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The era of graphene has not yet come

Views:5     Author:Site Editor     Publish Time: 2017-12-13      Origin:Site

Graphene, a two-dimensional carbon film with only one atom thick, is indeed an astonishing material. Although the name with graphite two words, but it does not rely on graphite reserves is not completely graphite characteristics: graphene conductivity strong, bending, mechanical strength, looks quite future magical material demeanor. If you open a list of potential uses--protective coatings, transparent, bent electronic components, oversized capacitors, and so on--that's a world-changing invention. Even the 2010 Nobel Prize in Physics was awarded to it!


But it has been 10 years since its birth, where is my transparent phone?


In fact, in 2012, Constantine Novosiolov (Konstantin Novoselov), who won the Nobel Prize for Graphene, and his colleagues once published an article on "Nature" to discuss the future of graphene, and the development of the past two years has largely proved their predictions. He argues that graphene, as a material, "The future is bright, the road is tortuous", although it may play a significant role in the future, but before overcoming several major difficulties, the scene will not come. More importantly, given the huge cost of industrial renewal, graphene's benefits may not be enough to simply replace the existing equipment--the real prospect of it, perhaps in a new application tailored to its unique features.
What exactly is graphene?


Graphene is the first material that people have discovered that consists of a single layer of atoms. The carbon atoms are connected to each other in a six-angle grid. The graphite in the pencil is the equivalent of countless layers of graphene, and carbon nanotubes are graphene rolls.


The relationship between graphene_carbon-e1286367575983.jpg graphite, graphene, carbon nanotubes and pellets. Photo from: enago.com


Because of the chemical bond between carbon atoms, graphene is tenacious: it can bend to a large angle without breaking, and can withstand high pressure. Because there is only one layer of atoms, the motion of electrons is limited to a plane, which brings new electrical properties to it. Graphene is transparent in visible light but not breathable. These features make it ideal for use as a protective layer and as a raw material for transparent electronic products.


But it's not as fast as it fits.
One of the problems: the method of preparation.


Many studies have shown us the astonishing characteristics of graphene, but there is a trap. These wonderful properties require very high quality samples. To obtain the best possible graphene samples for both electrical and mechanical properties, it takes the most time-consuming and costly means: mechanical stripping-adhesive tape to graphite, and stripping of graphene by hand.


Don't laugh, 2004 Novoselov they just made graphene.


The Novoselov team donated graphite, graphene and tape to Stockholm. The signature on the tape "Andre Geim" is the man who won the Nobel Prize with Novoselov. Photo from: Wikipedia


Although the required equipment and technical content seems to be very low, but the problem is the success rate is lower, to get a sample of the research can also be industrialized production? Joke. To industrialization, this means no use. Even if you master the world's graphite mine, one day can peel down a few pieces ...


Of course, we now have a lot of other ways to increase production and reduce costs--the trouble is that the quality of these products is falling down again. We have the liquid phase stripping method: The graphite or similar carbon material is placed in the surface tension of ultra-high liquid, and then the ultrasonic bombing of the graphite flakes blown down. We have chemical vapor deposition: let carbon-containing gases condense on the surface of copper, and a thin layer of graphene is stripped down. We also have a direct growth method that directly manages to grow a layer of graphene between the two layers of silicon. There are also chemical redox methods, which are separated by the insertion of oxygen atoms into the graphite layer, and so on. Methods have many, but also each have their own scope of application, but so far there is no real suitable for the industrialization of large-scale promotion of production technology.


Why can't these methods be high quality graphene? Give an example. Although the central part of a piece of graphene is the perfect six-yuan ring, the edge part tends to be disrupted to become a five-or seven-yuan ring. This may not seem like a big deal, but the "one piece" of graphene produced by chemical vapor deposition is not really a complete, growing piece of it. It is actually a number of points at the same time the growth of the "polycrystalline", and there is no way to ensure that these multiple points grow out of the small pieces can be fully aligned. As a result, these deformed rings are not only distributed in the edge, but also exist in each "piece" of graphene, which makes it a structural weakness and is easy to break. To make things worse, graphene's break point does not heal itself as much as polycrystalline metals, and is likely to continue to stretch. The result is that the strength of the entire graphene is halved. Material is a troublesome field, and it is not impossible to think of fish and cake, but certainly not so soon.


Ubtractedcopy_ copy. A piece of graphene under a JPG microscope, a pseudo color marker. Each "color block" represents a graphene "single crystal". Photo from: cornell.edu
Question two: electrical properties.


A promising direction for graphene is the display device--touch screen, electronic paper, and so on. But at present, the contact point resistance of graphene and metal electrodes is difficult to deal with. Novoselov estimated that the problem could be solved within 10 years.


But why can't we just dump the metal and use graphene? This is the most lethal issue in the field of electronic products. Modern electronic products are all built on semiconductor transistors, and it has a key attribute called "band gap": the interval between the electronic conductive energy band and the Non-conductive band. Because of this interval, the current flow can be asymmetric, the circuit can be opened and closed two states-however, the conductivity of graphene is very good, it does not have this band gap, can only open. Only wires without logic circuits are of no use. So to create a future electronic product, instead of a silicon-based transistor, we have to artificially implant a bandgap-but a simple implant will lose graphene's unique properties. There are many studies in this field: multilayer composites, adding other elements, changing structures and so on, but Novoselov and others think the problem should be solved for at least 10 years.
The third problem: environmental risk.


The graphene industry also has an unexpected problem: pollution. Graphene industry is one of the most mature products may be the so-called "oxidized graphene nanoparticles", it is very cheap, although not used to do batteries, bending touch screen and other high-end fields, as electronic paper and other uses is quite good; but this thing is likely to be poisonous to the human body. The poison doesn't matter, as long as it is honest in the electronic products, there is no problem, but the researchers have just discovered that it is very stable and very easy to diffuse in the surface water. Although it is too early to assert its environmental impact, it is a potential problem.
So what is the fate of graphene?


Given that there has been no new breakthrough in academia in the past few months, this sudden burst of "fiery", I am afraid, is essentially a speculative result of capital operation, which should be treated with caution. As an industrial technology, graphene seems to have many insurmountable difficulties. Novoselov noted that the application of graphene is still limited to material production, so products that use the lowest level of the cheapest graphene, such as graphene nanoparticles, will be first available, perhaps for a few years, but those that rely on high-purity graphene may be developed for decades. Novoselov remains sceptical about its ability to replace the existing product line.


On the other hand, if the business sector exaggerates its magic, it could lead to a bubble in the graphene industry; Scientific author Philippe Barr once wrote in The Guardian, "do not expect graphene to bring miracles," pointing out that all materials have their scope: steel hard and heavy, wood lightweight but perishable, even if seemingly "omnipotent" plastic is actually a variety of different polymer recount. Graphene is bound to play a huge role, but there is no reason to think that it can be a miracle material and change the world. Or, in Novoselov's own words: "The real potential of graphene can be fully demonstrated only in new applications: those that are designed to take into account the characteristics of the material, not to replace other materials in existing products." "As for the current printable, foldable electronic products, foldable solar cells, and supercapacitors, and so on, whether new areas can play its potential, let us calmly wait and see."


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