Molybdenum disilicide: Difference between revisions
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| IUPACName = Molybdenum disilicide |
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| OtherNames = Molybdenum(VIII) silicide |
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| CASNo = 12136-78-6 |
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| PubChem = 6336985 |
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| MolarMass = 152.11 g/mol |
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| Density = 6.26 g/cm<sup>3</sup><ref name=j1/><ref name=b1/> |
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| MeltingPtC = 2030 |
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| MeltingPt_ref = <ref name=b1>{{cite book|author1=Soo-Jin Park|author2=Min-Kang Seo|title=Interface Science and Composites|url=https://books.google.com/books?id=DewhZ53WgLwC&pg=PA563|date=2011|publisher=Academic Press|isbn=978-0-12-375049-5|pages=563–}}</ref> |
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| CrystalStruct = [[Tetragonal]]<ref name=j1>{{cite journal|doi=10.1016/0022-0248(93)90456-7 |title=Crystal growth and characterization of the transition metal silicides MoSi<sub>2</sub> and WSi<sub>2</sub>|journal=Journal of Crystal Growth|volume=129|issue =1–2|year= 1993|pages= 266–268|author=A. Nørlund Christensen |bibcode=1993JCrGr.129..266N}}</ref> |
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| SpaceGroup = I4/mmm (No. 139), [[Pearson symbol|tI6]] |
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| LattConst_a = 0.32112 nm |
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| LattConst_c = 0.7845 nm |
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| OtherCations = [[Chromium disilicide]]<br>[[Tungsten disilicide]] |
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'''Molybdenum disilicide''' (''' |
'''Molybdenum disilicide''' ('''MoSi<sub>2</sub>''', or '''molybdenum silicide'''), an [[intermetallic compound]], a [[silicide]] of [[molybdenum]], is a [[refractory material|refractory]] [[ceramic]] with primary use in [[heating element]]s. It has moderate [[density]], melting point 2030 °C, and is [[electrically conductive]]. At high temperatures it forms a [[Passivation (chemistry)|passivation layer]] of [[silicon dioxide]], protecting it from further oxidation. The thermal stability of MoSi<sub>2</sub> alongside its high [[emissivity]] make this material, alongside [[tungsten disilicide|WSi<sub>2</sub>]] attractive for applications as a high emissivity coatings in [[heat shield]]s for [[atmospheric entry]].<ref>[https://arxiv.org/ftp/arxiv/papers/1902/1902.03943.pdf High emissivity coatings on fibrous ceramics for reusable space systems] Corrosion Science 2019 </ref> |
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MoSi<sub>2</sub> is a gray metallic-looking material with [[tetragonal]] [[crystal structure]] (alpha-modification); its beta-modification is [[hexagonal (crystal system)|hexagonal]] and unstable.<ref>{{cite journal|journal=J. Appl. Phys. |volume=51|issue=11|pages= 5976–5980 |year=1980|doi=10.1063/1.327517 |title=Observations on the hexagonal form of MoSi<sub>2</sub> and WSi<sub>2</sub> films produced by ion implantation and on related snowplow effects|author=F. M. d’Heurle, C. S. Petersson, and M. Y. Tsai |bibcode=1980JAP....51.5976D}}</ref> It is insoluble in most acids but soluble in [[nitric acid]] and [[hydrofluoric acid]]. |
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| ⚫ | While MoSi<sub>2</sub> has excellent resistance to oxidation and high [[Young's modulus]] at temperatures above 1000 °C, it is [[brittle]] in lower temperatures. Also, at above 1200 °C it loses [[creep (deformation)|creep]] resistance. These properties limits its use as a [[structural material]], but may be offset by using it together with another material as a [[composite material]]. |
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[[Image:Kanthal-super.jpg|thumb|left|Heating elements of MoSi<sub>2</sub>]] |
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| ⚫ | While MoSi<sub>2</sub> has excellent resistance to oxidation and high [[Young's modulus]] at temperatures above 1000 |
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Molybdenum disilicide and MoSi<sub>2</sub>-based materials are usually made by [[sintering]]. [[Plasma spraying]] can be used for producing its dense monolithic and composite forms; material produced this way may contain a proportion of β-MoSi<sub>2</sub> due to its rapid cooling. |
Molybdenum disilicide and MoSi<sub>2</sub>-based materials are usually made by [[sintering]]. [[Plasma spraying]] can be used for producing its dense monolithic and composite forms; material produced this way may contain a proportion of β-MoSi<sub>2</sub> due to its rapid cooling. |
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Molybdenum disilicide heating elements can be used for temperatures up to 1800 |
Molybdenum disilicide heating elements can be used for temperatures up to 1800 °C, in electric [[Industrial furnace|furnace]]s used in laboratory and production environment in production of [[glass]], [[steel]], [[electronics]], [[ceramic]]s, and in [[heat treatment]] of materials. While the elements are brittle, they can operate at high power without aging, and their electrical resistivity does not increase with operation time. Their maximum [[operating temperature]] has to be lowered in atmospheres with low oxygen content due to breakdown of the passivation layer.<ref name="Park Seo 2011 p. 563">{{cite book |last1=Park |first1=S.J. |url=https://books.google.com/books?id=DewhZ53WgLwC&pg=PA563 |title=Interface Science and Composites |last2=Seo |first2=M.K. |publisher=Elsevier Science |year=2011 |isbn=978-0-12-375049-5 |series=Interface Science and Technology |page=563 |access-date=2023-09-09}}</ref> |
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Other ceramic materials used for heating elements |
Other ceramic materials used for heating elements include [[silicon carbide]], [[barium titanate]], and [[lead titanate]] [[composite material]]s. |
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Molybdenum disilicide is used in [[microelectronics]] as a contact material. It is often used as a [[shunt (electrical)|shunt]] over [[polysilicon]] lines to increase their conductivity and increase signal speed. |
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==References== |
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{{reflist}} |
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{{Molybdenum compounds}} |
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{{Silicides}} |
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[[Category:Ceramic materials]] |
[[Category:Ceramic materials]] |
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[[Category: |
[[Category:Group 6 silicides]] |
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[[Category:Molybdenum compounds]] |
[[Category:Molybdenum(II) compounds]] |
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[[Category:Refractory materials]] |
[[Category:Refractory materials]] |
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Latest revision as of 07:44, 30 October 2023
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| Names | |
|---|---|
| IUPAC name
Molybdenum disilicide
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| Other names
Molybdenum(VIII) silicide
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| Identifiers | |
| ECHA InfoCard | 100.032.016 |
PubChem CID
|
|
CompTox Dashboard (EPA)
|
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| Properties | |
| MoSi2 | |
| Molar mass | 152.11 g/mol |
| Appearance | gray metallic solid |
| Density | 6.26 g/cm3[1][2] |
| Melting point | 2,030 °C (3,690 °F; 2,300 K)[2] |
| Structure | |
| Tetragonal[1] | |
| I4/mmm (No. 139), tI6 | |
a = 0.32112 nm, c = 0.7845 nm
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Formula units (Z)
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2 |
| Hazards | |
| Flash point | Non-flammable |
| Related compounds | |
Other cations
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Chromium disilicide Tungsten disilicide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Molybdenum disilicide (MoSi2, or molybdenum silicide), an intermetallic compound, a silicide of molybdenum, is a refractory ceramic with primary use in heating elements. It has moderate density, melting point 2030 °C, and is electrically conductive. At high temperatures it forms a passivation layer of silicon dioxide, protecting it from further oxidation. The thermal stability of MoSi2 alongside its high emissivity make this material, alongside WSi2 attractive for applications as a high emissivity coatings in heat shields for atmospheric entry.[3] MoSi2 is a gray metallic-looking material with tetragonal crystal structure (alpha-modification); its beta-modification is hexagonal and unstable.[4] It is insoluble in most acids but soluble in nitric acid and hydrofluoric acid.
While MoSi2 has excellent resistance to oxidation and high Young's modulus at temperatures above 1000 °C, it is brittle in lower temperatures. Also, at above 1200 °C it loses creep resistance. These properties limits its use as a structural material, but may be offset by using it together with another material as a composite material.
Molybdenum disilicide and MoSi2-based materials are usually made by sintering. Plasma spraying can be used for producing its dense monolithic and composite forms; material produced this way may contain a proportion of β-MoSi2 due to its rapid cooling.
Molybdenum disilicide heating elements can be used for temperatures up to 1800 °C, in electric furnaces used in laboratory and production environment in production of glass, steel, electronics, ceramics, and in heat treatment of materials. While the elements are brittle, they can operate at high power without aging, and their electrical resistivity does not increase with operation time. Their maximum operating temperature has to be lowered in atmospheres with low oxygen content due to breakdown of the passivation layer.[5]
Other ceramic materials used for heating elements include silicon carbide, barium titanate, and lead titanate composite materials.
Molybdenum disilicide is used in microelectronics as a contact material. It is often used as a shunt over polysilicon lines to increase their conductivity and increase signal speed.
References
[edit]- ^ a b A. Nørlund Christensen (1993). "Crystal growth and characterization of the transition metal silicides MoSi2 and WSi2". Journal of Crystal Growth. 129 (1–2): 266–268. Bibcode:1993JCrGr.129..266N. doi:10.1016/0022-0248(93)90456-7.
- ^ a b Soo-Jin Park; Min-Kang Seo (2011). Interface Science and Composites. Academic Press. pp. 563–. ISBN 978-0-12-375049-5.
- ^ High emissivity coatings on fibrous ceramics for reusable space systems Corrosion Science 2019
- ^ F. M. d’Heurle, C. S. Petersson, and M. Y. Tsai (1980). "Observations on the hexagonal form of MoSi2 and WSi2 films produced by ion implantation and on related snowplow effects". J. Appl. Phys. 51 (11): 5976–5980. Bibcode:1980JAP....51.5976D. doi:10.1063/1.327517.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Park, S.J.; Seo, M.K. (2011). Interface Science and Composites. Interface Science and Technology. Elsevier Science. p. 563. ISBN 978-0-12-375049-5. Retrieved 2023-09-09.