The Power of Carbon: diverse yet unique properties of Carbon Nanotubes (CNTs)

Carbon Nanotubes (CNTs):

Carbon nanotubes are a unique material with outstanding properties that make them ideal for a variety of applications. First discovered in the early 1990s, CNTs quickly attracted the attention of scientists and engineers due to their mechanical, electrical, thermal and chemical properties.

The considered form of carbon occupies an intermediate position in its structure between graphite and fullerene. However, many properties of carbon nanotubes have nothing to do with these structures. This allows us to consider these carbon formations as an independent material.

Due to the peculiarities of their structure (high bond strength, record-high atomic packing density, absence or low density of structural defects), carbon nanotubes have unique properties (Fig. 1).

Figure 1. SEM image of CNT

Let's go through some of the properties of carbon nanotubes-:

1. Mechanical properties of carbon nanotubes

2. Electrical properties of carbon nanotubes

3. Thermal properties of carbon nanotubes

4. Chemical properties of carbon nanotubes

Mechanical properties of carbon nanotubes:

Mechanical properties of carbon nanotubes, One of the most remarkable properties of CNTs is their tensile strength. The strength of CNTs can reach up to 63 gigapascals (GPa), which is ten times higher than the strength of steel (usually about 0.4-2 GPa). This makes CNTs incredibly durable, despite their nanoscale dimensions. The reason for such high strength lies in the strong covalent bonds between carbon atoms, which form a hexagonal crystal lattice.

CNTs also have high rigidity. Young's modulus for carbon nanotubes can reach 1 terapascal (TPa), which is significantly higher than that of steel (200 GPa) and other traditional materials. High rigidity allows CNTs to maintain their shape and resist deformations even under significant loads.

In addition, carbon nanotubes exhibit exceptional elasticity. They can stretch to significant degrees without breaking and return to their original shape. This makes them suitable for applications where materials are subjected to cyclic loads and deformations.

Usage examples:

• Composite materials: CNTs are used to create high-strength and lightweight composites used in the aerospace and automotive industries (Fig.2).

• Sports equipment: The high strength and lightness of CNTs make them ideal for use in the manufacture of sports equipment such as tennis rackets and golf clubs.

Figure 2. CNT in polymer composite material

Electrical properties of carbon nanotubes:

Electrical properties of carbon nanotubes, CNTs have unique electrical properties that depend on their structure. They can behave like metals or semiconductors. Metal CNTs have a very high electrical conductivity, superior to that of copper (5.8 x 10^7 Siemens/meter). This makes them promising for use in nanoelectronics.

Semiconductor CNTs have the ability to switch between a conductive and non-conductive state, which allows them to be used in transistors and other electronic devices. This effect is enhanced by reducing the size, which makes CNTs ideal candidates for creating miniature electronic components.

Usage examples:

• Nanoelectronics: CNTs are used to create transistors, sensors and other nanoscale electronic devices (Fig. 3).

• Conductive films: CNTs are used to create flexible and transparent conductive films used in touchscreens and displays.

Figure 3. CNT as a nanoscale transistor

Thermal properties of carbon nanotubes:

Thermal properties of carbon nanotubes, Carbon nanotubes have outstanding thermal conductivity. They can conduct heat with an efficiency exceeding copper (401 W/(m·K)). The thermal conductivity of CNTs along their axis can reach up to 3500 W/(m·K). This makes them an excellent material for use in thermally conductive components and cooling systems.

The high thermal conductivity of CNTs is due to their unique structure, which minimizes the scattering of phonons, quasi-particles responsible for the transfer of thermal energy. This property allows the use of CNTs for efficient heat management in various applications.

Usage examples:

• Electronics cooling: CNTs are used in cooling systems for electronic devices such as processors and graphics cards to improve heat dissipation and improve performance.

• Thermally conductive composites: CNTs are added to polymers and other materials to create thermally conductive composites used in thermal interfaces and other components.

Chemical properties of carbon nanotubes:

Chemical properties of carbon nanotubesCarbon nanotubes exhibit high chemical inertness, which makes them resistant to corrosion and chemical attack. However, their surface can be functionalized by various chemical groups, which makes it possible to modify their properties and adapt them for specific applications.

The functionalization of the CNT surface opens up opportunities for the creation of new materials with desired properties, including improved compatibility with biological systems and improved adsorption properties. This makes CNTs attractive for use in biomedicine and environmental technologies.

Usage examples:

• Biomedicine: CNTs are used to create drug delivery systems, biosensors and other biomedical devices (Fig. 4).

• Water and air purification: CNTs are used in filtration and purification systems due to their adsorption properties and ability to destroy harmful substances.

Figure 4. CNT as a drug delivery system.

The increase in the variety of unusual properties of carbon nanotubes and the broad prospects for creating functional and structural materials based on them opens up the modification of CNTs, which can be carried out in several ways:

- filling of internal cavities with substances that change their electronic, magnetic or mechanical properties;

- "inoculation" to CNTs of various functional groups;

- substitution of a part of carbon atoms in CNTs for atoms of other elements;

- partial or complete "opening" of double bonds on the side surfaces by attaching certain reagents;

- intercalation (embedding) of atoms or molecules into the "inter-tube" space.

Carbon nanotubes have many unique properties such as high strength, rigidity, elasticity, electrical conductivity, thermal conductivity and chemical inertia. These properties make CNTs promising for a wide range of applications, from the creation of high-strength composite materials to the development of nanoelectronic devices and biomedical applications.

With the development of CNT production and functionalization technologies, we can expect further expansion of their application and the discovery of new areas where their unique properties will be in demand. Carbon nanotubes continue to be the object of intensive research and development, and their potential for changing modern technologies is beyond doubt. In the future, we can expect the emergence of new innovative materials and devices based on the unique properties of carbon nanotubes, which will open up new horizons for science and industry.