Future of energy storage with Graphite + Water

Future of energy storage with Graphite + Water

  1:56:00 PM    Science Lover

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A combination of two ordinary materials – graphite and water – could produce energy storage systems that perform on par with lithium ion batteries, but recharge in a matter of seconds and have an almost indefinite lifespan.

Graphene sheets. Credit: Gengping Jiang

Dr. Dan Li, of the Monash University Department of Materials Engineering, and his research team have been working with a material called graphene, which could form the basis of the next generation of ultrafast energy storage systems.

“Once we can properly manipulate this material, your iPhone, for example, could charge in a few seconds, or possibly faster.” said Dr. Li.

Graphene is the result of breaking down graphite, a cheap, readily available material commonly used in pencils, into layers one atom thick. In this form, it has remarkable properties.

Graphene is strong, chemically stable, an excellent conductor of electricity and, importantly, has an extremely high surface area.

Dr. Li said these qualities make graphene highly suitable for energy storage applications.



“The reason graphene isn’t being used everywhere is that these very thin sheets, when stacked into a usable macrostructure, immediately bond together, reforming graphite. When graphene restacks, most of the surface area is lost and it doesn’t behave like graphene anymore.”

Now, Dr. Li and his team have discovered the key to maintaining the remarkable properties of separate graphene sheets: water. Keeping graphene moist – in gel form – provides repulsive forces between the sheets and prevents re-stacking, making it ready for real-world application.

“The technique is very simple and can easily be scaled up. When we discovered it, we thought it was unbelievable. We’re taking two basic, inexpensive materials – water and graphite – and making this new nanomaterial with amazing properties,” said Dr. Li.

When used in energy devices, graphene gel significantly outperforms current carbon-based technology, both in terms of the amount of charge stored and how fast the charges can be delivered.

Dr. Li said the benefits of developing this new nanotechnology extend beyond consumer electronics.

“High-speed, reliable and cost-effective energy storage systems are critical for the future viability of electricity from renewable resources. These systems are also the key to large-scale adoption of electrical vehicles.

“Graphene gel is also showing promise for use in water purification membranes, biomedical devices and sensors.”

Provided by Monash University

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Nanotubes Weigh A Single Atom

Nanotubes Weigh A Single Atom

  5:49:00 PM    Science Lover

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How can you weigh a single atom? European researchers have built an exquisite new device that can do just that. It may ultimately allow scientists to study the progress of chemical reactions, molecule by molecule.

A diagram (above) and real-life image (inset) of a carbon nanotube.
(Credit: CARDEQ Project (www.cardeq.eu)

Carbon nanotubes are ultra-thin fibres of carbon and a nanotechnologist’s dream.

They are made from thin sheets of carbon only one atom thick – known as graphene – rolled into a tube only a few nanometres across. Even the thickest is more than a thousand times thinner than a human hair.

Interest in carbon nanotubes blossomed in the 1990s when they were found to possess impressive characteristics that make them very attractive raw materials for nanotechnology of all kinds.

“They have unique properties,” explains Professor Pertti Hakonen of Helsinki University of Technology. “They are about 1000 times stronger than steel and very good thermal conductors and good electrical conductors.”

Hakonen is coordinator of the EU-funded CARDEQ project (http://www.cardeq.eu/) which is exploiting these intriguing materials to build a device sensitive enough to measure the masses of atoms and molecules.

Vibrating strings

A carbon nanotube is essentially an extremely thin, but stiff, piece of string and, like other strings, it can vibrate. As all guitar players know, heavy strings vibrate more slowly than lighter strings, so if a suspended carbon nanotube is allowed to vibrate at its natural frequency, that frequency will fall if atoms or molecules become attached to it.

It sounds simple and the idea is not new. What is new is the delicate sensing system needed to detect the vibration and measure its frequency. Some nanotubes turn out to be semiconductors, depending on how the graphene sheet is wound, and it is these that offer the solution that CARDEQ has developed.

Members of the consortium have taken the approach of building a semiconducting nanotube into a transistor so that the vibration modulates the current passing through it. “The suspended nanotube is, at the same time, the vibrating element and the readout element of the transistor,” Hakonen explains.

“The idea was to run three different detector plans in parallel and then select the best one,” he says. “Now we are down to two. So we have the single electron transfer concept, which is more sensitive, and the field effect transistor concept, which is faster.”

Single atoms

Last November, CARDEQ partners in Barcelona reported that they had sensed the mass of single chromium atoms deposited on a nanotube. But Hakonen says that even smaller atoms, of argon, can now be detected, though the device is not yet stable enough for such sensitivity to be routine. “When the device is operating well, we can see a single argon atom on short time scales. But then if you measure too long the noise becomes large.”

CARDEQ is not alone in employing carbon nanotubes as mass sensors. Similar work is going on at two centres in California – Berkeley and Caltech – though each has adopted a different method to measuring the mass.

All three groups have announced they can perform mass detection on the atomic level using nanotubes, but CARDEQ researchers provided the most convincing data with a clear shift in the resonance frequency.

But a single atom is nowhere near the limit of what is possible. Hakonen is confident they can push the technology to detect the mass of a single nucleon – a proton or neutron.

“It’s a big difference,” he admits, “but typically the improvements in these devices are jump-like. It’s not like developing some well-known device where we have only small improvements from time to time. This is really front-line work and breakthroughs do occur occasionally.”

Biological molecules

If the resolution can be pared down to a single nucleon, then researchers can look forward to accurately weighing different types of molecules and atoms in real time.

It may then become possible to observe the radioactive decay of a single nucleus and to study other types of quantum mechanical phenomena.

But the real excitement would be in tracking chemical and biological reactions involving individual atoms and molecules reacting right there on the vibrating nanotube. That could have applications in molecular biology, allowing scientists to study the basic processes of life in unprecedented detail. Such practical applications are probably ten years away, Hakonen estimates.

“It will depend very much on how the technology for processing carbon nanotubes develops. I cannot predict what will happen, but I think chemical reactions in various systems, such as proteins and so on, will be the main applications in the future.”

The CARDEQ project received funding from the FET-Open strand of the EU’s Sixth Framework Programme for ICT research.

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