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A
network of porous carbon tubes that is three-dimensionally interwoven
at nano and micro level—this is the lightest material in the world. It
weights only 0.2 mg per cubic centimetre, and is therefore 75 times
lighter than Styrofoam, but it is very strong nevertheless. Scientists
of Kiel University (KU) and Hamburg University of Technology (TUHH) have
named their joint creation “Aerographite”. The scientific results were
published as the title story in the scientific journal Advanced
Materials on July 3.
The properties
It
is jet-black, remains stable, is electrically conductive, ductile and
non-transparent. With these unique properties and its very low density
the carbon-made material “Aerographite“ clearly outperformes all similar
materials.
“Our
work is causing great discussions in the scientific community.
Aerographite weights four times less than world-record-holder up to
now,” says Matthias Mecklenburg, co-author and Ph.D. student at the
TUHH. The hitherto lightest material of the world, a nickel material
that was presented to the public about six months ago, is also
constructed of tiny tubes. Only, nickel has a higher atomic mass than
carbon.
“Also,
we are able to produce tubes with porous walls. That makes them
extremely light”, adds Arnim Schuchard, co-author and Ph.D. student at
Kiel University. Professor Lorenz Kienle and Dr. Andriy Lotnyk were able
to decode the material’s atomic structure with the aid of a
transmission electron microscope (TEM).
Despite
of its low weight Aerographite is highly resilient. While lightweight
materials normally withstand compression but not tension, Aerographite
features both: an excellent compression and tension load. It is able to
be compressed up to 95% and be pulled back to its original form without
any damage, says professor Rainer Adelung of Kiel University.
“Up
to a certain point the Aerographite will become even more solid and
therefore stronger than before,” he points out. Other materials become
weaker and less stable when exposed to such stress. “Also, the newly
constructed material absorbs light rays almost completely. One could say
it creates the blackest black”, acknowledges Hamburg’s Professor Karl
Schulte.
The construction
“Think
of the Aerographite as an ivy-web, which winds itself around a tree.
And than take away the tree,” Adelung describes the construction
process. The “tree” is a so-called sacrificial template, a means to an
end. The Kiel-team, consisting of Arnim Schuchardt, Rainer Adelung,
Yogendra Mishra and Sören Kaps, used a zinc oxide in powder form. By
heating this up to 900 degrees Celsius, it was transformed into a
crystalline form.
From
this material, the scientists from Kiel made a kind of pill. In it, the
zinc-oxide formed micro and nano structues, so called tetrapods. These
interweave and construct a stable entity of particles that form the
porous pill. In that way, the tetrapods produce the network that is the
basis for Aerographite.
In a next step, the pill is positioned into the reactor for chemical vapour deposition at TUHH and heated up to 760 C.
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“In
a streaming gas atmosphere that is enriched with carbon, the zinc oxide
is being equipped with a graphite coating of only a few atomic layers.
This forms the tanged-web structures of the Aerographite.
Simultaneously, hydrogen is introduced. It reacts with the oxygen in the
zinc oxide and results in the emission of steam and zinc gas”,
continues Schulte. The remains are the characteristic interwoven,
tube-like carbon structure.
TUHH-scientist
Mecklenburg: “The faster we get the zinc out, the more porous the
tube’s walls get and the lighter is the material. There is considerable
scope.” Schuchard adds: “The great thing is that we are able to affect
the characteristics of the Aerographite; the template form and the
separation process are constantly being adjusted in Kiel and Hamburg.”
The application
Due
to its unique material characteristics, Aerographite could fit onto the
electrodes of Li-ion batteries. In that case, only a minimal amount of
battery electrolyte would be necessary, which then would lead to an
important reduction in the battery’s weight. This purpose was sketched
by the authors in a recently published article. Areas of application for
these small batteries might be electronic cars or e-bikes. Thus, the
material contributes to the development of green means of
transportation.
According
to the scientists, further areas of application could be the electrical
conductivity of synthetic materials. Non-conductive plastic could be
transformed, without causing it to gain weight. Statics, which occur to
most people daily, could hence be avoided.
The
number of further possible areas of application for the lightest
material in the world is limitless. After officially acknowledging
Aerographite, scientists of various research areas were bursting with
ideas. One possibility might be the use in electronics for aviation and
satellites because they have to endure high amounts of vibration. Also,
the material might be a promising aid in water purification. It might
act as an adsorbent for persistent water pollutants for it could oxidise
or decompose and remove these. Here, scientists would benefit from
Aerographite’s advantages namely mechanical stability, electronic
conductivity and a large surface. Another possibility might be the
purification of ambient air for incubators or ventilation.
Source: Kiel University
