Carbon Nanofibers Grown Without Ammonia
It can be easy to forget as we read about any number of products just what went in to creating them. For some products, the materials they contain were mined and for others they were synthesized, but either way there are some costs and risks involved. Researchers at North Carolina State University have recently found a way to reduce the cost and risk of producing vertically aligned carbon nanofibers by replacing ammonia with ambient air.
Typically producing vertically aligned carbon nanofibers (VACNFs) involves placing nickel nanoparticles on a substrate, within a vacuum chamber. The chamber is then heated to 700 ºC and it is filled with ammonia and a carbon containing gas, such as acetylene or acetone. A voltage is then applied to the substrate and an anode, which ionizes the gas and frees carbon atoms to grow nanofibers beneath the nickel. The purpose of the ammonia in this process is to prevent the nickel nanoparticles from becoming encrusted with carbon, which would stop the nanofiber growth. Even though they did not expect much to happen, the researchers decided to repeat this process, but with ambient air replacing the ammonia. To their surprise, the VACNFs that grew are similar in size, shape, and alignment to those grown with ammonia.
While ammonia gas is not particularly expensive, it is toxic so removing it from the process could make the process of growing vertically aligned carbon nanofibers much safer. Potentially it may even lead to growing them without the use of a vacuum chamber, which would allow them to be grown on a much larger scale than presently possible.
Source: North Carolina State University