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BERYLLIUM OXIDE

BERYLLIUM OXIDE

CAS Number:1304-56-9
Molecule Formula:BeO
Molecular Weight:25.011 g·mol−1

Beryllium oxide (BeO), also known as beryllia, is an inorganic compound with the formula BeO.
Beryllium oxide colourless solid is a notable electrical insulator with a higher thermal conductivity than any other non-metal except diamond, and exceeds that of most metals. As an amorphous solid, beryllium oxide is white.
Beryllium oxide is high melting point leads to its use as a refractory material.
Beryllium oxide occurs in nature as the mineral bromellite.
Historically and in materials science, beryllium oxide was called glucina or glucinium oxide.

-Computed Properties-
Molecular Weight: 25.012
Hydrogen Bond Donor Count: 0
Hydrogen Bond Acceptor Count: 1
Rotatable Bond Count: 0
Exact Mass: 25.0070977
Monoisotopic Mass: 25.0070977
Topological Polar Surface Area: 17.1 Ų
Heavy Atom Count: 2
Formal Charge: 0
Complexity: 2
Isotope Atom Count: 0
Defined Atom Stereocenter Count: 0
Undefined Atom Stereocenter Count: 0
Defined Bond Stereocenter Count: 0
Undefined Bond Stereocenter Count: 0
Covalently-Bonded Unit Count: 1
Compound Is Canonicalized: Yes

-Preparation and chemical properties-
Beryllium oxide can be prepared by calcining (roasting) beryllium carbonate, dehydrating beryllium hydroxide, or igniting metallic beryllium:

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

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

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

Odor: Odourless
Density: 3.01 g/cm3
Melting point: 2,507 °C (4,545 °F; 2,780 K)
Boiling point: 3,900 °C (7,050 °F; 4,170 K)
Solubility in water: 0.00002 g/100 mL
Band gap: 10.6 eV
Thermal conductivity: 330 W/(K·m)
Refractive index (nD): 1.719

-Structure-
BeO crystallizes in the hexagonal wurtzite structure, featuring tetrahedral Be2+ and O2− centres, like lonsdaleite and w-BN (with both of which it is isoelectronic).
In contrast, the oxides of the larger group-2 metals, i.e., MgO, CaO, SrO, BaO, crystallize in the cubic rock salt motif with octahedral geometry about the dications and dianions. At high temperature the structure transforms to a tetragonal form.

In the vapour phase, beryllium oxide is present as discrete diatomic molecules.
In the language of valence bond theory, these molecules can be described as adopting sp orbital hybridisation on both atoms, featuring one σ (between one sp orbital on each atom) and one π bond (between aligned p orbitals on each atom oriented perpendicular to the molecular axis). Molecular orbital theory provides a slightly different picture with no net sigma bonding (because the 2s orbitals of the two atoms combine to form a filled sigma bonding orbital and a filled sigma* anti-bonding orbital) and two pi bonds formed between both pairs of p orbitals oriented perpendicular to the molecular axis.
The sigma orbital formed by the p orbitals aligned along the molecular axis is unfilled.
The corresponding ground state is ...(2sσ)2(2sσ*)2(2pπ)4 (as in the isoelectronic C2 molecule), where both bonds can be considered as dative bonds from oxygen towards beryllium.

-Uses-
Beryllium oxide is used in high technology ceramics, electronic heat sinks, electrical insulators, microwave oven components, gyroscopes, military vehicle armor, rocket nozzles crucibles, thermocouple tubing, laser structural components, substrates for high-density electrical circuits, automotive ignition systems, and radar electronic countermeasure systems.

Electron tubes, resistor cores; windows in klystron tubes; transistor mountings; high-temperature reactor systems; additive to glass, ceramics and plastics; preparation of beryllium compounds; catalyst for organic reactions.

-Methods of Manufacturing-
-Beryllium oxide is produced by the following processes: beryllium hydroxide is first converted to high-purity beryllium sulfate tetrahydrate, as described above. This salt is calcined at carefully controlled temperatures, between 1150 and 1450 °C, selected to give the properties of the beryllium oxide powders required by individual beryllia ceramic fabricators. Alternatively, beryllium hydroxide may be purified first and then calcined directly to beryllium oxide powder.
-Produced by dissolving technical-grade beryllium hydroxide in sulfuric acid, precipitating out hydrated beryllium sulfate, which is then calcined at 1,150-1,450 °C.
-By heating of beryllium nitrate or hydroxide.
-Obtained directly from beryllium hydroxide by calcination or from the basic carbonate, acetate, or sulfate by ignition. The white, reactive powders differ in grain size, morphology, and impurity content.
-In the primary industrial process, beryllium hydroxide extracted from ore is dissolved in sulfuric acid. The solution is filtered and the filtrate is concentrated by evaporation and unpon cooling high purity beryllium sulfate, BeSO4.4H2O crystallizes. The salt is calcined at carefully controlled temperatures between 1150 and 1450 °C, selected to give tailored properties of the beryllium oxide powders.ı

-Applications-
High-quality crystals may be grown hydrothermally, or otherwise by the Verneuil method. For the most part, beryllium oxide is produced as a white amorphous powder, sintered into larger shapes. Impurities, like carbon, can give a variety of colours to the otherwise colourless host crystals.

Sintered beryllium oxide is a very stable ceramic.
Beryllium oxide is used in rocket engines and as a transparent protective over-coating on aluminised telescope mirrors.

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.
Beryllium oxide is used as a filler in some thermal interface materials such as thermal grease.
Some power semiconductor devices have used beryllium oxide ceramic between the silicon chip and the metal mounting base of the package to achieve a lower value of thermal resistance than a similar construction of aluminium oxide.
Beryllium oxide is also used as a structural ceramic for high-performance microwave devices, vacuum tubes, magnetrons, and gas lasers.
BeO has been proposed as a neutron moderator for naval marine high-temperature gas-cooled reactors (MGCR), as well as NASA's Kilopower nuclear reactor for space applications.

-Synonyms-
BERYLLIUM (II) OXIDE
Beryllium monoxide
BERYLLIUM OXIDE
Berylla
Beryllia
Beryllium oxide (BeO)
Beryllium oxide, alpha
berylliumoxide(beo)
bromellete
Glucina
naturalbromellite
Thermalox
thermalox995
BERYLLIUM OXIDE, 99.99%
Berylliumoxide(99.95+%-Be)
Beryllium oxide, 99.95% (metals basis)
Beryllium oxide, 99% (metals basis)

 
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