Have you ever heard of multiwalled carbon nanotubes? If you haven’t, you better start learning more about them, since you’re bound to hear about them often in the future. May this article serve as an introduction into the whole problematic…
Multiwalled carbon nanotubes – what are they?
To put it simply, the so-called “MWNTs” consist of several rolled layers of graphene, as opposed to the single-walled carbon nanotubes, which is – obviously – just a single graphene roll put together. The MWNTs usually come in two forms.
- In the first, colloquially called the “Russian doll” model, the graphene sheet cylinders are arranged concentrically, with one inserted into another. The “Russian doll” tends to be more common than another version, the so-called “Parchment”. Inside the “doll”, there may be only two tubes (DWNTs), but otherwise, their number can easily go over 100.
- The “Parchment” model is simply a single graphene sheet rolled around itself, like a scroll.
As for the dimensions of MWNTs, their outer diameters range from 2 to 100 nnm, and their length tends to be usually between 0,5 to 50um. But there are also nanotubes that can be much longer than that – up to 1mm long.
Which properties do the MWNTs feature?
As opposed to the single-walled nanotubes, MWNTs have more diverse properties, since they can come in a variety of forms, with each one of the nanotubes inside it having a different structure. Depending on the sequential arrangement of individual tubes, the MWNTs can then perform a variety of differing roles.
MWNTs may consist of sequence in which the concentric layers are the same, differing only in the diameter. Of course, there are also mixed arrangements, in which different types of tubes are layered in distinctive manner. Of course, the manner of layering, as well as the overall diameter, greatly influences the properties of individual MWNTS. Generally, these properties are as follows:
- Physical properties: The defect-free, MWNTs are known for their incredible tensile strength. This makes them suitable for integrating them into composite. For example, when introduced into thermoset or thermoplastic compounds, MWNTs can greatly increase their overall strength.
- Chemical properties: These nanotubes are an allotrope of hybridized carbon (not unlike graphite or fullerenes) and thus have a high chemical stability. But they can be modified in such a way as to enable both dispersibility and strength in composites they have been introduced to.
- Electrical properties: MWNTs can be great conductors – but it’s the outer layer that does the conducting, the other walls do not play a significant role in this.
- Thermal properties: The thermal stability of MWNTs is more than 600°C, depending, of course, on the purity of the material.
Based on these properties, MWNTs can be great additives, vastly improving the quality of products they have been introduced to.
What are the applications of multi-walled CNTs?
The range of uses these materials can be put into is truly vast, and thanks to the ongoing research in this field, the following list may not be nearly exhaustive:
- Medical implants & biotechnology
- Textile industry – you can learn more about their use in textile here.
- Sports & outdoor equipment
- As conducting or semiconducting materials in a range of industries.
- MWNTs can be used in aeroplane manufacturing.
To sum up, the potential of nanotubes is truly vast – this material can benefit countless industries by virtue of its properties, which could be enhanced and modified even further.
Do you know of or can think of any other uses nanotubes could be put to? Which are those? And how do you see the future of nanomaterial use? May it be hyped too much, or is it another technological revolution? Share your thoughts in the comments!