What Are Carbon Nanotubes and What Are They Used For?

Carbon nanotubes are incredible things. They can be stronger than steel while being thinner than a human hair.They are also highly stable, lightweight, and have incredible electrical, thermal and mechanical properties. For this reason, they hold the potential for the development of many interesting future materialsThey may also hold the key to building the materials and structures of the future, such as space elevators.
Here, we explore what they are, how they are made and what applications they tend to have

What are carbon nanotubes and their properties?

  • Energy storage solutions
  • Device modeling
  • Composite structures
  • Automotive parts, including potentially in hydrogen fuel cell cars
  • Boat hulls
  • Sporting goods
  • Water filters
  • Thin-film electronics
  • Coatings
  • Actuators
  • Electromagnetic shielding
  • Textiles
  • Biomedical applications, including tissue engineering of bone and muscle, chemical delivery, biosensors and more

What are multiwalled carbon nanotubes?

1. Arc dischargeWithin this process, graphite is combusted electronically. CNTs form in the gaseous phase, which is later separated out. 
2. Laser ablation of graphite
3. Plasma torch
4. Chemical vapor deposition (CVD)
5. Liquid electrolysis
Carbon nanotubes (CNTs for short), as the name suggests, are minute cylindrical structures made from carbon. But not just any carbon, CNT's consist of rolled-up sheets of a single layer of carbon molecules called graphene.
They tend to come in two main forms : 
1. Single-walled carbon nanotubes (SWCNTs) - These tend to have a diameter of less than 1 nm.
2. Multiwalled carbon nanotubes (MWCNTs) - These consist of several concentrically-interlinked nanotubes and tend to have diameters that can reach in excess of 100 nm
In either case, CNTs can have variable lengths from between several micrometers to centimeters.
As the tubes are exclusively built from graphene, they share many of its interesting properties. CNTs, for example, are bonded with sp2 bonds - these are extremely strong at the molecular level.
Carbon nanotubes also have the tendency to rope together via van der Waals forces. This provides them with high strength and low weight. They also tend to be highly electrically-conductive and thermally-conductive materials.Carbon nanotubes also have other amazing thermal and mechanical properties that make them attractive for developing new materials. 
For example :
  • CNT's can have mechanical tensile strength 400 times that of regular steel.
  • They are very light-weight as their density is one-sixth of that of steel.
  • CNTs thermal conductivity is better than that of a diamond.
  • Carbon nanotubes have a very high aspect ratio of greater than 1000. In other words, in relation to their length, they are extremely thin.
  • "Their tip-surface area is near the theoretical limit (the smaller the tip-surface area, the more concentrated the electric field, and the greater the field enhancement factor).
  • Like graphite, they are highly chemically stable and resist virtually any chemical impact unless they are simultaneously exposed to high temperatures and oxygen - a property that makes them extremely resistant to corrosion.
  • Their hollow interior can be filled with various nanomaterials, separating and shielding them from the surrounding environment - a property that is extremely useful for nanomedicine applications like drug delivery." 
They tend to have diameters that can reach in excess of 100 nmThey can reach in excess of centimeters in length and tend to have aspect ratios that vary between 10 and 10 million.
MWCNTs have some excellent properties which can be exploited in a large number of commercial applications. These include :

  • Electrical: MWNTs are highly conductive when properly integrated into a composite structure. It should be noted that the outer wall alone is conducting, the inner walls are not instrumental to conductivity.
  • Morphology: MWNTs have a high aspect ratio, with lengths typically more than 100 times the diameter, and in certain cases much higher. Their performance and application are based not just on aspect ratio, but also on the degree of entanglement and the straightness of the tubes, which in turn is a function of both the degree and dimension of defects in the tubes.
  • Physical: Defect-free, individual, MWNTs have excellent tensile strength and when integrated into a composite, such as a thermoplastic or thermoset compounds, can significantly increase its strength.
  • Thermal: MWNTs have thermal stability more than 600 °C, based on the level of defects and to a certain extent on the purity, as a residual catalyst in the product can also catalyze decomposition.
  • Chemical: MWNTs are an allotrope of sp2 hybridized carbon, similar to graphite and fullerenes, and as such have high chemical stability. However, one can functionalize the nanotubes to enhance both the strength and dispersibility of composites.

Thus carbo nanotubes play an important role and still there are researches being conducted to know about its specific features.

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