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Carbon nanotubes

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Carbon nanotubes

By the AVICENN team – Last updated April 2023

Different types of carbon nanotubes

Discovered two decades ago, carbon nanotubes are a new form of carbon.

There is a large variety and their physicochemical characteristics vary according to their manufacturing or implementation process.

These nano-objects are sheets of graphene wound on themselves, forming hollow cylinders, with at least two dimensions in the nanoscale.

They can be divided into two main groups:

  • single-walled carbon nanotubes (SWCNT), which are made of a sheet of graphene, wound in the form of a cylindrical tube
  • multi-walled carbon nanotubes (MWCNT) made up of several concentric tubes.

Their average diameter varies from a nanometer (SWCNT) to a few tens of nanometers (MWCNT), up to 100 nm.

Their length also varies from a few micrometers to a few hundred micrometers and can even reach several meters in some cases.

What are their properties?

Because of their exceptional properties – electrical conductivity, mechanical strength and thermal conductivity – carbon nanotubes have been touted as revolutionary materials for industrial sectors such as electronics, aerospace or nanomedicine.

The importance of their “length to diameter” ratio gives carbon nanotubes very specific properties, which are exploited or coveted:

  • for materials (electrostatic dissipation, mechanical reinforcement)
  • for coatings (electrical conductivity to adhesives and inks for example)
  • for energy (extending the life of energy storage systems by allowing a greater number of charge/discharge cycles; increasing the performance of li-ion batteries)
  • for catalysis
  • for the medical field1Cf. Saito, N. et al. Future Prospects for Clinical Applications of Nanocarbons Focusing on Carbon Nanotubes. Advanced sciences, 2022: drug delivery, imaging and even medical devices.

Yet, at the end of 2017, the “miracles” seem to have failed to materialize and working industrial applications are rare. Carbon nanotubes are difficult to combine with other materials, or when they are, they can lose the properties for which they were made2Fine felted nanotubes CAU research team develops new composite material made of carbon nanotubes, Kiel University, November 21, 2017.

How much is on the market?

By 2016, between one and ten tons* of carbon nanotubes had been reported to the R-nano registry as having been produced and/or imported into France in 2015. However, in 2019, less than 1 kg was reported in total nationally for 2018. The declared volume increased to the 1-10 tonnes range in the 2020 and 2021 reports. This range illustrates the weight given by the public authorities to industrial and commercial secrecy, which prevents us from having a good understanding of the quantities and uses of these nanomaterials, despite the increasingly pressing requests for information from a growing number of stakeholders. Moreover, this quantity is very small compared to what was suggested by the announcements around the promises of carbon nanotubes.

Some production sites (and their difficulties)

What are the risks?

The intrinsic physicochemical properties of carbon nanotubes raise many concerns about their effects on human health.

In view of the harmful effects that may be caused by certain carbon nanotubes (carbon nanotubes cause damage comparable to that caused by asbestos in the lungs and pleura), a classification is underway at the European level.

Elsewhere on the web

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In English:

Any questions or comments? This information sheet compiled by AVICENN is intended to be completed and updated. Please feel free to contribute.

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This sheet was originally posted in July 2017


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