition element) has two possible meanings: It commonly refers to any element in the d-block of the periodic table, including zinc, cadmium and mercury. ... A chalcogenide is a binary compound consisting of a chalcogen and a more electropositive element. ... For other uses, see acid (disambiguation). ... For other uses, see Graphite (disambiguation). ...

Production

Molybdenite ore is processed by flotation to give relatively pure MoS₂, the main contaminant being carbon. MoS₂ also arises by the thermal treatment of virtually all molybdenum compounds with hydrogen sulfide. Froth Flotation is a selective process for separating minerals from gangue by using surfactants and wetting agents. ... Hydrogen sulfide (or hydrogen sulphide) is the chemical compound with the formula H2S. This colorless, toxic and flammable gas is responsible for the foul odour of rotten eggs and flatulence. ...

Structure and basic properties

In MoS₂, each Mo(IV) center is trigonal prismatic, being bound to six sulfide ligands, each of which is pyramidal. The trigonal prisms are interconnected to give a layered structure, wherein molybdenum atoms are sandwiched between layers of sulfur atoms.^[3] Due to the weak van der Waals interactions between the sheets of sulfide atoms, MoS₂ has a low coefficient of friction, resulting in its lubricating properties. Other layered inorganic materials exhibit lubricating properties (collectively known as solid lubricants or dry lubricants) including graphite, which requires volatile additives, and hexagonal boron nitride.^[4] Johannes Diderik van der Waals, a 1910 Nobel Prize winner, was responsible for a number of advances in physical chemistry which are named after him. ... The coefficient of friction is a dimensionless quantity used to calculate the force of friction (static or kinetic). ... Boron nitride is a binary chemical compound, consisting of equal proportions of boron and nitrogen, with formula BN. Structurally, it is isoelectronic to carbon and takes on similar physical forms: a hexagonal, graphite-like one, and a cubic, diamond-like one. ...

MoS₂ is diamagnetic and a semiconductor. A semiconductor is a solid material that has electrical conductivity in between that of a conductor and that of an insulator; it can vary over that wide range either permanently or dynamically. ...

Use as lubricant

MoS₂ with particle sizes in the range of 1-100 µm is a common dry lubricant. Few alternatives exist that can confer the high lubricity and stability up to 350 °C in oxidizing environments. Sliding friction tests of MoS₂ using a pin on disc tester at low loads (0.1-2 N) give friction coefficient values of <0.1. This article is about the unit of length. ... The pin on disc tester is a piece of equipment used to measure the sliding wear and friction properties of surfaces. ...

Molybdenum disulfide is often a component of blends and composites where low friction is sought. A variety of oils and greases are used, since they retain their lubricity even in cases of almost complete oil loss, thus finding a use in critical applications such as aircraft engines. When added to plastics, MoS₂ forms a composite with improved strength as well as reduced friction. Polymers that have been filled with MoS₂ include nylon, with the trade name Nylatron, Teflon, and Vespel. Self-lubricating composite coatings for high-temperature applications have been developed consisting of molybdenum disulfide and titanium nitride by chemical vapor deposition. [1] Synthetic motor oil being poured. ... Grease is a lubricant of higher initial viscosity than oil, consisting originally of a calcium, sodium or lithium soap jelly emulsified with mineral oil. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... For other uses, see Plastic (disambiguation). ... A cloth of woven carbon fiber filaments, a common element in composite materials Composite materials (or composites for short) are engineered materials made from two or more constituent materials with significantly different physical or chemical properties and which remain separate and distinct on a macroscopic level within the finished structure. ... For other uses of this word, see nylon (disambiguation). ... A trade name, also known as a trading name or a business name, is the legal name of a business, or the name which a business trades under for commercial purposes. ... Teflon is a trademark of DuPont and is commonly used for the chemical compound polytetrafluoroethylene. ... Vespel is the trademark of a durable high-performance polyimide-based polymer (or plastic) manufactured by DuPont. ... TiN coated drill Dark gray TiCN coating on a Gerber pocketknife Titanium nitride (TiN) is an extremely hard (~85 Rockwell C Hardness or ~2500 Vickers Hardness)1, ceramic material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve the substrates surface properties. ... DC plasma (violet) enhances the growth of carbon nanotubes in this laboratory-scale PECVD apparatus. ...

Specific uses

It is often used in two-stroke engines, e.g., motorcycle engines. MoS₂ is also used in CV and universal joints. During the Vietnam War, the molybdenum disulfide product "Dri-Slide" was used to lubricate weapons, although it was supplied from private sources, not the military.[2] MoS₂-coatings allow bullets easier passage through the rifle barrel with less deformation and better ballistic accuracy. The two-stroke cycle of an internal combustion engine differs from the more common four-stroke cycle by having only two strokes (linear movements of the piston) instead of four, although the same four operations (intake, compression, power, exhaust) still occur. ... Cross-section through a typical outer CV joint (Saab 96) 3D rendering of the internals of a simple CV joint Constant Velocity Joints (aka homokinetic or CV joints) allow a rotating shaft to transmit power through a variable angle, at constant rotational speed, without an appreciable increase in friction or... A universal joint A universal joint, U joint, Cardan joint or Hardy-Spicer joint is a joint in a rigid rod that allows the rod to bend in any direction. ... Combatants Republic of Vietnam United States Republic of Korea Thailand Australia New Zealand The Philippines National Front for the Liberation of South Vietnam Democratic Republic of Vietnam People’s Republic of China Democratic Peoples Republic of Korea Strength US 1,000,000 South Korea 300,000 Australia 48,000... This article is about firearms projectiles. ...

Use in petrochemistry

Synthetic MoS₂ is employed as a catalyst for desulfurization in petroleum refineries, e.g., hydrodesulfurization.^[5] The effectiveness of the MoS₂ catalysts is enhanced by doping with small amounts of cobalt, and the intimate mixture is supported on alumina. Such catalysts are generated in situ by treating molybdate/cobalt-impregnated alumina with H₂S or an equivalent reagent. It has been suggested that this article or section be merged into Catalysis. ... Petrochemistry is the branch of chemistry that studies the transformation of crude oil (petroleum) and natural gas into usefull products and raw materials. ... Hydrodesulfurization is one means of lowering the sulfur content of liquids from oil/coal. ... In semiconductor production, doping refers to the process of intentionally introducing impurities into an extremely pure (also referred to as intrinsic) semiconductor in order to change its electrical properties. ... Aluminium oxide (or aluminum oxide) (Al2O3) is a chemical compound of aluminium and oxygen. ...

Future Developments (lubrication)

There are currently no clear lubrication alternatives to molybdenum disulfide or the very similar tungsten disulfide that can resist temperatures higher than 350°C in oxidizing environments. Research has been conducted on compacted oxide layer glazes, which form during metallic surface sliding wear at several hundred degrees Celsius. However, because these oxide layers are physically-unstable, their use has currently not proven practical. Tungsten(IV) sulfide is the chemical compound with the formula WS2. ... Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style. ...

References

1. ^ G. L. Miessler and D. A. Tarr “Inorganic Chemistry” 3rd Ed, Pearson/Prentice Hall publisher, ISBN 0-13-035471-6.
2. ^ Shriver, D. F.; Atkins, P. W.; Overton, T. L.; Rourke, J. P.; Weller, M. T.; Armstrong, F. A. “Inorganic Chemistry” W. H. Freeman, New York, 2006. ISBN 0-7167-4878-9.
3. ^ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
4. ^ Thorsten Bartels, Wolfgang Bock, Jürgen Braun, Christian Busch, Wolfgang Buss, Wilfried Dresel, Carmen Freiler, Manfred Harperscheid, Rolf-Peter Heckler, Dietrich Hörner, Franz Kubicki, Georg Lingg, Achim Losch, Rolf Luther, Theo Mang, Siegfried "Lubricants and Lubrication" in Ullmann's Encyclopedia of Industrial Chemistry, Wiley VCH: Weinheim, 2002. DOI: 10.1002/14356007.a15_423.
5. ^ Topsøe, H.; Clausen, B. S.; Massoth, F. E. "Hydrotreating Catalysis, Science and Technology"; Springer-Verlag: Berlin, 1996.

External links

• Molybdenum sulfide MSDS
• Molybdenum Disulfide specifications