Misplaced Pages

Boron trioxide

Article snapshot taken from Wikipedia with creative commons attribution-sharealike license. Give it a read and then ask your questions in the chat. We can research this topic together.
(Redirected from B2O3)
Boron trioxide
Crystal structure of B2O3
Names
IUPAC name Diboron trioxide
Other names boron oxide, diboron trioxide, boron sesquioxide, boric oxide, boria
Boric anhydride
Identifiers
CAS Number
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.013.751 Edit this at Wikidata
EC Number
  • 215-125-8
Gmelin Reference 11108
PubChem CID
RTECS number
  • ED7900000
UNII
CompTox Dashboard (EPA)
InChI
  • InChI=1S/B2O3/c3-1-5-2-4Key: JKWMSGQKBLHBQQ-UHFFFAOYSA-N
  • InChI=1/B2O3/c3-1-5-2-4Key: JKWMSGQKBLHBQQ-UHFFFAOYAI
SMILES
  • O=BOB=O
Properties
Chemical formula B2O3
Molar mass 69.6182 g/mol
Appearance white, glassy solid
Density 2.460 g/cm, liquid;

2.55 g/cm, trigonal;
3.11–3.146 g/cm, monoclinic

Melting point 450 °C (842 °F; 723 K) (trigonal)
510 °C (tetrahedral)
Boiling point 1,860 °C (3,380 °F; 2,130 K) , sublimes at 1500 °C
Solubility in water 1.1 g/100mL (10 °C)
3.3 g/100mL (20 °C)
15.7 g/100mL (100 °C)
Solubility partially soluble in methanol
Acidity (pKa) ~ 4
Magnetic susceptibility (χ) −39.0·10 cm/mol
Thermochemistry
Heat capacity (C) 66.9 J/(mol⋅K)
Std molar
entropy
(S298)
80.8 J/(mol⋅K)
Std enthalpy of
formation
fH298)
−1254 kJ/mol
Gibbs free energyfG) −832 kJ/mol
Hazards
Occupational safety and health (OHS/OSH):
Main hazards Irritant
GHS labelling:
Pictograms GHS08: Health hazard
Signal word Danger
Hazard statements H360FD
Precautionary statements P201, P202, P281, P308+P313, P405, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamondHealth 2: Intense or continued but not chronic exposure could cause temporary incapacitation or possible residual injury. E.g. chloroformFlammability 0: Will not burn. E.g. waterInstability 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g. liquid nitrogenSpecial hazards (white): no code
2 0 0
Flash point noncombustible
Lethal dose or concentration (LD, LC):
LD50 (median dose) 3163 mg/kg (oral, mouse)
NIOSH (US health exposure limits):
PEL (Permissible) TWA 15 mg/m
REL (Recommended) TWA 10 mg/m
IDLH (Immediate danger) 2000 mg/m
Supplementary data page
Boron trioxide (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C , 100 kPa). checkverify (what is  ?) Infobox references
Chemical compound

Boron trioxide or diboron trioxide is the oxide of boron with the formula B2O3. It is a colorless transparent solid, almost always glassy (amorphous), which can be crystallized only with great difficulty. It is also called boric oxide or boria. It has many important industrial applications, chiefly in ceramics as a flux for glazes and enamels and in the production of glasses.

Structure

Boron trioxide has three known forms, one amorphous and two crystalline.

Amorphous form

The amorphous form (g-B2O3) is by far the most common. It is thought to be composed of boroxol rings which are six-membered rings composed of alternating 3-coordinate boron and 2-coordinate oxygen.

Because of the difficulty of building disordered models at the correct density with many boroxol rings, this view was initially controversial, but such models have recently been constructed and exhibit properties in excellent agreement with experiment. It is now recognized, from experimental and theoretical studies, that the fraction of boron atoms belonging to boroxol rings in glassy B2O3 is somewhere between 0.73 and 0.83, with 0.75 = 3/4 corresponding to a 1:1 ratio between ring and non-ring units. The number of boroxol rings decays in the liquid state with increasing temperature.

Crystalline α form

The crystalline form (α-B2O3) is exclusively composed of BO3 triangles. Its crystal structure was initially believed to be the enantiomorphic space groups P31(#144) and P32(#145), like γ-glycine; but was later revised to the enantiomorphic space groups P3121(#152) and P3221(#154) in the trigonal crystal system, like α-quartz

Crystallization of α-B2O3 from the molten state at ambient pressure is strongly kinetically disfavored (compare liquid and crystal densities). It can be obtained with prolonged annealing of the amorphous solid ~200 °C under at least 10 kbar of pressure.

Crystalline β form

The trigonal network undergoes a coesite-like transformation to monoclinic β-B2O3 at several gigapascals (9.5 GPa).

Preparation

Boron trioxide is produced by treating borax with sulfuric acid in a fusion furnace. At temperatures above 750 °C, the molten boron oxide layer separates out from sodium sulfate. It is then decanted, cooled and obtained in 96–97% purity.

Another method is heating boric acid above ~300 °C. Boric acid will initially decompose into steam, (H2O(g)) and metaboric acid (HBO2) at around 170 °C, and further heating above 300 °C will produce more steam and diboron trioxide. The reactions are:

H3BO3 → HBO2 + H2O
2 HBO2 → B2O3 + H2O

Boric acid goes to anhydrous microcrystalline B2O3 in a heated fluidized bed. Carefully controlled heating rate avoids gumming as water evolves.

Boron oxide will also form when diborane (B2H6) reacts with oxygen in the air or trace amounts of moisture:

2B2H6(g) + 3O2(g) → 2B2O3(s) + 6H2(g)
B2H6(g) + 3H2O(g) → B2O3(s) + 6H2(g)

Reactions

Molten boron oxide attacks silicates. Containers can be passivated internally with a graphitized carbon layer obtained by thermal decomposition of acetylene.

Applications

See also

References

  1. ^ Gurr, G. E.; Montgomery, P. W.; Knutson, C. D.; Gorres, B. T. (1970). "The Crystal Structure of Trigonal Diboron Trioxide". Acta Crystallographica B. 26 (7): 906–915. doi:10.1107/S0567740870003369.
  2. 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 978-1-56677-261-7.
  3. ^ Patnaik, P. (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. p. 119. ISBN 978-0-07-049439-8. Retrieved 2009-06-06.
  4. ^ NIOSH Pocket Guide to Chemical Hazards. "#0060". National Institute for Occupational Safety and Health (NIOSH).
  5. "Boron oxide". Immediately Dangerous to Life or Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
  6. L. McCulloch (1937): "A Crystalline Boric Oxide". Journal of the American Chemical Society, volume 59, issue 12, pages 2650–2652. doi:10.1021/ja01291a05
  7. I.Vishnevetsky and M.Epstein (2015): "Solar carbothermic reduction of alumina, magnesia and boria under vacuum". Solar Energy, volume 111, pages 236-251 doi:10.1016/j.solener.2014.10.039
  8. Ferlat, G.; Charpentier, T.; Seitsonen, A. P.; Takada, A.; Lazzeri, M.; Cormier, L.; Calas, G.; Mauri. F. (2008). "Boroxol Rings in Liquid and Vitreous B2O3 from First Principles". Phys. Rev. Lett. 101 (6): 065504. Bibcode:2008PhRvL.101f5504F. doi:10.1103/PhysRevLett.101.065504. PMID 18764473.
  9. Ferlat, G.; Seitsonen, A. P.; Lazzeri, M.; Mauri, F. (2012). "Hidden polymorphs drive vitrification in B2O3". Nature Materials Letters. 11 (11): 925–929. arXiv:1209.3482. Bibcode:2012NatMa..11..925F. doi:10.1038/NMAT3416. PMID 22941329. S2CID 11567458.
  10. Hung, I.; et al. (2009). "Determination of the bond-angle distribution in vitreous B2O3 by rotation (DOR) NMR spectroscopy". Journal of Solid State Chemistry. 182 (9): 2402–2408. Bibcode:2009JSSCh.182.2402H. doi:10.1016/j.jssc.2009.06.025.
  11. Soper, A. K. (2011). "Boroxol rings from diffraction data on vitreous boron trioxide". J. Phys.: Condens. Matter. 23 (36): 365402. Bibcode:2011JPCM...23.5402S. doi:10.1088/0953-8984/23/36/365402. PMID 21865633. S2CID 5291179.
  12. Joo, C.; et al. (2000). "The ring structure of boron trioxide glass". Journal of Non-Crystalline Solids. 261 (1–3): 282–286. Bibcode:2000JNCS..261..282J. doi:10.1016/s0022-3093(99)00609-2.
  13. Zwanziger, J. W. (2005). "The NMR response of boroxol rings: a density functional theory study". Solid State Nuclear Magnetic Resonance. 27 (1–2): 5–9. doi:10.1016/j.ssnmr.2004.08.004. PMID 15589722.
  14. Micoulaut, M. (1997). "The structure of vitreous B2O3 obtained from a thermostatistical model of agglomeration". Journal of Molecular Liquids. 71 (2–3): 107–114. doi:10.1016/s0167-7322(97)00003-2.
  15. Alderman, O. L. G. Ferlat, G. Baroni, A. Salanne, M. Micoulaut, M. Benmore, C. J. Lin, A. Tamalonis, A. Weber, J. K. R. (2015). "Liquid B2O3 up to 1700K: X-ray diffraction and boroxol ring dissolution" (PDF). Journal of Physics: Condensed Matter. 27 (45): 455104. Bibcode:2015JPCM...27S5104A. doi:10.1088/0953-8984/27/45/455104. PMID 26499978. S2CID 21783488.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  16. Gurr, G. E.; Montgomery, P. W.; Knutson, C. D.; Gorres, B. T. (1970). "The crystal structure of trigonal diboron trioxide". Acta Crystallographica B. 26 (7): 906–915. doi:10.1107/S0567740870003369.
  17. Strong, S. L.; Wells, A. F.; Kaplow, R. (1971). "On the crystal structure of B2O3". Acta Crystallographica B. 27 (8): 1662–1663. doi:10.1107/S0567740871004515.
  18. Effenberger, H.; Lengauer, C. L.; Parthé, E. (2001). "Trigonal B2O3 with Higher Space-Group Symmetry: Results of a Reevaluation". Monatshefte für Chemie. 132 (12): 1515–1517. doi:10.1007/s007060170008. S2CID 97795834.
  19. Aziz, M. J.; Nygren, E.; Hays, J. F.; Turnbull, D. (1985). "Crystal Growth Kinetics of Boron Oxide Under Pressure". Journal of Applied Physics. 57 (6): 2233. Bibcode:1985JAP....57.2233A. doi:10.1063/1.334368.
  20. Brazhkin, V. V.; Katayama, Y.; Inamura, Y.; Kondrin, M. V.; Lyapin, A. G.; Popova, S. V.; Voloshin, R. N. (2003). "Structural transformations in liquid, crystalline and glassy B2O3 under high pressure". JETP Letters. 78 (6): 393–397. Bibcode:2003JETPL..78..393B. doi:10.1134/1.1630134. S2CID 189764568.
  21. Kocakuşak, S.; Akçay, K.; Ayok, T.; Koöroğlu, H. J.; Koral, M.; Savaşçi, Ö. T.; Tolun, R. (1996). "Production of anhydrous, crystalline boron oxide in fluidized bed reactor". Chemical Engineering and Processing. 35 (4): 311–317. doi:10.1016/0255-2701(95)04142-7.
  22. AirProducts (2011). "Diborane Storage & Delivery" (PDF). Archived from the original (PDF) on 2015-02-04. Retrieved 2013-08-21. {{cite journal}}: Cite journal requires |journal= (help)
  23. Morelock, C. R. (1961). "Research Laboratory Report #61-RL-2672M". General Electric. {{cite journal}}: Cite journal requires |journal= (help)

External links

Boron compounds
Boron pnictogenides
Boron halides
Acids
Boranes
Boron oxides and sulfides
Carbides
Organoboron compounds
Oxides
Mixed oxidation states
+1 oxidation state
+2 oxidation state
+3 oxidation state
+4 oxidation state
+5 oxidation state
+6 oxidation state
+7 oxidation state
+8 oxidation state
Related
Oxides are sorted by oxidation state. Category:Oxides
Oxygen compounds
Categories: