**7. Fiber morphology**

*Composite and Nanocomposite Materials - From Knowledge to Industrial Applications*

out to be exceptionally financial contrasted with other carbon filaments.

**5. Mass production of vapor-grown carbon nanofibers (VGCFs)**

consideration for the large scale manufacturing of these materials.

represented by the size of the impetus particles.

filaments and residue were constantly gotten.

to deliver carbon nanofibers with diameter of 50–100 nm.

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

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

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

expectation.

Methane, hydrogen and an inert gas are utilized to develop the fibers at atmospheric pressures on nesting cylindrical substrates inside a growth tube. Lower centralizations of the methane-hydrogen blends are utilized for fiber extending, though higher concentrations are utilized for thickening. As methane is an economical feedstock in certain parts of the world, the production of VGCFs can turn

On account of their unique properties, for example, high strength and electric conductivity and special functional properties, researchers have indicated a lot of

1.The physical properties of vapor grown carbon fibers, with littler diameters across ought to be more grounded than those with larger diameters fume developed carbon filaments and exploratory outcomes demonstrated this

2.Furthermore, it was accounted for that the distance across of the nanofibers is

3.For the large scale manufacturing of VGCFs the key procedure is the seeding of the impetus particles. VGCFs with distances across of 50–100 nm was created effectively utilizing a blend of ferrocene and fluid hydrocarbon in a vertical heater. The outcomes show that this strategy gives the chance of large scale manufacturing. Be that as it may, in view of the trouble of proficiently scattering little Fe particles in showering impetus arrangement, vague blends of

Carbon nanofibers were manufactured with diameters of 50–80 nm from catalytic decomposition of hydrocarbon gas with catalyst metal powder utilizing the support catalyst method. In spite of the fact that the support catalyst technique can create high quality fibers, the preparation and defined scattering of ultrafine catalyst particles are very difficult and are exceptionally troublesome, the yield of this strategy is spendthrift to be in any way marketed. So as to tackle the above issues the floating catalyst technique was created with the help of support catalyst

**54**

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.

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 can be halfway eased by the formation of the crenulations.

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 be nearer to that of the other carbon fibers.

The effect of diverse oxidative surface treatments (nitric acid, plasma, air and carbon dioxide) on the fibers surface reactivity has been studied [30].

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 by a pitting mechanism [40].

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

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 network.
