Boron carbide
| Names | |
|---|---|
| IUPAC name
Boron carbide
| |
| Other names
Borocarbide
Carbon tetraboride Tetrabor | |
| Properties | |
| B4C | |
| Molar mass | 55.255 g/mol |
| Appearance | Dark gray or black solid |
| Odor | Odorless |
| Density | 2.50 g/cm3 |
| Melting point | 2,350–2,450 °C (4,260–4,440 °F; 2,620–2,720 K) [1][2][3] |
| Boiling point | 3,500 °C (6,330 °F; 3,770 K) |
| Insoluble | |
| Solubility | Insoluble in all solvents |
| Vapor pressure | ~0 mmHg |
| Thermochemistry | |
| Hazards | |
| Safety data sheet | Sigma-Aldrich |
| Related compounds | |
| Related compounds
|
Silicon carbide |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Boron carbide (B4C) is an inorganic chemical compound. In bulk, it is an extremely hard ceramic material, commonly used in tank armor, bulletproof vests, engine sabotage powders, as well as numerous industrial applications. Recently, it has been used as green colorant in fireworks, as it is less toxic than barium salts.
Although its chemical formula is accepted as B4C, in reality its structure is highly complex, with a mixture of C-B-C chains and B12 icosahedra. Because of the B12 structural unit, the chemical formula of "ideal" boron carbide is often written not as B4C, but as B12C3, and the carbon deficiency of boron carbide described in terms of a combination of the B12C3 and B12C2 units.
Contents
Properties
Chemical
Boron carbide resists the action of most reagents, like acids and alkali.
Finely powdered B4C is much more reactive, and will burn when mixed with oxidizers, producing a green flame.
Physical
Boron carbide is a black solid, odorless, insoluble in any solvent. It has an average density of 2.5 g/cm3.
Boron carbide is known as a robust material having extremely high hardness (about 9.5 up to 9.75 on Mohs scale of mineral hardness), high cross section for absorption of neutrons (i.e. good shielding properties against neutrons), stability to ionizing radiation. Its Vickers hardness (38 GPa), elastic modulus (460 GPa) and fracture toughness (3.5 MPa·m1/2) approach the corresponding values for diamond (1150 GPa and 5.3 MPa·m1/2), making it one of the hardest known materials, behind cubic boron nitride and diamond.
Availability
Boron carbide can be bought from chemical suppliers, or online.
Preparation
Boron carbide can be prepared by reduction of boron trioxide either with carbon or magnesium in presence of carbon in an electric arc furnace. In the case of carbon, the reaction occurs at temperatures above the melting point of B4C and is accompanied by liberation of large amount of carbon monoxide:
- 2 B2O3 + 7 C → B4C + 6 CO
If magnesium is used, the reaction can be carried out in a graphite crucible, and the magnesium byproducts are removed by treatment with acid.
Projects
- Superhard ceramic materials
- Green colorant in fireworks
- Compound collecting
- Abrasive
- Neutron absorber
Handling
Safety
Boron carbide has low toxicity, and thus it's safe to handle. Sharp pieces however may pose a safety hazard, as they can be very sharp and cut deeply if mishandled.
Storage
No special storage is required. Can be kept in any clean container.
Disposal
No special disposal is required, though shards of this material may pose a safety hazard, as they can cut badly, so dispose of them properly.
References
- ↑ Pring, J. N.; Fiedling, W.; Journal of the Chemical Society; vol. 95; (1909); p. 1497 - 1506
- ↑ Ridgway, R. R.; Chemical and Engineering News; vol. 21; (1943); p. 858 - 862
- ↑ Ordan'yan; Boldin; Prilutskii; Russian Journal of Applied Chemistry; vol. 73; nb. 12; (2000); p. 2128 - 2130
- ↑ Kelley, K. K.; Journal of the American Chemical Society; vol. 63; (1941); p. 1137 - 1139
