GRAPHENE Carbon’s better half

INTRODUCTION: WHAT IS GRAPHENE?

▪ 2-D hexagonal allotrope of carbon

▪ Each atom forms a vertex

▪ Foundation building block for other carbon-based allotropes

▪ Graphite

▪ Charcoal

▪ Carbon nanotubes

▪ Fullerenes

▪ Categorized as an ‘indefinitely large aromatic molecule’

▪ Aromatic molecule: cyclic, planar ring of resonance bonds

https://www.youtube.com/watch?v=_cDh4B6knKw

INTERESTING AND UNIQUE FACTS

▪ 200 times stronger than steel

▪ One of the most conductive materials of both heat and electricity in the world

▪ Virtually transparent

▪ Thinnest material on earth – 1 million times thinner than a human hair

▪ Stretchable, flexible, and impermeable

▪ Can repair itself when exposed to pure carbon molecules

HISTORY

▪ Discovered in 1859

▪ Benjamin Collins Brodie was the first to acknowledge its existence

▪ Structure was revealed in 1924

▪ 8 years after discovering the structure of graphite

▪ Difficult to isolate and produce in large, economic quantities

INITIAL CREATION AND ISOLATION

▪ Take ordinary graphite

▪ Use tape to remove small chunks that stick to the tape

▪ Some of these pieces would have a molecular structure that resembled graphene and could be used and applied towards things such as electronics

CHEMICAL PROPERTIES • Only form of carbon where every individual atom has the

potential for chemical reaction • Atoms at the edges of a sheet are the most chemically

reactive • Combusts at 350°C (620 K) • Reactivity stems from imperfections in 2-D lattice

• Perfectly flat graphene void of any vacancy defects or interstitial hydrogen/oxygen molecules is chemically inert

• Capable of being doped

ELECTRONIC PROPERTIES Graphene possesses ‘remarkable electron mobility’ @ room temp.

▪ Reported values exceeding 15,000 cm2.V-1.s-1

▪ Hole and electron mobilities are expected to be nearly identical

▪ Resistivity of 10-6 Ohms.cm

▪ Less than that of Silver, which is the lowest otherwise at room temp.

▪ In 2015, it was discovered that lithium-coated graphene has displays extraordinary ‘superconductivity’

▪ Exactly zero electrical resistance and ‘expulsion of magnetic flux fields’

▪ May be a suitable material for the construction of quantum computers

▪ Charge fractionalization

THERMAL PROPERTIES

• Early predictions suggested graphene’s melting point hovered around 4125K.

• Further investigation however, increased this temperature to 5000 K (where the surface of the sun has an average temperature of 5777 K)

• At 6000 K graphene melts into a pile of double bonded chains before vaporizing shortly after

MECHANICAL PROPERTIES

▪ Carbon-carbon bond length is approximately .142 nm

▪ When graphene stacks, it simply forms graphite with a planar spacing of .335 nm

▪ Strongest material ever tested

▪ Tensile strength of 130 Gpa

▪ Young’s Modulus E = 1 Terapascal (150,000,000 psi)

▪ ‘The Nobel announcement illustrated this by saying that a 1 square meter graphene hammock would support a 4 kg cat but would weigh only as much as one of the cat's whiskers, at 0.77 mg’

MECHANICAL PROPERTIES (CONT.)

▪ Despite absurdly high strength measurements, graphene lacks ductility

▪ Fracture toughness = 4 Mpa/m2

▪ Acts like a ceramic due to how brittle it is

▪ Most metals have a fracture toughness between 15-50 Mpa/m2

▪ “Later in 2014, the researchers announced that graphene showed a greater ability to distribute force from an impact than any known material, ten times that of steel per unit weight”

▪ Transmitted throughout the structure at a speed of 22.2 km/s

APPLICATIONS: WHAT MAKES GRAPHENE SO INNOVATIVE?

https://www.youtube.com/watch?v=LTa_ileMJxE

APPLICATIONS - MEMBRANES

▪ Filtration:

▪ Graphene oxide can form a ‘perfect’ barrier

▪ Liquids and gases can not penetrate

▪ Separate organic solvent from water (nitrates, nitrites, phosphorus from agricultural run-off etc.

▪ Remove water vapor from a gaseous mixture

▪ Can even block Helium

▪ Coatings:

▪ A single layer acting as a perfect barrier can revolutionize industrial processes and open doors to whole new markets

APPLICATIONS – COMPOSITES AND COATINGS

▪ Potential to prevent oxidization of metals (rust corrosion)

▪ Graphene-infused paint could prevent rusting of cars, ships, etc. entirely

▪ Could impact aerospace industry drastically

▪ Graphene-based composite aircraft wing

▪ Significantly decrease weight while increasing strength

▪ Increase fuel efficiency

▪ Reduce impact of lightning strike damage

APPLICATIONS - ENERGY

▪ Augment quality of existing technology

▪ Increase lifespan of traditional Lithium ion battery

▪ Charged more quickly and operate for longer on a single charge

▪ Batteries light enough to be stitched into clothing

▪ Innovative military application

▪ Graphene supercapacitors

▪ Massive power output while consuming less energy than current technology

APPLICATIONS- BIOMEDICAL

▪ Multiple forms

▪ Graphene sheets

▪ Few-layer graphene flakes

▪ Graphene oxide ▪ Offers a variety of unique, versatile properties that can be manipulated to appeal to numerous

biomedical applications

▪ Lateral dimensions can be adjusted

▪ Thickness ranging anywhere from a dozen nanometers to fractions of a millimeter

▪ Creative design capabilities suggests the possibility of: ▪ Drug delivery systems

▪ Ultrasensitive biosensors

APPLICATIONS - SENSORS ▪ Ideal for sensors

▪ Every atom is exposed to the environment, allowing it to sense changes in the surroundings

▪ Chemical reactivity

▪ Can detect even a single molecule of a potentially dangerous substance

▪ Detection of contaminants on the molecular level

▪ Monitoring crops

▪ Detect presence of harmful gases and take action before crop fields are harmed

▪ Extreme sensitivity for early detection warning systems ▪ Detect the presence of chemical warfare agents and explosives

▪ Save the lives of soldiers in the field

APPLICATIONS - ELECTRONICS

▪ Improve current computer technology

▪ Circuitry coating that makes electronics incredibly fast

▪ Due to very high conductive properties

▪ Could even be the key to next-generation futuristic electronics

▪ Graphene’s flexibility allows for interesting ideas

▪ Tablet you could roll up like a newspaper, or smartphone you can wrap around your wrist

APPLICATIONS – ELECTRONICS (CONT.)

▪ Worlds smallest transistor

▪ Smaller the size, better they perform in circuitry

▪ Unique properties of thickness and conductivity

▪ Incredible applications as a semiconductor

▪ Replace existing technology for computer chips

▪ Much faster than currently existing silicon chips

CONCLUSION

▪ Graphene is the material of the future

▪ Combines multiple properties into one, highly adaptive and multi-functional material

▪ Not only combines, but also has some of the most impressive qualities known to man when compared to every other material we currently work with

▪ Biggest obstacle is cost, but it is steadily declining and becoming a more affordable and realistic option

▪ Some tennis rackets are already manufactured using graphene to reinforce strength and durability

▪ $100 / gram

REFERENCES

1. Wikipedia:

https://en.wikipedia.org/wiki/Graphene

2. Graphene Experts

https://www.graphenea.com/pages/graphene#.WRzJE1yPYk4

3. Manchester University

http://www.graphene.manchester.ac.uk/