Carbon nanotubes in graphene

The structure of graphene

Graphene is a "single-layer graphite sheet", which is the basic structural unit that constitutes graphite; while carbon nanotubes are cylindrical structures formed by curling graphene. As another carbon material whose structure is based on graphene, the basic components of carbon nanotubes and graphene are the same, especially unclosed carbon nanotubes. Both are the coupling of six carbon rings, so the two The preparation method is also similar.

Perfect graphene is a new carbonaceous material in which carbon atoms are closely packed into a single-layer two-dimensional honeycomb-like smooth lattice structure. Its local structure is composed of carbon six rings. In practice, there is often carbon in defective places. Five rings and carbon seven rings. A small amount of carbon five rings will warp the graphene, and the cylinder formed by the carbon six rings will form a closed carbon nanotube.

The emergence of graphene has broken many previous understandings of materials. Before, regardless of theory or experiment, scientists believed that a perfect ideal two-dimensional structure could not exist stably in practice.

The structure of graphene

The development process of graphene is very similar to that of carbon nanotubes. Before the discovery of carbon nanotubes, there were three main crystal structures of carbon: graphite, diamond and fullerene. At that time, there had been sufficient research on both carbon fiber (industrialized) and carbon nanofiber; after the discovery of carbon nanotubes, people began to pay attention to the similarities and differences between carbon nanotubes and carbon nanofibers.

On the surface, in terms of crystal structure, carbon nanofibers have relatively poor crystallization degree, many defects, discontinuous arrangement of graphite sheets, large diameter, and do not really belong to the crystal structure of carbon, or are only graphite. A derivative.

Before graphene was discovered experimentally, some tiny graphite grains, whiskers or graphite layers (with more layers) had been synthesized and studied extensively. Expanded graphite is also based on the concept of exfoliated graphite, and related technologies have been well developed and have been used in industrial applications for a long time. Similar to the relationship between single-wall, double-wall, and thin-walled carbon nanotubes, in addition to graphene (single layer) in the strict sense, double-layer and few-layer graphite sheets are also significantly different from block in structure and performance. Bulk graphite is also classified as graphene in a broad sense.

The emergence of graphene has triggered a debate between it and the prospects and future of carbon nanotubes. However, one-dimensional materials represented by nanotubes are often at a disadvantage in the competition with two-dimensional materials. Take 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 cannot obtain carbon nanotube crystals with macroscopic dimensions, thus limiting the carbon Application of nanotubes.

The advantage of graphene is that it is a two-dimensional crystal structure with several record-breaking properties (strength, electrical conductivity, and thermal conductivity), and can achieve continuous growth in a large area. Therefore, graphene does not have to undergo a complicated separation process when constructing devices, and it is more practical than carbon nanotubes.

Information source: Feldspar New Energy
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