Allotropes of Carbon: Diamond

There are many allotropes of carbon which means the elements have similar chemical structures but different physical forms. Allotrope of carbon – diamond is a crystalline, amorphous form of carbon packed in a 3-dimensional lattice structure. Diamond is a precious, rare, and expensive element used extensively for designing luxurious jewellery and manufacturing glass or ceramic cutters and rock drillers. The allotrope of carbon – diamond is mined from the upper mantle Earth surface and majorly extracted from the metamorphic rock. The topic discusses diamonds’ different aspects, including their structure, properties, uses, and extraction.

Allotropes of Carbon Diamond Structure

• The structure of diamond makes it the hardest element
• Each carbon atom in the diamond is in sp3 hybridisation
• It consists of a three-dimensional network of carbon atoms, and each of the carbon atoms is connected with the help of strong covalent bonds
• Each carbon atom is bound in a rigid tetrahedral network, and each carbon atom is equidistant from its neighbouring carbon atom
• The common crystal structure of diamond is known as diamond cubic
• Each corner carbon atom is shared by eight unit cells
• Each atom in the centre of the cubic face is shared by two unit cells
• There are eight atoms in the structural unit of diamond and hence fundamentally arranged in a cube
• This makes the allotrope of carbon diamond structure highly stable and rigid

Mechanical Properties of Diamond

• Amongst all the allotropes of carbon – diamond is the hardest element, and it ranks ten on the Mohs hardness scale
• The hardness of a diamond depends on its crystalline perfection and purity
• The diamonds are arranged in a tetrahedral lattice arrangement; it is rigid and hard 
• Diamonds have a high level of toughness and resist breakage despite the forceful impact
• The allotrope of carbon – diamond is compressive and has a yield strength of 130 -140 GPa
• Hence, it can resist high pressure and intensity
• Diamonds have high elasticity and tensile strength
• The diamond crystal leads to fracture if attempted to bend due to its brittle property
• It can be stretched elastically by 9 to 10% tensile strain
• Since diamond does not have a free-flowing electron, it is a poor conductor of electricity
• However, few types of diamonds are used as semiconductors
• It has high thermal conductivity and heat resistance 

The Chemical Property of Diamond

The allotrope of carbon – diamond is hydrophobic and lipophilic. This means diamonds do not get wet when soaked in water but are easily stuck with oil. However, specialised treatment and modifying the diamond with certain ions make it hydrophilic and stabilise layers of water. Chemicals are chemically inert, and hence, they do not react with chemical reagents like strong bases or acids. 

Optical Properties of Diamond 

The allotropes of carbon – diamond have multiple optical properties, including its lustre, transparency, colour, and light refraction. Diamond has a high refractive index, and hence due to this property, it sparkles under sunlight. The lustre of the diamond is maintained due to its light refraction properties. The colour of diamond varies from blue, red, orange, brown, white, black etc. The blue diamond is the most expensive one used in making jewellery out of all the colours. 

Extraction of Diamond 

The allotropes of carbon – diamond are rare and precious and extracted through geological processes. The diamond is formed under intense pressure and temperature under the Earth’s surface. A process like volcanic eruption brings the diamond to the upper mantle and hence is extracted from the metamorphic rocks. The majority of the diamonds are mined on land, and there are only fewer marine mines. The most common technique employed in the mining process is an open pit or open cast mining. In this extraction process, a pit is created, and it has steep sides which connect to larger mines through a cone-shaped narrowing. The large cone that connects to the mine is called a kimberlite pipe. Hence, the material is removed in bulk and cleaned in the processing plant. 

Uses of allotropes of Carbon: Diamond

• Diamond is largely used in the jewellery industry and makes expensive, luxurious jewellery
• Nearly 30% of the extracted natural diamond is used for gem trading
• Blue diamond has a high refractive index and is hence the best quality for solitaire and diamond jewellery
• The allotropes of carbon – diamond have high thermal conductivity and are used as heat sinks in supercomputers
• It absorbs the excess heat and prevents the computers from being damaged from overheating
• Diamond is the hardest element, and hence it is appropriate for designing glass cutters, ceramic cutters, and rock drill machines
• Allotropes of carbon – diamond are used in the cosmetic industry to develop facial and other products, which helps reduce the ageing effect
• Diamond is used in designing speakers that produce high-quality sound and reduce the rate of vibration

Conclusion 

Diamond is one of the precious metals, and hence it is quite expensive. The allotropes of carbon–diamond have mechanical properties like the highest hardness and good thermal conductivity but are poor electrical conductors. The lustre and the transparency of diamonds depend on the purity and grade of diamonds. The allotropes of carbon diamond structure are packed in a three-dimensional structure, and each carbon is linked to neighbouring carbon through a covalent bond. This creates a tetrahedral lattice structure which makes it solid and rigid.