Molybdenum (IV) sulfide

Crystal structure
__ Mon 4+      __ S 2−
General
Surname	Molybdenum (IV) sulfide
other names	Molybdenum disulfide as a mineral also molybdenum luster or molybdenite and jordinite
Ratio formula	MoS 2
Brief description	black, odorless solid
External identifiers / databases
CAS number 1317-33-5 EC number 215-263-9 ECHA InfoCard 100,013,877 PubChem 14823 Wikidata Q424257
properties
Molar mass	160.07 g mol −1
Physical state	firmly
density	5.06 g cm −3
Melting point	1750 ° C
solubility	practically insoluble in water
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Molybdenum (IV) sulfide , also called molybdenum disulfide , with the formula MoS ₂ , is a gray-black, crystalline sulfide of the chemical element molybdenum . It is insoluble in water and in dilute acids . In addition to molybdenum disulfide, other molybdenum sulfides are also known.

Occurrence

Molybdenum (IV) sulfide is found in nature in the form of two minerals known as molybdenite ( molybdenum luster ) and jordisite , the latter being one of the few amorphous minerals.

Extraction and presentation

Molybdenum (IV) sulfide can be obtained by reacting molybdenum (IV) oxide with sulfur in the presence of potassium carbonate .

${\displaystyle \mathrm {MoO_{2}+3\ S\longrightarrow MoS_{2}+SO_{2}} }$

The representation from the elements is also possible.

${\displaystyle \mathrm {Mo+2\ S\longrightarrow MoS_{2}} }$

properties

Molybdenum disulfide

Structure and physical properties

The structure of molybdenum (IV) sulfide is graphite-like ; H. a layering of molybdenum and intermediate sulfur particles similar to a sandwich. Due to the space-parallel arrangement, the layers can easily be moved relative to one another, which leads to a lubricating effect. The layer structure makes it possible to produce two-dimensional crystals (similar to those of graphene ). Like graphite , hexagonal molybdenum (IV) sulfide is a semiconductor and is diamagnetic . Its band gap energy is 1.2 eV, with atomically thin layers (monolayers) this value increases to 1.8 eV. The compound exists in one of two modifications (2H and 3R) or a mixture of both, with the 2H form being dominant. The crystal structure of the 2H form is hexagonal with the space group P 6 ₃ / mmc (space group no. 194) and two formula units per unit cell. The 3R-shape has the space group R 3 m (space group no.160) . Molybdenum (IV) sulfide is an electron conductor, the conductivity of which increases when exposed to light. Molybdenum disulphide is not soluble in water and dilute acids.

Chemical properties

Molybdenum (IV) sulfide is stable in air; but above 315 ° C it is oxidized to molybdenum trioxide by the oxygen in the air :

${\displaystyle \mathrm {2\ MoS_{2}+9\ O_{2}\longrightarrow 2\ MoO_{3}+4\ SO_{3}} }$.

In the absence of air, MoS _{2 is} stable up to about 930 ° C, although different values ​​are given in the literature. The value often given in the literature for the melting temperature of 1185 ° C is incorrect, as Peter Cannon pointed out in 1959 . He determined a melting temperature of at least 1800 ° C and estimated a melting temperature of 2375 ° C if molybdenum (IV) sulfide behaves according to the Tammann rule for sintering temperatures. More recent studies assume a melting point of around 1600 ° C under helium at 1 bar for massive molybdenum (IV) sulfide. The actual value depends on the conditions (e.g. heating rate, existing crystal form, ...) and is not easy to determine because of the decomposition that has already started. For single-layer molybdenum (IV) sulfide layers, a melting temperature of 3700 K due to dimerization and further formation of small polymers is assumed.

Molybdenum (IV) sulfide dissolves with decomposition in aqua regia ; Sulfuric acid breaks it down to molybdenum (IV) oxide . It is oxidized to molybdenum pentachloride by chlorine :

${\displaystyle \mathrm {2\ MoS_{2}+7\ Cl_{2}\longrightarrow 2\ MoCl_{5}+2\ S_{2}Cl_{2}} }$.

It is reduced by hydrogen at around 1100 ° C to the trivalent sulfide Mo ₂ S ₃ ( dimolybdenum trisulfide ). By butyllithium there is a reduction to the trivalent state, with lithium between layers of the sulfur is MoS ₂ pushed, it is the intercalation LIMO ₂ :

${\displaystyle \mathrm {2\ MoS_{2}+2\ BuLi\longrightarrow 2\ LiMoS_{2}+Bu_{2}} }$.

use

This article or the following section is not adequately provided with supporting documents ( e.g. individual evidence ). Information without sufficient evidence could be removed soon. Please help Wikipedia by researching the information and including good evidence.

- Electriccat ( discussion ) 13:05, 23 Apr 2019 (CEST)

Applications as a lubricant

Finely powdered molybdenum (IV) sulfide with particle sizes between 1 and 100 µm is a dry technical lubricant. It was first marketed in the 1940s by the Dow Corning company under the trade name “Molykote” , which is still synonymous with molybdenum (IV) sulfide today. At Dow Corning, however, other specialty lubricants are also called that today. In the air it is oxidized from 315 ° C. If oxygen is excluded, it can be used up to 1100 ° C.

• It is often added to various lubricating oils, which leads to an improvement in lubricity. In addition to a longer service life of machine components, this also leads to damage prevention in the event of sudden total oil losses. The lubricating effect can be maintained for a while due to the adhesive effect of the oil, which z. B. in aircraft engines, ultracentrifuges (z. B. Beckman Coulter under the name Spinkote ) and other long-running engines and turbines is important (see also emergency running property ).
• Likewise, greases enriched with molybdenum (IV) sulfide are used on components that are difficult to access and thus the maintenance intervals are very long (maintenance-free connections, joint constructions, etc.).
• It is also used in massive forming and generally in forming processes (cold, warm and hot forming). It is often applied when bonding . This is usually done with a carrier layer on which the molybdenum (IV) sulfide is then applied. Often this also happens through “drumming”. The parts come into a kind of washing machine drum and are immersed in the bath, the drum remains in the medium for some time and rotates. The parts rotate with it and are wetted with molybdenum (IV) sulfide. The advantage of massive forming compared to normal soap is the higher temperature resistance of the solid lubricant. It is also used at high forming temperatures ≥ 200 ° C (especially with cold massive forming), due to very high forming and thus high friction in the tool.
• It is also used as a lubricating additive in special plastics, primarily nylon and Teflon .
• Molybdenum (IV) sulphide is also used to coat the projectiles of smaller caliber firearms. The coating leads to less friction between the bullet jacket and barrel. This on the one hand reduces the contamination of the barrel with lead or tombac residue, on the other hand increases the bullet speed and improves the overall ballistic properties.
• Self-lubricating composite films for high temperature applications were developed at Oak Ridge National Laboratory . The condensation of the chemical vapor of molybdenum (IV) sulfide and titanium nitride creates a smear layer on the component surface.

Other uses

• Molybdenum (IV) sulfide is used as a catalyst , e.g. B. in the petrochemical industry as an aid in desulfurization. Nanostructured MoS ₂ is to be used as a replacement for platinum catalysts in fuel cells ; It could also be used as a catalyst in water electrolysis .
• The Canadian company Moli Energy Limited manufactured rechargeable cells and batteries with MoS ₂ as a lithium storage material in the 1980s . They supplied a voltage below 2 V. After they were withdrawn from the market in 1989 due to safety concerns due to their lithium metal anode, which led to the bankruptcy of Moli Energy, they were replaced by today's lithium-ion batteries , the voltages of 3.5-4 Hold V.
• Scientists from Berkeley National Laboratory succeeded in producing a transistor using molybdenum (IV) sulfide, consisting of nickel electrodes and carbon nanotubes as control electrodes. In the future, this could lead to the production of transistors below the smallest possible size for silicon transistors of five nanometers. Investigations by IMEC show that MoS ₂ as a 2D material could enable the extremely scalable structures of integrated circuits .

Web links

Commons : Molybdenum disulfide  - Collection of images, videos and audio files

Individual evidence

1. ↑ ^{a b c d e} Entry on molybdenum (IV) sulfide in the GESTIS substance database of the IFA , accessed on November 19, 2013 (JavaScript required)
2. ↑ Jordisite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( PDF 59.7 kB ).
3. ↑ ^{a b c} Georg Brauer: Handbook of preparative inorganic chemistry . 3., reworked. Edition. tape III . Enke, Stuttgart 1981, ISBN 3-432-87823-0 , pp. 1551 .
4. ↑ Changgu Lee et al. a .: Frictional Characteristics of Atomically Thin Sheets . In: Science . tape 328 , no. 5974 , February 4, 2010, p. 76-80 , doi : 10.1126 / science.1184167 .
5. ↑ Hans-Dieter Jakubke, Ruth Karcher (Ed.): Lexicon of Chemistry , Spectrum Academic Publishing House, Heidelberg, 2001.
6. ↑ B. Radisavljevic, A. Radenovic, J. Brivio, V. Giacometti & A. Kis: Single-layer MoS ₂ transistors . In: Nature Nanotechnology . No. 6 , 2011, p. 147-150 .
7. ↑ KK Kam, BA Parkinson: Detailed Photocurrent Spectroscopy of the Semiconducting Group VI Transition Metal Dichaicogenides . In: The Journal of Physical Chemistry . tape 86 , no. 4 , February 1, 1982, p. 463-467 , doi : 10.1021 / j100393a010 .
8. ↑ Kin Fai Mak, Changgu Lee, James Hone, Jie Shan, Tony F. Heinz: Atomically Thin MoS ₂ : A New Direct-Gap Semiconductor . In: Physical Review Letters . tape 105 , no. 13 , September 24, 2010, p. 136805 , doi : 10.1103 / PhysRevLett.105.136805 .
9. ↑ B. Schönfeld, JJ Huang, SC Moss: Anisotropic mean-square displacements (MSD) in single-crystals of 2H- and 3R-MoS2. In: Acta Crystallographica Section B Structural Science. 39, 1983, p. 404, doi: 10.1107 / S0108768183002645 .
10. ↑ Roger Blachnik (Ed.): Paperback for chemists and physicists . Volume III: Elements, Inorganic Compounds and Materials, Minerals . founded by Jean d'Ans, Ellen Lax. 4th, revised and revised edition. Springer, Berlin 1998, ISBN 3-540-60035-3 , pp. 580 ( limited preview in Google Book search).
11. ↑ Shanmin Wang, Jianzhong Zhang, Duanwei He, Y. i. Zhang, Liping Wang, Hongwu Xu, Xiaodong Wen, Hui Ge, Yusheng Zhao: Sulfur-catalyzed phase transition in MoS2 under high pressure and temperature . In: Journal of Physics and Chemistry of Solids. 75, 2014, p. 100, doi: 10.1016 / j.jpcs.2013.09.001 .
12. ^ The Thermal Stability and Friction of the Disulfides, Diselenides, and Ditellurides of Molybdenum and Tungsten in Vacuum (10-9 To 10-6 Torr) by William A. Brainard Lewis Research Center Cleveland, Ohio, NASA April 1969
13. ↑ PETER CANNON: Melting Point and Sublimation of Molybdenum Disulphide. In: Nature. 183, 1959, p. 1612, doi: 10.1038 / 1831612a0 .
14. ^ TJ Wieting, M. Schlueter: Electrons and Phonons in Layered Crystal Structures . Springer Science & Business Media, 2012, ISBN 978-94-009-9370-9 , pp. 384 ( limited preview in Google Book Search).
15. ↑ Sandeep Kumar Singh, M. Neek-Amal, S. Costamagna, FM Peeters: Rippling, buckling, and melting of single- and multilayer MoS ₂ . In: Physical Review B. 91, 2015, doi: 10.1103 / PhysRevB.91.014101 .
16. ^ Daniel Merki, Stéphane Fierro, Heron Vrubel, Xile Hu: Amorphous molybdenum sulfide films as catalysts for electrochemical hydrogen production in water . In: Chemical Science . tape 2 , no. 7 , 2011, p. 1262-1267 , doi : 10.1039 / C1SC00117E .
17. ↑ Patent US4224390 : Lithium molybdenum disulphide battery cathode. Filed August 30, 1979 , published September 23, 1980 , inventors: Rudolph R. Haering, James AR Stiles, Klaus Brandt. ‌
18. ↑ Fred C. Laman, JAR Stiles, RJ Shank, Klaus Brandt: Rate limiting mechanisms in lithium-molybdenum disulfide batteries . In: Journal of Power Sources . tape 14 , no. 1 -3 (January-March), 1985, S. 201-207 , doi : 10.1016 / 0378-7753 (85) 88031-9 .
19. ↑ Klaus Brandt, Fred C. Laman: Reproducibility and reliability of rechargeable lithium / molybdenum disulfide batteries . In: Journal of Power Sources . tape 25 , no. 4 , April 1989, pp. 265-276 , doi : 10.1016 / 0378-7753 (89) 85014-1 .
20. ↑ FAZ: The transistors continue to shrink. In: FAZ.net . October 23, 2016, accessed October 13, 2018 . 
21. ^ Neil Tyler: 2D materials paving the way to extreme scaling. New Electronics, December 9, 2019, accessed December 10, 2019 .