Aligning vapor-grown carbon fibers in polydimethylsiloxane using dc electric or magnetic field

Abstract A trace amount of vapor-grown carbon fibers (VGCFs), which, as received, had an aggregated lump form, was completely dispersed in polydimethylsiloxane, a nonpolar viscous liquid, at room temperature by mechanical stirring. Using this uniformly dispersed sample as a starting material, a dc electric or magnetic field was applied to induce the formation of an aligned structure. In situ transmission optical microscopy was carried out to observe the structural development of VGCFs in polydimethylsiloxane under the dc electric or magnetic field, which was applied both parallel and perpendicular to the observation direction. Upon application of a dc electric field, an aligned ramified network structure of VGCFs developed between the electrodes. In the formation of the network structure, ends of VGCFs became connected to ends of other VGCFs, which was followed by rotation and orientation of the VCGFs. On the other hand, upon application of a magnetic field, the VGCFs were only rotated, without the formation of a network. The electric resistivity of the network structure was evaluated. Additionally, the influence of the viscosity of the polydimethylsiloxane matrix on the structural formation process was examined.