By Nick Gilbert
Topics CoveredIntroductionProperties of AerographiteWhy is Aerographite Special?How is Aerographite Made?Aerographite Applications
What do you get if you make a material from predominantly air entrapped within a very fine structure of porous carbon nanotubes?
You get one of the worlds lightest materials - Aerographite.
Scientists from Kiel University (KU) and Hamburg University of Technology (TUHH) have created the new material 'Aerographite' by carefully growing an interlinking chain of Carbon nanotubes within a sacrificial template made from Zinc Oxide. Creating a network of porous carbon tubes three-dimensionally interwoven at nano and micro level.
Weighing in at only 0.2 milligrams per cubic centimetre, Aerographite is officially the lightest material in the world - reported to be 75 times lighter than Styrofoam! Not only is this material extremely light, it is also extremely strong, based largely on the unique properties of Carbon Nanotubes, but also on the innovative structure of the material.
Properties of Aerographite
Aerographite is extremely lightweight but it also has a number of interesting properties. Including:
- Electrically conductive
- Highly ductile
- Non-transparent - Jet black appearance
- Extremely strong
- Is chemically stable
Image 1. Aerographite is water-repellent, jet-black (which is currently analysed) and electrically conductive. Source: KU
The scientists responsible for the development of Aerographite state that it is up to 4x lighter than the previous world record holder for 'Lightest Material' - a Nickel based tubular based material. The main benefit of Aerographite and its current 'winning formula' is the ability to make Carbon Nanotubes porous, thus allowing scientists to reduce the weight by reducing density without compromising strength.
Aerographite also absorbs a very high proportion of light rays, resulting in an extremely black appearance. "One could say it creates the blackest black" mentions Professor Karl Schulte from Hamburg University of Technology (TUHH).
Why is Aerographite Special?
Even though Aerographite is extremely light, it is also exhibits some interesting characteristics under stress. For example, most ultra lightweight materials perform well under compression but often lack in strength under tensile forces. Aerographite is unique because not only does it withstand large crushing forces, compressible up to 95% with the ability to spring back to its original form without any damage (much like a household sponge). It also exhibits high tensile strength.
How is Aerographite Made?
Aerographite is made by 'growing' porous Carbon Nanotubes around a sacrificial template. The template is made from heating a zinc powder to 900 °C at which point it takes a crystalline form. Using this Crystallized Zinc Oxide, shaped into a pill, the scientists are then able to exploit the tetrapod nanostructures to help form the Aerographite. The network of interwoven pores create a stable, porous structure within which Aerographite can be formed.
Image 2 The tetrapods of the zinc oxide form an ideal basis for the robust material Aerographite.
To Form the Carbon Nanotubes, the porous structure is then heated in a chemical vapour deposition reactor, where it is also exposed to a streaming gas enriched with Carbon. As the gas passes through the pores of the structure, an extremely fine covering of graphite (only a few atomic layers thick) forms on the inner surface of the tetrapod structure.
The next step is then to start removing the sacrificial template, this is done by simultaneously introducing hydrogen which reacts with the Zinc Oxide and results in a breakdown of the template and the emission of Zinc gas. What remains is the interwoven form of the porous Carbon Nanotubes, a tube like structure = Aerographite.
Interestingly, the faster you can get the Zinc template out of the process, the more porous and lighter the Aerographite structure will be. Thus, providing considerable scope for customization, material development and more efficient manufacturing processes.
Such an interesting material presents, scientists and engineers with a diverse range of potential applications. Scientists at Kiel University (KU) and Hamburg University of Technology (TUHH) believe that Aerographite could potentially be used for the following applications, amongst many many more.
- Lightweight Batteries -for use in green transport / Electric cars / bikes etc.
- Electrical conductivity of synthetic materials - making plastics conductive without gaining too much weight
- Electrically conductive adhesives
- Electronics in aviation
- Electronics in motor sport
- Electronics in Satellites
- Pollution absorbent
Scientists are now working hard to further sketch out the limitless possibilities for this super lightweight material.