Posted on 01/12/2017 2:33:20 PM PST by 2ndDivisionVet
Once again, graphene has proven itself to be a rather special material: an international research team led by Professor Fritz Aumayr from the Institute of Applied Physics at TU Wien was able to demonstrate that the electrons in graphene are extremely mobile and react very quickly. Impacting xenon ions with a particularly high electric charge on a graphene film causes a large number of electrons to be torn away from the graphene in a very precise spot. However, the material was able to replace the electrons within some femtoseconds. This resulted in extremely high currents, which would not be maintained under normal circumstances. Its extraordinary electronic properties make graphene a very promising candidate for future applications in the field of electronics.
The Helmholtz-Center Dresden-Rossendorf and the University of Duisburg-Essen participated in the experiment alongside TU Wien. The international team received theoretical support from Paris and San Sebastian as well as from in-house staff (Institute of Theoretical Physics at TU Wien).
Highly charged ions
‘We work with extremely highly-charged xenon ions,’ explains Elisabeth Gruber, a PhD student from Professor Aumayr’s research team. ‘Up to 35 electrons are removed from the xenon atoms, meaning the atoms have a high positive electric charge.’
These ions are then fired at a free-standing single layer of graphene, which is clamped between microscopically small brackets. ‘The xenon ion penetrates the graphene film, thereby knocking a carbon atom out of the graphene – but that has very little effect, as the gap that has opened up in the graphene is then refilled with another carbon atom,’ explains Elisabeth Gruber. ‘For us, what is much more interesting is how the electrical field of the highly charged ion affects the electrons in the graphene film.’
This happens even before the highly charged xenon ion collides with the graphene film. As the highly charged ion is approaching it starts tearing electrons away from the graphene due to its extremely strong electric field. By the time the ion has fully passed through the graphene layer, it has a positive charge of less than 10, compared to over 30 when it started out. The ion is able to extract more than 20 electrons from a tiny area of the graphene film.
This means that electrons are now missing from the graphene layer, so the carbon atoms surrounding the point of impact of the xenon ions are positively charged. ‘What you would expect to happen now is for these positively charged carbon ions to repel one another, flying off in what is called a Coulomb explosion and leaving a large gap in the material,’ says Richard Wilhelm from the Helmholtz-Center Dresden-Rossendorf, who currently works at TU Wien as a postdoctoral assistant. ‘But astoundingly, that is not the case. The positive charge in the graphene is neutralised almost instantaneously.’
This is only possible because a sufficient number of electrons can be replaced in the graphene within an extremely short time frame of several femtoseconds (quadrillionths of a second). ‘The electronic response of the material to the disruption caused by the xenon ion is extremely rapid. Strong currents from neighbouring regions of the graphene film promptly resupply electrons before an explosion is caused by the positive charges repelling one another,’ explains Elisabeth Gruber. ‘The current density is around 1000 times higher than that which would lead to the destruction of the material under normal circumstances – but over these distances and time scales, graphene can withstand such extreme currents without suffering any damage.’
Ultra-fast electronics
This extremely high electron mobility in graphene is of great significance for a number of potential applications: ‘The hope is that for this very reason, it will be possible to use graphene to build ultra-fast electronics. Graphene also appears to be excellently suited for use in optics, for example in connecting optical and electronic components,’ says Aumayr.
It is really quite simple to explain. (After all, Einstein said that if you can’t explain it simply then you don’t really understand it.) The simple explanation is that I copied and pasted that out of wiki a couple of years ago and have kept it around for whenever graphene comes up. Now you know as much about it as I do.
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What is the best way to invest in graphene? Seems like the next big wave.
Re: “Where do these replacement electrons come from?”
My first question, too.
If they come from nearby carbon atoms, why doesn’t that electron loss cause a Coulomb explosion in the donor atoms?
I was just asking my hubby the same thing .
Yes, really. Chinese batteries for toys doesn’t move it out of the dud category.
Compared to the thousands of breathless research articles over the years, it isn’t much.
Just the end of their feet.
According to this guy who did a teardown the batteries are a scam. The cells are made by A123, and nothing says battery scam like A123.
https://www.youtube.com/watch?v=fBy4eoDVp_g
GPHOF over the counter - trading at 7.1 cents/share today. Highly speculative!
Wow! Sounds to me like they’re close to having the technology for making nano-electric-chairs for executing rogue viruses!
” I’ve always wondered, even with photoelectrics: The photon drives off electrons to generate a current, but the silicon remains. HOW? Where do the “new” electrons come from?”
the electrons move in a closed circle called a circuit, with the photovoltaic effect providing the energy to excite the electrons to move in the closed circuit. no electrons are gained or lost, they are simply impelled to move in a circle, which by definition is a current.
I found that presentation to be wonderfully bouffant.
Bulbous even.
Big Battery Bike Build - Testing The EESD [Made with graphene]
https://www.youtube.com/watch?v=P266pdT71tI
Robert has a lot more videos about graphene on his youtube channel. He also has developed and ran tests of graphene composite materials that do a good job of stopping rifle bullets that might be of interest.
That was the other ping.
;)
Like "jumbo shrimp", I suppose. Huge currents on the 0.000000001 scale. Well, impressive, on a pico scale.
Writers are weird.
I was knocked off my feet trying to decipher the complexity of your graphene description. Now I know how receptionists felt when I explained building data rooms, and interconnecting servers with routers and getting all their computers to interact. Now that you explained the magic, some of the awe factor is gone... but maybe I can use your explanation to awe some others... (Just kidding. You really had me going there.)
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