boron carbide

Boron carbide
IUPAC name	Boron carbide
Other names	Tetrabor B4-C B4C Black Diamond
Identifiers
CAS number	12069-32-8 Y
PubChem	123279
SMILES	B12B3B4B1C234
InChI	1/CB4/c2-1-3(2)5(1)4(1)2
InChI key	INAHAJYZKVIDIZ-UHFFFAOYAS
ChemSpider ID	109889
Properties
Molecular formula	B4C
Molar mass	55.255 g/mol
Appearance	dark gray or black powder, odorless
Density	2.52 g/cm3, solid.
Melting point	2350 °C, 2623 K, 4262 °F
Boiling point	3500 °C, 3773 K, 6332 °F
Solubility in water	insoluble
Acidity (pKa)	6-7 (20 °C)
Structure
Crystal structure	Rhombohedral
Hazards
MSDS	External MSDS
Main hazards	Harmful, irritant.
Related compounds
Related compounds	Boron nitride
Y (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 carbide (chemical formula B₄C) is an extremely hard ceramic material used in tank armor, bulletproof vests, and numerous industrial applications. With a hardness of 9.3 on the mohs scale, it is one of the hardest materials known, behind cubic boron nitride and diamond.

Boron carbide was discovered in the 19th century as a by-product of reactions involving metal borides, however, its chemical formula was unknown. It was not until the 1930s that the formula was determined to be B₄C.^[1] Boron carbide is now produced industrially by the carbo-thermal reduction of B₂O₃ (boron oxide) in an electric arc furnace.

Its ability to absorb neutrons without forming long lived radionuclides makes the material attractive as an absorbent for neutron radiation arising in nuclear power plants. Nuclear applications of boron carbide include shielding, control rod and shut down pellets. Within control rods, boron carbide is often powdered, to increase its surface area.

Uses

• Padlocks
• Personal and vehicle anti-ballistic armor plating.
• Grit blasting nozzles.
• High-pressure water jet cutter nozzles.
• Scratch and wear resistant coatings.
• Cutting tools and dies.
• Abrasives.
• Neutron absorber in nuclear reactors.
• Metal matrix composites.

Preparation

Boron carbide is prepared by reduction of boron trioxide either with carbon or magnesium in presence of carbon in an electric furnace at a temperature above 1400 °C. If magnesium is used, the reaction may be carried out in a graphite furnace and the magnesium byproducts are removed by treatment with acid.^[2]

Notes

References

• Alan W. Weimer (1997). Carbide, Nitride and Boride Materials Synthesis and Processing. Chapman & Hall (London, New York). ISBN 0-412-54060-6. 

External links

• National Pollutant Inventory - Boron and compounds
• NIST Chemistry Database Entry for Boron Carbide
• Chemistry Daily:Boron carbide