**9. Applications of VGCFs**

## **9.1 In composites**

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

The modulus and the elasticity of VGCFs can be found easily [34]. The calculated modulus value varies from 100 to over 1000 GPa. The stiffness of VGCF depends upon their diameters. Even though the fibers are produced in the same experiment the diameters increased from 6 to 32 nm, the modulus decreases

The degree of favored orientation of graphitic basal planes is related to the stiffness of pyrolytic carbon. The stiffness of a graphite fiber is connected as a component of the orientation point of the graphitic plane. This model was fitted to the stiffnessdata of VGCFs by measuring their orientation parameter. This model was fitted to the solidness information of VGCFs by estimating their direction parameter. As the main fitting parameter utilized in the model is free of fiber diameter, the dwindle in the solidness of thicker fibers was assigned to the decrease in their graphitic requesting. This again is because of a swifter deposition of pyrolytic carbon during the thickening period. This is as per the finding that that increasing the graphitization of VGCF by heat-treatment also additionally increases their modulus considerably. In one example, the modulus of vapor grown fibers more than doubled to about

Heat-treated fibers are unsuccessful more commonly in the "sword-in-sheath" mode and in this mode; grouping of circumferential breaks along the internal rings permits continuous cylinders to slide telescopically inside one another, slowly diminishing the load bearing limit of the fiber. It is obvious from these outcomes that the modulus and the disappointment method of vapor grown carbon fibers are

The values of the tensile strength of VGCF are progressively reliable, changing from 2.5 to 3.5 GPa for fibers with diameters across just beneath 10 μm. The reliance on the diameter however is strong [33, 34, 41]. This was clarified by accepting that thicker fibers have a larger flaws population, and a more prominent likelihood of

The carbon structure and potential graphitization of VGCFs by heat-treatment makes them a fascinating possibility for thermal and electrical applications. VGCFs are known to have the most noteworthy electrical and thermal conductivities among carbon fibers because of their conceivable high structural perfection [42]. It was verified that VGCFs heat-treated at lower temperature have a resistivity that is practically constant with temperature. The resistivity of fibers heat-treated at higher temperatures decreases with the operating temperature. At the most elevated temperatures, the resistivity of the VGCFs approaches that of single crystal graph-

resistivity with fiber diameter across is ascribed to the expanded arranged graphite

The thermal conductivity of VGCFs is astoundingly high [31]. The thermal conductivity of both s-grown VGCFs and the other VGCFs heat-treated to 3000°C were evaluated through a temperature range of 10–300 K. It was demonstrated that

ohm cm at 300 K. Besides, the decrease in

**8. Properties of VGCFs**

**8.1 Mechanical properties**

300–1200GPa [33, 34].

connected to their structure.

failure, than thinner ones.

**8.2 Electrical properties**

ite, with a resistivity of about 5 × 10<sup>−</sup><sup>7</sup>

regions as the diameter increases.

**8.3 Thermal properties**

500 GPa when they were heated at 2200°C [30].

**56**

In recent times, there has been a developing enthusiasm for the utilizations of VGCF in carbon and polymer matrix composites. The primary thermoplastic submicron-size VGCF composites, utilizing polycarbonate and nylon as a matrix was reported [36]. The growing mechanical and thermal properties were calculated with fiber volume fraction, despite the fact that this increase is less than could be theoretically expected. The composites were compression molded utilizing a straightforward set-up bringing about a fiber arrangement that was believed to be irregular in three dimensions. It was anticipated higher properties if a process like injection molding was utilized to stimulate fiber alignment.

The process ability of submicron VGCFs in thermoplastic matrices was analyzed by extruding polycarbonate-VGCF composites in a single screw extruder and subsequently melt-drew the composites to induce fiber orientation. It was concluded that the dispersion of the fibers in the matrix was very poor at 2 vol% fiber fraction and turned out to be much less fortunate when the fiber content was expanded to 5 vol%. It was recommended that grinding or melt-blending the fiber with the polymer before extrusion may bring better result in better dispersion.

The utilization of submicron VGCFs as arbitrary layers between layers of ceaseless carbon fibers in an epoxy matrix was studied [43] and it was found that the VGCFs improve appreciably the damping capacity of the composites at fiber fractions as low as 0.6 vol%.

The utilization of VGCFs for fabricating thin paper was made effectively by supplanting the generally utilized commercial chopped ex-PAN and ex-pitch fibers to acquire planar isotropy [44].

Submicron VGCFs were used in cement-matrix composites, an application wherein they could be amazingly valuable, because of the relative minimum cost and simple process ability [41]. With a fiber heap of just 1.5 vol%, they accomplished the most noteworthy electromagnetic interference (EMI) shielding effectiveness ever achieved for a cement-matrix composite.

Composites based on VGCF-mats were made and heat-treated at 2800°C and their thermal conductivity was studied [45]. It was acquired that the 36 vol% composite exhibited a room-temperature thermal conductivity of 564 W/mK. This value is some extent higher than that of copper (+/− 450 W/mK) and it was ascribed to the greatly graphitic nature of the VGCF mats.

Aluminum matrix and carbon-carbon composites based on VGCFs were fabricated and compared [46]. For the aluminum-VGCF composites at 36.5 vol% the thermal conductivity of 642 W/mK was found. An outstanding value of 910 W/mK was observed for a 70 vol% carbon-VGCF composite which is double the value of copper.


#### **Table 1.**

*Basic properties of submicron VGCFs [48].*

The mechanical properties of VGCF-carbon composites was studied and arrived the result that the tensile properties of these composites are lower than anticipated It was concluded that the thermal properties of VGCFs are preferred and converted into composites.

#### **9.2 Application in batteries**

The fibers acquired by the floating reactant method have a thin diameter distribution (from 0.1 to 0.2 mm), indicating nearly a similar morphology when contrasted with that of normal VGCFs (10–20 mm), which comprise of a central filament and an external deposit of pyrolytic carbon with the annular structure of a tree. Moreover, these fibers have a high possibility for application as filler in composites and as an anode material in lithium ion batteries, including additives to anode materials, because of incredible conductivity and high surface to volume ratio.

For s-VGCFs acquired by a floating reactant technique, the fundamental properties and micro structural development of these fibers with Heat Treatment Temperature (HTT), the physical properties of a solitary fiber and in the massive state were assessed to apply this material as the filler in electrodes of lead acid batteries and in the Li-ion battery system. Graphitized s-VGCFs showed attractive desirable properties when utilized as filler in electrodes, for example, genuinely high mechanical strength and electrical conductivity in a single fiber, a high degree of resiliency and good volume conductivity in the bulky state. These desirable properties should yield improved execution performance in actual batteries (**Table 1**) [47, 49–51].

### **10. Conclusion**

Vapor grown carbon fiber composites for batteries and supercapacitors have been extensively studied worldwide. The CNFs and their composites can be utilized in numerous fields; they have unique mechanical, electrical and thermal properties that may be useful in making composite materials like polycarbonate-VGCF, epoxy-VGCF, PAN-VGCF and aluminum-VGCF and filler in electrodes of lead-acid batteries and the Li-ion battery system.

**59**

**Author details**

J. Manivannan1

Karur, Tamilnadu, India

India

, S. Kalaiselvan1

provided the original work is properly cited.

\* and R. Padmavathi<sup>2</sup>

1 Department of Chemistry, SNS College of Technology, Coimbatore, Tamilnadu,

© 2020 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

2 Department of Chemistry, M. Kumarasamy College of Engineering,

\*Address all correspondence to: kalaichem82@gmail.com

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

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

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

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

**s-VGCFsa**

 Lattice constant 6.900 A 6.775 A XRD Diameter of fiber 0.2 mm 0.2 mm SEM Length of fiber 10–20 mm 10–20 mm SEM Volume density 0.02–0.07 g/cm3 0.02–0.07 g/cm3 Tapping Real density 1.9 g/cm3 2.1 g/cm3 Pycnometer

7 Ash content 1.5% 0.03% SDK 8 pH 5 7 PH Meter

**Graphitized s-VGCFsb**

550°C 650°C TGA

/g 15 m2

**Method needed for characterization**

/g N absorption

**S.No Properties Carbonized** 

6 Surface area (BET) 37 m2

oxidation

*Carbonized s-VGCFs indicate the sample heat treated at 1200°C.*

*Graphitized s-VGCFs indicate the sample heat treated at 2800°C.*

9 Starting temperature of

*Basic properties of submicron VGCFs [48].*

The mechanical properties of VGCF-carbon composites was studied and arrived the result that the tensile properties of these composites are lower than anticipated It was concluded that the thermal properties of VGCFs are preferred and converted

The fibers acquired by the floating reactant method have a thin diameter distribution (from 0.1 to 0.2 mm), indicating nearly a similar morphology when contrasted with that of normal VGCFs (10–20 mm), which comprise of a central filament and an external deposit of pyrolytic carbon with the annular structure of a tree. Moreover, these fibers have a high possibility for application as filler in composites and as an anode material in lithium ion batteries, including additives to anode materials, because of incredible conductivity and high surface to volume ratio. For s-VGCFs acquired by a floating reactant technique, the fundamental properties and micro structural development of these fibers with Heat Treatment Temperature (HTT), the physical properties of a solitary fiber and in the massive state were assessed to apply this material as the filler in electrodes of lead acid batteries and in the Li-ion battery system. Graphitized s-VGCFs showed attractive desirable properties when utilized as filler in electrodes, for example, genuinely high mechanical strength and electrical conductivity in a single fiber, a high degree of resiliency and good volume conductivity in the bulky state. These desirable properties should yield improved execution performance in actual batteries (**Table 1**) [47, 49–51].

Vapor grown carbon fiber composites for batteries and supercapacitors have been extensively studied worldwide. The CNFs and their composites can be utilized in numerous fields; they have unique mechanical, electrical and thermal properties that may be useful in making composite materials like polycarbonate-VGCF, epoxy-VGCF, PAN-VGCF and aluminum-VGCF and filler in electrodes of lead-acid

**58**

into composites.

*a*

*b*

**Table 1.**

**10. Conclusion**

batteries and the Li-ion battery system.

**9.2 Application in batteries**
