Fabrication of Ultrafine Carbon Fibers Possessing a Nanoporous Structure from Electrospun Polyvinyl Alcohol Fibers Containing Silica Nanoparticles

Abstract

Ultrafine carbon fibers with a nanoporous structure were fabricated by the template method using silica nanoparticles (NPs) embedded in fibers of approximate diameter 500 nm, electrospun from an aqueous solution of polyvinyl alcohol,CoCl2, silica NPs, andN,N-dimethylformamide. Black, conductive fibers were obtained by heat treatment in air and a chemical vapor deposition reaction under methanol vapor for more than 5 h. Transmission electron microscopy (TEM) demonstrated that the fabricated fibers after silica removal had a porous structure originating from 15 nm diameter silica NPs. Energy dispersive X-ray analysis combined with TEM confirmed the removal of silica from the fibers by NaOH treatment at 80°C. Total surface area and total pore volume of the fibers after silica removal, determined by nitrogen adsorption measurement, were 318 m2/g and 1.67 cm3/g, respectively. The sheet resistivities of the fabricated fibers were 35.1–477 Ω/□, which were relatively high, compared with that reported for polyacrylonitrile-based fibers carbonized at 800°C. D and G bands detected in the Raman spectrum of the NaOH-treated fibers showed that the prepared carbon fibers were more crystalline than natural carbonaceous materials.