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Graphene times yet to come

Number of visits: Date:2015-06-15
Graphene times yet to come

Wei Langer posted by 2014-06-20 18:10
Not long ago, ren said in a media interview, 10-20 years in the future is going to be a revolution, "I think the future of this era's largest Subversion is Graphene age subversion of the silicon age," "chip now limit width, limit seven Nano-silicon, is approaching the border, graphite is the technology frontier". Graphene is mentioned here, what is sacred? Did it really amount to a Subversion?
Graphene, a two-dimensional carbon only one atom thick film – is kind of surprising materials. Although the name Word with graphite, but it does not rely on graphite reserves and is not characteristic of graphite: Graphene bending strength, electrical conductivity, mechanical strength, and style look magical material of the future. If it's potential uses have a list-protective coatings, transparent bent components, large-capacity capacitor, and so on--that it is the invention that changed the world. Even the 2010 Nobel Prize in physics is awarded to it too!
     But it has since its inception ten years ago, my transparent phone where is it?
     In 2012, because of Graphene, Nobel Prize-winning kangsitanding·nuowoxiaoluofu (Konstantin Novoselov) and his colleagues have published articles in nature, discuss the future of Graphene, two years also proved their forecasts. He is considered as a material, Graphene, "prospects are bright, the road has twists and turns", although it could play a major role in the future, but before overcoming several major difficulties, this scenario will not come. Most importantly, considering the huge costs to the industry update, Graphene's advantage may not be enough to replace the existing equipment make it simple--the real prospects, is tailored to the unique characteristics of new applications.

What is Graphene?
Graphene is the first to be found by a single layer of atoms of the material. Between carbon atoms are connected into a hexagonal grid. Pencil graphite in countless layers of Graphene stacked together, and carbon nanotubes, Graphene is rolled up into a tube shape.
Graphite and Graphene, carbon nanotubes and the relationship between ball vinyl. Due to the nature of chemical bonds between carbon atoms, Graphene is tough: can be bent to a large angle without breaking and can withstand very high pressure. Because only one atom, electron movement is restricted to a plane, for it brings a whole new electrical properties. Graphene is transparent in the visible light, but not breathable. These characteristics make it ideal as a protective layer and transparent materials of electronic products.
But for fit, really do not so fast.

Problem: to prepare the way.
Many studies have shown us the amazing characteristics of Graphene, but there is a trap. These wonderful properties on the sample quality is very high. To achieve electrical and mechanical properties are the best samples of Graphene, require the most time-consuming and costly means: mechanical exfoliation--gummed on the graphite, hand-pulling down the Graphene.
Don't laugh, 2004 novoselov is how they prepare Graphene.
Novoselov team donated to graphite and Graphene in Stockholm and tape. Signature on the tape, "Andre Geim" is and who won the Nobel Prize with novoselov. Photo: Wikipedia
Although the necessary equipment and technical content seems very low, but the problem is the success rate is low, research can also get some samples, industrial production? Just joking. Discussion on the industrialization, it means useless. Even if you have acquired a graphite mine in the world, and stripped off a few slices of the day ... ...
Of course, now we have a lot of other methods, to increase production and reduce costs--trouble is the quality of these products also fell. We have liquid peeling method: graphite or carbon-containing materials into similar high surface tension liquids and ultrasonic bomb blast Graphene flakes. We have a catalytic chemical vapor deposition method: carbon-containing gases in the condensation on the surface of copper, the formation of Graphene thin strip down. We also have a direct method of growth, managed to grow directly in between two layers of Silicon layer Graphene. There are chemical oxidation and reduction, insert a graphite sheet separation by oxygen atoms, and so on. There are many, each with its own scope of application, but so far have not really suitable for industrial scale production technology.
Why these approaches can't work out high quality Graphene? To cite an example. Although the central part of a Graphene is perfect six-membered rings, but at the edges tend to be disrupted, five-or seven-membered ring. It seems no big deal, but produced by chemical vapor deposition method "a" Graphene is not really complete, from growing out of one. It is multiple points at the same time the growth of "poly", and no way to guarantee the multiple small growing points are fully aligned. So, these deformed ring not only distributed at the edges, still exists in each "piece" done out of Graphene, structural weaknesses, prone to breakage. And to make matters worse, Graphene this fracture does not heal like polycrystalline metals, and is likely to keep going. Result is that the entire strength of Graphene in half. Material is a problem area, wants to have its cake and eat it too is not impossible, but certainly not as fast.

Second problem: electrical properties.
Graphene is a promising direction display devices – a touch-screen, electronic paper, and so on. Now, but Graphene and the metal contact of the electrode resistance is hard to deal with. Novoselov is estimated that the problem can be solved in less than a decade.
But why do we not simply discarded metal, Graphene it? This is it in most fatal problem in the field of electronic products. Modern electronic products are all based on semiconductor transistor, but it has a key property called "band gap": the electron conductive and non-conductive belt range. Is because of this interval, the flow of current in order to have asymmetric, the circuit to open and close the two States--but, the conductivity of Graphene is too good, it did not have the band gap, can open not close. Only wire there is no logic is useless. So if you want to use Graphene to create electronic products, replacing the silicon transistor, we must artificially implanted a band gap – but simple implant will lose its unique properties of Graphene. Now for a substantial amount of research in this area: laminated, adding other elements, structural change, and so on; but novoselov, who thinks the problem to solve, but also for at least ten years.

Question three: environmental risk.
Graphene industries also have an unexpected problem: pollution. Graphene industries is currently one of the most sophisticated products may be called "graphene oxide nano-particles", which is very cheap, although not used for high end areas such as batteries, bend touching screen, uses such as electronic paper is a fairly good but this is likely to be toxic to the human body. Toxic does not matter, as long as it stay in electronics, that there would be no problem; but researchers have just found it shortly before in the surface water is stable, very easy to spread. While under the influence of the environment on it now asserts that it was too early, but this is a potential problem.

So, how does Graphene's fate?
In view of the past few months and no new breakthroughs in the circle, recently it's this sudden "hot", I am afraid that capital running essentially the speculation results, should be treated with caution. As industrial technology, Graphene looks there are many failed to overcome difficulties. Novoselov pointed out that current Graphene's application is limited to material production, so those with the lowest levels of the most cheap graphite products (such as graphene oxide nano-particles), will be the first one available, possibly in just a few years, but products that rely on high-purity Graphene may take decades to develop. It can replace the existing product line, novoselov remained skeptical.
The other hand, if commercial exaggerated its magical, may result in Graphene into foam; when they burst, then perhaps technology and industrial progress will not save it. Feilipu·Baer science author once wrote in the guardian of the don't expect wonders of Graphene, pointing out that all materials have their scope: hard and heavy steel, wood, light but easy to rot, even seemingly "universal" plastic variety of different polymer to the situation. Graphene will play a huge role, but there is no reason to think it will be a miracle material, changing the world. Alternatively, novoselov's own words: "the true potential of Graphene can show only new applications in the field of: those who design fully considers the material characteristics of products, and other materials are not a replacement for an existing product. "As for the current product printable, foldable electronic, foldable solar panels, and Super capacitors and so on can play to its potential in new areas, let us calm down and wait. (Edit: Calo)

References
1.K. S. Novoselov et al.(2012). A roadmap for graphene. Nature 490, 192–200 (11 October 2012) doi:10.1038/nature11458
2.Zhigong Song et al. (2013).Pseudo Hall–Petch Strength Reduction in Polycrystalline Graphene. Nano Lett., 2013, 13 (4), pp 1829–1833 doi: 10.1021/nl400542n
3.A Schinwald et al.(2012) Graphene-Based Nanoplatelets: A New Risk to the Respiratory System as a Consequence of Their Unusual Aerodynamic Properties. ACS Nano, 2012, 6, 736 DOI: 10.1021/nn204229f
4.Lanphere Jacob D.et al.(2014) Stability and Transport of Graphene Oxide Nanoparticles in Groundwater and Surface Water. Environmental Engineering Science. doi:10.1089/ees.2013.0392.
5.Matthew Francis, The Graphene Age isn't (quite) here yet. Ars Tecnica, 17 October 2012
6.Philip Ball, Don't expect graphene to perform miracles. The Guardian, 28 December 2012 

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