Esta modesta estructura ha captado la atención de los laboratorios de investigación más avanzados del mundo, desde Londres hasta Texas, y desde Solar Tech hasta IBM.
En esos laboratorios ya están estudiando el grafeno para una amplia variedad de aplicaciones: baterías para los vehículos eléctricos, chips de ordenador, dispositivos de comunicación, pantallas táctiles o acumuladores de energía. El grafeno podría incluso aplicarse en el cableado eléctrico de alta tensión.
El grafeno es una capa de átomos de carbono 200 veces más resistente que el acero y en la que los electrones tienen una movilidad 100 veces superior a la que les ofrece el silicio (el material con el que se fabrican los microprocesadores de los ordenadores).
En abril, investigadores de la Universidad de Texas publicaban en Science que habían logrado producir la primera muestra de grafeno de un centímetro de longitud. Hasta ahora, solo había sido posible construir microcristales de este material, útiles para el estudio experimental, pero insuficientes para pensar en una aplicación práctica.
En mayo, también en Science, investigadores del Georgia Institute of Technology y el National Institute of Standards and Technology (EEUU) publican una medición del espectro energético de este compuesto de carbono de propiedades exóticas. Una de estas características, a la que los electrones pueden deber su gran movilidad dentro del grafeno, es que éstas y otras partículas que transportan cargas eléctricas se comportan como si no tuviesen masa.
La existencia teórica del grafeno se había planteado desde hace décadas, pero se creía que un cristal bidimensional, hecho con una sola capa de átomos, se desharía. Hasta que en 2004 un equipo de la Universidad de Manchester dirigido por Andre Geim logró demostrar que era posible crear cristales bidimensionales.
Ahora, el trabajo de un gran número de equipos científicos en el mundo consiste en preparar cantidades de este material suficientes para su uso en electrónica o construcción de otros materiales. Este es el caso de Ignacio Paredes y su equipo en el Instituto Nacional del Carbón (CSIC). "Para obtener los grafenos, tomamos grafito y lo modificamos por oxidación. Después es posible exfoliarlo y obtener láminas individuales del material", explica Paredes. "El problema es que los métodos químicos necesarios para obtener el grafeno lo degradan, y hacen que pierda sus virtudes. Eso es lo que queremos mejorar", añade.
En el estudio publicado en Science, los investigadores desvelan que las capas de grafeno se presentan disociadas de otras capas adyacentes. Este dato puede ayudar a desarrollar nuevos métodos para fabricar tiras de grafeno grandes y uniformes para emplear en electrónica, y en un futuro como base de una nueva generación de baterías.
El grafeno consistente en una sola capa de grafito, y es lo que en química se conoce como alótropo. La alotropía implica cualquiera de las formas en que se pueden organizar los electrones de un elemento, sin dejar de ser ese elemento, lo cual le proporciona la capacidad de adoptar diferentes propiedades.
Es el caso del grafito (un material suave) y del diamante (el material más duro que se conoce). Ambos se originan de un mismo elemento: el carbono (la distinta disposición de los átmos de carbono). El diamante, el grafito y el grafeno son alótropos del carbono.
La alotropía es un fenómeno que ha sido estudiado durante décadas, sin embargo, no parecía tecnológicamente importante, hasta que los científicos empezaron a buscar reemplazos para el silicio, el elemento que ahora domina en el campo de la electrónica. Entonces apareció el grafeno, un hermano del grafito y el diamante.
En 2004 físicos de la Universidad de Manchester en Inglaterra encontraron una manera simple de producir grafeno: separar capas de grafito mediante un método conocido como exfoliación mecánica. Y esto generó una pequeña revolución en el campo de la investigación.
El grafeno tiene varias características muy atractivas. Sus electrones afrontan 100 veces menos resistencia de la que enfrentan los componentes de silicio (los buenos conductores eléctricos tienen baja resistencia).
Y ello es debido a que el grafeno es tan delgado que puede considerarse un material bidimensional (como una hoja de papel), construir dispositivos más pequeños y controlar el flujo de electricidad dentro de ellos es más fácil que con las alternativas tridimensionales como los transistores de silicio.
Delgado, transparente, extremadamente conductivo y fuerte, el grafeno parece ser el material ideal para una amplia diversidad de aplicaciones en el mundo de la electrónica .
Los investigadores que buscan construir la próxima generación de chips tienen planes muy ambiciosos para el grafeno. “Por ejemplo, los chips de silicio han alcanzado ya su punto más alto en lo que se refiere a su velocidad en gigahertz”, dice Walt de Heer, un físico de Georgia Tech. Heer estima que el grafeno puede operar a frecuencias de terahertz (billones de operaciones por segundo). Y asegura que su reducida resistibilidad ayudará a evitar el sobrecalentamiento.
“El grafeno es tan estable que pequeños transistores de unos pocos átomos pueden sostener corrientes eléctricas muy elevadas. Es un material asombroso”, concluye este experto.
Las propiedades eléctricas del grafeno son también modificables. Actualmente, un chip típico es un sandwich de tres pisos de capas de conducción, aislamiento y semiconducción, cada una hecha de materiales diferentes. Pero el grafeno puede ser aprovechado para llevar a cabo las tres funciones de manera simultánea.
No obstante, el reto más grande en la explotación del grafeno es usarlo como semiconductor. Un equipo de científicos de IBM está trabajando en transistores hechos de grafeno, el cual es particularmente útil para amplificar las señales débiles en los sistemas de alta frecuencia.
IBM espera que los transistores de grafeno permitan amplificar las señales entre las torres de comunicación de los teléfonos móviles y con el tiempo usarlos dentro de los propios móviles (lo que implicaría que las torres no serían necesarias).
El grafeno podría incluso revolucionar las industrias del automóvil y de la energía solar y eólica, las cuales sufren actualmente el problema del almacenamiento adecuado, pero los investigadores piensan que los ultracapacitores de grafeno podrían ser la respuesta a este inconveniente.
El ultracapacitor es un dispositivo de almacenamiento de energía que funciona a través de separar las cargas eléctricas, en lugar de almacenarlas químicamente (como hacen las baterías).
Los ultracapacitores de grafeno podrían tener el doble o el triple de la capacidad de almacenamiento de los disponibles actuales.
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Graphene Could Become World’s Best Super Battery
You know graphene, the super material that’s strong enough to withstand diamond cutters? Turns out that not only may it replace silicon as the de rigeur component of microchips, it’s on track to becoming the next megabattery as well. Engineers at the University of Texas in Austin have found a way to store electrical charge in graphene-based ultracapacitor devices, and their discovery could revolutionize the renewable energy industry.
There are two ways to store electrical energy today—through traditional rechargeable batteries or in ultracapacitors, a newer tech that runs safer, cooler, and longer. The UofT researchers think their breakthough could end up doubling the capacity of current ultracapacitors, which are made with a different, less awesome form of carbon.
If everything works out, it could give a much needed boost to solar and wind energy industries, whose main challenge right now is energy storage for when the sun isn’t shining and the wind isn’t blowing. Beyond that, graphene ultracapacitors could end up improving the efficiency of all electrical appliances—cars, buses, trains, you name it.
Breakthrough In Energy Storage: New Carbon Material Shows Promise Of Storing Large Quantities Of Renewable Electrical Energy
Engineers and scientists at The University of Texas at Austin have achieved a breakthrough in the use of a one-atom thick structure called "graphene" as a new carbon-based material for storing electrical charge in ultracapacitor devices, perhaps paving the way for the massive installation of renewable energies such as wind and solar power.
The researchers believe their breakthrough shows promise that graphene (a form of carbon) could eventually double the capacity of existing ultracapacitors, which are manufactured using an entirely different form of carbon.
"Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power," says Rod Ruoff, a mechanical engineering professor and a physical chemist. "There are reasons to think that the ability to store electrical charge can be about double that of current commercially used materials. We are working to see if that prediction will be borne out in the laboratory."
Two main methods exist to store electrical energy: in rechargeable batteries and in ultracapacitors which are becoming increasingly commercialized but are not yet as popularly known. An ultracapacitor can be used in a wide range of energy capture and storage applications and are used either by themselves as the primary power source or in combination with batteries or fuel cells. Some advantages of ultracapacitors over more traditional energy storage devices (such as batteries) include: higher power capability, longer life, a wider thermal operating range, lighter, more flexible packaging and lower maintenance, Ruoff says.
Ruoff and his team prepared chemically modified graphene material and, using several types of common electrolytes, have constructed and electrically tested graphene-based ultracapacitor cells. The amount of electrical charge stored per weight (called "specific capacitance") of the graphene material has already rivaled the values available in existing ultracapacitors, and modeling suggests the possibility of doubling the capacity.
"Our interest derives from the exceptional properties of these atom-thick and electrically conductive graphene sheets, because in principle all of the surface of this new carbon material can be in contact with the electrolyte," says Ruoff, who holds the Cockrell Family Regents Chair in Engineering #7. "Graphene’s surface area of 2630 m2/gram (almost the area of a football field in about 1/500th of a pound of material) means that a greater number of positive or negative ions in the electrolyte can form a layer on the graphene sheets resulting in exceptional levels of stored charge."
The U.S. Department of Energy has said that an improved method for storage of electrical energy is one of the main challenges preventing the substantial installation of renewable energies such as wind and solar power. Storage is vital for times when the wind doesn’t blow or the sun doesn’t shine. During those times, the stored electrical energy can be delivered through the electrical grid as needed.
Ruoff’s team includes graduate student Meryl Stoller and postdoctoral fellows Sungjin Park, Yanwu Zhu and Jinho An, all from the Mechanical Engineering Department and the Texas Materials Institute at the university. Their findings will be published in the Oct. 8 edition of Nano Letters. The article was posted on the journal’s Web site this week.
This technology, Stoller says, has the promise of significantly improving the efficiency and performance of electric and hybrid cars, buses, trains and trams. Even everyday devices such as office copiers and cell phones benefit from the improved power delivery and long lifetimes of ultracapacitors.
Ruoff says significant implementation of wind farms for generation of electricity is occurring throughout the world and the United States, with Texas and California first and second in the generation of wind power.
According to the American Wind Energy Association, in 2007 wind power installation grew 45 percent in this country. Ruoff says if the energy production from wind turbine technology grew at 45 percent annually for the next 20 years, the total energy production (from wind alone) would almost equal the entire energy production of the world from all sources in 2007.
"While it is unlikely that such explosive installation and use of wind can continue at this growth rate for 20 years, one can see the possibilities, and also ponder the issues of scale," he says. "Electrical energy storage becomes a critical component when very large quantities of renewable electrical energy are being generated."
Funding and support was provided by the Texas Nanotechnology Research Superiority Initiative, The University of Texas at Austin and a Korea Research Foundation Grant for fellowship support for Dr. Park.
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Graphene-Based Super Batteries
Researchers at The University of Texas at Austin have developed a new class of carbon material and demonstrated their performance in an ultracapacitor cell as a way to store electrical energy.
It’s almost become cliche about renewable energy: the problem of “when the wind doesn’t blow or the sun doesn’t shine”. Storage is key, and according to the U.S. Department of Energy, remains a principal challenge in rolling out solar and wind energy technology.
Graphene may be a key element in meeting that challenge.
Say Rod Ruoff. a mechanical engineering professor and physical chemist at the University: “Through such a device, electrical charge can be rapidly stored on the graphene sheets, and released from them as well for the delivery of electrical current and, thus, electrical power. There are reasons to think that the ability to store electrical charge can be about double that of current commercially used materials. We are working to see if that prediction will be borne out in the laboratory”.
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Quercus Trust’s Latest Energy Storage Play: Graphene Energy
Graphene Energy, an Austin-based developer of ultracapacitor technology, has raised $500,000 in seed investment from Quercus Trust and 21Ventures. The investment represents yet another move by David Gelbaum’s Quercus Trust, which was the third-most active venture fund investing in cleantech in all of 2008, according to the Cleantech Group.
Graphene Energy works with the strongest material ever tested — a one-atom thick sheet of graphite — to build ultracapacitors. The material, known as graphene, was hailed as the new silicon last year when researchers discovered that electrons could travel up to 100 times faster in graphene than silicon.
Around the same time, a new generation of ultracapacitors emerged that aimed to seize the future of the auto industry. With ultra-fast charge times, they can absorb voltage drops and surges to extend battery life — or store electricity on their own. But capacity has lagged somewhere around 5 percent of battery’s storage capacity.
Graphene Energy plans to solve this problem by stacking several sheets of graphene (pictured below), which it says could as much as double the capacity offered by today’s commercial ultracapacitors (usually made with activated carbon). The company, which emerged from research at the University of Texas, foresees applications in electric and hybrid vehicles, mobile devices, and wind- and solar-powered electric grids.
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Welcome to Graphene Energy
Welcome to Graphene Energy, Inc. We are leading the development of next generation nano-technology based Ultracapacitors for energy storage. This technology utilizes a unique form of Carbon, called Graphene, for electrode material.
Existing battery technologies fail to address the marketplace needs for high-power energy storage. With significant emphasis on renewable energy, including a rapid ramp-up of Solar, Wind and Geothermal technologies and government mandated requirements for high efficiency vehicles, there is a critical need for cost-effective, high-power and high-capacity energy storage solutions. Graphene is one of the most promising materials for Ultracapacitor electrodes with expectation of power densities surpassing any other known form of activated Carbon electrodes due to its large and readily accessible surface area.
Unlike batteries, Ultracapacitors can store and deliver energy in very short time, thus making them most suitable for high power density applications. Furthermore, a combination of Ultracapacitors and traditional batteries is identified as the most cost effective and reliable solution for applications where lifecycle and reliability are paramount. Applications of this material and technology include regenerative braking in electric and hybrid vehicles, energy balancing for the power grid, storage for Solar and Wind and Geothermal plants, hydraulic and actuator systems requiring high power densities, etc.
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The Rise of the UltraCapacitor
Between the Superbowl yesterday and Super Tuesday tomorrow, you will be forgiven for overlooking Maxwell Technologies’ announcement today that the company’s San Diego plant has just been ISO (International Organization for Standardization) certified to produce ultracapacitors. But if you’re interested in the future of the auto industry, you might want to sit up and take notice.
This week’s Economist brands new so-called “ultracapacitors” a potentially “disruptive technology” for the 21st century, one that could actually supplant rather than just supplement traditional car batteries. Did someone say time-travelling Delorean?
The news is that while capacitors have traditionally been used for quick bursts of speed, rather than endurance, ultracapacitors differ from traditional ones in that they can potentially match a battery in both areas. That’s thanks to new technology that uses interactions of positively and negatively charged ions coupled with an electrolyte instead of static charges. This development gives capacitors 5 percent of a battery’s storage capacity, but in order for ultracapacitors to seriously challenge batteries, that number needs to be much higher.
Scientists at MIT are working on a nano-engineered version that coats the surface area of the ultracapacitors with our old friends carbon nanotubes, which they claim can boost its capacity up to 50 percent of a battery. Also in the hunt is Cedar Park, Texas-based EEStor (that we wrote about here), which does away with the electrolyte and instead uses an insulator called barium titanate, which the company claims can store “very high“ levels of energy. One sign they might be on to something is that the company recently inked a deal with Lockheed Martin for its “electrical energy storage units” to be used to charge military gear once production starts later this year.
Another exciting application for ultra capacitors could be in recharging electric cars, a process which until now has been painfully slow. Refilling capacitors in the same way you top off the tank at the gas station would make electric vehicles much more practical and attractive. Canadian electric car firm called Zenn has signed a deal with EEStor to replace the current lead-acid batteries in its small urban vehicles with the EEStor units, in hopes of making its cars highway ready.
All of this sounds promising, but whether ultracapacitors can really unseat the mighty battery remains to be seen. The conversation, however, has been started, and battery technology is going to be forced to adapt to catch up.
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Team of researchers achieves major step toward faster chips
GAINESVILLE, Fla. — New research findings could lead to faster, smaller and more versatile computer chips.
A team of scientists and engineers from Stanford University, the University of Florida and Lawrence Livermore National Laboratory is the first to create one of two basic types of semiconductors using an exotic, new, one-atom-thick material called graphene. The findings could help open the door to computer chips that are not only smaller and hold more memory — but are also more adept at uploading large files, downloading movies, and other data- and communication-intensive tasks.
A paper about the findings, co-authored by eight researchers, is set to be published Friday in the journal Science.
“There are still enormous challenges to really put it into products, but I think this really could play an important role,” said Jing Guo, a UF assistant professor of electrical and computer engineering and one of two UF authors who contributed.
The team made, modeled and tested what is known in the industry as an “n-type” transistor out of graphene nanoribbon. Graphene is a form of carbon that has been called “atomic chicken wire,” thanks to its honeycomb-like structure of interconnected hexagons. A graphene nanoribbon is a nanometer-wide strip cut from a graphene layer.
The team’s feat is significant because basic transistors come in only two forms — “p-type” and “n-type” — referring to the presence of holes and electrons, respectively. “P-type” graphene semiconductors had already been achieved, so the manufacture of an “n-type” graphene semiconductor completes the fundamental building blocks.
“This work is essentially finding a new way to modify a graphene nanoribbon to make it able to conduct electrons,” Guo said. “This addresses a very fundamental requirement for graphene to be useful in the production of electronics.”
First isolated in 2004, graphene has spurred a great excitement in the chip research community because of its promising electrical properties and bare-minimum atomic size.
Scientists and engineers believe that after decades of development, silicon is fast reaching the upper limits of its physical performance. If the rapid evolution of ever-shrinking, ever-more-powerful, ever-cheaper semiconductors is to continue, they say, new materials must be found to complement or even replace silicon. Graphene is among the leading candidates for these nanoelectronics of the future.
Researchers at a number of institutions have reported using graphene to create a variety of simple transistor devices recently, with the Massachusetts Institute of Technology reporting in March the successful test of a graphene chip that can multiply electrical signals.
Guo said the team built and modeled the first-ever graphene nanoribbon n-type “field-effect transistor” using a new and novel method that involves affixing nitrogen atoms to the edge of the nanoribbon. The method also has the potential to make the edges of the nanometer-wide ribbon smoother, which is a key factor to make the transistor faster.
“This uses chemistry to really address the major challenges of electrical engineering when you get into such these small nanoscale dimensionalities,” he said. “It is very unusual for electrical engineers, who are used to dealing with bulk structures of at least millions of atoms.”
As exciting as the findings are, researchers must overcome many challenges before graphene semiconductors could be manufactured in bulk for use in consumer products, Guo said. For one thing, graphene is extremely expensive, so its cost would have to be reduced substantially. Also, to mimic or exceed silicon, engineers would have to figure out how to build not just one, but billions of transistors, on a tiny graphene fleck.
Five Stanford researchers led by Hongjie Dai, J.G. Jackson-C.J. Wood Professor of Chemistry, did the experimental work behind the findings. Guo and fellow author Youngki Yoon, who earned his doctoral degree from UF last December and is now at the University of California, Berkeley, did the computer modeling and simulation. The team also included Peter Webber of Lawrence Livermore National Laboratory.
Said Dai, “This work is just a beginning. It suggests that graphene chemistry and chemistry at the edges are rich areas to explore for both fundamental and practical reasons for this material.”
The UF portion of the research was funded by the National Science Foundation and the Office of Naval Research. The Stanford portion was funded by MARCO MSD, Intel and the Office of Naval Research.
www.sciencedaily.com/releases/2008/09/080916143910.htm
news.ufl.edu/2009/05/07/graphene/
