In 1991, Sumio Iijima first observed the clear structure of carbon nanotubes using a high-resolution transmission electron microscope. Afterward, carbon nanotubes gained attention for their excellent properties in optics, mechanics, electromagnetism, and thermodynamics. This has also set off a wave of research on carbon nanotube manufacturing. How to manufacture carbon nanotubes? This article explores the key manufacturing techniques and their advantages.
What Are Carbon Nanotubes (CNTs)?
Before discussing the manufacturing process, it is important to understand the basics of carbon nanotubes.
Carbon nanotubes can be regarded as seamless hollow cylinders formed by curling graphene sheets according to certain chirality. The two ends are often closed by hemispherical structures containing pentagons or heptagons. The diameter is between a few nanometers and tens of nanometers, and the length can reach several micrometers or even millimeters.
Types of CNTs
Single-walled carbon nanotubes are formed by curling a single layer of graphene. The structure is simple.
Multi-walled carbon nanotubes are nested with multiple concentric single-walled carbon nanotubes. The interlayer spacing is similar to that of graphite.

SWCNTs have better electrical and thermal conductivity. Due to their high performance, they are often used in cutting-edge technology. MWCNTs have excellent strength and durability. Due to their low cost and wide application, they have become an important choice in the industrial and material fields.
How to Manufacture Carbon Nanotubes?
Manufacturing carbon nanotubes is varied. Each method has advantages and challenges. Below are several common manufacturing techniques.
1. Arc Discharge Method
This is one of the earliest technologies used to manufacture carbon nanotubes.
Two graphite electrodes are placed in a reaction chamber filled with inert gas. Electricity is applied to generate an arc. Under high-temperature conditions, graphite evaporates, and carbon atoms recombine into carbon nanotubes. Carbon nanotubes are collected from the walls of the reaction chamber and purified.
Advantages:
It can produce high-purity and well-crystalline products.
Disadvantages:
There is a low yield and impurities (such as fullerene). Also, the conditions are harsh and difficult to control.
2. Chemical Vapor Deposition (CVD)
A substrate (such as silicon or quartz) is coated with catalysts. The material is usually a metal such as iron, nickel or cobalt. A carbon-containing gas is introduced into the reaction chamber. These include methane (CH₄), acetylene (C₂H₂) or ethylene (C₂H₄). The reaction chamber is heated to a high temperature to cause the carbon gas to crack and deposit to form carbon nanotubes. Collect carbon nanotubes from the walls of the reaction chamber and purify them.



Advantages:
The CVD method is flexible, easy to control, and highly yield. It is the current mainstream method.
Disadvantages:
This method will cause different degrees of metal impurities to remain due to differences in catalyst activity. Problems such as uneven tube diameter distribution have yet to be solved.
3. Laser Ablation
This method is usually used to produce high-quality carbon nanotubes.
Place a graphite target containing a catalyst in the reaction chamber. Irradiate the graphite target with a high-energy laser beam. Gasify the graphite at high temperature and cool it to condense into carbon nanotubes. Collect carbon nanotubes and purify them.
Advantages:
The product quality of this method is excellent. The structure of carbon nanotubes can be precisely controlled.
Disadvantages:
The equipment is expensive, and energy consumption is high. The output is limited, and it isn’t easy to achieve scale.
Mass Preparation Method- Chemical Vapor Deposition (CVD)
CVD is currently China’s first choice for large-scale batch preparation of carbon nanotube powder.
Take the fluidized bed CVD process as an example. The gaseous carbon source and carrier gas are preheated. Then, they are continuously introduced into the fluidized bed reactor filled with nano-scale catalyst particles. The catalyst fully contacts the carbon source in the fluidized state. The carbon gas is cracked into carbon atoms at high temperature. Then, through the self-assembly effect of the catalyst, it is efficiently converted into high-value-added carbon nanotube powder. The carbon nanotube powder product is continuously collected after filtering and cooling.

Future optimization directions of this method:
- Developing a catalyst system with higher activity, longer life, and easy purification
- Precisely controlling process parameters such as uniform flow field, thermal field, and gas space velocity
- Solving the amplification effect of switching to a larger diameter reactor
Ensure large-scale, low-cost, high-quality, stable preparation. The goal is to meet customer indicators and ultimately meet industrial application needs.
Applications of Carbon Nanotubes
Carbon nanotubes have a wide range of applications. Common applications include:
- Electronics: Carbon nanotubes have excellent electrical conductivity. They are used to produce transistors, sensors, and conductive films.
- Material Science: They are used to enhance the strength, durability, and flexibility of composite materials.
- Energy Storage: Carbon nanotubes are used in batteries to improve energy storage capacity and efficiency.
- Nanomedicine: Carbon nanotubes can penetrate cell membranes. They are being used in drug delivery systems and cancer treatments.
Conclusion
The above describes how carbon nanotubes are manufactured. Manufacturing carbon nanotubes requires advanced technology and precise control of production conditions. Methods such as CVD, arc discharge, and laser ablation have advantages and disadvantages in different applications.
At present, the carbon nanotube manufacturing process is more diversified. Producing high-quality carbon nanotubes is still a complex and costly process. However, with the advancement of technology, carbon nanotubes will be more and more widely used in the commercial field. With their unique properties, carbon nanotubes have disruptive potential in many industries.