The Structure and ferromagnetism of carbon nanofibers from polyacrylonitrile/ polyvinylpyrrolidone

Abstract

Room-temperature ferromagnetism was successfully induced in carbon. Carbon nanofibers were fabricated using sequential electrospinning of polyacrylonitrile (PAN) and polyvinylpyrrolidone (PVP). The morphologies, crystal structures, chemical bonding states and magnetic properties were characterized over three different weight ratios which were 10:0, 7:3 and 6:4 of PAN/PVP. The carbon nanofibers obtained after pyrolysis of polymer fibers were placed inside a tube furnace using a three steps process: stabilization, carbonization, and activation at 800℃. XRD patterns indicated the amorphous structure of carbon. The average diameter of the carbon nanofibers was between 340 nm to 511 nm. Raman analysis was used to determine the carbon qualities in the samples by the numbers of sp3/sp2 hybridized atoms. The chemical analysis obtained XPS indicated that there were no magnetic contaminants. The PAN/PVP weight ratio of 6:4 showed ferromagnetic carbon nanofibers with the highest specific saturation magnetization as ~144.2 m-emu×g-1 at 300 K. This indicated that the mixing of sp2-sp3 carbon system had localized magnetic moments. This finding suggests an inexpensive method for preparing magnetic particles and human-friendly ways to produce magnetic material without metals. These results inspire us to further research on the potential of carbon materials, as a completely new class of magnetic devices.