Effect of growth of carbon nanofibers on the electrical conductivity of carbon fibers

Abstract

Recently, research on various carbon materials such as carbon fibers (CFs), carbon black (CB), carbon nanofibers (CNFs), carbon nanotubes (CNTs), fullerenes, and graphene has received considerable attention. In particular, CFs that exhibit a graphite-layered structure have a strong structural anisotropy, and the alignment of CFs along the direction of an applied electrochemical application field (antistatic material, electromagnetic interference shielding material, sensing elements, heating elements, and packing of electronic components and equipment) has been attempted by utilizing their mechanically strong, durable and electrically conductive properties. Most recently, there have been many studies of the improvement of electrical conductivity of CFs. Its electrical conductivity strongly depends on the thermal treatment, microtexture, hybridization, surface treatments, content of heteroatoms, length. A number of studies have shown that the various methods for the enhancement of electrical conductivity of CFs such as plating with conductive metals electrochemical or plasma oxidation, fluorination, and the growth of carbon nanomaterials on its surfaces, etc. For example, Park et al. prepared the activated carbon fibers (ACFs) coated with CNFs for enhancement electrical conductivity of ACFs due to the CNFs have unique electrical properties. Jiang et al. reported that the use of Ag as a metallic film is coated onto the surface of chopped CFs or ACFs to increase the conductivity of conductive fillers. Zeng et al. synthesized the CNTs on CFs substrate by the floating catalyst method for field electron emission material. The catalytic chemical vapor deposition (CCVD) was a most common method for the synthesis of carbon nanomaterials on the different substrates. However, there are some problems in the synthesis of carbon nanomaterials (CNFs or CNTs) on CF surfaces by CCVD method: (a) the ununiformly dispersed-metal catalysts (such as Fe, Ni, and Co catalyst) on CF surfaces due to its low specific surface area; (b) the metal catalysts were easily diffused into the CFs; (c) the metal catalysts were easily aggregated into large particles and formed mixed phases of carbon materials (CNFs, CNTs, and amorphous carbon); (d) the products require the purity process. So, the uniform dispersion of catalysts is a critical process to get uniformly grown CNFs on CF surfaces. As few research reported, the mesoporous silica films are excellent catalyst supports and have been used in the growth of carbon nanomaterials. Zheng et al. reported that ordered meso silica films can direct the growth of CNTs from perpendicular to parallel to the substrate surface through control of the distribution of catalysts. In this work, we have synthesized CNFs on CF surfaces by using Ni-doped mesoporous silica film at different temperatures, and the density of CNFs on CF surfaces is uniform and densely. The Ni-doped mesoporous silica film was used to control the distribution of catalysts on CF surfaces. We examined the microstructure of CNFs coated CFs, physical properties, electrical conductivity, of the paper.