Share on Facebook Share on Twitter Email
Answers.com

Boron trioxide

 
Wikipedia: Boron trioxide
Boron trioxide
B2O3powder.JPG
Kristallstruktur Bortrioxid.png
Other names boron oxide, diboron trioxide, boron sesquioxide, boric oxide, boria, anhydric boric acid
Identifiers
CAS number 1303-86-2 Yes check.svgY
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;
3.11–3.146 g/cm3, monoclinic

Melting point

450 °C (trigonal)
510 °C (tetrahedral)

Boiling point

1860 °C[1], sublimates at 1500 °C[2]

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
NFPA 704.svg
0
2
0
 
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
 Yes check.svgY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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

See also

References

  1. ^ 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. 
  2. ^ 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. 
  3. ^ Eckert, H. (1992). "Structural characterization of noncrystalline solids and glasses using solid state NMR". Prog. NMR Spectrosc. 24: 159. doi:10.1016/0079-6565(92)80001-V. 
  4. ^ 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:10.1016/S0926-2040(96)01280-5. 
  5. ^ 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:10.1107/S0567740870003369. 
  6. ^ 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. 
  7. ^ 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:10.3103/S1063457608010097. 

External links


Search unanswered questions...
Enter a question here...
Search: All sources Community Q&A Reference topics
 
 
Learn More
boric oxide (inorganic chemistry)
boron (element – in chemistry)
ammonia (in chemistry)

What is borons? Read answer...
What is boron made of? Read answer...
What does boron do to a plant? Read answer...

Help us answer these
How do you make 50ppm arsenic trioxide?
What metal reduces dichlorine trioxide?
What is the colour of sulphur trioxide?

Post a question - any question - to the WikiAnswers community:

 

Copyrights:

Wikipedia. This article is licensed under the Creative Commons Attribution/Share-Alike License. It uses material from the Wikipedia article "Boron trioxide" Read more