Aluminium dodecaboride

Aluminium dodecaboride (AlB12) is a superhard chemical compound with 17% aluminium content by weight.

Aluminium dodecaboride
Names
IUPAC name
Aluminium dodecaboride
Other names
AlB12
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.737
EC Number
  • 234-924-2
Properties
AlB12
Molar mass 156.714 g/mol[1]
Appearance Yellow to black solid[1]
Density 2.55 g/cm3[1]
Melting point 2,070 °C (3,760 °F; 2,340 K)=[1]
insoluble
Solubility soluble in hot nitric acid (decomposes),[2]
soluble in nitric acid (decomposes),[3]
soluble in sulfuric acid (decomposes)[3]
Structure
Tetragonal (α-form)
Orthorhombic (β-form)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

It is the hardest boride of the aluminium-boron system, which also includes AlB10, AlB4, AlB2 and AlB.

Properties

There are two crystalline forms, α-AlB12, and γ-AlB12. Both forms are very similar and consist of a framework with three-dimensional networks of B12 and B20 units.[4] The phase β-AlB12 is now believed to be the ternary boride C2Al3B48.[5]

Preparation

The β-form can be prepared by the reaction of boron(III) oxide with sulfur and aluminum, then adding carbon to the mixture.


Uses

AlB12 extreme hardness makes it a favorable component of PCBN inserts, which are mainly used in cutting & grinding to replace diamond or corundum.

See also


Footnotes
  1. Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.45. ISBN 1439855110.
  2. Martienssen, Werner; Warlimont, Hans (2005). Martienssen, Werner; Warlimont, Hans (eds.). Springer Handbook of Condensed Matter and Materials Data. Springer Handbook of Condensed Matter and Materials Data. Springer-Verlag. p. 1025. Bibcode:2005shcm.book.....M. ISBN 9783540443766.
  3. Rebekoff Reeve, Martin (1991) Method of producing an aluminium boride. EP 0130016 B1
  4. Higashi, Iwami (2000). "Crystal chemistry of α-AlB12 and γ-AlB12". Journal of Solid State Chemistry. 154 (1): 168–176. Bibcode:2000JSSCh.154..168H. doi:10.1006/jssc.2000.8831.
  5. Matkovich, V. I; Giese, R. F; Economy, J (1965). "Phases and twinning in C2Al3B48 (β-AlB12)". Zeitschrift für Kristallographie. 122 (1–2): 108. Bibcode:1965ZK....122..108M. doi:10.1524/zkri.1965.122.1-2.108.
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