Carbides
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| Discuss Carbides CARBIDES
All the various compounds of carbon with metals or other more electropositive elements are termed as carbides. True Carbides have the ion C4- (e.g. Al4C3). The properties of carbides resembles to those of salts. On hydrolysis they give methane and thus, were formerly called methanides. Dicarbides are compounds containing the ion C2-, these are also salt like. On hydrolysis these yield ethyne and thus, were formerly called acetylides. Both true and di carbides are generally ionic ( except carbides of boron and silicon, which have giant molecular structures)
The transition metals form a range of interstitial carbides in which the carbon atoms occupy interstitial positions in the metal lattice. They are usually hard materials with metallic conductivity.
Some metals like Cr, Mn, Fe, Co and Ni, have atomic radii that are too small to allow individual carbon atoms in the interstitial holes. In this case, they form carbides in which the metal lattice is distorted and chains of carbon atoms exist. The properties of this type of carbides is intermediate between those of ionic and interstitial carbides.
USES
- Calcium carbide is used in the preparation of acetylene.
- The carbide of tungsten is used for cutting tools, and in the manufacture of ball point pens and dies.
- Silicon carbide, owing to its hardness, is used in grinding as an abrasive.
- Silicon carbide is also used in the construction of atomic reactors. This is due to its ability to withstand high temperatures and due to its property of thermal conductivity.
- Boron carbide is used both as an abrasive and as a radiation shield.
