**2. Synthesis and properties of carbon fibers**

Since the temperature and pressure essential to synthesize a carbon fiber from the fluid stage is at the triple point (Temperature—4100 K, Pressure—123 kbar), it would be practically difficult to get ready carbon fibers from the liquefy under modern preparing conditions. As a result, carbon fibers are arranged from organic precursors. This preparation is commonly done in three stages, including stabilization of a precursor fiber in air (at 300°C), carbonization at 1100°C, and subsequent graphitization (*>* 2500°C). Fibers undergoing only the first two steps are commonly called carbon fibers, while fibers undergoing all three steps are called graphite fibers.

Carbon fibers are commonly utilized for their high strength, while graphite fibers are utilized for their high modulus. Graphitic whiskers were developed under conditions close to the triple point of graphite. At that point, the structural model was proposed, in which the layers comprising of graphene sheets are twisted around the axis like as in rolling up a carpet. These whiskers were utilized as the presentation focus in the beginning times of carbon fiber technology, despite the fact that they have never been manufactured on a large scale.

Carbon fibers are


The PAN-based fibers comprise of little sp2 -carbon structural units specially lined up with the carbon hexagonal portions corresponding to the fiber axis. This orientation is liable for the tensile strength of PAN-based carbon fibers [28].

**53**

1000°C.

*Vapor-Grown Carbon Fiber Synthesis, Properties, and Applications*

[29]. PAN-based fibers are one of the distinctive hard carbons.

By shifting the preparing conditions (e.g., oxidation conditions, choosing of precursor material, and particularly by increasing the heat treatment temperature) of PAN fibers, a better arrangement of the graphene layers can be accomplished, thus leading to stiffer, higher-modulus PAN fibers, however with lower strength

MPCFs comprise of perfectly-aligned graphitic layers equivalent to the corresponding fiber axis, and this high level of favored direction is liable for their high modulus or stiffness just as their high graphitizability. The structures depicted above suggest ascent to various physical properties, although each kind of fiber highlights carbon hexagonal systems, having the sturdiest covalent bonds in nature (C▬C bonds). These sturdy interatomic bonds lie in sheets basically corresponding to the fiber axis, and are liable for the high mechanical performance of these

PAN- based fibers have high strength and MPCFs have high modulus, while VGCFs afford fundamentally ultra-high modulus materials. VGCFs have an extremely unique structure like annular-rings and are prepared by something diverse arrangement process than that used to prepare PAN-based and MPCFs. Specifically, VGCFs are not prepared from a fibrous precursor, but instead from hydrocarbon gas, utilizing a catalytic growth process [5, 11–15]. Ultrafine transition metal particles, for example, iron particles with diameter under 10 nm, are scattered on a ceramic substrate, and a hydrocarbon, for example, benzene diluted with hydrogen gas is introduced at temperatures of around 1100°C. Hydrocarbon decomposition happens on the catalytic particle, showing a ceaseless carbon take-up by the catalytic particle and a persistent output by the particle of efficient

times quicker than that analyzed for the development of normal metal whiskers [30], permits the production of commercially suitable amounts of VGCFs.

While portraying the production of VGCF, two distinct strategies can be discriminated. In the primary strategy, the fibers are manufactured on catalyst-seeded substrates, in two independent consecutive stages. In the first stage, the impetus molecule, for the most part with iron being the prevalent constituent, starts a long, thin, somewhat graphitic fiber when presented to a hydrocarbon gas close or more

A petite fraction of these fibers grows to macroscopic lengths when exhibited to a low carburizing potential gas, while keeping up the outside diameter of the initial catalytic particle. The sizes of these particles, and subsequently the filament diameter, have been considered from 10 to 200 nm [31–33]. The development of the filament may extend as quickly as 1 mm/min and persevering for a few minutes until the catalytic particle is deactivated [33]. At this stage filament lengths of a few

In the second stage, when the gas potential is increased, the filament thickens because of the deposition of pyrolytic carbon. Fibers with diameters up to 100 nm have been produced in batch conditions by this method. Pyrolytic carbon is deposited with the basal planes specially arranged corresponding to the surface, the

carbon. The swift development rate which is 106

*DOI: http://dx.doi.org/10.5772/intechopen.92300*

carbon fibers.

**3. Vapor-grown carbon fibers**

tubular filaments of hexagonal sp2

centimeters might be acquired.

properties of the fiber are moderately graphitic [34].

**4. Vapor grown carbon Fiber growth**

*Vapor-Grown Carbon Fiber Synthesis, Properties, and Applications DOI: http://dx.doi.org/10.5772/intechopen.92300*

By shifting the preparing conditions (e.g., oxidation conditions, choosing of precursor material, and particularly by increasing the heat treatment temperature) of PAN fibers, a better arrangement of the graphene layers can be accomplished, thus leading to stiffer, higher-modulus PAN fibers, however with lower strength [29]. PAN-based fibers are one of the distinctive hard carbons.

MPCFs comprise of perfectly-aligned graphitic layers equivalent to the corresponding fiber axis, and this high level of favored direction is liable for their high modulus or stiffness just as their high graphitizability. The structures depicted above suggest ascent to various physical properties, although each kind of fiber highlights carbon hexagonal systems, having the sturdiest covalent bonds in nature (C▬C bonds). These sturdy interatomic bonds lie in sheets basically corresponding to the fiber axis, and are liable for the high mechanical performance of these carbon fibers.
