Stories tagged graphene

Aug
02
2012

Graphene fixes itself: Graphene uses loose carbon atoms to re-knit its damaged structure.
Graphene fixes itself: Graphene uses loose carbon atoms to re-knit its damaged structure.Courtesy kso
As a happy accident, scientists from the University of Manchester learned that graphene (sheets of carbon atoms arranged in a honeycomb crystal lattice, just one atom thick – think chicken wire) can repair itself spontaneously. Graphene is a semi-metal that conducts electricity very easily. It has potential uses in not only electronics, but also DNA sequencing, desalination, and it has been found to be a great antimicrobial.

The Manchester researchers were originally trying to understand how metals react with graphene, which will be an important part of incorporating it into everyday electronic devices. They found, much to their dismay, that some metals actually damaged graphene’s structure by punching holes in its neatly-arranged lattice. This is not a good thing if you’re trying to create a graphene-based device. However, quite unexpectedly, the graphene started to mend itself spontaneously, using nearby loose carbon atoms! As stated by the Scientific Director at the Daresbury Laboratory, Dr. Quentin Ramasse, this could mean the “difference between a working device and a proof of concept with no real application.” It also means that graphene just jumped to the top of my “baller carbon allotropes” list.

Graphene Looks a Little Like Chicken Wire
Graphene Looks a Little Like Chicken WireCourtesy By English Wikipedia [CC-BY-SA-3.0-migrated-with-disclaimers or GFDL-en], from Wikimedia Commons
What would happen if you stretched a piece of graphene (a chicken-wire looking sheet of carbon one atom wide) across a teacup, then rested the weight of a truck on top of a pencil on top of the whole thing? NOTHING. Cool.

Check out what the New York Times had to say about it.

Jul
25
2010

Graphene, the wonder material

Graphene: Unzip it and add oxygen to get graphene oxide
Graphene: Unzip it and add oxygen to get graphene oxideCourtesy Dr Thomas Szkopek
If you look at my posts about graphene you will understand why I think graphene is a super material. One chemically converted graphene product of interest (CCG) is graphene oxide (GO). Graphene oxide, an insulating version of graphene, is expected to be used for all kinds of material and electronic applications. Graphene oxide is also biodegradable. Bacteria from the genus Shewanella easily convert GO to harmless graphene.

Safer, more efficient way to make graphene oxide

A new paper in ACSNano from the lab of Rice chemist James Tour demonstrates an environmentally friendly way to make bulk quantities of graphene oxide (GO). Scientists have been making GO since the 19th century, but the new process eliminates the need for explosive or toxic ingredients.

The researchers suggested the water-soluble product could find use in polymers, ceramics and metals, as thin films for electronics, as drug-delivery devices and for hydrogen storage, as well as for oil and gas recovery. Science Dailey

Learn more about improved synthesis of graphene oxide

Graphene oxide gets green EurekaAlert

Feb
06
2010

Graphene
GrapheneCourtesy Carbophiliac

Graphene is great

Graphene is a single atom thick layer of carbon atoms in a honeycomb like arrangement (read more about graphene here in ScienceBuzz.org)

Graphene transistors are the fastest

Transistors are like valves that can turn the flow of electricity off and on. Computers can use transistors and logic circuits to solve all kinds of problems. These problems can be solved faster if the transistors can turn on and off faster. Transistors made out of graphene now can switch on and off 100 billion times per second (100 GigaHertz). State-of-the-art silicon transistors of the same gate length have a switching frequency of about 40 GigaHertz.

IBM develops next-generation transistors

IBM just announced their breakthrough in the magazine Science.

Uniform and high-quality graphene wafers were synthesized by thermal decomposition of a silicon carbide (SiC) substrate. The graphene transistor itself utilized a metal top-gate architecture and a novel gate insulator stack involving a polymer and a high dielectric constant oxide. The gate length was modest, 240 nanometers, leaving plenty of space for further optimization of its performance by scaling down the gate length. ScienceDaily

Graphene is again proving to be the super material. Micro ribbons of graphene are out performing copper wires, both in current carrying capacity and in heat dissipation.

In widths as narrow as 16 nanometers, graphene has a current carrying capacity approximately a thousand times greater than copper – while providing improved thermal conductivity. Georgia Tech

Dec
28
2008

Graphene memory is smaller

Graphene transistors: Graphene is an atomic-scale chicken wire made of carbon atoms.
Graphene transistors: Graphene is an atomic-scale chicken wire made of carbon atoms.Courtesy Carbophiliac
Computer memory devices become cheaper, faster, and smaller every year. A team of researchers at Rice University led by James Tour has found a method of creating a new type of memory from a strip of graphite only 10 atoms thick. Individual memory bits smaller than 10 nanometers that have only two terminals will allow super thin sheets of memory to be stacked in layers, multiplying the storage capacity.

Graphene memory is resistant to heat and cold

The graphene memory is able to operate in a very wide temperature range. The researchers have tested the system to minus 75 to over 200 degrees Celsius.

Graphene memory is faster and lasts longer

Researchers say that the new switches are faster than the lab's testing equipment can measure and they promise long life as well.

"We’ve tested it in the lab 20,000 times with no degradation,” said Tour. “Its lifetime is going to be huge, much better than flash memory."

Graphene memory is cheap and easy to produce

"The processes uses graphene deposited on silicon via chemical vapor deposition making for easy construction that can be done in commercial volumes with methods already available," says Tour.

Abstract of Rice University article in Nature

Here, we report that two-terminal devices consisting of discontinuous 5–10 nm thin films of graphitic sheets grown by chemical vapour deposition on either nanowires or atop planar silicon oxide exhibit enormous and sharp room-temperature bistable current–voltage behaviour possessing stable, rewritable, non-volatile and non-destructive read memories with on/off ratios of up to 107 and switching times of up to 1 mus (tested limit). Nature Materials

Source: Rice University News

Jul
22
2008

Hey, wait a second...: How could you ever balance one of those on a pencil? Bad science!
Hey, wait a second...: How could you ever balance one of those on a pencil? Bad science!Courtesy Matthieu :: giik.net/blog
All y’all up on graphene?

I knew you were. You’re Buzzketeers, the best of the best, the biggest of the brains, the coolest of the cids.

There’s no need to explain graphene to this team (the Lil’ Professors), so it would be totally unnecessary for me to point out that graphene is a fancy material made of a single layer of carbon atoms attached to each other in a honeycomb pattern. It’s about as flat as can be, and when you roll it up you get those little things Science Buzz is so crazy about: carbon nanotubes.

Nanotubes are awesome, and if you click on the link above you can learn about all the awesome things they can do. But graphene…graphene itself may be pretty awesome too. The problem with testing just how awesome graphene is is that it has been exceptionally difficult to a) make a piece of graphene so small that it hasn’t got any of the imperfections that naturally come in large chunks of things, and b) make a device to actually hold the itty bitty graphene well enough to really test the stuff out.

But science has now done those things! Using a tiny sheet of perfect graphene (about 1/100s the width of a human hair) and a really tiny diamond…poker-thing (about 10 billionths of a meter wide), scientists have finally been able to find out exactly how strong graphene is.

So, how strong is it? It’s the strongest! That is to say, the strongest material measured so far. It’s about 200 times the strength of structural steel, or, says Columbia Professor James Hone, “It would take an elephant, balanced on a pencil, to break through a sheet of graphene the thickness of Saran Wrap.”

This statement, of course, wins professor Hone July’s “Awesome explanation, Scientist” award. That’s a good mental image, and it shows a non-scientist like me how strong graphene is.

So…awesome explanation, Scientist! More of that, please!

Mar
30
2008

Graphene potentially 100x better than silicon

Graphene computer chips: The slightly darker purple area is the graphene, and the lighter purple is the substrate material (SiO2/Si).
Graphene computer chips: The slightly darker purple area is the graphene, and the lighter purple is the substrate material (SiO2/Si).Courtesy S. Cho and M. S. Fuhrer, University of Maryland
Graphene could replace silicon as the material of choice for many applications like high-speed computer chips and biochemical sensors.

Michael Fuhrer in a paper published online in Nature Nanotechnology explains that in graphene, the intrinsic limit to the mobility, a measure of how well a material conducts electricity, is higher than any other known material at room temperature.

If other extrinsic factors that limit mobility in graphene, such as impurities and lattice vibrations in the substrate on which graphene sits, could be eliminated, the intrinsic mobility in graphene would be more than 100 times higher than silicon.

The low resistivity and extremely thin nature of graphene makes it ideal for applications like touch screens, photovoltaic cells, and chemical and biochemical sensors. The research group was led by principal investigator Michael Fuhrer of the University of Maryland's Center for Nanophysics and Advanced Materials and the Maryland NanoCenter.

Better than silver or gold

Fuhrer said the electrical current in graphene is carried by only a few electrons moving much faster than the electrons in a metal like silver.

"Our current samples of graphene are fairly 'dirty' due to some extraneous sources of resistivity,"
"Once we remove that dirt, graphene, at room temperature, should have about 35 percent less resistivity than silver, the lowest resistivity material known at room temperature."

Roadmap for progress

Because graphene is only one atom thick, current samples must sit on a substrate, in this case silicon dioxide. The electron mobility within the graphene is effected by the substrate. Trapped electrical charges in the silicon dioxide (a sort of atomic-scale dirt) and vibrations of the silicon dioxide atoms can also have an effect on the graphene which are stronger than the effect of graphene's own atomic vibrations.

"We believe that this work points out the importance of these extrinsic effects, and creates a roadmap for finding better substrates for future graphene devices in order to reduce the effects of charged impurity scattering and remote interfacial phonon scattering." Fuhrer said.

Source:University of Maryland news release

Mar
11
2007

Graphene transistor tiniest ever

Graphene from graphite: Graphene is one layer of carbon atoms linked chickenwire-like within graphite. Mattman723 / CC BY-SA 2.5
Graphene from graphite: Graphene is one layer of carbon atoms linked chickenwire-like within graphite. Mattman723 / CC BY-SA 2.5
Only one atom thick and less than 50 atoms wide, these "nano" transistors are the smallest in the world. Graphene transistors originally produced at the end of 2004 were very “leaky”. Transistors are like a valves, controlling the flow of an electric current. If they cannot be totally turned off, the leakage results in drained batteries.

Leakage problem solved

Now the Manchester team has found an elegant way around the problem and made graphene-based transistors suitable for use in future computer chips.

Graphene remains highly stable and conductive even when it is cut into strips of only a few nanometres wide.
All other known materials - including silicon - oxidise, decompose and become unstable at sizes tens times larger.
Professor Geim does not expect that graphene-based circuits will come of age before 2025. DailyTech

Professor Andre Geim and Dr Kostya Novoselov from The School of Physics and Astronomy at The University of Manchester reveal details of these transistors, in the March issue of Nature Materials.

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