What is Graphene?

 

 

Graphene is a crystalline allotrope of carbon with 2-dimensional properties. Graphene is very thin and Reduced_Graphene_Oxide_Oven_Dried_SE_Image1(x5000)
nearly transparent and is a single layer of graphite. It is remarkably strong at 200 times stronger than steel and conducts heat and electricity with great efficiency. Graphene is one million times thinner than a single human hair; so thin that it is actually considered two dimensional. Graphene is carbon atoms densely packed in a regular chicken wire (hexagonal) pattern. Columbia University stated it is “so strong it would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap”.

Graphene was identified in 2004 by Andre Geim and Konstantin Novoselov at Manchester University. They used adhesive tape to remove single layers from the surface of graphite and deposit them on a silicon wafer. The isolation of graphene was a breakthrough for which Geim and Novoselov were awarded the 2010 Nobel prize for Physics. In its purest form, graphene possesses an unsurpassed combination of electrical, mechanical and thermal properties, which gives it the potential to replace existing materials in a wide range of applications and, in the long term, to enable new applications.

The key properties of graphene for intended application development are detailed below.

Electrical properties

Graphene is great conductor; electrons are able to flow through graphene more easily than through copper. TheGraphene_Oxide_Air_Dried_SE_Image2(x2000) electrons travel through the graphene sheet as if they carry no mass and as fast as one hundredth that of the speed of light. 

Mechanical strength

Graphene is 7x harder than diamond and about 200 times harder than steel. To put this into context, it will take the weight of an elephant balanced on a needle-point in order to break this one atom thick fabric! The tensile strength of graphene exceeds 1 TPa. Even though graphene is so strong, it is also very stretchable. You can stretch graphene up to 20% of its initial length. 

Thermal conductivity

Graphene is an excellent thermal conductor. Graphene’s thermal conductivity measured much higher than the value7_6 observed in all the other carbon structures as carbon nanotubes, graphite and diamond (> 5000 W/m/K). Graphite, the 3 D version of graphene, shows a thermal conductivity about 5 times smaller (1000 Wm-1K-1). The phenomenon is governed by the presence of elastic waves propagating in the graphene lattice, called phonons. The study of thermal conductivity in graphene may have important implications in graphene-based electronic devices. As devices continue to shrink and circuit density increases, high thermal conductivity, which is essential for dissipating heat efficiently to keep electronics cool, plays an increasingly larger role in device reliability.

Optical properties

Graphene, despite being the thinnest material ever made, is still visible to the naked eye. Due to its unique electronic6-4 properties, it absorbs a high 2.3% of light that passes through it, which is enough that you can see it in air (if you could manage to hold it up!). To help enhance the visibility of graphene flakes we deposit them on to silicon wafers which have a thin surface layer of silicon dioxide. Light shining on to these three-layer structures will be partially transmitted and partially reflected at each interface.

Source: The Universityof Manchester

Fun Graphene Facts:

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 (about 0.001% of the weight of 1 m2 of paper)

If an ordinary piece of paper the length of a football field were as strong as graphene, you could hold it at one end with no breaking and no bending. That being said, graphene is remarkably elastic. Graphene can be stretched 20% of its length and endlessly bend without breaking.

Nanotechnology: how big is a nano?

A nano is .o n e  –  b i l l i o n t h of something.

nanometer is a billionth of a meter.

In numbers, a nano looks like this:  1 x 10-9  = OR =  1/1,000,000,000

To get a sense of how small graphene actually is, consider this:  A sheet of graphene is about 0.22 nm thick.

Graphite and Graphene

Graphene & Graphite – How Do They Compare?  “The attributes of graphene – transparency, density, electric and thermal conductivity, elasticity, flexibility, hardness resistance and capacity to generate chemical reactions with other substances – harbour the potential to unleash a new technological revolution of more magnificent proportions than that ushered in by electricity in the 19th …

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