Used as an additive, Baytubes® carbon nanotubes (CNT) from Bayer
MaterialScience AG significantly improve the mechanical properties of powder
metallurgy aluminum. For example, the hardness is then several times greater
than that of unalloyed aluminum, tensile strengths comparable to those of steel
can be achieved, and the impact strength and thermal conductivity of the lightweight
metal can be improved significantly.
The compression and extrusion of aluminum powder hardened through high-energy milling leads to a significant loss in hardness and tensile strength. This effect can be prevented through the addition of Baytubes®. Extruded semi-finished goods made of CNT-reinforced aluminum therefore have similar hardness values to aluminum hardened by high-energy milling.
"Together with competent partners in industry, we want to exploit the
considerable application potential that arises from this optimization in properties,”
says Dr. Horst Adams, Vice President of Future Technologies at Bayer MaterialScience,
explaining: “We are partnering with Alcan, PEAK and Zoz to develop customized,
CNT-reinforced aluminum materials."
Based in Montreal (Quebec), Canada, Alcan Inc. is not only one of the world's
largest suppliers of raw materials for aluminum manufacturing, it also is a
leading producer of this lightweight metal and products made from it. PEAK Werkstoff
GmbH, headquartered in Velbert, Germany, specializes in the development of high-performance
aluminum materials, which it uses to produce powder metallurgy semi-finished
and finished goods. Zoz GmbH based in Wenden, Germany, is a global supplier
of innovative facilities and equipment, in particular for the production of
nanostructured materials, and has comprehensive expertise, for example, in the
high-energy milling and mechanical alloying of these materials.
Until now, high hardness levels and tensile strengths could only be achieved
in aluminum by a complex alloying process based on rare and expensive metals.
"Our carbon nanotubes are an attractive alternative to such complicated
alloys. Baytubes® can also significantly reinforce aluminum materials already
alloyed with metals," says Adams.
The density of CNT-reinforced aluminum is only around one third that of steel,
and the material can therefore support any number of applications in which the
aim is to reduce weight and energy consumption by means of lightweight construction.
With its combination of high strength and low weight, it is an alternative to
steel, expensive specialty metals such as titanium, and carbon-fiber-reinforced
plastics. "This new class of materials has great potential for the production,
for example, of screws and other connecting elements, allowing existing manufacturing
processes (stamping, CNC) to be retained. Lightweight, heavy-duty components
for wheelchairs or athletic equipment are also ideal candidates for the material,"
says Adams. Promising applications exist too in the automotive and aircraft
industries. In addition, Baytubes®-reinforced aluminum I-beams could conceivably
be manufactured for the construction industry. Because they are much lighter
than steel I-beams, they would make it possible to construct much higher buildings.
On account of their inherent weight, steel I-beams currently are a factor limiting
the maximum height of a skyscraper.