Carbon Nanotubes

In my last post, I explored the idea and the possibility for a real-life space elevator, a literal elevator to space, which, if built, would do nothing short of radically transform human space operations and exploration. However, I also mentioned that in order to construct such a mammoth structure, we would need to potentially braid entire meters of carbon nanotubes into rope, a feat that, at this present moment, is impossible(although much work is being done to make this a reality in the future). In this post, I will examine the carbon nanotube itself, diving into the nature of this fascinating material and the many possibilities that it holds for future human technology.

Fundamentally, carbon nanotubes(CNTs) are graphene rolled up into a tube(hence the name). Graphene, not to be confused with the graphite that composes pencil lead, is a compound that consists of a sheet of single carbon atoms, bonded together as seen in the picture above. This material is in itself incredibly durable and flexible, with many extraordinary properties that can be harnessed in modern and future technology. We’re not here to learn about graphene, though – we’re here for what happens when you roll this stuff up. CNTs were first discovered in June 1991 by a Japanese scientist by the name of Sumio Iijima, who won the Balzan Prize in Nanoscience in 2007 for his work. CNTs, like graphene, are flexible and durable, and are excellent conductors of heat and electricity. They come in various forms, with the main two being single-walled and multi-walled(multi-walled CNTs were discovered first). In addition,a CNT can be capped of at one or both ends with a hemispherical buckyball(a sheet of graphene folded into a sphere). Single-walled CNTs have a diameter of less than 1 nm, while multi-walled ones can have diameters of upwards of 100 nm. CNT lengths range between a few nanometers to even some millimeters.

Interstingly, different forms of CNTs have different electrical properties. While multi-walled CNTs always conduct and have similar conductivity to metals, the way in which a single-walled CNT is folded, also known as its chiral vector, can impact its electrical properties. They can behave like a conductor, a semiconductor, or an insulator, giving them great versatility in a variety of applications. Other CNT advantages include:

  • A tensile strength of up to 400x that of steel
  • A density 1/6 that of steel
  • Thermal conductivity better than that of diamond
  • Great chemical stability
  • And the potential for them to be filled with various nanomaterials

Because of this, CNTs can be used in things such as transistors, electronic devices, batteries, chemical and biosensors, cathode ray tubes, synthetics, materials, etc.

CNTs themselves can be made in a variety of ways, including using lasers or electricity to combust the material, using metals such as iron and nickel as catalysts. In addition, they can be created using the CVD process, in which a metal catalyst is used with carbon-containing reaction gases such as CO in order to create CNTs like in a furnace. This method is most viable for the future, for it allows larger quantities of CNTs to be created.

In the future, with advancements to the CVD method and with the development of more practical applications for CNTs as a whole, we will almost certainly see them integrated into more and more technological advancements. As for that space elevator, only time will tell how quickly(or slowly) we will be able to get that up and running…

Sources:

https://www.nanowerk.com/nanotechnology/introduction/introduction_to_nanotechnology_22.php

https://www.balzan.org/en/prizewinners/sumio-iijima/the-discovery-of-carbon-nanotubes-iijima

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