What are the unique properties of materials

World record: the lightest material in the world comes from northern Germany

Press release 212/2012 from July 17th, 2012 | to the print version | german version


A network of porous carbon tubes that are three-dimensionally fused into one another at the nano and micro level - this is the lightest material in the world. At 0.2 milligrams per cubic centimeter, it is 75 times lighter than styrofoam and still withstands a lot. The scientists at the Christian-Albrechts-Universität zu Kiel (CAU) and the Technical University Hamburg-Harburg (TUHH) named their joint development "Aerographit". The research results were published as the cover story in the journal “Advanced Materials” on July 3rd and presented to the public today (Tuesday, July 17th).

The properties
It is pitch black, stable, electrically conductive, malleable and opaque - with its unique properties and its low density, the carbon material “aerographite” outperforms all its competitors. “Our development triggers lively discussions in scientific circles. The aerographite is more than four times lighter than the previous world record holder, ”says co-author Matthias Mecklenburg, doctoral student at the TUHH. The nickel material presented six months ago, which was considered the lightest material until the current publication, also consisted of a tiny tube system. However, from the outset, nickel has a higher atomic weight. “We can also manufacture tubes that consist of porous walls and are therefore extremely light,” adds Arnim Schuchardt, co-author and doctoral student at CAU. The Kiel analysts Professor Lorenz Kienle and Dr. Deciphering Andriy Lotnyk using the transmission electron microscope (TEM).

Despite its low weight, Aerographite is very resilient. While lightweight materials can usually withstand pressure but not tension, aerographite is characterized by its excellent stability under pressure and tensile loads. It can be compressed by up to 95 percent and pulled back into its original shape, says Kiel professor Rainer Adelung: "The aerographite is even firmer to a certain degree, and thus stronger than before." Other materials would pass through such loads become increasingly weaker and more unstable. “In addition, the material almost completely absorbs light rays. You could say that it produces the blackest black, ”adds Professor Karl Schulte from Hamburg.

The production
“You can think of aerographite as a rapidly growing ivy network that winds around a tree, removing the tree itself,” says Adelung, explaining the manufacturing process. The tree is what is known as a “sacrificial template,” that is, the means to an end. The CAU team, consisting of Arnim Schuchardt, Rainer Adelung, Yogendra Mishra and Sören Kaps, used a powdered zinc oxide to produce the template. They brought this into a crystalline form by heating it in an oven at 900 degrees Celsius.

In the further processing, the materials scientists from Kiel produce a kind of tablet. In it, the finished zinc oxide forms micro- and nanostructures, called tetrapods (see, for example, Figure 4), which penetrate each other and thus firmly connect the individual particles to form the porous tablet. The tetrapods are the network on the basis of which the aerographite is created.

In the next step, the pellet-shaped material is placed in the reactor at 760 degrees Celsius for "chemical vapor deposition" at the TUHH. “In a flowing, carbon-enriched gas phase, the zinc oxide is encased in a graphite layer that is only a few atomic layers thick, which forms the intergrown network structure of the aerographite. The hydrogen supplied at the same time reacts with the oxygen in the zinc oxide. Water vapor and zinc escape as a gas, ”says Schulte. What remains is the typically cross-linked and tubular carbon structure. TUHH young scientist Mecklenburg: “The faster we get the zinc out in our process, the more holey the walls of the tubes are and the lighter the material becomes. There is still a lot of leeway. ”And his colleague Schuchardt from Kiel adds:“ The nice thing is that we can specifically influence the aerographite properties: We constantly coordinate the shape of the template here in Kiel and the deposition process in Hamburg. ”

The application
Thanks to the special material properties of aerographite, it could be ideally adapted, for example, in Li-ion batteries. This means that only a minimal amount of battery electrolyte has to be used, which should lead to an important weight reduction in the batteries. The author outlined this use in the recently published publication. These smaller batteries can be used in electric cars or e-bikes. The material thus contributes, among other things, to the development of environmentally friendly means of transport.

The scientists see further applications in making non-conductive plastics electrically conductive with the help of aerographite without them gaining weight. In this way, static charges that are familiar from everyday life can be avoided.

The number of additional applications for what is currently the lightest material in the world is only limited by the imagination of the scientists. As soon as the aerographite became known, the ideas were also sparkling among colleagues from a wide range of specialist areas. Use in aviation and satellite electronics is being considered, as these must be able to withstand particularly high vibrations. The material also promises great potential in water purification. As a sorbent for persistent water pollutants, it could electrochemically oxidize, i.e. decompose, and thus degrade them. The advantages of aerographite, namely mechanical stability, electrical conductivity and a high surface area, would come into play. These benefits are also useful in the potential purification of outside air for incubators or ventilators.


More information at:
Original publication: "Aerographite: Ultra Lightweight, Flexible Nanowall,
Carbon Microtube Material with Outstanding Mechanical
Performance"; DOI: 10.1002 / adma.201200491
onlinelibrary.wiley.com

Images and other material are available for download:

Click to enlarge

Caption: The illustration shows an electron microscope section of the lightest material in the world: aerographite. Open carbon tubes form a fine network and thus enable a low density of up to 0.2 milligrams per cubic centimeter.
Source: TUHH

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-1.png

Click to enlarge

Caption: In the reactor at temperatures above 760 degrees Celsius, gaseous zinc and water vapor escape. In the picture: Zinc oxide can still be seen in the dark areas. The graphitic shell remains (light areas).
Source: CAU

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-2.png

Click to enlarge

Caption: During the creation process, the so-called sacrificial template, the crystalline zinc oxide (here strongly white), is decomposed by hydrogen. Water vapor and zinc escape. The tubes of the aerographite remain.
Source: TUHH

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-3.png

Click to enlarge

Caption: The tetrapods of zinc oxide form the ideal basis for the robust material aerographite.
Source: TUHH

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-4.png

Click to enlarge

Caption: The almost finished aerographite: Fascinating structures with incredible potential, for example in the manufacture of batteries.
Source: TUHH

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-5.png

Click to enlarge

Caption: Aerographite is water-repellent, blacker than black (currently being investigated) and electrically conductive.
Source: CAU

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-6.jpg

Click to enlarge

Video: Aerographite can be compressed up to 95 percent and then pulled apart again. Unlike other materials, this even makes it more and more rigid (diameter nine millimeters).
Source: CAU

Video to download:
www.uni-kiel.de/download/pm/2012/2012-212-7.avi

Click to enlarge

Video: The very small masses of the aerographite enable very rapid changes of direction. First it stands up, then it jumps onto the plastic rod and back onto the table: this is how Aerographit picks up charge from the rod and transfers it to the table.
Source: CAU

Video to download:
www.uni-kiel.de/download/pm/2012/2012-212-8.avi

Click to enlarge

Caption: The proud authors of the research publication (from left): Matthias Mecklenburg, Yogendra Kumar Mishra, Arnim Schurchardt, Lorenz Kienle, Karl Schulte, Sören Kaps, Rainer Adelung (not in the picture: co-author Andriy Lotnyk).
Copyright: CAU, Photo: Claudia Eulitz

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-9.jpg

Click to enlarge

Caption: Small crumbs really big: Aerographite can absorb light very well, like the light from a laser pointer here.
Copyright: CAU, Photo: Stefanie Maack

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-10.jpg

Click to enlarge

Caption: Simple but ingenious: the crystalline structure of zinc oxide is the basis for the lightest material in the world.
Copyright: CAU, Photo: Stefanie Maack

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-11.jpg

Click to enlarge

Caption: The blackest black: aerographite.
Copyright: CAU, Photo: Claudia Eulitz

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-12.jpg

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Caption: Yogendra Mishra shows the zinc oxide template in the "witch's kitchen" at Kiel University.
Copyright: CAU, Photo: Stefanie Maack

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-13.jpg

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Caption: It takes 900 degrees Celsius to manufacture the zinc base for aerographite.
Copyright: CAU, Photo: Stefanie Maack

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-14.jpg

Click to enlarge

Caption: The doctoral students of the moment: Arnim Schuchardt (left, CAU) and Matthias Mecklenburg (TUHH) developed the aerographite together with their Hamburg and Kiel colleagues.
Copyright: CAU, Photo: Claudia Eulitz

Photo to download:
www.uni-kiel.de/download/pm/2012/2012-212-15.jpg

Contact:
Kiel University
Press office
Claudia Eulitz
Phone: 0431 / 880-7110
Email: [email protected]


TU Hamburg-Harburg
Press office
Jutta Katharina Werner
Telephone: 040/428784321
Email: [email protected]



Christian Albrechts University in Kiel
Press, communication and marketing, Dr. Boris Pawlowski, text: Claudia Eulitz
Postal address: D-24098 Kiel, phone: (0431) 880-2104, fax: (0431) 880-1355
e-mail: [email protected]