Here's a guest article that Olan Dantes from Farnell sent us, regarding Graphene and Super Capacitors:
Electronic devices can become smaller and smaller to the point that it becomes invisible to the naked eye. But no matter what size they can have, they will still produce a lot of heat. The interconnecting wires as well as the multitude of transistors inside these devices at nano and micro scales are more than capable of creating heat spots. There could have been nothing wrong with the produced heat if it didn't induce damage.
Scientists and engineers have found hope on graphene, a material that has the unique characteristic of conducting and dispersing heat. If it could replace the traditional materials that are used in electronic devices, then the problems of high heat dissipation would be finally alleviated. But besides the prevention of overheating, graphene has also shown a lot of promise for power storage. Thus, it is now closely studied by capacitor distributors such as Premier Farnell, manufacturers and enthusiasts.
Graphene is derived from graphite and as such, it is formed by carbon atoms. The atoms form a thin layer within a lattice that closely resembles a chicken wire. Although graphene has a thickness of a single atom, it is mechanically strong and provides great electron mobility besides having a notable thermal conductivity. Graphene can have a thermal conductivity as high as 600 watts per meter per Kelvin near room temperature. In contrast, copper only has a conductivity of approximately 250 watts while silicon has only 10 watts. These two are the thin films currently used in electronic devices.
Scientists had problems in producing large amounts of graphene which is necessary for it to be useful in real world applications. Physicists from University of California found that layering a few graphene sheets on top of the other will help it retain its remarkable heat transferring properties. This was an answer to a previous study done months before it wherein a graphene layer was placed on a silicon dioxide substrate although there was a decrease in conductivity. Nevertheless, multiple graphene sheets are easier to manufacture.
Meanwhile, Graphene has been in the discussion as an electrode in supercapacitor designs. The carbon-based material is projected to help them charge in a shorter amount of time as well as store more energy. Engineers from the University of Texas created a new activated carbon material that could enhance the holding capacity of a supercapacitor.
Porous, sponge-like sheets were created by the researchers through applying potassium hydroxide to graphene. A “pore” on this material is only 1 to 5 nanometers thick resulting in a maximum surface area of 3,100 square meters per gram. To give you an idea on how large this is, a gram of this material would stretch from the end zone of a football field to its 50-yard line. This increased surface area allows the electrode on a supercapacitor to hold more energy, which is what researchers have been aiming at for years.
These are great for frequent recharging and quick energy fixes although they still hold less energy compared to batteries. Batteries steadily and slowly discharge over time. What researchers want is for a supercapacitor to store as much energy as a battery, swiftly take in and release its charge and endure as much recharging cycles as possible. This could be useful in electric vehicles and in power grids that need to regulate varying influxes from wind and solar farms.
Another group of researchers had a different design for a graphene supercapacitor which only took less than 200 milliseconds to be fully charged. Led by Rodney Ruoff, professor of materials science and mechanical engineering at the University Texas, the team combines the attributes of both graphene and a capacitor. Ruoff said that their material will have a broad range of impact on energy storage and conversion technology because of the relative ease of manufacturing it. Ruoff is talking about the abundance of the element carbon in our surrounding.
But before the Texan researchers could be sure of what they created, they needed a closer look. Powerful electron microscopes at the Brookhaven National Laboratory in New York helped them do so. Zooming in on the material’s atomic structure, the scientists could see the novel 3-dimensional material consisted of curved walls just one atom thick.
The Texan researchers needed all the help they can, like having a “closer look” with the help of a powerful electron microscope. The Brookhaven National Laboratory in New York answered their heed. With the help of Brookhaven’s microscope, they were able to zoom in on the material’s structure and see the 3D material made up of curved walls with a thickness equivalent to a single atom.
“We’re still working with Ruoff and his team to pull together a complete description of the material structure,” says Eric Stach of Brookhaven. He added that they are adding computational studies to help us understand how this three-dimensional network forms. They hope that they can tailor the pore sizes so that it could fit for specific applications, including capacitive storage, catalysis, and fuel cells.
Graphene on supercapacitor electrodes has a lot of promise. In the same time, it could work well with silicon inside microchips although it is impossible it would replace the latter totally. Other possible applications for graphene’s thermal abilities include transparent electrodes in solar cells, heat spreaders within computer chips, and super-fast transistors for radio frequency communications. It would still take a few more years though before the graphene’s potential is realized.