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Graphite - Uses, Introduction, Occurrence, Structure and Properties

 

Consider a chef preparing two dishes using the same main ingredient but using slightly different techniques. This one-step of difference can make a world of difference between the two dishes. Consider the difference between cooking rice in water and then straining it versus cooking rice in milk and then adding sugar at the end. The first will serve you a plate of boiled rice with some side dishes for lunch, while the second will serve you rice-kheer for dessert.

image

Carbon, an element present probably since eternity, is also capable of showing such magical properties where the same element can take up multiple forms and reveal huge diversity in properties, look and feel. Diamond and Graphite are very similar in composition, with some slight differences in structural orientation. That itself has made the two substances differ from each other to such a degree! 

Let’s find out more about one such form of elemental carbon i.e., graphite, on this page.

TABLE OF CONTENTS

  • Graphite - Introduction and Occurrence
  • Graphite - Structure
  • Graphite - Properties
  • Graphite - Uses
  • Practice Problems
  • Frequently Asked Questions - FAQ

Graphite - Introduction and Occurrence

The word "graphite" comes from the Ancient Greek word "graphein," which means "to write/draw." In 1795, Nicholas-Jacques Conte, a chemist serving under Napoleon Bonaparte, produced modern graphite pencils by combining clay with graphite.

When carbon is exposed to heat and pressure in the Earth's crust and upper mantle, natural graphite is formed. To make graphite, you'll need a pressure of roughly 75,000 psi and temperatures around 750 degrees Celsius.

Graphite is a mineral that occurs in both metamorphic and igneous rocks. Graphite is also thought to be a naturally occurring crystalline carbon form.

Occurrence

  • At convergent plate boundaries, the majority of the natural graphite found on the Earth's surface today was created. Shales and limestones were subjected to the heat and pressure of regional metamorphism, resulting in marble, schist, and gneiss, which contain small graphite crystals and flakes.
  • Graphite is the most stable crystalline form of carbon that exists in nature. Graphite is a black substance. It has a metal-like sheen and is opaque. It is also known as plumbago.
  • Pitch and coke particles are used to create artificial graphite. Electrodes in electric arc furnaces, moderators in nuclear power plants, microcircuits on silicon chips, and semiconductors are all popular uses. Artificial graphite can also be utilised in the batteries of electric vehicles!

Graphite - Structure

  • Graphite has a layered structure held by weak van der Waals forces and the distance between any two layers is 340 pm.
  • Each layer of graphite consists of planar hexagonal rings of sp2 hybridised carbon atoms. 
  • The C—C bond length within the layers is 141.5 pm.
  • Each carbon atom in a hexagonal ring makes three sigma bonds with three neighbouring carbon atoms and the fourth electron forms a π bond.
  • Electrons are mobile and are delocalised over the whole sheet. Therefore, graphite conducts electricity along the sheet.
  • As graphite cleaves easily between layers, it is very soft and slippery.

image

Graphite - Properties

  • Graphite is a soft material that easily cleaves under light pressure, is oily, and has low specific gravity. Furthermore, this mineral is black or greyish in colour. It is a good conductor of electricity and heat, and it can tolerate high temperatures. Another notable feature of this mineral is its chemical inertness, which means it is unaffected by the majority of chemicals and acids.
  • When graphite is exposed to extreme pressures and temperatures, it transforms into diamonds.
  • The carbon atoms in graphite form a hexagon, and the hexagons are stacked one on top of the other. It can be found in crystalline, amorphous, lump, and graphite fibre forms.
  • Rhombohedral (𝝱 form) and hexagonal (𝝰 form) graphite are the two types of graphite. Both are quite anisotropic. As a result, it is chemically resistant and can sustain high temperatures. 
  • Graphite has a density of 2.26 g/cm3 at 300 K and 1 atm pressure, and a boiling point of 4560 K.
  • Electrical conductivity of graphite > Electrical conductivity of diamond
  • Thermal conductivity of graphite < Thermal conductivity of diamond
  • Graphite is thermodynamically the most stable allotrope of carbon. Hence, image of graphite is taken as zero.
  • image (Diamond) =1.90 kJ mol-1 and image (Fullerene, C60) =38.1 kJ mol-1.

Graphite - Uses

Refractory, battery, steel, expanded graphite, brake linings, foundry facings, and lubricants are just a few of the applications for graphite. Graphene, the layered sheets constituting graphite, has remarkable physical properties and is one of the most powerful compounds ever discovered. 

Pencil Lead and Artistry

  • The most popular and well-known application of graphite is as a pencil nib. The lead is not pure graphite, however, since a small quantity of clay is utilised to produce the lead of the pencil, allowing the lead to be a little stronger.
  • Physical abrasion makes a mark on the paper that can be easily erased with rubber, but graphite is otherwise impervious to moisture, most chemicals, ultraviolet light, and natural ageing.

Batteries

  • The cathode and anode electrodes are found in batteries. Graphite is the most common material used to make the anode of most batteries.
  • Graphite is one of the most preferred materials for the manufacture of anodes for ion batteries because of its great conductivity due to the existence of free electrons, as well as its spectacular porosity, durability, lightweight, and low cost. 
  • Graphene, which is a single sheet of graphite organised in a two-dimensional honeycomb lattice, exhibits significant improvements in these qualities, making it suitable for application in the production of fast-charging batteries for smartphones.
  • A graphene battery may be small, light, and strong, making it perfect for energy storage with high capacity and quick charging times.
  • It will extend battery life, which is negatively connected with the amount of energy sprayed on the surface and delivered to the electrodes to achieve conductivity, and graphene gives conductivity without requiring the large volumes of carbon used in traditional batteries.
  • High-grade graphite is also utilised in fuel cells, solar cells, semiconductors, LEDs, and nuclear reactors, in addition to Li-ion anodes.

Refractory

  • Graphite is a refractory substance, which means it can withstand high temperatures, pressure, and even chemical attack. Before the 1900s, graphite was employed to retain molten metal, and it has subsequently been used in defence. In reality, an invoice for the provision of Graphite crucibles for cannonball manufacture to the Napoleonic armoury may be seen at the Kendal Graphite Mine in the United Kingdom.
  • Molten metals are still held and cast in natural graphite. Gold and silver can be melted in small crucibles, while unusual metals can be melted in bigger ones. Because of its refractory qualities, graphite is also employed as a gasket for high-temperature sealing.
  • Graphite is a frequently utilised refractory material due to its high heat endurance and unchangeability. It is used in the manufacturing industry to aid in the production of glass and steel, as well as iron processing.

Repellants

  • Since graphite behaves as a strong repellant, a variety of industrial organisations use graphite as a component in repellent treatments. Metal protectors are one of the most common graphite-based repellents.
  • Graphite is water-repellant and hence used in the paint industry to make paints of a longer durability and give ultimate protection to walls.

Lubricants

  • One of the most noticeable characteristics of graphite is its ability to lubricate. Dry lubricants such as graphite, are solid compounds that can reduce friction between two surfaces moving against each other without the use of a liquid oil medium.
  • The layers of graphene sheets contained in graphite can slide over each other with a low coefficient of friction due to the presence of weak van der Waals forces.
  • Compared to liquid and oil-based lubricants, it provides lubrication at higher operating temperatures.
  • Although graphite is commonly used for lubrication in large machinery, it can also be found in everyday goods such as locks, piano gears, ball bearings, brass instrument valves, and so on. It is also used in air compressors, railway track joints, the food sector, and other applications.

Nuclear Reactors

  • Because graphite has a large capacity for absorbing moving neutrons, it is frequently used to stabilise or neutralise the reactions of neutrons and hence finds great usage in nuclear reactors.

Touch Screens

  • Graphene offers an amazing mix of two properties: transparency and conductivity, similar to glass and metals.
  • These two characteristics are one of the most essential prerequisites for touchscreen efficiency. Capacitive touch screens work by sensing capacitance at several points on the screen and then interpolating between them to get a precise position.
  • The capacitor's simplest form is two parallel conductive plates on opposite sides of an insulator, with capacitance proportional to the area of intersection of the two plates and the insulator's dielectric constant, and inversely proportional to the distance between the plates.
  • One plate is a transparent conductor on the backside of the glass in the case of a touch screen, and the other is the touch screen itself.

Sensors

  • Graphite has become a popular material in the electronics industry due to its outstanding electrical and thermal conductivity. 
  • Numerous electrochemical sensors have been developed and effectively used in various fields in the last few decades, including gas sensors for the detection of dangerous gases, metal sensors for water quality measurement, and so on.
  • In analytical chemistry, pencil graphite electrodes (PGE) are frequently utilised as voltammetric sensors for various electrochemical experiments.
  • Its abundance at ultra-low costs, combined with a variety of interesting properties like mechanical flexibility, chemical inertness, low background current, wide potential window, analyte adsorption, and ease of miniaturisation, has made it a popular material for electrochemical sensor manufacturing.

Car Brakes

  • Friction is the most critical component in your vehicle's braking system. 
  • Graphite regulates the braking effect of friction by enhancing the removal of energy from the contact region and preventing friction elements from overheating, thanks to its lubricating characteristics and good thermal conductivity.

Headphones

  • The 40mm acoustic drivers that provide sound to the ear are made of graphene.
  • To move a cone and produce sound waves, dynamic drivers, also known as moving coil drivers, use an electrically charged voice coil.
  • These drivers are made up of more than 95% graphene and retain the majority of the material's mechanical properties while being easy to shape and fabricate.

Electrical Industry

  • Graphite is employed in a variety of ways in electrical circuits. The most common form of graphite is crystalline graphite.

Graphene Sheets

  • Graphene, a graphite derivative, 10 times lighter and 100 times stronger than steel, is the world's strongest recognised substance and has been used to create super-strength, lightweight sporting equipment.
  • Graphene is chemically resistant, has a high electrical conductivity, and absorbs little light. Its qualities make it a good candidate for future applications as a material. It is employed in medical implants like artificial hearts, as well as flexible electronic components and aviation parts.

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Practice Problems

Q1. Graphite is slippery because of

A. Covalent bond
B. Coordinate bonding
C. Electrostatic Force of Attraction
D. van der Waals Force

Answer: Because of the weak van der Waals' force of attraction between its layers, graphite is slippery, and each layer can slide over the other. 

So, option D) is the correct answer.

Q2. “Graphite is isotropic.” Mention whether the statement is True or False.
Answer: Anisotropic substances are those that have differences in physical properties when measured in different orientations. Graphite is one of them due to its layered structure. Wood and graphite, for example, are anisotropic. 

So, the given statement is false.

Q3. The geometry of molecular graphite is

A. Trigonal planar
B. Tetrahedral
C. Octahedral 
D. Pyramidal

Answer: Each carbon in graphite is sp2 hybridised. Graphite has a trigonal planar molecular geometry with a bond angle of 120 degrees. In graphite, the three bonds associated with each carbon atom tend to shift widely apart in order to reduce electron pair repulsion. They are situated at the three points of a triangle. The hybridised carbon atoms are stacked in hexagonal layers in various levels.

So, option A) is the correct answer.

Q4. Which of the following allotropes of carbon is a good conductor of electricity?

A. Coal
B. Graphite
C. Fullerenes
D. Diamond

Answer: Only three of a carbon atom's four valence electrons are utilised for bonding in case of graphite, whereas the fourth is relatively free and can travel from one carbon atom to another. Graphite is a good conductor of electricity and a good lubricant because of these free electrons. Rest are non-conductors.

So, option B) is the correct answer.

Frequently Asked Questions - FAQ

Question 1. How was graphite manufactured on earth?
Answer: Edward Acheson accidently developed graphite while doing high-temperature tests on carborundum. At roughly 4150 °C (7500 °F), the silicon in carborundum evaporated, leaving the carbon in graphite form behind. A patent for graphite manufacture was granted to Acheson in 1896.

Since 1918, petroleum coke has been the major raw material for creating 99 to 99.5 % pure graphite, as it is made up of microscopic, imperfect graphite crystals surrounded by organic compounds.

Question 2. Is graphite carcinogenic?
Answer: Shortness of breath, cough, and other respiratory problems can be caused by graphite, but it is not carcinogenic, meaning it does not cause cancer.

Question 3. Which is stronger steel or graphene?
Answer: Graphene, a graphite derivative, 10 times lighter and 100 times stronger than steel, is the world's strongest recognised substance and has been used to create super-strength, lightweight sporting equipment.

Question 4. Graphite is an element or compound?
Answer: Graphite is an elemental form of carbon. So, it is an element. It is an allotrope of carbon. since carbon is a non-metal, graphite is also a non-metal, although its physical state is solid.

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Phosphorus halides

Potassium

Phosphine

Alkali Metals

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