| Boron trioxide | |
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| Other names | boron oxide, diboron trioxide, boron sesquioxide, boric oxide, boria, anhydric boric acid |
| Identifiers | |
| CAS number | 1303-86-2  |
| PubChem | 518682 |
| RTECS number | ED7900000 |
| Properties | |
| Molecular formula | B2O3 |
| Molar mass | 69.6182 g/mol |
| Appearance | white, glassy solid |
| Density | 2.460 g/cm3, liquid; 2.55 g/cm3, trigonal; |
| Melting point |
450 °C (trigonal) |
| Boiling point | |
| Solubility in water | 2.2 g/100 mL |
| Solubility | partially soluble in methanol |
| Acidity (pKa) | ~ 4 |
| Hazards | |
| MSDS | External MSDS |
| EU classification | Repr. Cat. 2 |
| NFPA 704 |
 0
2
0
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| LD50 | 3150 mg/kg (oral, rat) |
| Supplementary data page | |
| Structure and properties |
n, εr, etc. |
| Thermodynamic data |
Phase behaviour Solid, liquid, gas |
| Spectral data | UV, IR, NMR, MS |
| (what is this?) (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Boron oxide is one of the oxides of boron. It is white, glassy, and solid, also known as diboron trioxide, formula B2O3. It is almost always found as the vitreous (amorphic) form; however, it can be crystallized after extensive annealing. It is one of the most difficult compounds known to crystallize.
Glassy boron oxide (g-B2O3) is thought to be composed of boroxol rings which are six-membered rings composed of alternating 3-coordinate boron and 2-coordinate oxygen. The rings make a few BO3 triangles, but mostly link (polymerize) into ribbons and sheets.[3][4] The crystalline form (α-B2O3) see structure in the infobox[5]) is exclusively composed of BO3 triangles. This trigonal, quartz-like network undergoes a coesite-like transformation to monoclinic β-B2O3 at several gigapascals and is 9.5 GPa.[6]
Contents |
Preparation
Boron trioxide is produced by treating borax with sulfuric acid in a fusion furnace. At temperatures above 750 °C, the molten boric acid layer separates out from sodium sulfate. It is then decanted, cooled and obtained in 96-97% purity.[2]
Hardness
The bulk modulus of β-B2O3 is rather high (K = 180 GPa). The Vickers hardness of g-B2O3 is 1.5 GPa and of β-B2O3 is 16 GPa.[7]
Applications
- Fluxing agent for glass and enamels
- Starting material for synthesizing other boron compounds such as boron carbide
- An additive used in glass fibres (optical fibres)
- It is used in the production of borosilicate glass
- The inert capping layer in the LEC process for the production of gallium arsenide single crystal
- As an acid catalyst in organic synthesis
See also
References
- ^ High temperature corrosion and materials chemistry: proceedings of the Per Kofstad Memorial Symposium. Proceedings of the Electrochemical Society. The Electrochemical Society. 2000. p. 496. ISBN 1566772613. http://books.google.com/books?id=ZrxSWmueNMQC&pg=PA496.
- ^ a b Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. p. 119. ISBN 0070494398. http://books.google.com/books?id=Xqj-TTzkvTEC&pg=PA119. Retrieved 2009-06-06.
- ^ Eckert, H. (1992). "Structural characterization of noncrystalline solids and glasses using solid state NMR". Prog. NMR Spectrosc. 24: 159. doi:.
- ^ S.-J. Hwang, C. Femandez, J.P. Amoureux, J. Cho, S.W. Martin & M. Pruski. (1997). "Quantitative study of the short range order in B,O, and B,S, by MAS and two-dimensional triple-quantum MAS 11B NMR". Solid State Nuclear Magnetic Resonance 8: 109-121. doi:.
- ^ G.E. Gurr, P.W. Montgomery, C.D. Knutson, B.T.Gorres (1970). "The Crystal Structure of Trigonal Diboron Trioxide". Acta Cryst. B 26: 906-915. doi:.
- ^ V. V. Brazhkin et al. (2003). "Structural transformations in liquid, crystalline and glassy B2O3 under high pressure". JETPh Lett. 78: 845. http://www.jetpletters.ac.ru/ps/47/article_679.ps.
- ^ V. A. Mukhanov, O. O. Kurakevich, and V. L. Solozhenko (2008). "On the Hardness of Boron (III) Oxide". Journal of Superhard Materials 30: 71. doi:.
External links
- National Pollutant Inventory: Boron and compounds
- Australian Government information
- US NIH hazard information. See NIH.
- Material Safety Data Sheet
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