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Research On Graphene and Carbon Nanotubes Materials

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Update time : 2020-02-25 16:51:14
Carbon is a pervasive element in nature, graphene and carbon nanotubes are allotropes of carbon. There is a lot of information between them that we need to understand and use. Now, let's learn along with this article.
 

General introduction of graphene

Graphene is a kind of two-dimensional carbon nanomaterial, which is composed of carbon atoms and SP 2 hybrid orbital. With excellent optical, electrical, and mechanical properties, it has significant application prospects in materials science, micro-nano processing, energy, biomedicine, and drug delivery. It is considered to be a revolutionary material in the future.
 
 

As a concept, graphene is not a new concept. Scientists have long recognized that graphite is made of layers of graphene; when they found carbon nanotubes, scientists also used curly graphene to describe the structure of carbon nanotubes, that is to say, graphene is a single layer of graphene. Graphene is a two-dimensional structure, but in fact, it is not flat, but wavy. In a two-layer system, this fluctuation is not apparent, and it will disappear entirely in a multi-layer order. Each carbon atom in graphene is connected with three surrounding carbon atoms by a unique single bond, and the remaining electron can move freely so that graphene can conduct electricity.

To some extent, it can be considered that the whole graphene sheet forms a large π bond. The preparation of graphene is quite simple. We have been preparing graphene since we were young. When we write with a pencil, the single layer of graphene can be peeled off to form graphene with a very slight force.

 

General introduction of carbon nanotubes

Carbon nanotubes (CNTs), also known as Ba based tubes, are one-dimensional quantum materials with unique structures (radial size is nanometer, axial dimension is micron, and both ends of the cells are sealed). Carbon nanotubes are mainly composed of hexagonal carbon atoms, which form several to dozens of concentric tubes. The distance between layers is about 0.34nm, and the diameter is generally 2 ~ 20nm. According to the different orientation of the carbon hexagon along the axial direction, it can be divided into three types: zigzag, armchair, and spiral. Among them, helical CNTs have chirality, while zigzag and armchair CNTs have no chirality.
 
Carbon nanotubes are not always straight, but locally convex and concave, which is due to the pentagonal and heptagonal formation of hexagons. If the Pentagon just appears at the top of the CNT, the sealing of the CNT will be formed. The nanotubes are concave when they are heptagonal. These topological defects can change the helical structure of CNTs and the electronic band structure near the faults. Besides, the two adjacent carbon nanotubes are not directly bonded together, but keep a certain distance.

Graphene vs. carbon nanotubes

Graphene is the "single-layer graphite sheet," which is the basic structural unit of graphite, while carbon nanotubes are the cylinder structure formed by the curling of graphene. As the representative of one-dimensional (1D) and two-dimensional (2D) nanomaterials, they are complementary in composition and performance. From the structure point of view, carbon nanotubes are a one-dimensional crystal structure of carbon. At the same time, graphene is only composed of a single carbon atom layer, which is the real two-dimensional crystal structure. In terms of properties, graphene has the same or better features as carbon nanotubes, such as high conductivity and thermal conductivity, high carrier mobility, free-electron moving space, high strength, and stiffness. At present, the research on carbon nanotubes has reached a certain depth and breadth in preparation technology, performance characterization, and application exploration. The close connection between composition and structure makes them have many similarities in research methods. Many types of research on graphene were initiated by the related studies of carbon nanotubes.
 
The development process of graphene is very similar to that of carbon nanotubes, but it may be very different in the future. There are many reasons, but it can be attributed to the dispute between one-dimensional materials and two-dimensional materials. Nanowires and nanotubes are often at a disadvantage in the competition with thin-film materials. Taking carbon nanotubes as an example, a single carbon nanotube can be regarded as a single crystal with a high aspect ratio. However, the current synthesis and assembly technology can not obtain a macro size carbon nanotube crystal, which limits the application of carbon nanotubes. The advantage of graphene is that it is a two-dimensional crystal structure, which can realize large-area continuous growth. Both graphene and carbon nanotubes have bright future.
 
I hope this article can help you!