Carbon nanotube (CNT) are allotropes of carbon that are cylindrical honeycomb-shaped with nano diameter.
There are numerous properties of CNTs like mechanical strength, elasticity, lightweight, electrical and thermal conductivity that makes it the most promising material.
Many industries include electronics, medicine, energy storage, sensors, and many more are utilizing CNTs in high numbers. The increasing demand has put constant pressure on upscaling the manufacturing of CNTs.
This large scale production of CNTs has become the main challenge that hinders their applications.
Tackling the Challenge :
Usually, Scientists prefer growing CNT forests rather than growing them individually. CNT forests are vertically aligned CNT arrays that are self-assembled.
This is usually carried out through the process of chemical vapor deposition in presence of a fixed catalyst on a substrate which is later on separated from the CNT forest in order to yield high purity material.
Although this process offers an abundance of merits, the only major issue faced is the length.
Until now the researchers have been able to grow the CNT forest up to to 2 cm using catalysts like ferrous (Fe) on aluminum oxide (Al2O3) support (the length of CNTs plays a vital role when it comes to its properties hence it’s necessary to consider this aspect).
This affects its industrial value by limiting the supply and increasing the cost of the material.
There has been a revolutionary discovery that has totally changed the game.
Recently a team of scientists from Japan has recorded the length of CNT forest up to 14 cm through a novel approach. Their study has been published in Carbon recently.
Hisashi Sugime, Assistant Professor at Waseda University, and his team found out that CNTs stopped growing because of the gradual structural change in the catalyst(Fe-Al2Ox) that was used previously.
Basically, the density of the CNTs, which is dependent on the number of active catalysts, is insufficient to maintain a self-supporting structure, the forest growth terminates.
Therefore, the catalyst used must remain structurally and chemically stable.
Their approach was to change the technique to suppress this instability.
They achieved it by adding the gadolinium (Gd) layer to the earlier catalyst coated with an n-type silicon substrate.
Gadolinium layer helped in preventing the catalyst from deteriorating and in turn allowing the CNT forest to grow by 5cm.
Further to achieve the desired length, they kept the catalyst in a chamber called the cold-gas chemical vapor deposition (CVD) chamber.
The catalyst was pretreated by maintaining the temperature up to 750°C and providing small concentrations of Fe and Al vapors at room temperature.
This helped in maintaining the catalyst structure for up to 26 hours which in turn promoted the growth of the CNT forest.
After careful analyses, they could successfully record the length of the CNT forest by 14 cm.
Their accomplishment has set a new horizon for the developing industries.This remarkable progress has widened the application aspects of CNTs.
It could change the approach to nanotechnology and nano-science for future research.
To read the complete research article published refer to the DOI below.
Hisashi Sugime, Toshihiro Sato, Rei Nakagawa, Tatsuhiro Hayashi, Yoku Inoue, Suguru Noda. Ultra-long carbon nanotube forest via in situ supplements of iron and aluminum vapor sources. Carbon, 2020; https://doi.org/10.1016/j.carbon.2020.10.066
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