**6. Vapor grown carbon nanofiber by floating reactor method**

Vapor-grown carbon fibers (VGCFs) have been developed by the deterioration of hydrocarbons, for example, benzene and methane, utilizing transition metal particles as a catalyst at a development temperature of 1000–1300°C [31–35]. These fibers have been portrayed regarding the profoundly favored orientation of their graphitic basal planes corresponding to the fiber pivot, with an annular ring surface in the cross segment. This structure offers ascend to amazing mechanical properties, high electrical and thermal conductivity, and a high graphitizability of the fibers [32, 33]. In this way, numerous scientists have attempted to arrive at the last objective of large scale manufacturing of these fibers filaments with ease.

Among the different preparing techniques, the most significant one has been the advancement of the floating reactant technique [36, 37], which permits a

**55**

network.

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

three-dimensional scattering of the hydrocarbon together with the catalytic particles got from the pyrolysis of organometallic compounds, for example, ferrocene, in a reaction chamber, ensuing about a high yield and a fairly uniform diameter across of the resulting fibers. Thus, the floating reactant strategy is believed to be a promising method for the large scale manufacturing of carbon fibers at generally

Because of their production method, VGCFs arrive in an assortment of morphologies that are fundamental to understand their properties. A few unique morphologies have been accounted in the literature [38]. Somewhat, these morphologies emulate the internal structure of the fiber. The structure of VGCFs looks like that of a tree trunk, with concentric annular rings. The original filament lies in the middle of axis of symmetry. The layers are in part aligned turbostratic carbon, with the average basal plane skewed from the fiber axis by around 10–15° [30]. In thinner fibers, or in fibers submitted to high temperature heat-treatments, cracks are observed between consecutive rings, and the external surfaces are often crenulated. Cracks are seen between consecutive rings when thinner fibers, or in fibers exposed

to high temperature, and the external surfaces are frequently crenulated.

can be halfway eased by the formation of the crenulations.

be nearer to that of the other carbon fibers.

by a pitting mechanism [40].

When the pyrolytic carbon is subjected to cooling, it shrinks more quickly in the radial than in the tangential direction. The ensuing radial stress (tension) will be reduced if circumferential cracking between the rings happens. Then again, the contraction in the tangential direction prompts a high compressive pressure that

The uniform geometry and the basically carbon structure of the VGCFs makes the fibers very graphitizable. Swift graphitization increased with increased temperatures [28]. Above 2600°C, VGCFs structure moves toward like a single crystal graphite structure. Evidently, this property will let improvement to a specific level, tailoring of the fiber properties to preferred values. In recent years, a widen interest has been appeared in the surface properties of VGCFs, as this can be identified with the interfacial properties of the fiber in composites. It was pointed out that the surface reactivity of VGCFs is lower than that of ex-pitch or ex-PAN carbon fibers [39]. On the other hand, the surface reactivity can be increased by oxidation treatment to

The effect of diverse oxidative surface treatments (nitric acid, plasma, air and

It was observed that, surface oxidation of carbon fibers is the standard innovation to increase adhesion between fiber and matrix, air and carbon dioxide treatments do not fundamentally expand the fiber's surface reactivity, in spite of extensive weight reduction. This was ascribed to the presence of traces of iron left on the VGCF from the growth stages, that may have catalyzed carbon gasification

Cleansing of the VGCFs with HCl to remove the iron can prevent this behavior. Although nitric acid and plasma treatments were found to increase surface reactivity without altering significantly the morphology of the fibers, the latter appeared

To expel the iron, VGCFs is cleaned with HCl can obviate this behavior. Though nitric acid and plasma treatments were found to increase surface reactivity without changing fundamentally the morphology of the fibers, the latter gave off an impression of being progressively great in improving the adhesion of VGCFs to a

carbon dioxide) on the fibers surface reactivity has been studied [30].

to be more favorable in improving the adhesion of VGCFs to a matrix.

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

economical.

**7. Fiber morphology**

three-dimensional scattering of the hydrocarbon together with the catalytic particles got from the pyrolysis of organometallic compounds, for example, ferrocene, in a reaction chamber, ensuing about a high yield and a fairly uniform diameter across of the resulting fibers. Thus, the floating reactant strategy is believed to be a promising method for the large scale manufacturing of carbon fibers at generally economical.
