Carbon Nanotubes

Moritz Plötzing, Benedikt Lorbach, Meike Spiess

Since their discovery in 1991, carbon nanotubes have attracted a lot of interest from academia and industry for their unusual properties. The one to two nanometer wide tubes fascinated us and we wanted to succeed in fabricating them at school. We investigated several possibilities, including a simple fabrication method based on household articles and an electric arc. However, the initial results were not convincing and therefore we focused on a chemical method based on a homemade CVD chamber. We grew our first carbon nanotubes on silicon inside this acetylene-filled glass chamber and we studied our samples using a scanning electron microscope at RWTH Aachen University. However, the gas was a major risk factor and this method was only suitable for the less interesting multi-walled carbon nanotubes. Therefore we developed a new reaction chamber that we used to ignite an electric arc in an inert gas atmosphere using a welding apparatus. After resolving the challenges relating to the construction of the reaction chamber, we had to look into a crucial aspect that we had overlooked so far: the source of carbon. Initially we used the graphite electrodes of our school's arc lamp and later we tried other carbon-based materials in our chamber. We found that only pure graphite rods were suitable. In addition, the fabrication of single wall carbon nanotubes required catalysts. We used a mixture of nickel and yttrium. Eventually we succeeded in fabricating a fibrous carbon material. We optimized the fabrication method, for example with regard to pressure and the catalyst mixture. We were able to show with high resolution transmission electron microscope images that our samples consist of single-walled carbon nanotubes. However, we wanted to be able to also demonstrate this at our school. Therefore, we tried to make buckypaper from our samples, but despite some progress this method turned out to be too time consuming. By now, we have found a simple indirect proof of single-walled carbon nanotubes in our samples, which only requires a normal camera flash. In contrast to graphite dust and multi-walled carbon nanotubes, single-walled carbon nanotubes ignite in response to a bright flash of light. Our final challenge was the adjustment of our synthesis method so that it could be realized at any school without our reaction chamber. We found a simple fabrication method for single-walled carbon nanotubes based on a normal metal bucket, a helium bottle and a welding device. Even though the results are not as good as those achieved with our reaction chamber, they are sufficient to integrate a current research topic into school lessons.

Versuchskammer, elektronenmikroskopische Aufnahme eines Nanoröhrchens, Nachweis von Singlewall-Nanoröhrchen
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