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  • Writer's pictureElina Isaeva

Revolutionizing Material Science: The Promise of Carbon Nanotubes (CNTs)

Carbon nanotubes (CNTs) are structures made of carbon in the shape of a tubular filament (Fig.1). They have unique electrical, mechanical and thermal properties, which makes them one of the most promising materials for various fields of science and technology.


CNT

Figure 1. Carbon Nanotubes

CNT: History

The history of carbon nanotubes began at the end of the 20th century and is associated with the discovery of new forms of carbon. The prerequisites for the emergence of CNTs were laid in 1952, when Raymond Bragg put forward the idea of their possible existence. However, it was only in 1991 that Japanese scientists Sumio Iijima and Tomio Izumi discovered single-layer carbon nanotubes (SWCNT) while studying the structure of fullerene C60 (Fig.2).


Sumio Iijima

Sumio Iijima

Figure 2. Japanese scientists Sumio Iijima


Types of CNT: SWCNT and MWCNT

Carbon nanotubes can be single-layered (SWNT) or multi-layered (MWNT) (Fig.3). SWNT are tubes consisting of a single carbon layer, and MWNT are several carbon layers forming concentric tubes.


SWCNT AND MWCNT

Figure 3. Single-layered (SWNT) or multi-layered (MWNT) Carbon Nanotubes

 

Carbon nanotubes (CNTs) can be classified according to various criteria such as structure, diameter, number of layers and synthesis method. Depending on the structure, CNTs are divided into single-layer (SWNT) and multi-layer (MWNT).


1. Single-layer carbon Nanotubes (SWNT):

- Structure: SWNT are cylindrical structures consisting of a single carbon layer forming a tube. The carbon atoms in SWNT are connected to each other in hexagonal rings, forming a hexagonal lattice.

- Diameter: SWNT diameter can range from 0.4 nm to several nanometers.

- Electrical properties: SWNTs have semiconductor or metallic properties depending on their chirality (rotation) and structure.

- Application: SWNT is widely used in electronics, sensors, medicine and other fields due to its unique properties.


2. Multilayer Carbon Nanotubes (MWNT):

- Structure: MWNT consist of several layers of carbon forming concentric tubes. Each layer can be single-layered or multi-layered.

- Diameter: The diameter of MWNT is usually larger than that of SWNT and can reach several tens of nanometers.

- Mechanical properties: MWNT have high mechanical strength and elasticity due to their structure.

- Application: MWNT are used in composite materials, electrode materials, protective coatings and other fields.

The differences between SWNT and MWNT are in their structure, electrical and mechanical properties, as well as in the methods of synthesis. Both types of CNTs have a wide range of applications and are the object of active research in the field of nanotechnology.


How CNT is made?

There are several methods for the synthesis of carbon nanotubes:


1. Chemical Deposition Method (CVD): This is one of the most common methods of CNT synthesis. It is based on the chemical deposition of carbon on a catalyst at high temperature. In the CVD process, gaseous carbon precursors such as methane or ethane are decomposed into carbon atoms, which are then deposited on the surface of the catalyst in the form of nanotubes.


2. Arc discharge method: In this method, carbon nanotubes are synthesized by applying high electrical energy to vaporize graphite electrodes in an inert atmosphere. As a result, plasma is formed, which leads to the formation of nanotubes.


3. Method of chemical reduction of oxides: this method is based on the reduction of carbon oxides at high temperatures in an atmosphere of hydrogen or other reducing gases. As a result, carbon oxides are converted into carbon nanotubes.


4. Laser evaporation method: In this method, carbon nanotubes are synthesized by irradiating a graphite target with a high-power laser. This leads to the evaporation of carbon and the formation of nanotubes.


These methods of carbon nanotube synthesis have their own characteristics and advantages, and the choice of method depends on the specific requirements for the resulting nanotubes.


Applications of CNT

Carbon nanotubes are used in many fields such as electronics, materials science, medicine and even the space industry. They are used in the creation of nanoelectronic devices, sensors, composite materials and other innovative technologies. Here are some examples:


- Electronics: Carbon nanotubes have excellent electrical conductivity and can be used as a material to create electronic devices such as transistors, sensors and diodes.


- Materials: CNTs have high strength and rigidity, which makes them an excellent material for creating lightweight and durable composites. They can be used in the aviation and automotive industries.


- Medicine: Carbon nanotubes can be used as nanocarriers to deliver drugs into the body, as well as to create biosensors and diagnostic devices.


- Energy: CNTs can be used as electrodes for lithium-ion batteries, supercapacitors and other energy-intensive devices.


- Catalysis: Carbon nanotubes can be used as catalysts for various chemical reactions such as hydrogen storage or carbon dioxide conversion.


These are just a few examples of the use of carbon nanotubes. Due to their unique properties, they have huge potential for various fields of science and technology. In the future, CNTs may become a key material for the development of new technologies and devices.

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