How To Make Carbon Nanotubes: A Guide for All Scientists

Carbon nanotubes (CNTs) have become an indispensable part of nanoscience in the last decade. They are the strongest known nanomaterial with high conductivity and thermal insulation properties. Conductive, semiconducting and insulating carbon nanotubes all exist in nature. These cylindrical nanoparticles are made up of carbon atoms arranged in hexagonal structures. Their properties can be manipulated to serve specific applications or needs to produce different types. Carbon nanotubes can also be manufactured directly from raw graphite with additives such as nickel or iron. Several methods have been proven effective for manufacturing carbon nanotubes: Chemical Vapor Deposition (CVD), Arc Discharge and Catalytic Chemical Vaporization process, which we’ll explain in this article.

Chemical Vapor Deposition (CVD)

The chemical vapour deposition method of carbon nanotube manufacturing is a process that has been in use for over 30 years. It’s a method of growing carbon nanotubes that involves a combination of catalytic decomposition of hydrocarbons and chemical reaction with carbon-containing compounds. Generally, the raw material used for making CNTs can be acetylene or ethylene. It can also be methane, ethane or other hydrocarbon gases. The gases are usually mixed with hydrogen and fed into a rotating cylinder. The rotating cylinder is heated to a high temperature, causing the gases to break down into their respective elements. Then a catalyst is added to accelerate the process of carbon nucleation. The catalyst is usually nickel, cobalt, iron or palladium. The catalyst is placed in the rotating cylinder or on the inner wall of the rotating cylinder. It is also applied to the surface of the rotating cylinder.

Arc Discharge Process

A chemical vapour deposition process produces carbon nanotubes with an arc discharge. The arc discharge produces plasma and carbon nanoparticles. The carbon nanotubes are formed by co-feeding hydrocarbon gas and reducing agents such as iron or cobalt. The arc discharge process has been used to make carbon nanotubes since the late 1990s. The arc discharge process produces carbon nanotubes and carbon nanofibers. The carbon nanotubes and carbon nanofibers can be collected and separated.

Catalytic Chemical Vaporization Process

The catalytic chemical vaporization process for carbon nanotube manufacturing is a method for growing carbon nanotubes directly from plain graphite with additives such as nickel or iron. The graphite is placed in a rotating cylinder and heated to a high temperature. The gases are then injected into the rotating cylinder and are decomposed into their respective elements. Then the additives in the graphite are used as catalysts to accelerate the process of carbon nucleation. The growing of carbon nanotubes occurs in the entire rotating cylinder. The rotating cylinder is typically rotated for about a day. Then the rotating cylinder is cooled down to room temperature to stop the process of carbon nanotube growth.

Brief Summary of the three methods to manufacture carbon nanotubes

The chemical vapour deposition method is a process that involves the use of catalytic decomposition of hydrocarbons and chemical reactions with carbon-containing compounds. The catalytic chemical vaporization process uses graphite with additives such as nickel or iron to grow carbon nanotubes directly. The arc discharge method produces carbon nanotubes and carbon nanofibers from plain graphite.

Conclusion
Several methods for manufacturing carbon nanotubes include:
• Chemical vapour deposition process
• Arc discharge process
• Catalytic chemical vaporization process
The chemical vapour deposition process combines catalytic decomposition of hydrocarbons and chemical reactions with carbon-containing compounds. The catalytic chemical vaporization process uses graphite with additives such as nickel or iron to grow carbon nanotubes directly. The arc discharge process produces carbon nanotubes and nanofibers from plain graphite using plasma.