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Nanoscience and Materials
1983$3995
1992$1400
2002$480
2009$199
These advances in technology would not have been possible without nanotechnology.
Nokia Morph : The Next Generation of Mobile Phones?
What affects our choice of materials?
• What do they have in common?
– Both are forms of carbon.
• How are they different?
– Appearance, hardness, conductivity.
Diamond and Graphite
• Both are forms of carbon.
• However, changes in the arrangement of the atoms at the nanoscale cause these materials to behave differently.
• Within diamond, every carbon atom is bonded to 4 other carbon atoms.
• Within graphite, every carbon atom is bonded to 3 other carbon atoms.
Why do they behave differently?
This structure is known as a tetrahedron.
The 4 bonds to the central carbon atom spread out evenly, so the base structure of diamond is a 3-D shape.The structure builds up because every carbon atom is bonded to another 4 carbon atoms.
Diamond
The bonds to the central carbon atom in graphite spread out evenly, so the base structure is a 2-D shape (has length and width but no height).
The structure of graphite sheets builds up because every carbon atom is bonded to 3 other carbon atoms.
Bonds to 3 C atoms.
The hexagonal pattern in which the atoms are arranged can now be seen.
Graphite
• As the structure continues to build up, it remains 2- Dimensional (flat).
• A 3-D shape is formed by the layering down of a number of these 2-D structures (called Graphite sheets) on one another.
Sheets of graphite in pencil lead – taken in CRANN using a SEM.
Graphite
• Very weak forces - means that sheets can be peeled off easily.
• This is why graphite is soft and a useful material for pencils.
• These layers are kept together by a force of attraction known as Van Der Waals forces.
Van der Waals forces
•This means that a single layer of graphite is very strong.
•In 2004, a single layer of graphite was isolated for the first time.
•This single layer of graphite is known as Graphene, and consists of a sheet of carbon atoms, just one atom thick.
However, the bonds IN the graphite sheet are very strong due to their partial double bond nature.
Graphene
• One of the strongest materials known - 200 times stronger than steel, but still bendable!
• Excellent electric conductor.
• Transparent.
• Impermeable - substances as small as helium (He) atoms cannot pass through the hexagonal patterns.
Graphene: amazing properties
• How do we isolate graphene from graphite?
+ =
• In CRANN scientists have isolated graphene sheets using soap!
• Why isolate graphene? What could it be used for?
Isolating graphene
• Electronics devices – used to make transistors and display screens e.g. e-paper, smart phones, transparent loudspeakers.
• Extremely sensitive sensors for gases and diseases. • Stronger, lighter materials, e.g. household products, sports,
transport.• Invisibility cloaks!
Graphene will change the world around us!
• Apart from graphene, other “layered” materials can be split into single layered “nanosheets”.
• Offering a whole range of new “super” materials.• Can be metallic, semiconducting or insulating, depending on their
chemical composition.• Uses – added to plastic to make strong materials; supercapacitors,
thermoelectric devices.
Other “super” materials
• A form of carbon with a cylindrical nanostructure.• Walls consist of one-atom thick sheet of carbon.• Discovered in 1991.
Carbon nanotubes
• Nanotubes can be imagined as rolled up sheets of graphene.
• The graphene sheet can be rolled in 3 different ways to form different types of nanotubes.
• These subtle differences cause the nanotubes to have different electrical properties.
Carbon nanotubes
• Mechanical - nanotubes have a very high strength to weight ratio; they are at least 100 times stronger than steel but only one sixth as heavy.
• Electrical - nanotubes in the Armchair configuration conduct electricity very well; nanotubes in the Zigzag and Chiral configuration are semi-conductor materials.
Properties of nanotubes
• Electronics– nanotube transistors for use in computers and phones?
• Reinforce plastics and concrete structures e.g. aircraft and bridges.
• Energy– hydrogen fuel cells?• Sports industry to create robust,
lightweight equipment.
Some possible uses of CNTs
• Could carbon nanotubes be the ideal material for a cable that would extend all the way to outer space because of their high strength to weight ratio?
Space elevator - Royal Society Christmas Lecture [12 min YouTube]
Space elevator
• Nanowires e.g. silver could be used in flexible electronic display panels like e-paper.
• Nanoparticles e.g. zinc, titanium have made suncreams “invisible”.
Network of silver nanowires. e-paper.
More nanomaterials
• Nanoelectronics in mobile phones, e-readers, notebooks.
• In clothing, to repel dirt and water.
• Cosmetics and sunscreens.
• In tennis rackets and bicycle frames.
• Socks – silver nanoparticles to keep your feet cleaner!
• Coatings on cars and sunglasses to make them anti-misting and scratch-proof.
• In paints to make them anti-microbial.
Nanotechnology is already here!
• When choosing a material, its properties, performance and cost need to be considered.
• There are different forms of carbon which differ in the arrangement of carbon atoms at the nanoscale.
– Diamond.
– Graphite (and graphene).
– Carbon nanotubes (CNTs).
– Buckyballs.
• A lot of research is being conducted with graphene and CNTs for their commercial application, particularly in:
– Electronics.
– Energy- thermo-electrics, supercapacitors.
– Reinforcing materials to make them stronger and lighter.
• Nanomaterials are becoming more common in everyday use.
Summary