Silane 188972 224625981 2008-07-09T18:38:27Z 128.83.206.150 sp error {{Chembox new | Name = Silane | ImageFileL1 = Silane-2D.png <!-- | ImageSizeL1 = 100px --> | ImageNameL1 = Silane | ImageFileR1 = Silane-3D-vdW.png <!-- | ImageSizeR1 = 100px --> | ImageNameR1 = Silane | IUPACName = Silane | OtherNames = Silicon tetrahydride<br />Silicon hydride<br />Monosilane<br />Silicane | Section1 = {{Chembox Identifiers | CASNo = 7803-62-5 | UNNumber = 2203 | RTECS = VV1400000 }} | Section2 = {{Chembox Properties | Formula = SiH<sub>4</sub> | MolarMass = 32.12 g mol<sup>−1</sup> | Appearance = Colorless gas | Density = ? kg m<sup>−3</sup> (solid)<br />0.7 g/ml (liquid)<br /> 1.342 g L<sup>−1</sup> (gas) | Solubility = Insoluble | MeltingPt = 88 K (−185°C) | BoilingPt = 161 K (−112°C) }} | Section3 = {{Chembox Structure | MolShape = [[tetrahedral]] | Dipole = 0 [[Debye|D]] }} | Section4 = {{Chembox Thermochemistry | DeltaHf = -1615 kJ mol<sup>−1</sup> | Entropy = 283 J mol<sup>−1</sup> K<sup>−1</sup> }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = low toxicity,<br />avoid exposure to skin,<br />irritant, may cause<br />redness and swelling, extremely flammable, pyrophoric | NFPA-H = 1 | NFPA-F = 4 | NFPA-R = 3 | FlashPt = N/A | Autoignition = 294 K (21°C) | RPhrases = | SPhrases = }} | Section8 = {{Chembox Related | Function = silanes | OtherFunctn = [[disilane]]<br />[[trisilane]]<br />[[tetrasilane]]<br />[[cyclosilane]] | Function = hydrides | OtherFunctn = [[methane]] | OtherCpds = [[disilene]] }} }} '''Silane''' is a [[chemical compound]] with [[chemical formula]] [[silicon|Si]][[hydrogen|H]]<sub>4</sub>. It is the [[silicon]] [[Analog (chemistry)|analogue]] of [[methane]]. At [[room temperature]], silane is a gas, and is [[pyrophoric]] — it undergoes spontaneous [[combustion]] in [[air]], without the need for external ignition.<ref>{{ cite journal | author = Emeléus, H. J. and Stewart, K. | title = The oxidation of the silicon hydrides | year = 1935 | journal = Journal of the Chemical Society | pages = 1182 - 1189 | doi = 10.1039/JR9350001182}}</ref> However, the difficulties in explaining the available (often contradictory) combustion data are ascribed to the fact that silane itself is stable and that the natural formation of larger silanes during production, as well as the sensitivity of combustion to impurities such as moisture and to the catalytic effects of container surfaces causes its pyrophoricity.<ref>{{ cite journal | author = Koda, S. | title = Kinetic Aspects of Oxidation and Combustion of Silane and Related Compounds | year = 1992 | journal = Progress in Energy and Combustion Science | volume = 18 | issue = 6 | pages = 513-528 | doi = 10.1016/0360-1285(92)90037-2}}</ref><ref name=timms/> Above 420°C, silane decomposes into silicon and [[hydrogen]]; it can therefore be used in the [[chemical vapor deposition]] of silicon. More generally, a silane is any silicon analogue of an [[alkane]] hydrocarbon. Silanes consist of a chain of silicon atoms [[covalent bond|covalently bound]] to hydrogen atoms. The general formula of a silane is Si<sub>n</sub>H<sub>2n+2</sub>. Silanes tend to be less stable than their carbon analogues because the Si–Si [[chemical bond|bond]] has a strength slightly lower than the C–C bond. [[Oxygen]] decomposes silanes easily, because the silicon-oxygen bond is quite stable. There exists a regular nomenclature for silanes. Each silane's name is the word silane preceded by a numerical prefix (di, tri, tetra, etc.) for the number of silicon atoms in the molecule. Thus Si<sub>2</sub>H<sub>6</sub> is [[disilane]], Si<sub>3</sub>H<sub>8</sub> is trisilane, and so forth. There is no need for a prefix for one; SiH<sub>4</sub> is simply silane. Silanes can also be named like any other inorganic compound; in this naming system, silane is named silicon tetrahydride. However, with longer silanes, this becomes cumbersome. A [[cyclosilane]] is a silane in a ring, just as a [[cycloalkane]] is an alkane in a ring. Branched silanes are possible. The [[radical (chemistry)|radical]] ·SiH<sub>3</sub> is termed silyl, ·Si<sub>2</sub>H<sub>5</sub> is disilanyl, and so on. Trisilane with a silyl group attached to the middle silicon is named silyltrisilane. The nomenclature parallels that of [[alkyl]] radicals. Silanes can also incorporate the same functional groups as alkanes, e.g. [[Hydroxyl#Hydroxyl group|–OH]] to make a [[silanol]]. There is (at least in principle) a silicon analogue for all carbon alkanes. ==Production== Industrially, silane is produced from metallurgical grade silicon in a two-step process. In the first step, powdered silicon is reacted with [[hydrogen chloride]] at about 300°C to produce [[trichlorosilane]], HSiCl<sub>3</sub>, along with [[hydrogen]] gas, according to the [[chemical equation]]: :Si + 3HCl → HSiCl<sub>3</sub> + H<sub>2</sub> The trichlorosilane is then boiled on a [[resin]]ous bed containing a [[catalyst]] which promotes its [[disproportionation]] to silane and [[silicon tetrachloride]] according to the chemical equation: :4HSiCl<sub>3</sub> → SiH<sub>4</sub> + 3SiCl<sub>4</sub> The most commonly used catalysts for this process are [[metal]] [[halogen|halides]], particularly [[aluminium chloride]]. ==Properties== Silane has a repulsive smell.<ref>[http://www.c-f-c.com/specgas_products/silane.htm CFC Startec properties of Silane]</ref> <noinclude>Silane has recently been shown to act as superconductor under extremely high pressures (96 and 120 GPa), with a transition temperature of 17 K.<ref name="Science2008"/> Unfortunately, there was briefly an EE Times article that grossly exaggerated this achievement and claimed that room-temperature superconductivity had been achieved.</noinclude> ==Applications== Several industrial and medical applications exist for silanes. For instance, silanes are used as coupling agents to adhere [[fiberglass|glass fiber]]s to a [[polymer]] matrix, stabilizing the [[composite material]]. They can also be used to couple a bio-inert layer on a [[titanium]] [[prosthesis|implant]]. Other applications include water repellents, [[masonry]] protection, control of [[graffiti]],<ref>[http://www.protectosil.com/protectosil/en/otherregions/graffiticontrol/default Graffiti protection systems]</ref> applying [[polycrystalline silicon]] layers on silicon wafers when manufacturing semiconductors, and sealants. Semiconductor industry alone used about 300 [[metric ton]]s per year of silane in the late 1990s.<ref name=timms>{{ cite journal | author = Timms, P. L. | title = The chemistry of volatile waste from silicon wafer processing | year = 1999 | journal = Journal of the Chemical Society - Dalton Transactions | issue = 6 | pages = 815-822 | doi = 10.1039/a806743k}}</ref> More recently, a growth in low-cost [[solar panel]] manufacturing has lead to substantial consumption of silane for [[PECVD|depositing]] [[amorphous silicon]] on glass and other surfaces. Silane is also used in [[supersonic]] combustion [[ramjet]]s to initiate combustion in the compressed air stream. Silane and similar compounds containing Si-H-bonds are used as reducing agents in organic and organometallic chemistry.<ref>[http://www.organic-chemistry.org/chemicals/reductions/silanes.shtm Reductions of organic compounds using silanes]</ref> "[[Mars sand]]" exposes regular sand to [[trimethylhydroxysilane]] vapors to make the sand waterproof. Silane may be used to fabricate a super-compressed, superconducting compound.<ref name="Science2008">{{cite journal | author = M. I. Eremets, I. A. Trojan, S. A. Medvedev, J. S. Tse, Y. Yao | title = Superconductivity in Hydrogen Dominant Materials: Silane | journal = Science | volume = 319 | issue = 5869 | pages = 1506–1509 | year = 2008 | doi = 10.1126/science.1153282 | pmid = 18339933 }}</ref> ==Safety and precautions== A number of fatal industrial accidents produced by detonation and combustion of leaked silane in air have been reported.<ref>{{ cite journal | author = Chen, J. R. | title = Characteristics of fire and explosion in semiconductor fabrication processes | year = 2002 | journal = Process Safety Progress | volume = 21 | issue = 1 | pages = 19-25 | doi = 10.1002/prs.680210106}}</ref><ref>{{ cite journal | author = Chen, J. R.; Tsai, H. Y.; Chen, S. K.; Pan, H. R.; Hu, S. C.; Shen, C. C.; Kuan, C. M.; Lee, Y. C.; and Wu, C. C. | title = Analysis of a silane explosion in a photovoltaic fabrication plant | year = 2006 | journal = Process Safety Progress | volume = 25 | issue = 3 | pages = 237-244 | doi = 10.1002/prs.10136}}</ref><ref>{{ cite journal | author = Chang, Y. Y.; Peng, D. J.; Wu, H. C.; Tsaur, C. C.; Shen, C. C.; Tsai, H. Y.; and Chen, J. R. | title = Revisiting of a silane explosion in a photovoltaic fabrication plant | year = 2007 | journal = Process Safety Progress | volume = 26 | issue = 2 | pages = 155-158 | doi = 10.1002/prs.10194}}</ref> Dilute silane mixtures with inert gases such as nitrogen or argon are even more likely to ignite when leaked into open air, compared to pure silane: even a 1% mixture of silane in pure nitrogen easily ignites when exposed to air.<ref>{{ cite journal | author = Kondo, S.; Tokuhashi, K.; Nagai, H.; Iwasaka, M.; and Kaise, M. | title = Spontaneous Ignition Limits of Silane and Phosphine | year = 1995 | journal = Combustion and Flame | volume = 101 | issue = 1-2 | pages = 170-174 | doi = 10.1016/0010-2180(94)00175-R}}</ref> Unlike methane, silane is also fairly toxic: the lethal concentration in air for rats ([[Median lethal dose|LC<sub>50</sub>]]) is 0.96% over a 4-hour exposure. In addition, contact with eyes may form silicic acid with resultant irritation.<ref>See [http://www.vngas.com/pdf/g97.pdf MSDS for silane].</ref> ==References== <references/> ==See also== *[[silanization]] [[Category:Silicon compounds]] [[Category:Hydrides]] [[cs:Silan]] [[de:Monosilan]] [[es:Silano]] [[fr:Silane]] [[gl:Silano]] [[it:Silano]] [[ja:シラン (化合物)]] [[pl:Silany]] [[pt:Silano]] [[ru:Кремневодороды]] [[fi:Silaani]] [[sv:Silan]] [[zh:硅烷]]