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Graphene and 2D Materials

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[University of Toronto]

 Heading for the Graphene Revolution



- Overview

Graphene is ultra-light and very tough, yet flexible and stretchable. Graphene, which typically has excellent electronic properties, was first discovered when physicists stripped the top atoms from graphite. 

The discovery is revolutionary because the inlaid substance exhibits extremely high electrical conductivity, flexibility and a similar ability to store electricity (just to give you some quick specs, it's harder than diamond and stronger than steel 300 times more transparent, 1,000 times better conductor than copper). 

Made from a single layer of carbon atoms, graphene has properties that make researchers salivating. It is hundreds of times stronger than steel and far better than any material used in electronics today. 

Since graphene was first isolated in 2004, this Nobel Prize-winning feat has sparked a whole new and exciting field of materials science research, and 2D materials have had various proposed applications. 

Now, at the forefront of research, materials scientists have discovered that stacked layers of these atomically thin materials can open up a whole new world of fascinating and useful properties.


- Superconductors and the Graphene Revolution

A material supreme: How graphene will shape the world of tomorrow - MIT researchers find that graphene can function as a superconductor. Superconductors can carry large currents without generating any waste heat and are key to many scientific and medical applications. They may also be critical to future energy-efficient technologies. But most superconductors only work at temperatures close to absolute zero (–273 ˚C). Only in recent years have physicists managed to get some to work above 0 ˚C, using high pressure anvils.

When it comes to graphene, it seems that superconductivity runs in the family. Graphene is a single-atom-thin material that can be exfoliated from the same graphite found in pencil lead. The ultrathin material is made entirely of carbon atoms arranged in simple hexagons, similar to barbed wire. Since its isolation in 2004, graphene has been found to exhibit many remarkable properties in its monolayer form. 

In 2018, MIT researchers discovered that twisted bilayer structures can exhibit strong superconductivity if two graphene layers are stacked at a very specific "magic" angle, a widely sought material A state in which current can flow with zero energy loss. Recently, the same group discovered a similar superconducting state in twisted trilayer graphene - a structure in which three graphene layers are stacked at precise new magic angles.


- Graphene

Graphene - a single layer of carbon atoms - may be the most amazing and versatile substance available to mankind. Simply put, graphene is a two-dimensional crystal of atoms composed of carbon atoms arranged in a hexagonal lattice. Due to its unique combination of superior properties, graphene is a reliable starting point for new disruptive technologies across a wide range of fields. 

Graphene is the thinnest compound known to man, only one atom thick (a million times thinner than a human hair), the strongest compound ever discovered (100-300 times stronger than steel), and the lightest known material (one square meter weighs about 0,77 mg) and is very flexible. 

It is also impermeable to molecules and has high electrical and thermal conductivity - graphene allows electrons to flow faster than silicon. It is also a transparent conductor that combines electrical and optical functions in a special way. 

Graphene can be considered a huge molecule that can be used for chemical modification, with potential for a wide range of applications ranging from electronics to composites. It is also relatively inexpensive to produce compared to other materials. 


- Graphite Vs Graphene

Graphene is just an atomic layer of graphite - a layer of sp2-bonded carbon atoms arranged in a hexagonal or honeycomb lattice. Graphite is a common mineral composed of multiple layers of graphene. Graphene and graphite differ slightly in their structural composition and how they are made.  

Graphite is a naturally occurring crystalline carbon. It is a natural elemental mineral found in metamorphic and igneous rocks. Graphite is an extreme mineral. It is very soft, cuts with very light pressure and has a very low specific gravity. 

By contrast, it is extremely heat resistant and nearly inert in contact with almost any other material. These extreme properties lend themselves to a wide range of uses in metallurgy and manufacturing.

Graphite has metallic and non-metallic properties that make it suitable for many industrial applications. Metal properties include thermal and electrical conductivity. Non-metallic properties include inertness, high heat resistance and lubricity. Some of the major end uses of graphite are high temperature lubricants, motor brushes, friction materials, and batteries and fuel cells.


- 2D Materials

Silicon-based electronics are approaching their physical limitations and new materials are needed to keep up with current technological demands. 

Two-dimensional (2D) materials have a rich array of properties, including superconductivity and magnetism, and are promising candidates for use in electronic systems, such as transistors. However, precisely controlling the properties of these materials is extraordinarily difficult. 

For 2D materials, the thickness of the material can often be reduced to a single atom. This is the case with the most famous 2D material, graphene, and where the most interesting changes in properties occur.

Some 2D materials can be highly conductive of electricity. 2D materials can be stacked together or combined to have tunable semiconductor bandgaps, which can make them the perfect materials for producing super-efficient solar panels, perfectly tuned to the wavelengths of light from the sun.   

The field of graphene science and technology is relatively new, having emerged since Geim and Novoselov’s work in 2004. In the decades that followed, it remained difficult to say which applications would prove to be the most popular. 

Progress depends not only on the basic science but also on the development of new ways to produce graphene on an industrial scale. (Obtaining graphene by exfoliation is too expensive for mass production.) 

Methods proposed include the formation of graphene layers by burning silicon carbide or by chemical vapour deposition of carbon on the surface of some metals such as copper or nickel. These methods would allow the production of samples of graphene that were macroscopically large in two dimensions (up to tens of centimetres) but still atomically thin.


[More to come ...]


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