Today, countless industries, including optics, electronics, water purification and drug delivery, innovate on an unprecedented scale with nanometer-wide honeycomb-shaped coils known as carbon nanotubes (CNTs). ). Features such as light weight, ergonomic structure, great mechanical strength, outstanding thermal and electrical conductivity, and stability put CNTs one notch above other material alternatives. However, in order to meet their growing industrial needs, their production must be continually expanded, and that is the main challenge facing the use of CNT.
While the scientists were able to develop individual CNTs approximately 50 cm long, when they tested the plaques or forests, they hit the ceiling about 2 cm. This is because the catalyst, the key to CNT growth occurring, is shut down and / or depleted before the CNT in the forest can grow any longer, increasing the cost of money and raw materials. and threaten to limit its industrial use.
Now, a strategy to overcome the ceiling has been devised by a group of scientists from Japan. In their research is published in CarbonThe team presented a new approach to a conventional technique that yielded CNT forests of a record length: ~ 14 cm – seven times larger than the previous maximum. Hisashi Sugime, Assistant Professor at Waseda University who leads the group, explains, “In conventional engineering, CNTs stop growing due to a gradual structural change in the catalyst, so we focus developing a new technique that suppresses this structural change and allows the CNTs to evolve for a longer period of time. “
The team created a catalyst based on their findings in an earlier study. They added a gadolinium layer (Gd) to the common iron-aluminum oxide (Fe / Al2Ox) coated with a silicon (Si) catalyst. This Gd layer has prevented the depletion of the catalyst to a certain extent, allowing the forest to grow up to about 5 cm in length.
To prevent further catalyst degradation, the team placed the catalyst in their original chamber called a refrigerant chemical vapor deposition chamber (CVD). There, they heated it to 750 ° C and gave it small concentrations (parts per million) of Fe and Al vapor at room temperature.
This keeps the catalyst active for 26 hours, during which time a dense CNT forest can grow up to 14 cm. Various analyzes to characterize the grown CNTs show that they have a high purity and competitive strength.
This achievement not only overcomes obstacles to the widespread application of CNTs in industry, but also opens the door in nanoscience research. “This simple yet novel approach significantly prolonging catalyst life by supplying vapor sources at ppm is a profound way of catalyst engineering in many fields,” Sugime said. other such as petrochemical and nanomaterial growth ”. “Knowledge here could play an important role in making nanomaterials a pervasive reality.”
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Hisashi Sugime et al, Super long carbon nanotube forests through the on-site addition of iron and aluminum vapor sources, Carbon (Year 2020). DOI: 10.1016 / j.carbon.2020.10.066
Provided by Waseda University
Quote: Scientists planted carbon nanotube forests much longer than anywhere else (2020, November 4) retrieved November 4, 2020 from https://phys.org/news/2020 -11-scientists-carbon-nanotube-forest-longer.html
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