Carbon nanotubes are materials that possess remarkable properties and offer extraordinary possibilities. This article gives a brief overview of the physico-chemical nature and characterization of multi-walled carbon nanotubes (MWNTs).
Single-walled carbon nanotubes and multi-walled carbon nanotubes share some similarities, but also some of significant differences. Multi-walled carbon nanotubes can be thought of as a series of single walled tubes nested within one another. There may be as few as 2, or as many as 100 plus concentric walls. Their diameters may, therefore, be as great as 50nm as opposed to 0.7 - 2.0 nm for a typical single-walled carbon nanotubes. Just the outer wall generally contributes to the electrical and mechanical properties of multi-walled carbon nanotubes when used in composites, for example, affording the opportunity for much lower loading of single-walled carbon nanotubes versus multi-walled carbon nanotubes.
Multi-walled carbon nanotubes have excellent properties and are being employed in a large number of commercial applications. The properties of multi-walled carbon nanotubes are:
Physical: Defect–free, individual, multi-walled carbon nanotubes have an excellent tensile strength and when integrated into a composite, such as a thermoplastic or thermoset compounds, can significantly increase its strength.
Electrical: Multi-walled carbon nanotubes are highly conductive when properly integrated into a composite structure. One must note that the outer wall alone is conducting; the inner walls are not instrumental to conductivity.
Chemical: Multi-walled carbon nanotubes 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.
Thermal: Multi-walled carbon nanotubes have a thermal stability more than 600 °C, based on the level of defects and to certain extent on the purity as residual catalyst in the product can catalyze decomposition.
Applications of multiple-walled carbon nanotubes:
Multi-walled carbon nanotubes are used in additives in polymers
Multi-walled carbon nanotubes are used in wafer processing fabrication.
Multi-walled carbon nanotubes are used in RFI shielding materials.
Multi-walled carbon nanotubes are used in water filtration membranes.
Multi-walled carbon nanotubes are used in electron field emitters for cathode ray lighting elements.
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