Carbon is an essential element in our universe. It gives rise to the countless life forms on earth and a primary source of our major fuels. Today, thanks to the immense advances in science, we have discovered and synthesized various forms of carbon. Carbon nanotubes and graphene are two of the most recently discovered forms of carbon. The main difference is, the Graphene is a single thin layer 2D film, while the carbon nanotubes in a thin film rolled like a 3D tube or cylinder.
Although they share numerous similar properties, each has its unique uses and applications.
What is Graphene?
Graphene is classified as a semi-metal and is an allotrope of carbon. It is a 2-dimensional, single layer of graphite, made of 6 carbon molecules join with others to form a perfect hexagonal lattice-shaped structure. Incidentally, graphene is the fundamental structural element of other carbon allotropes, including carbon nanotubes.
Graphene is also known as the ‘wonder material,’ thanks to its various impressive properties. It is not only the most durable material known to man but is also extremely malleable and elastic. Since it is only one-atom-thick, graphene is nearly transparent however it is also an excellent electrical and thermal conductor.
What are Carbon Nanotubes (CNTs)?
Carbon nanotubes, or CNTs, are an allotropic form of carbon, which develops in a cylindrical shape. There are two main types of CNTs –
- Single-Walled Carbon Nanotubes (SWCNTs)
- Multi-Walled Carbon Nanotubes (MWCNTs)
Similar to graphene, the carbon nanotubes are also extremely strong and display excellent conductivity for heat and electricity. They also have a higher aspect ratio than any other conventional material in use today.
Similarities and Differences between Carbon Nanotubes and Graphene
Following are the similarities and differences that found between carbon nanotubes and graphene.
In terms of their properties, graphene and carbon nanotubes show remarkable properties. Some of the similarities between the two materials include an sp2 bond between their carbon atoms. That makes both of them extremely strong, even stronger than diamond, the most stringent material known till then.
Apart from having the highest tensile strength, both of these materials are better at conducting heat and electricity, thanks to their unique molecular arrangement.
The property difference between these two is that although graphene is a zero-gap semiconductor with an anomalous quantum Hall effect, carbon nanotubes can either be semi-conducting with a different band-gap or can be entirely metallic, depending on the type of structure.
When talking about their applications, there are several differences as to the fields of demand for graphene and carbon nanotubes.
On the one hand, graphene is very thin and flexible yet is highly conductive. Hence, it finds potential application as a transparent conductor for use in photovoltaic cells and other types of flexible electronic devices. Also, its larger ratio of surface area to mass makes it excellent potential for use in energy storage or chemical sensing.
On the other hand, carbon nanotubes are strong and light at the same time. It makes them a perfect choice for using as reinforcing additive in composite fibers, to make them extremely strong and electrically conductive simultaneously. There is enormous potential for the nanotubes to used in the design and development of space elevators, bulletproof wear, clothing and others. Also, the sufficient electrical and thermal conductivity of carbon nanotubes makes them potentially useful in revolutionizing the industry with use in solar cells, as sensors, in batteries, and in transistors.
There are differences in the growth or synthesizing methods for fabricating graphene and carbon nanotubes.
The growth methods for graphene include:
- Epitaxial growth on SiC
- Chemical vapor disposition (CVD) on metal catalysts
The growth methods for carbon nanotubes include:
- Catalytic chemical vapor disposition (CCVD)
- Laser ablation
- Arc discharge
Although sharing similar traits and properties, the variations in their properties make graphene and carbon nanotubes two of the most versatile and promising materials for advances in science.