Graphite

Graphite

Graphite sample

Graphite is an allotrope of carbon. It is a naturally occurring form of crystalline carbon and is known for its use in pencils and as a lubricant. Graphite is one of the softest materials and is also a good conductor of electricity.

Structure

Graphite layers side view

Graphite has a layered, planar structure. In each layer, the carbon atoms are arranged in a hexagonal lattice. The layers are held together by weak van der Waals forces, allowing them to slide over each other easily, which accounts for graphite's lubricating properties.

Graphite layers top view

The covalent bonds within the layers are strong, making the layers themselves very stable. This structure also contributes to graphite's electrical conductivity, as electrons can move freely within the layers.

Properties

Graphite is known for its high thermal and electrical conductivity, chemical inertness, and lubricating properties. It is opaque and has a metallic luster. Graphite is also resistant to heat and can withstand temperatures up to 3000°C in a vacuum.

Graphite unit cell

Occurrence

Graphite occurs naturally in metamorphic rocks such as marble, schist, and gneiss. It is also found in igneous rocks and meteorites.

Graphite from Kimmirut, Canada

Uses

Graphite is used in a variety of applications, including:

• Pencils: Graphite is mixed with clay to form the "lead" in pencils.
• Lubricants: Due to its slippery nature, graphite is used as a dry lubricant in applications where "wet" lubricants cannot be used.
• Electrodes: Graphite is used in electrolysis and battery electrodes due to its conductivity.
• Nuclear reactors: Graphite is used as a moderator in nuclear reactors.

Phase Diagram

Carbon phase diagram

Graphite is stable under standard conditions, but it can transform into diamond at high pressures and temperatures. The phase diagram of carbon shows the conditions under which graphite and diamond are stable.

Pressure-Volume Relationship

Graphite pressure-volume relationship

The pressure-volume relationship of graphite is important in understanding its behavior under different conditions, such as in high-pressure environments.

Related Pages

• Carbon
• Diamond
• Allotropy
• Van der Waals force
• Hexagonal lattice