Carbides

Carbide is a chemical compound formed by the combination of carbon and a metallic or semi-metallic element. Carbides are used in various industrial, technical, and home applications. Calcium carbide is a significant contributor to acetylene and other chemicals. Steel, silicon, tungsten, and other element carbides are desired for their mechanical toughness, durability, and resistance to chemical degradation, even at extremely high temperatures. Iron carbide (cementite) is a key component of steel and cast iron.

What is a carbide?

A carbide is a chemical compound made up of carbon and metallic or semi-metallic components. It can be found in ionic form. The ionic or covalent link connects the carbide group to the metal or semi-metallic element. The symbol C2-2 denotes carbide. It denotes that carbide ions are composed of two carbon atoms. The carbide formula indicates that the carbide occurs in dianionic form. Based on the carbide ion formula, we can tell what lone pairs and hybridisation are.

Structure of a carbide

Two carbon atoms are joined together by three covalent bonds in a carbide formation. Two of such covalent bonds are pi-bonds. This lateral overlaying of the p-orbitals results in the formation of such pi-bonds. Another type of bond is the sigma bond, created by the s-orbitals overlapping head-on. The carbon in the carbide structure exhibits sp hybridisation. Each carbon has a single lone pair on it.

Basic characteristics of carbides

• Carbides usually have a fairly high melting point.
• Carbides are excellent electrical conductors.
• Carbides are good thermal conductors.
• Carbides have a lustrous appearance in general.

Classification of carbides

Carbides are classed broadly based on the sort of chemical linkages they contain, as follows:

(i) salt-like (ionic) compounds

(ii) covalent compounds

(iii) interstitial compounds, and

(iv) transition metal carbides classified as “intermediate.”

1) Salt-like or saline carbides are made of highly electropositive atoms combined with carbon, such as alkali, alkali earth, and group-III metals.

2) Covalent carbides are present in silicon and boron carbides. Because of their close electronegativity and size to carbon, these two elements produce “covalent” carbides. As a result, their bond is covalent. Silicon carbide exists in two crystalline forms connected to diamond structures.

3) Interstitial carbides are transition metal carbides of groups IV, V, and VI. These carbides have metallic and refractory properties.

4) The transition-metal ion in intermediate transition metal carbides is smaller than the crucial 135 pm, and the configurations are not interstitial but rather complicated. Several stoichiometries are quite common. These carbides are more reactive than interstitial carbides; for example, the carbides of Cr, Mn, Fe, Co, and Ni are all hydrolysed by dilute acids, and occasionally by water, to produce a combination of hydrogen and hydrocarbons. These compounds have properties in common with both inert interstitials and much more reactive salt-like carbides.

Silicon carbide

Silicon carbide, often known as carborundum, is a silicon and carbon combination. Silicon carbide is a semiconductor material that is becoming more popular in semiconductor devices. It is a very significant industry ceramic substance. It had a significant part in the industrial revolution and is currently widely used in abrasion, steel addition, and construction ceramics.

• Structure: Silicon carbide crystallises in a densely packed structure that is covalently bound to itself. The atoms are organised in such a way that two main coordination tetrahedral structures are generated, with four carbon and four silicon atoms bound to a core Si and C atom. These tetrahedra are connected at the corners and layered to produce polar formations.
• Properties: It has fascinating electrical properties due to its semiconductor features, with resistance ranging by as much as seven orders of magnitude between various compositions. Except for hydrofluoric acid and acid fluorides, it is resistant to most organic and inorganic acids, alkalis, and salts in various concentrations.
• Uses: Carbides are used to produce high-speed, high-temperature, and high-voltage devices. Because of its homogeneity, abrasion resistance, and structural integrity, it is used in finishing work. Light-emitting diodes (LEDs) and detectors are examples of electrical equipment that use this compound.

Calcium carbide

CaC2 is the chemical formula for pure calcium carbide, which is a colourless and odourless solid. Calcium acetylide, phenyl glyceryl ether diacetate, and glycerol phenyl ether diacetate are other names. At room temperature, calcium carbide occurs as a colourless crystalline solid with a rock-like morphology. On the other hand, commercial calcium carbide can have a broad variety of colours based on the contaminants present.

It is utilised in manufacturing calcium hydroxide and acetylene and in the synthesis of polyvinyl chloride. It is utilised to produce calcium cyanamide and to remove sulphur from iron. It is included in lights like carbide lamps. As with ethylene, it is used as a ripening agent. It is also utilised as a deoxidiser, which aids in eliminating oxygen during the steel-making process.

Conclusion

Carbide is a compound made up of carbon and a less electronegative element, most commonly a metal or metal oxide. Whenever the term “carbide” is used alone, it typically refers to calcium carbide or tungsten carbide. Carbon carbide is a chemical compound made up of carbon and metal or semi-metallic components. It can be found in ionic form. The ionic or covalent bond connects the carbide group to the metal or semi-metallic element. Carbide is denoted by the symbol C2-2. It denotes that carbide ions are composed of two carbon atoms.