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Beryllium oxide

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Beryllium oxide
Beryllium-oxide-3D-balls.png
Other names Beryllia, Thermalox, Berlox, Super beryllia, Beryllia ceramic, Bromellite
Identifiers
CAS number 1304-56-9
PubChem 14775
EINECS number 215-133-1
RTECS number DS4025000
Properties
Molecular formula BeO
Molar mass 25.0116 g/mol
Appearance white solid
Density 3.02 g/cm3 [1]
Melting point

2507 °C

Boiling point

3900 °C

Solubility in water soluble (powder)
Solubility in KOH, NH4CO3 soluble
Hazards
EU classification Carc. Cat. 2
Highly toxic (T+)
Irritant (Xi)
EU Index 004-003-00-8
NFPA 704
NFPA 704.svg
0
4
0
 
R-phrases Plantilla:R49, Plantilla:R25, Plantilla:R26, Plantilla:R36/37/38, Plantilla:R43, Plantilla:R48/23
S-phrases Plantilla:S53, Plantilla:S45
Flash point Non-flammable
LD50 2062 mg/kg (mouse, oral)
Related compounds
Other anions Beryllium sulfide
Beryllium selenide
Beryllium telluride
Other cations Magnesium oxide
Calcium oxide
 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

Beryllium oxide (BeO) is a white crystalline oxide. It is notable as it is an electrical insulator with a thermal conductivity higher than any other non-metal except diamond, and actually exceeds that of some metals.[2] Its high melting point leads to its use as a refractory[3]. It occurs in nature as the mineral bromellite. Historically beryllium oxide was called glucina or glucinium oxide.

Preparation and ChemistryEditar

Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide or igniting the metal:

BeCO3→ BeO + CO2
Be(OH)2 → BeO + H2O
2Be + O2 → 2BeO

Igniting beryllium in air gives a mixture of BeO and the nitride Be3N2.[2]
Unlike oxides formed by the other group 2 (alkaline earth metals), beryllium oxide is amphoteric rather than basic.

Beryllium oxide formed at high temperatures (>800°C) is inert but may be easily dissolved in hot aqueous ammonium bifluoride (NH4HF2) or a hot solution of concentrated sulfuric acid (H2SO4) and ammonium sulfate ((NH4)2SO4).

StructureEditar

BeO at normal temperatures has the hexagonal wurtzite, form.[2] This contrasts with other members of group 2, whose oxides, MgO, CaO, SrO, BaO have the cubic rock salt structure.[2]. At high temperature the structure transforms to a tetragonal form.[4]. BeO is a unique metallic compound in that it is a non-ionic oxide.

ApplicationsEditar

Sintered beryllium oxide, which is very stable, has ceramic characteristics. Beryllium oxide is used for rocket engines, catalysts, semiconductors, moderators of atomic reactors, and neutron reflectors.

Beryllium oxide is used in many high-performance semiconductor parts for applications such as radio equipment because it has good thermal conductivity while also being a good electrical insulator. It is used as a filler in some thermal interface materials such as thermal grease.[5] Some power semiconductor devices have used beryllium oxide ceramic between the silicon chip and the metal mounting base of the package in order to achieve a lower value of thermal resistance than for a similar construction made with aluminium oxide. It is also used as a structural ceramic for high-performance microwave devices, vacuum tubes, magnetrons, and gas lasers.

Currently there are only two companies in the United States that manufacture Beryllium Oxide which are American Beryllia Inc. of Haskell New Jersey, and Brush Ceramics of Tucson Arizona.

SafetyEditar

BeO powder is carcinogenic if the powder is ingested or inhaled and may cause chronic beryllium disease. However, once fired into solid form, it is safe to handle as long as it is not subjected to any machining that creates dust.[6]

Beryllium oxide ceramic is not a hazardous waste under Federal law and its use is not banned, restricted or otherwise limited by any country worldwide.

ReferencesEditar

  1. Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
  2. 2,0 2,1 2,2 2,3 Greenwood, N. N.; Earnshaw, A. (1997). Chemistry of the Elements (2nd Edition ed.). Oxford:Butterworth-Heinemann. ISBN 0-7506-3365-4. 
  3. Raymond Aurelius Higgins, (2006), Materials for Engineers and Technicians, Newnes, ISBN 0750668504
  4. Wells A.F. (1984) Structural Inorganic Chemistry 5th edition Oxford Science Publications ISBN 0-19-855370-6
  5. Greg Becker, Chris Lee, and Zuchen Lin (July 2005). "Thermal conductivity in advanced chips — Emerging generation of thermal greases offers advantages". Advanced Packaging: pp.2–4. Retrieved on 2008-03-04.
  6. http://www.americanberyllia.com/safety.html

External linksEditar


Plantilla:Beryllium compounds



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