Editing Silicon dioxide (section)

==Production==
Silicon dioxide is mostly obtained by mining, including [[sand mining]] and purification of [[quartz]]. 
Quartz is suitable for many purposes, while chemical processing is required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product.<ref>{{Cite book |url=http://link.springer.com/10.1007/978-3-642-22161-3 |title=Quartz: Deposits, Mineralogy and Analytics |date=2012 |publisher=Springer Berlin Heidelberg |isbn=978-3-642-22160-6 |editor-last=Götze |editor-first=Jens |series=Springer Geology |location=Berlin, Heidelberg |language=en |doi=10.1007/978-3-642-22161-3 |bibcode=2012qdma.book.....G |editor-last2=Möckel |editor-first2=Robert}}</ref><ref>{{Cite journal |last1=Pan |first1=Xiaodong |last2=Li |first2=Suqin |last3=Li |first3=Yongkui |last4=Guo |first4=Penghui |last5=Zhao |first5=Xin |last6=Cai |first6=Yinshi |date=2022 |title=Resource, characteristic, purification and application of quartz: a review |url=https://linkinghub.elsevier.com/retrieve/pii/S0892687522002102 |journal=Minerals Engineering |language=en |volume=183 |pages=107600 |doi=10.1016/j.mineng.2022.107600|bibcode=2022MiEng.18307600P |url-access=subscription }}</ref>

===Precipitated silica===
Precipitated silica or amorphous silica is produced by the acidification of solutions of [[sodium silicate]]. The gelatinous precipitate or [[silica gel]], is first washed and then dehydrated to produce colorless microporous silica.<ref name="Greenwood"/>  The idealized equation involving a trisilicate and [[sulfuric acid]] is:
:<chem>Na2Si3O7 + H2SO4 -> 3 SiO2 + Na2SO4 + H2O</chem>

Approximately one billion kilograms/year (1999) of silica were produced in this manner, mainly for use for polymer composites – tires and shoe soles.<ref name=Ull/>

===On microchips===
Thin films of silica grow spontaneously on [[silicon wafer]]s via [[thermal oxidation]], producing a very shallow layer of about 1 [[nanometre|nm]] or 10 [[angstrom|Å]] of so-called native oxide.<ref>{{cite book|url=https://books.google.com/books?id=Qi98H-iTgLEC|title=Handbook of Semiconductor Manufacturing Technology|publisher=CRC Press|year=2007|isbn=9781574446753|veditors=Doering R, Nishi Y}}</ref>
Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures between 600 and 1200&nbsp;°C, using so-called dry  oxidation with [[oxygen|O<sub>2</sub>]]
:<chem>Si + O2 -> SiO2</chem>

or wet oxidation with H<sub>2</sub>O.<ref name="Sunggyu Lee">{{cite book|title=Encyclopedia of chemical processing|author=Lee S|publisher=CRC Press|year=2006|isbn=9780824755638}}</ref><ref name="Morgan&Board">{{cite book|title=An Introduction To Semiconductor Microtechnology|vauthors=Morgan DV, Board K|publisher=John Wiley & Sons|year=1991|isbn=9780471924784|edition=2nd|location=Chichester, West Sussex, England|pages=72}}</ref>
:<chem>Si + 2 H2O -> SiO2 + 2 H2</chem>

The native oxide layer is beneficial in [[microelectronics]], where it acts as [[electric insulator]] with high chemical stability. It can protect the silicon, store charge, block current, and even act as a controlled pathway to limit current flow.<ref>{{Cite news|url=https://spectrum.ieee.org/the-silicon-dioxide-solution|title=The Silicon Dioxide Solution: How physicist Jean Hoerni built the bridge from the transistor to the integrated circuit|last=Riordan M|date=2007|work=[[IEEE Spectrum]]|access-date=11 Feb 2019}}</ref>

===Laboratory or special methods===
==== From organosilicon compounds ====
Many routes to silicon dioxide start with an organosilicon compound, e.g., HMDSO,<ref>{{Cite journal|last1=Chrystie|first1=Robin S. M.|last2=Ebertz|first2=Felix L.|last3=Dreier|first3=Thomas|last4=Schulz|first4=Christof|date=2019-01-28|title=Absolute SiO concentration imaging in low-pressure nanoparticle-synthesis flames via laser-induced fluorescence|journal=Applied Physics B|language=en|volume=125|issue=2|pages=29|doi=10.1007/s00340-019-7137-8|issn=1432-0649|bibcode=2019ApPhB.125...29C|s2cid=127735545}}</ref> TEOS. Synthesis of silica is illustrated below using [[tetraethyl orthosilicate]] (TEOS).<ref>{{Cite journal|last1=Romero-Jaime|first1=A. K.|last2=Acosta-Enríquez|first2=M. C.|last3=Vargas-Hernández|first3=D.|last4=Tánori-Córdova|first4=J. C.|last5=Pineda León|first5=H. A.|last6=Castillo|first6=S. J.|date=August 2021|title=Synthesis and characterization of silica–lead sulfide core–shell nanospheres for applications in optoelectronic devices|url=https://link.springer.com/10.1007/s10854-021-06648-1|journal=Journal of Materials Science: Materials in Electronics|language=en|volume=32|issue=16|pages=21425–21431|doi=10.1007/s10854-021-06648-1|s2cid=236182027|issn=0957-4522}}</ref>  Simply heating TEOS at 680–730&nbsp;°C results in the oxide:

:<chem>Si(OC2H5)4 -> SiO2 + 2 O(C2H5)2</chem>

Similarly TEOS combusts around 400&nbsp;°C:

:<chem>Si(OC2H5)4 + 12 O2 -> SiO2 + 10 H2O + 8 CO2</chem>

TEOS undergoes [[hydrolysis]] via the so-called [[sol-gel process]].  The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is:<ref>{{Cite journal|display-authors=3|vauthors=Nandiyanto AB, Kim SG, Iskandar F, Okuyama K|year=2009|title=Synthesis of spherical mesoporous silica nanoparticles with nanometer-size controllable pores and outer diameters|journal=Microporous and Mesoporous Materials|volume=120|issue=3|pages=447–453|doi=10.1016/j.micromeso.2008.12.019|bibcode=2009MicMM.120..447N }}</ref>

:<chem>Si(OC2H5)4 + 2 H2O -> SiO2 + 4 HOCH2CH3</chem>

====Other methods====
Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of [[silane]] gives silicon dioxide.  This reaction is analogous to the combustion of methane:

:<chem>SiH4 + 2 O2 -> SiO2 + 2 H2O</chem>

However the [[chemical vapor deposition]] of silicon dioxide onto crystal surface from silane had been used using nitrogen as a carrier gas at 200–500&nbsp;°C.<ref name="Morgan&Board2">{{cite book|title=An Introduction To Semiconductor Microtechnology|vauthors=Morgan DV, Board K|publisher=John Wiley & Sons|year=1991|isbn=9780471924784|edition=2nd|location=Chichester, West Sussex, England|pages=27}}</ref>