Monday, 23 July 2012 08:14
July 23, 2012
Society tends to love stories of people who make something of nothing, but one group of researchers is making waves by making nearly nothing out of something.
Two engineering research teams at Kiel University and the Hamburg University of Technology announced earlier this month that they had successfully developed the lightest material ever produced, what the scientists have dubbed "aerographite."
Super-light carbon mesh
In general, the key to making extremely light materials has been making an open structure that can maintain a stable shape without requiring large amounts of the component materials as support. One of the primary methods of making these stable structures is the creation of intricate nets of tubes, similar to the sturdy carbon nanotubes that have revolutionized materials science.
To this point, the most successful of these materials was a mesh of nickel created by groups at the University of California at Ervine and the California Institute of Technology. These researchers famously posed their new material on top of the head of a dandelion without the seeds breaking off.
However, the German group managed to top even this accomplishment by creating a similar mesh of tubes, but using a significantly lighter base material. Whereas the American teams created a material composed primarily of nickel, aerographite uses tubes of carbon, creating a mesh that ultimately weighs only 0.2 milligrams per cubic centimeter. That makes the material around 75 times lighter than styrofoam.
Ivy around a tree
Making a complex series of interweaving carbon tubes on a nano scale is not simply a matter of constructing a set of pipework, however. Working on this scale, researchers must develop processes that can essentially accomplish what they want for them.
In this case, the approach is to create a sort of molecular scaffolding around which to build the new material.
"Think of the Aerographite as an ivy-web, which winds itself around a tree," explained professor Rainer Adelung of Kiel University. "And than take away the tree."
The researchers took zinc oxide powder and heated it up to 900 degrees Celsius, then allowed it to cool into a crystalline form. These crystals created an airy, porous lattice work that could then be exposed to heated air filled with carbon.
This carbon would be deposited upon the zinc oxide crystals in incredibly thin layers then, when the porous crystals had been coated, the combination would be exposed to hydrogen, which would react with the oxygen in the material to produce water and now-unattached zinc gas.
Unique properties and diverse applications
The resultant material, aside from being extraordinarily light, also boasts a variety of interesting properties, being stable, highly conductive, non-transparent and capable of withstanding both significant compression and tension.
"Up to a certain point the Aerographite will become even more solid and therefore stronger than before [when compressed]," explained Adelung. "Also, the newly constructed material absorbs light rays almost completely. One could say it creates the blackest black."
These different properties recommend a number of different uses in emerging industries for aerographite. Its conductive properties combined with its light weight could make it extremely attractive for lithium-ion batteries by helping to reduce the necessary electrolyte, thus making the batteries lighter and more compact.
Because the material is so resilient, it could also prove extremely useful in aeronautics and astronautics, given how much vibration such craft tend to experience as they travel through the air. Even traditional plastics could be supplemented with the material, adding in conductive components without significantly increasing the weight of the object.
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