Synthesis of Helical Carbon Fibers and Related Materials: A Review on the Past and Recent Developments

Abstract

Helical carbon fibers (HCFs) have been widely studied due to their unique helical morphology and superior properties, which make them efficient materials for several potential applications. This review summarizes the past and current advancement on the synthesis of HCFs. The review focuses and discusses synthesis strategies and effect of experimental parameters on the growth of HCFs. The effect of preparation method of catalyst, catalyst nature, catalyst composition, catalyst size, catalyst initial and final shape, reaction temperature, reaction time, carbon source, impurities, and electromagnetic field on the growth of HCFs is reviewed. We also discuss the growth mechanism for HCFs and the synthesis of HCFs related materials. Finally, we conclude with a brief summary and an outlook on the challenges and future prospects of HCFs.

Keywords: catalyst particle; composite material; growth mechanism; helical carbon fibers (HCFs); synthesis.

Figure 1

Schematic representations of carbon nanofibers (CNFs): (A) “platelet”; (B) “herringbone”; and (C) “tubular” ([6], Rodriguez et al., 1995).

Figure 2

Various morphologies of carbon fibers: (A) double-helix regular circular carbon coils ([7], Motojima and Chen, 1999); (B) regularly ribbon-like flat coiled carbon fibers ([13], Motojima et al., 1995); (C) nanobraids (together with a carbon nanofiber) ([14], Liu et al., 2003); and (D) intertwined carbon fibers with symmetrical growth mode and centrally located Cu catalyst particle ([15], Shaikjee et al., 2011).

Figure 3

Schematic illustration for fiber diameter, coil diameter, and coil pitch ([16], Shaikjee and Coville, 2012).

Figure 4

Representative carbon coils growing vertically on the substrate ([7], Motojima and Chen, 1999).

Figure 5

Microstructure of a catalyst nanoparticle located at the node of HCNFs; (a) transmission electron microscopy (TEM) image; (c) high resolution transmission electron microscopy (HRTEM) image; (b, d, and e) magnified images of areas marked in Figure 5(c), respectively ([57], Tang et al. 2006).

Figure 6

Effect of reaction temperature on the coil diameter: (a) regular carbon coils with small coil diameter, reaction temperature 750 °C; and (b) carbon coils with larger coil diameter and slightly irregular forms, reaction temperature 820 °C ([60], Chen and Motojima, 1999).

Figure 7

Growth stages of carbon coils. Reaction time: (a) 5 min; (b) 10 min; (c) 15 min; (d) 30 min; (e) 60 min; and (f) 120 min ([112], Chen and Motojima, 1999).

Figure 8

TEM images of (a) HCNFs and (b) Palladium nanoparticle decorated HCNFs (inset: HRTEM of Pd-HCNFs) ([77], Jia et al. 2013).

Figure 9

(A) Simplified scheme for the growth mechanism of HCF: (a) Ni compound seed (single crystal) on tip part of pair-HCF, (b) growth mechanism of pair-HCF; and (B) growth process of pair-HCF ([113], Kawaguchi et al., 1992).

Figure 10

(A) carbon coils during the initial growth stage;and (B) an enlarged view. Arrow indicates a Ni catalyst grain, X and Y: paired coils, A, B, C, A’, B’, C’: carbon fibers grown from a Ni catalyst grain (arrow); (C) Postulated Ni catalyst grain. a‒h: cubic Ni grain embedded in a node of six fibers; (D) 3D growth model of the carbon coils. A‒C: three crystal faces, order of the catalytic activity for the carbon deposition: A > B > C ([7], Motojima and Chen, 1999).

Figure 11

3D model for thegrowth mechanism of coiled carbon nanofibers ([59], Wen and Shen, 2001).