What Is a CNT?
Carbon nanotubes (CNTs) are three-dimensional molecular structures created by rolling graphene sheets into cylinders. These sheets consist of benzene rings composed of six carbon atoms, and uniformly arranged in the X-Y plane. CNTs are characterized by their composition of carbon atoms, nanometer range molecular size, and tubular structure.
CNTs, formed by the strong bonding of carbon atoms, range in size from approximately 0.4nm to 50nm. Despite their extremely low density compared to metallic molecules, CNTs are known for their exceptional properties, such as strong tensile strength, high conductivity, thermal conductivity, and heat resistance.
The application of CNTs, whether individually or in small units, is associated with the development of cutting-edge technologies in fields like ultra-fine electronic circuits and mechatronics, a realm known as nanotechnology. There are various types of CNTs based on their tubular structure, including single-layer, double-layer with nested tubes of varying diameters, and multi-layer CNTs with multiple tubes of different diameters stacked in layers.
Uses of CNTs
CNTs, known for their excellent mechanical and electrical properties, are expected to find a wide range of applications in both individual and composite materials. In practical terms, CNTs have already advanced the field of composite materials by being used as an additive in industrial materials. Carbon fiber reinforced plastic (CFRP), created by adding carbon fibers to resin to enhance functionality, is widely used in various products. Materials incorporating CNTs as additives have been applied in items such as tennis rackets and bicycle frames. Additionally, the development of composite materials with metals, rubber, and others is being pursued.
CNTs have extremely high conductivity, capable of carrying about 1,000 times the current of metals. Their use in circuit wiring enables the flow of a large amount of current through thinner wires than current standards. Moreover, leveraging their properties of being about 1/20th the weight and 100 times the tensile strength of metals, research is ongoing for the development of lightweight and strong ropes capable of lifting heavy loads. While still often discussed in the realm of science fiction, one futuristic concept involves the use of CNTs in space elevators.
Principles of CNTs
CNTs were discovered in the soot generated during experiments involving arc discharge. Currently, CNTs are produced using methods such as arc discharge, laser vaporization (laser ablation), and chemical vapor deposition (CVD).
Structure of CNTs
Graphene, a two-dimensional structure of closely and uniformly connected hexagonal benzene rings, forms the basis of CNTs. Rolling graphene into a cylindrical shape yields a carbon nanotube. Single-layer CNTs have simple tubular structures and exhibit different electrical properties based on their alignment.