Graphene Oxide Paper Could Spawn a New Class of Materials
04 August 2007
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| A cross-section after fracture of a paper-material comprising individual and layered sheets of graphene oxide (prepared by Sasha Stankovich). This is a scanning electron microscope image, scale bar is 1 micrometer in length. The inset shows a strip of this graphene oxide paper held with metal tweezers. (Images by Dmitriy Dikin.) |
Researchers at Northwestern University have fabricated a graphene oxide “paper”—a new carbon nanocomposite material based on nanoscale graphene oxide sheets that are interlocked and tiled together in a near-parallel fashion. Graphene is a sheet of carbon only one atom thick.
The unique interlocking-tile arrangement of the nanoscale graphene oxide sheets results in a combination of macroscopic flexibility and stiffness. Because of its properties,the new graphene-based paper could be used in a wide variety of applications, including membranes with controlled permeability and for batteries or supercapacitors for energy applications.
Graphene oxide paper could also be infused to create hybrid materials containing polymers, ceramics or metals, where such composites would perform much better than existing materials as components in, for example, airplanes, cars, buildings and sporting goods products.
In a paper published 26 July in Nature, researchers led by Rod Ruoff, John Evans Professor of Nanoengineering in the Robert R. McCormick School of Engineering and Applied Science, report on the development of the graphene oxide material. Ruoff’s research team was the first to develop graphene-based composite materials, which was reported in Nature last year.
The mechanical, thermal, optical and electrical properties of graphene are exceptional. or example, the stiffness and strength of these graphene-like sheets should be superior to all other materials, with the possible exception of diamond.
—Rod Ruoff
To form the graphene oxide paper, the group oxidized graphite to create graphite oxide, which falls apart in water to yield well-dispersed graphene oxide sheets. After filtering the water, the team was able to fabricate pieces of graphene oxide ‘paper’ more than five inches in diameter and with thicknesses from about one to 100 microns, in which the individual micron-sized graphene oxide sheets are stacked on top of each other.
I have little doubt that very large-area sheets of this paper-material could be made in the future.
—Rod Ruoff
In addition to their superior mechanical properties as individual sheets, the graphene oxide layers stack well, which could be key to the development of other materials. The microscale sheets can be stacked together and chemically linked, allowing for the further optimization of the properties of the resulting object, according to Ruoff.
Of further interest are the electrical properties of the graphene oxide paper in comparison to graphene sheets.
When we oxidize the graphene sheets to create graphene oxide, the material goes from being an electrical conductor to an electrical insulator. This is an important step and in the future it will be possible to tune the material as a conductor, semiconductor or insulator. One will be able to control the electrical properties without sacrificing exceptional mechanical properties.
—Rod Ruoff
The development of this paper-like material is the latest of several recent advancements by Ruoff’s team in launching the new field of graphene-based materials. In a paper in the July issue of Nano Letters, the group reported that graphene sheets could be embedded into glass films to make them electrically conductive. These transparent thin films could find applications in solar cells or a variety of transparent electronics such as electronic paper and flexible color screens. The processing of these films may provide a cheaper alternative to the widely used indium tin oxide coatings that are typically used as the transparent conductive film.
In addition to Ruoff, other authors on the Nature paper are Dmitry Dikin, Sasha Stankovich, Eric Zimney, Richard Piner, Geoffrey Dommett, Guennadi Evmenenko and SonBinh Nguyen. For the Nano Letters paper, this group of researchers was also joined by coauthors Supinda Watcharotone, and from the National Cheng Kung University in Taiwan, Shang-En Wu, Shu-Fang Chen and Chuan-Pu Liu.
The work reported in Nature and in Nano Letters was supported by NASA and the National Science Foundation.
Resources:
“Preparation and characterization of graphene oxide paper”; Dmitriy A. Dikin, Sasha Stankovich, Eric J. Zimney, Richard D. Piner, Geoffrey H. B. Dommett, Guennadi Evmenenko, SonBinh T. Nguyen & Rodney S. Ruoff; Nature 448, 457-460 (26 July 2007) | doi:10.1038/nature06016
“Graphene-Silica Composite Thin Films as Transparent Conductors”; Supinda Watcharotone, Dmitriy A. Dikin, Sasha Stankovich, Richard Piner, Inhwa Jung, Geoffrey H. B. Dommett, Guennadi Evmenenko, Shang-En Wu, Shu-Fang Chen, Chuan-Pu Liu, SonBinh T. Nguyen, and Rodney S. Ruoff; Nano Lett.; 2007; 7(7) pp 1888 - 1892; (Letter) DOI: 10.1021/nl070477+"
“Graphene-based composite materials”; Sasha Stankovich, Dmitriy A. Dikin, Geoffrey H. B. Dommett, Kevin M. Kohlhaas, Eric J. Zimney, Eric A. Stach, Richard D. Piner, SonBinh T. Nguyen and Rodney S. Ruoff; Nature 442, 282-286 (20 July 2006) | doi:10.1038/\\
Imagine a tire carcass made out of a graphene sheet stack material. If you could find a way to let the layers slide against each other freely just a little bit while preserving robustness, you could achieve a revolutionary low rolling resistance.
As for this graphene oxide, I would try making it into a waferboard-like pressed, molded sheet. Waferboard forklift pallets illustrate how you might make a composite car body part. Unlike graphite fiber, you don't need to weave or anything that means a lot of labor.
Posted by: P Schager | 04 August 2007 at 08:27 AM
P Schaeger -
when sheets of atoms slide relative to one another, that's called plastic deformation and generates heat. Graphene is a form of pure carbon and will catch fire if exposed to a flame or high friction heat.
So far, the process can "only" deliver flat sheets of some macroscopic dimension. These should prove very useful, especially in electrical applications and selected mechanical stress members (uniaxial and planar stress). However, for full utility in doubly curved automotive panels, someone will need to figure out how to introduce defects (5-sided rings) into the sheets at precisely defined locations to obtain crumple-free bends.
Posted by: Rafael Seidl | 04 August 2007 at 01:46 PM
Rafael:
If you bend your clothing, a stranded wire or a magazine, surfaces slide past one another and it's not plastic deformation, just flexibility with very low friction. Especially when the sheer slip per layer is very low. The same thing could be engineered on a nanoscale. And graphite is known as a lubricant precisely because of its ultralow sliding friction between planes. Standard rubber tires will burn if you roll them fast enough, but low rolling resistance tires would leave them in the dust. Unlike rubber, graphite won't oxidize at low temperatures and could last indefinitely. Just use rubber or polyurethane for the treads and make them replaceable.
Waferboard is made by using flat sheets of some small dimension, and you can make complex 3D curves out of flakes that bend in at most one dimension because they are a small part of the maximum bend radius and easily approximate the curve; the small gaps can be filled in by resin. The tricky part is getting them to all lay parallel; one solution is multiple press-molding after sprinkling successive thin layers.
Posted by: P Schager | 04 August 2007 at 03:01 PM
P Schager
If you make a tire with zero siding resistance material, your car will go no-where. It will be like rotating the axle dipped in water.
However, materials like this can find use in moving parts like gears and pistons.
Posted by: SM | 04 August 2007 at 05:29 PM
Low sliding resistance internal to the tire carcass. Tread is still a rubbery material. Trick of course is to keep it from flaking apart too easily.
It does sound like you could use graphene oxide paper laminate stacks to make very strong engine parts, once you're ready to make them composites. Graphene itself might make excellent sealing rings for a Stirling engine that would need no oil lubricant in the cylinder, so that you can go to really high operating temperatures and thus gain unprecedented heat engine efficiencies and on any fuel, and high power densities in a Stirling. Now all you need is an oxygen separator.
Posted by: P Schager | 05 August 2007 at 04:58 AM
"The microscale sheets can be stacked together and chemically linked, allowing for the further optimization of the properties of the resulting object, according to Ruoff."
Does this mean that 5" sheets could be chemically cross-linked like staples through paper? Does that then suggest that you could make a longer-than-5" ribbon by stapling lots of sheets together?
Posted by: Brock | 06 August 2007 at 09:12 PM
All very interesting comments. As we are moving our lab to UT-Austin, I will be brief. Consider that the individual layers (the molecular sheets) of chemically functionalized graphene are less than 1 nanometer thick, but have diameters of more than a micron. One thing to aim for in the future is indeed a sort of "stapling" which however is achieved at the molecular level through chemical bonding. Stitching the individual sheets together, and inventing methods to scale up size for manufacturing, are exciting goals for the future. You might enjoy my discourse on Scitizen, a European web site devoted to exchange between scientists and the public. Easily found by web seaching, I think. Also,
http://www.engr.utexas.edu/news/articles/200707251292/index.cfm
Loading a big rig with a full lab is time consuming in its planning, so I will unfortunately not be able to respond further, but enjoyed reading the comments.
Sincerely, Rod Ruoff
Posted by: Rod Ruoff | 17 August 2007 at 03:45 AM