What is Graphene and Why is it Special?

Graphene is a new material that was first isolated in 2004. It is made up of a single layer of graphite – the same graphite used in pencil lead. Geim and Novoselov first isolated graphene by repeatedly separating graphite fragments with sticky tape until they created one-atom-thick flakes.

Although graphene’s discovery may sound simple, its structure is remarkable. Graphene has a two-dimensional crystalline structure; the atoms’ flat layer consists of hexagonal rings of carbon, which gives a ‘honeycomb’ structure. The layer itself is approximately 0.33 nanometres thick. Before graphene, it was believed that two-dimensional molecules could not exist due to thermal instability.

This structure gives graphene unique properties. Experiments have shown it to be the most robust material now known to us, being at least 200 times stronger than steel due to its strong electrostatic forces and lack of defects. Graphene is also an excellent conductor of heat and electricity thanks to its flat, hexagonal structure, meaning there is little resistance for electrons’ movement.

As well as being extremely strong, graphene is a lightweight material weighing only 0.77 milligrams per square meter. It is also very flexible; research has shown it can be stretched up to 25% of its original length without breaking.

All these properties are remarkable on their own. However, it is the combination of them in one material that has led graphene to be dubbed a wonder material with potential applications in all different types of industries.

What is Graphene Currently Used for?

Graphene’s properties open many doors for it to be used in various applications. Over 15 years since it was first isolated, many graphene products have come to the market and graphene is expanding into new sectors year on year.

One of the markets where graphene first appeared was in applications with low entry barriers, such as sports equipment. Within this industry, the multimillion-dollar company Head has taken advantage of graphene’s strength and flexibility by incorporating it into the frame of a new tennis racket line, Grays has incorporated graphene into their hockey sticks, Vittoria and Goodyear have launched graphene-enhanced bicycle tires, and Standard Graphene in Korea has previously showcased a very lightweight bicycle frame infused with graphene.

Beyond sports equipment, sports clothing was another early adopter of graphene thanks to its thermal regulation and durability in textiles, with Deewear initially leading the way alongside Directa Plus. Inov-8, a sportswear brand, worked with the National Graphene Institute based in Manchester, UK, to release the company’s first graphene-enhanced running shoe in 2018, eventually expanding into a full range. Inov-8 states that the graphene-enhanced rubber is 50% stronger and 50% more elastic than regular rubber.

Beyond the sports industry, companies such as Graphene-X have been taking to Kickstarter to launch everyday-use graphene-enhanced jackets and pants with great success.

One area where graphene has been trialed a lot is in coatings, with both electronically conductive coatings (for printable circuits) and barrier coatings being developed, a lot of which have found use for protecting the hulls of ships.

 

The main ones are as follows:

1. Mechanical peeling method

advantages:

the preparation cost is very low (almost negligible), easy to learn, and the graphene obtained by this method is very good in quality, has few defects, and has excellent performance.

Disadvantage:

the size of graphene obtained Very small, generally between 10-100um, and it is completely impossible to prepare on a large scale.

2. SiC epitaxial growth

Advantages:

can grow in larger sizes (reported by 4 inches), and the performance of the obtained graphene is excellent.

Disadvantage:

High cost, high equipment cost, high growth temperature (1400°), general equipment is not available, and it is difficult to grow graphene of too large size.

3.  graphite oxide reduction method:

advantages:

simple method, raw material cost Not high, basically no equipment cost, and easy to scale preparation

Disadvantages:

This method has a lot of graphene defects, electrical and mechanical properties are poor

4. CVD, chemical vapor deposition method

advantages:

single growth size can be very large (near 20 inches), it is possible to scale production, and the graphene produced by the performance is very good.

Disadvantages: :

the transfer is a problem, and the growth is generally polycrystalline.

The most common idea for preparing graphene is to first oxidize the graphite, and then use graphite, high temperature, etc. to peel off the graphite layer by layer (of course, maybe several layers) and finally reduce it.

There are no mass productions in the industry this year, and a small amount of preparations can be seen in the laboratories of enterprises, research institutes or universities. Let me talk about how to get graphite oxide.

There are three ways: Hummers, Brodie, and Staudenmaier.

After the experiment, everyone found that the most convenient and most suitable is the Hummers method, so the other two methods will not be said. Hummers method: use 23 mL of concentrated sulfuric acid, 4 g of potassium permanganate and 1 g of graphite to mix uniformly, react at 40 ° C for 30 minutes, then dilute, add 5 mL of 30% hydrogen peroxide to remove potassium permanganate, wash with 250 mL of 10% diluted hydrochloric acid, and finally not Drying blasting above 30 degrees Celsius yields a yellow graphite oxide solid.

This is followed by stripping of the graphite oxide. The graphite oxide is ground into a powder and rapidly heated to 500 degrees under microwave irradiation. Or take 0.02% solution of graphite oxide and put it in 150W ultrasonic for 15min, and then carry out reduction reaction with hydrazine hydrate (mass ratio of graphite oxide to 7:10) at 85 degrees to obtain single or multi-layer graphene dispersion. .  said that tearing down the tape for half a month to get a dozen layers is too exaggerated, in fact, you can do it in 5 minutes, listen to me decomposition.

Assume that each time you tear, the graphite on each side of the tape is half, and the graphite has one million layers. Then after repeating the operation of “sticking and tearing” 20 times, it is a million squares divided by 2 (2 The 20th power is equal to 1000000), which is about equal to one floor.

That is to say, you can divide a million layers of graphite into one layer by repeatedly tearing it 20 times.

The graphene obtained by this method is easily attached to the tape by a layer, and it is easy to observe and test with experimental equipment. Finally, this new material was discovered in 2004 and won the 2010 Nobel Prize in Physics.