Synopsis:
1.1. banale ict: 0. denumiri si prea generale ict: Graphene:
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Coming up 24 墉 oe29 April The European Science Foundation is holding a week-long conference devoted to the science and technology of graphene, in Obergurgl,
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Royal Society intake Among 44 fellows elected to the Royal Society in London on 20 may were Nobel-prizewinning graphene researcher Kostya Novoselov of the University of Manchester;
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and to develop the potential of graphene. The projects should each receive  1  billion (US$1. 3  billion) over ten years.
Multilayered flakes or discs of graphene nanoplatelets which may find use in adding strength and conductivity to composites and coatings, are produced mainly in The americas and Asia, according to analysts Lux Research in Boston, Massachusetts.
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Huge grains of copper promote better graphene growthto technology insiders graphene is certified a big deal.
Graphene-based electronics promise advances such as faster internet speeds cheaper solar cells novel sensors space suits spun from graphene yarn and more.
and Technology (NIST) in Boulder Colo. may help bring graphene's promise closer to reality.
While searching for an ideal growth platform for the material investigators developed a promising new recipe for a graphene substrate:
--but their relative bulk enables them to survive the high temperatures needed for graphene growth explained NIST researcher Mark Keller.
The inability of most copper films to survive this stage of graphene growth has been one problem preventing wafer-scale production of graphene devices Keller said.
To demonstrate the viability of their giant-grained film the researchers successfully grew graphene grains 0. 2 millimeters in diameter on the new copper surface.
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#Mix of graphene nanoribbons, polymer has potential for cars, soda, beera discovery at Rice university aims to make vehicles that run on compressed natural gas more practical.
By adding modified single-atom-thick graphene nanoribbons (GNRS) to thermoplastic polyurethane (TPU) the Rice lab made it 1000 times harder for gas molecules to escape Tour said.
The researchers acknowledged that a solid two-dimensional sheet of graphene might be the perfect barrier to gas
but the production of graphene in such bulk quantities is not yet practical Tour said. But graphene nanoribbons are already there.
Tour's breakthrough unzipping technique for turning multiwalled carbon nanotubes into GNRS first revealed in Nature in 2009 has been licensed for industrial production.
But the overlapping 200-to 300-nanometer-wide ribbons dispersed so well that they were nearly as effective as large-sheet graphene in containing gas molecules.
The GNRS'geometry makes them far better than graphene sheets for processing into composites Tour said.
The Air force Research Laboratory through the University Technology Corp. the Office of Naval Research MURI graphene program and the Air force Office of Scientific research MURI program supported the research.
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That makes it a true one-dimensional material unlike atom-thin sheets of graphene that have a top
and is double that of graphene. Scientists had calculated already it would take an elephant on a pencil to break through a sheet of graphene.*
*It has twice the tensile stiffness of graphene and carbon nanotubes and nearly three times that of diamond.*
*Stretching carbyne as little as 10 percent alters its electronic band gap significantly.**If outfitted with molecular handles at the ends it can also be twisted to alter its band gap.
You could look at it as an ultimately thin graphene ribbon reduced to just one atom
Artyukhov said the nominal specific area of carbyne is about five times that of graphene. Researchers are now taking a more rigorous look at the conductivity of carbyne
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#White graphene halts rust in high temps: Nano-thin films of hexagonal boron nitride protect materials from oxidizingatomically thin sheets of hexagonal boron nitride (h-BN) have the handy benefit of protecting
One or several layers of the material sometimes called white graphene keep materials from oxidizing
They also grew h-BN on graphene and found they could transfer sheets of h-BN to copper and steel with similar results.
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However until recently scientists believed that growing the high density of tiny graphene cylinders needed for many microelectronics applications would be difficult.
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After combining equal amounts of RTIL and naturally occurring Bentonite clay into a composite paste the researchers sandwiched it between layers of reduced graphene oxide
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#Graphene onion rings have delicious potentialconcentric hexagons of graphene grown in a furnace at Rice university represent the first time anyone has synthesized graphene nanoribbons on metal from the bottom up--atom by atom.
As seen under a microscope the layers brought onions to mind said Rice chemist James Tour until a colleague suggested flat graphene could never be like an onion.
Usually graphene grown in a hot furnace by chemical vapor deposition starts on a seed--a speck of dust or a bump on a copper or other metallic surface.
Experiments in Tour's lab to see how graphene grows under high pressure and in a hydrogen-rich environment produced the first rings.
Under those conditions Tour Rice theoretical physicist Boris Yakobson and their teams found that the entire edge of a fast-growing sheet of graphene becomes a nucleation site
The edge lets carbon atoms get under the graphene skin where they start a new sheet.
But because the top graphene grows so fast it eventually halts the flow of carbon atoms to the new sheet underneath.
The bottom stops growing leaving a graphene ring. Then the process repeats. The mechanism relies on that top layer to stop carbon from reaching the bottom so easily Tour said.
The Tour lab pioneered the bulk manufacture of single-atom-thick graphene nanoribbons in 2009 with the discovery that carbon nanotubes could be unzipped chemically into long thin sheets.
The atomic configuration at the edge helps determine graphene's electrical properties. The edges of hexagonal graphene onion rings are zigzags
which make the rings metallic. The big news here he said is that we can change relative pressures of the growth environment of hydrogen
This is dramatically different from regular graphene. Graduate student Zheng Yan a member of Tour's lab and lead author of the paper discovered the new route to nanoribbons
while experimenting with graphene growth under hydrogen pressurized to varying degrees. The sweet spot for rings was at 500 Torr he said.
Yan also determined the top sheet of graphene could be stripped away with argon plasma leaving stand-alone rings.
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#Not-weak knots bolster carbon fiberlarge flakes of graphene oxide are the essential ingredient in a new recipe for robust carbon fiber created at Rice university.
Credit goes to the unique properties of graphene oxide flakes created in an environmentally friendly process patented by Rice a few years ago.
Like with pitch the weak Van der waals force holds the graphene flakes together. Unlike pitch the atom-thick flakes have an enormous surface area
Because graphene oxide has very low bending modulus it thinks there's no knot there he said.
The Rice researchers also created a second type of fiber using smaller 9-micron flakes of graphene oxide.
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#Unzipped nanotubes unlock potential for batteriesresearchers at Rice university have come up with a new way to boost the efficiency of the ubiquitous lithium ion (LI) battery by employing ribbons of graphene that start as carbon nanotubes.
Proof-of-concept anodes--the part of the battery that stores lithium ions--built with graphene nanoribbons (GNRS)
Since then the researchers have figured out how to make graphene nanoribbons in bulk and are moving toward commercial applications.
In the new experiments the Rice lab mixed graphene nanoribbons and tin oxide particles about 10 nanometers wide in a slurry with a cellulose gum binder and a bit of water spread it on a current collector
Graphene nanoribbons make a terrific framework that keeps the tin oxide nanoparticles dispersed and keeps them from fragmenting during cycling he said.
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and to analyze their characteristics The hope is that MDS could be joined with graphene which has no band gap
Last year Lou and Ajayan revealed their success at making intricate patterns of intertwining graphene and hbn among them the image of Rice's owl mascot.
The study of graphene prompted research into a lot of 2-D materials; molybdenum disulfide is just one of them.
Essentially we are trying to span the whole range of band gaps between graphene which is a semimetal and the boron nitride insulator.
MDS is distinct from graphene and hbn because it isn't exactly flat. Graphene and hbn are flat with arrays of hexagons formed by their constituent atoms.
But while MDS looks hexagonal when viewed from above it is actually a stack with a layer of molybdenum atoms between two layers of sulfur atoms.
We would like to stick graphene and MDS together (with hbn) into what would be a novel 2-D semiconductor component.
or graphene Najmaei said. We started learning that we could control that nucleation by adding artificial edges to the substrate
With ORNL's images in hand they were not only able to calculate the energies of a much more complex set of defects than are found in graphene
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#Even with defects, graphene is strongest material in the worldin a new study published in Science Columbia Engineering researchers demonstrate that graphene
even if stitched together from many small crystalline grains is almost as strong as graphene in its perfect crystalline form.
Graphene consists of a single atomic layer of carbon arranged in a honeycomb lattice. Our first Science paper in 2008 studied the strength graphene can achieve
if it has no defects--its intrinsic strength says James Hone professor of mechanical engineering who led the study with Jeffrey Kysar professor of mechanical engineering.
But defect-free pristine graphene exists only in very small areas. Large-area sheets required for applications must contain many small grains connected at grain boundaries
This our second Science paper reports on the strength of large-area graphene films grown using chemical vapor deposition (CVD)
and we're excited to say that graphene is back and stronger than ever. The study verifies that commonly used methods for postprocessing CVD-grown graphene weaken grain boundaries resulting in the extremely low strength seen in previous studies.
The Columbia Engineering team developed a new process that prevents any damage of graphene during transfer.
We substituted a different etchant and were able to create test samples without harming the graphene notes the paper's lead author Gwan-Hyoung Lee a postdoctoral fellow in the Hone lab. Our findings clearly correct the mistaken consensus that grain boundaries of graphene
are weak. This is great news because graphene offers such a plethora of opportunities both for fundamental scientific research and industrial applications.
In its perfect crystalline form graphene (a one-atom-thick carbon layer) is the strongest material ever measured as the Columbia Engineering team reported in Science in 2008--so strong that as Hone observed it would take an elephant balanced on a pencil to break through a sheet
of graphene the thickness of Saran wrap. For the first study the team obtained small structurally perfect flakes of graphene by mechanical exfoliation or mechanical peeling from a crystal of graphite.
But exfoliation is a time-consuming process that will never be practical for any of the many potential applications of graphene that require industrial mass production.
Currently scientists can grow sheets of graphene as large as a television screen by using chemical vapor deposition (CVD) in
which single layers of graphene are grown on copper substrates in a high-temperature furnace. One of the first applications of graphene may be as a conducting layer in flexible displays.
But CVD graphene is stitched'together from many small crystalline grains--like a quilt--at grain boundaries that contain defects in the atomic structure Kysar explains.
These grain boundaries can severely limit the strength of large-area graphene if they break much more easily than the perfect crystal lattice
and so there has been intense interest in understanding how strong they can be. The Columbia Engineering team wanted to discover what was making CVD graphene so weak.
In studying the processing techniques used to create their samples for testing they found that the chemical most commonly used to remove the copper substrate also causes damage to the graphene severely degrading its strength.
Their experiments demonstrated that CVD graphene with large grains is exactly as strong as exfoliated graphene showing that its crystal lattice is just as perfect.
And more surprisingly their experiments also showed that CVD graphene with small grains even when tested right at a grain boundary is about 90%as strong as the ideal crystal This is an exciting result for the future of graphene
because it provides experimental evidence that the exceptional strength it possesses at the atomic scale can persist all the way up to samples inches
or more in size says Hone. This strength will be invaluable as scientists continue to develop new flexible electronics and ultrastrong composite materials.
Strong large-area graphene can be used for a wide variety of applications such as flexible electronics
and strengthening components--potentially a television screen that rolls up like a poster or ultrastrong composites that could replace carbon fiber.
Or the researchers speculate a science fiction idea of a space elevator that could connect an orbiting satellite to Earth by a long cord that might consist of sheets of CVD graphene
since graphene (and its cousin material carbon nanotubes) is the only material with the high strength-to-weight ratio required for this kind of hypothetical application.
The team is excited also about studying 2d materials like graphene. Very little is known about the effects of grain boundaries in 2d materials Kysar adds.
Our work shows that grain boundaries in 2d materials can be much more sensitive to processing than in 3d materials.
This is due to all the atoms in graphene being surface atoms so surface damage that would normally not degrade the strength of 3d materials can completely destroy the strength of 2d materials.
However with appropriate processing that avoids surface damage grain boundaries in 2d materials especially graphene can be nearly as strong as the perfect defect-free structure.
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#Diamonds, nanotubes find common ground in graphenewhat may be the ultimate heat sink is only possible because of yet another astounding capability of graphene.
A diamond film/graphene/nanotube structure was one result of new research carried out by scientists at Rice university
when graphene is used as a middleman surfaces considered unusable as substrates for carbon nanotube growth now have the potential to do so.
By its very nature one-atom-thick graphene is all surface area. The same could be said of carbon nanotubes which are basically rolled-up tubes of graphene.
A vertically aligned forest of carbon nanotubes grown on diamond would disperse heat like a traditional heat sink but with millions of fins.
Graphene and metallic nanotubes are also highly conductive in combination with metallic substrates they may also have advanced uses in electronics he said.
To test their ideas the Honda team grew various types of graphene on copper foil by standard chemical vapor deposition.
They then transferred the tiny graphene sheets to diamond quartz and other metals for further study by the Rice team.
They found that only single-layer graphene worked well and sheets with ripples or wrinkles worked best.
The researchers think graphene facilitates nanotube growth by keeping the catalyst particles from clumping. Ajayan thinks the extreme thinness of graphene does the trick.
In a previous study the Rice lab found graphene shows materials coated with graphene can get wet
but the graphene provides protection against oxidation. That might be one of the big things about graphene that you can have a noninvasive coating that keeps the property of the substrate
but adds value he said. Here it allows the catalytic activity but stops the catalyst from aggregating.
Testing found that the graphene layer remains intact between the nanotube forest and the diamond or other substrate.
On a metallic substrate like copper the entire hybrid is highly conductive. Such seamless integration through the graphene interface would provide low-contact resistance between current collectors
and the active materials of electrochemical cells a remarkable step toward building high-power energy devices said Rice research scientist
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Graphene a single sheet of carbon atoms is the thinnest electrical conductor we know. With the addition of the monolayer molybdenum disulfide and other metal dichalcogenides we have all the building blocks for modern electronics that must be created in atomically thin form.
For example we can now imagine sandwiching two different monolayer transition metal dichalcogenides between layers of graphene to make solar cells that are only eight atoms thick--20 thousand times smaller than a human hair!
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The scientists also tested the Mosoy catalyst anchored on sheets of graphene--an approach that has proven effective for enhancing catalyst performance in electrochemical devices such as batteries supercapacitors fuel cells and water electrolyzers.
and Materials Science Department the scientists were able to observe the anchored Mosoy nanocrystals on 2d graphene sheets.
The graphene-anchored Mosoy catalyst surpassed the performance of pure platinum metal. Though not quite as active as commercially available platinum catalysts the high performance of graphene-anchored Mosoy was extremely encouraging to the scientific team.
The direct growth of anchored Mosoy nanocrystals on graphene sheets may enhance the formation of strongly coupled hybrid materials with intimate seamless electron transfer pathways
thus accelerating the electron transfer rate for the chemical desorption of hydrogen from the catalyst further reducing the energy required for the reaction to take place Sasaki said.
The scientists are conducting additional studies to gain a deeper understanding of the nature of the interaction at the catalyst-graphene interface
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#Even graphene has weak spotsgraphene the single-atom-thick form of carbon has become famous for its extraordinary strength.
The kryptonite to this Superman of materials is in the form of a seven-atom ring that inevitably occurs at the junctions of grain boundaries in graphene where the regular array of hexagonal units is interrupted.
At these points under tension polycrystalline graphene has about half the strength of pristine samples of the material.
They could be important to materials scientists using graphene in applications where its intrinsic strength is a key feature like composite materials and stretchable or flexible electronics.
Graphene sheets grown in a lab often via chemical vapor deposition are almost neverperfect arrays of hexagons Yakobson said.
Domains of graphene that start to grow on a substrate are lined not necessarily up with each other
Most common of the defects in graphene formation studied by Yakobson's group are adjacent five-and seven-atom rings that are a little weaker than the hexagons around them.
Graphene is usually a quilt made from many pieces. I thought we should test the junctions.
and good old mathematical analysis that in a graphene quilt the grain boundaries act like levers that amplify the tension (through a dislocation pileup) and concentrate it at the defect either where the three domains meet or where a grain boundary between two domains ends.
And graphene is a brittle material so a crack might go a really long way.
For graphene we call this a pseudo Hall-Petch because the effect is very similar
because you cannot avoid the effect in polycrystalline graphene. It's also ironic because polycrystals are considered often
If you need a patch of graphene for mechanical performance you'd better go for perfect monocrystals
or graphene with rather small domains that reduce the stress concentration. Co-authors of the paper are graduate student Zhigong Song and his adviser Zhiping Xu an associate professor of engineering mechanics at Tsinghua.
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Hybrid ribbons a gift for powerful batterieshybrid ribbons of vanadium oxide (VO2) and graphene may accelerate the development of high-power lithium-ion batteries suitable for electric cars and other demanding applications.
The high-conductivity graphene lattice that is literally baked in solves that problem nicely he said by serving as a speedy conduit for electrons and channels for ions.
The atom-thin graphene sheets bound to the crystals take up very little bulk. In the best samples made at Rice fully 84 percent of the cathode's weight was the lithium-slurping VO2
One challenge to production was controlling the conditions for the co-synthesis of VO2 ribbons with graphene Yang said.
The process involved suspending graphene oxide nanosheets with powdered vanadium pentoxide (layered vanadium oxide with two atoms of vanadium and five of oxygen) in water and heating it in an autoclave for hours.
while the graphene oxide was reduced to graphene Yang said. The ribbons with a weblike coating of graphene were only about 10 nanometers thick up to 600 nanometers wide and tens of micrometers in length.
These ribbons were the building blocks of the three-dimensional architecture Yang said. This unique structure was favorable for the ultrafast diffusion of both lithium ions
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if laboratories striving to grow graphene from carbon atoms kept winding up with big pesky diamonds.
when it becomes graphene. And boron clumps aren't nearly as sparkly. Yakobson and his Rice colleagues have made progress toward 2-D boron through theoretical work that suggests the most practical ways to make the material
Earlier calculations by the group indicated 2-D born would conduct electricity better than graphene.
Yakobson's lab first reported in a Nano Letters paper last year that unlike graphene 2-D boron rolled into a nanotube would always be metallic.
Also unlike graphene the atomic arrangement can change without changing the nature of the material.
Instead of the steady rank-and-file of hexagons in a perfect graphene sheet 2-D boron consists of triangles.
Here we have conceived a material that resembles graphene but is always conductive no matter what form it takes.
or gold substrates in a process called chemical vapor deposition commonly used to make graphene.
Then like graphene these atom-thick boron sheets could be applied to other surfaces for testing and ultimately for use in applications.
For example 2-D boron is more conductive than graphene because of its unique electronic structure and atomic arrangement.
In fact comparing (boron) with graphene is very helpful he said. The state-of-art synthesis methods for graphene provide us good templates to explore 2-D boron synthesis. Yakobson is thinking a step beyond the current work.
There are many groups at Rice and elsewhere working on 2-D boron he said. To appreciate this work you have to stand back
and contrast it with graphene; in some sense the synthesis of graphene is trivial. Why?
Because graphene is given a God material he said. It forms at the global minimum (energy) for carbon atoms--they go there willingly.
But boron is a different story. It does not have a planar form as a global minimum
another new paper from Rice on a hybrid graphene-hexagonal boron nitride shows the need for a 2-D semiconductor to complement the material's conducting
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The materials at play--graphene and hexagonal boron nitride--have been merged into sheets and built into a variety of patterns at nanoscale dimensions.
Graphene has been touted as a wonder material since its discovery in the last decade. Even at one atom thick the hexagonal array of carbon atoms has proven its potential as a fascinating electronic material.
Graphene-based electronics require similar compatible 2-D materials for other components and researchers have found hexagonal boron nitride (h-BN) works nicely as an insulator.
H-BN looks like graphene with the same chicken-wire atomic array. The earlier work at Rice showed that merging graphene
and h-BN via chemical vapor deposition (CVD) created sheets with pools of the two that afforded some control of the material's electronic properties.
He has concluded since that the area of two-dimensional materials beyond graphene has grown significantly and will play out as one of the key exciting materials in the near future.
His prediction bears fruit in the new work in which finely detailed patterns of graphene are laced into gaps created in sheets of h-BN.
The interface between elements seen clearly in scanning transmission electron microscope images taken at Oak ridge National Laboratories shows a razor-sharp transition from graphene to h-BN along a subnanometer line.
After the masks were washed away graphene was grown via CVD in the open spaces where it bonded edge-to-edge with the h-BN.
While there's much work ahead to characterize the atomic bonds where graphene and h-BN domains meet and to analyze potential defects along the boundaries Liu's electrical measurements proved the components'qualities remain intact.
And the graphene still looks very good. That's important because we want to be sure
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#New insight into graphene grain boundariesusing graphene--either as an alternative to or most likely as a complementary material with--silicon offers the promise of much faster future electronics along with several other advantages over the commonly used semiconductor.
However creating the one-atom thick sheets of carbon known as graphene in a way that could be integrated easily into mass production methods has proven difficult.
When graphene is grown lattices of the carbon grains are formed randomly linked together at different angles of orientation in a hexagonal network.
These boundaries scatter the flow of electrons in graphene a fact that is detrimental to its successful electronic performance.
Beckman Institute researchers Joe Lyding and Eric Pop and their research groups have given now new insight into the electronics behavior of graphene with grain boundaries that could guide fabrication methods toward lessening
The researchers grew polycrystalline graphene by chemical vapor deposition (CVD) using scanning tunneling microscopy and spectroscopy for analysis to examine at the atomic scale grain boundaries on a silicon wafer.
We obtained information about electron scattering at the boundaries that shows it significantly limits the electronic performance compared to grain boundary free graphene Lyding said.
Grain boundaries form during graphene growth by CVD and while there is much worldwide effort to minimize the occurrence of grain boundaries they are a fact of life for now.
Boundary free graphene is a key goal. In the interim we have to live with the grain boundaries
Lyding compared graphene lattices made with the CVD method to pieces of a cyclone fence.
The research involved Pop's group led by Beckman Fellow Josh Wood growing the graphene at the Micro
In the paper the researchers were able to report on their analysis of the orientation angles between pieces of graphene as they grew together
and the GBS are continuous across graphene wrinkles and Si02 topography. They reported that analysis of those patterns indicates that backscattering
and intervalley scattering are the dominant mechanisms responsible for the mobility reduction in the presence of GBS in CVD-grown graphene.
Lyding said that the relationship between the orientation angle of the pieces of graphene and the wavelength of an electron impinges on the electron's movement at the grain boundary leading to variations in their scattering.
The more difficult you make that the lower the quality of the electronic performance of any device made from that graphene.
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