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Researchers have developed the tallest “forest” of carbon nanotubes (CNTs) ever, using a new technique that they believe could make nanomaterials an “omnipresent reality”.
Describing it as a “new approach to a conventional technique”, the Japanese team used the process to grow CNT forests about 14 cm in length, seven times longer than the previous maximum.
Many industries, including optics, electronics, water purification and drug delivery, are innovating rapidly using CNTs. The nano-sized rolls of honeycomb-shaped graphite sheets offer features such as low weight, convenient structure, immense mechanical strength, superior thermal and electrical conductivity and stability. However, the increase in demand means that production must increase.
While the scientists have grown individual CNTs to about 50cm in length, when they attempt to run arrays or forests, they reach a ceiling of about 2cm. This is because the catalyst, which is the key to the growth of CNTs, is deactivated or depleted before they can grow further. This raises costs and threatens to limit its industrial use, the Japanese researchers said.
Team leader Hisashi Sugime, assistant professor at Waseda University, said: “In the conventional technique, CNTs stop growing due to a gradual structural change in the catalyst, so we focused on developing a new technique that suppresses this change. structural and allows CNTs to grow for a longer period. “
To begin with, the researchers created a catalyst based on their findings in a previous study. They added a layer of gadolinium (Gd) to the conventional iron-aluminum oxide (Fe / Al2ORX) catalyst coated on a silicon (Si) substrate. The Gd layer prevented the catalyst from deteriorating to some extent, allowing the forest to grow to about 5 cm.
To further prevent catalyst deterioration, the team placed the catalyst in a cold gas chemical vapor deposition chamber. There, they heated it to 750 ° C and provided it with small concentrations (parts per million) of Fe and Al vapors at room temperature.
This kept the catalyst running for 26 hours, during which time dense CNT forests could grow up to 14 cm. The analysis reportedly showed they had high purity and “competitive” strength.
“This achievement not only overcomes obstacles to the widespread industrial application of CNTs, but opens the door to nanoscience research,” a research announcement said.
Sugime added: “This simple yet innovative method that drastically extends the life of the catalyst by providing vapor sources at the ppm level is intuitive to catalyst engineering in other fields, such as petrochemistry and nanomaterial crystal growth … knowledge here could be key to making nanomaterials a ubiquitous reality. “
The study was published in Carbon.
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