Highly Oriented Carbon Nanotubes
Carbon nanotubes (CNT) consist of carbon atoms arranged in a honeycomb-like pattern and have a diameter of 1 to 50 nm. Single-wall CNTs can achieve tensile strengths of 50 Gpa; tensile strengths of up to 150 GPa have already been measured on multi-wall CNTs. These unique mechanical properties can be utilized fully in larger structures only if all CNTs are oriented in the same direction. A group of material scientists from Jena has now made a significant advance in this field of research. They first incorporated multi-wall CNTs into a polymer melt that was subsequently subjected to significant stretching. In this way, they created films containing highly oriented CNTs.
According to their report, interface crystallization occurs during solidification of the polymer melt. The polymer crystals grow in an ordered manner on the CNTs and bond with them. During stretching, the polymer chains in the amorphous part of the polymer catch on the crystals adhering to the carbon nanotubes, pulling them all in one direction. This results in an extremely high degree of nanotube orientation that was not possible before now.
In this regard, the researchers from Jena also point out that such oriented CNTs might be suitable for use as a cable for a space lift. In this concept – which is not possible with current technology – a cable connects a geostationary satellite to the surface of the earth. For a cable with a length of 36,000 km to withstand the resulting forces, calculations performed by NASA indicate that materials with a tensile strength of about 62 GPa would be needed. According to estimates, such a space lift could reduce the costs to transport objects into space from the current approx. 60,000 EUR/kg to about 75 EUR/kg.
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