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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/
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