Poly（vinyl pyrrolidone）（PVP）/Fe 3O 4 composite nanofibers were successfully prepared by using electrospinning technique.The composite nanofibers were characterized by means of TEM（transmission electron microscopy）,XRD（X-ray diffraction）and TGA（thermogravimetric analysis）.Transmission electron microscope images of the PVP/Fe3O4 nanofibers show that the Fe3O4 nanoparticles with a diameter about 10.5 nm were dispersed in PVP fiber matrices.The XRD results show that the particles in PVP fibers were indeed Fe3O4 nanoparticles.And the TGA of PVP/Fe3O4 nanofibers show that the content of Fe3O4 nanoparticles in the composite was about 36.8%（mass fraction）.The PVP/Fe3O4 nanofibers were found to be superparamagnetic.The hysteresis loop at room temperature showed a high saturated magnetization（M s=15.1 emu/g）and a low coercive force（μ c=0）.
The preparation and formation mechanism of silica/polyvinylpyrrolidone（PVP）-polyacrylonitrile（PAN） coaxial nanofibers were presented in this paper. The PVP-PAN composite nanofibers were obtained via an electrospinning technique, while SiO2 nanoparticles were prepared according to a Stber method. The measurements of water contact angle（WCA）, the compared results of silica coating PVP-PAN composite nanofibers with PAN nanofibers indicate that much PVP resided on the composite nanofiber surface, which results in the occurrence of SiO2@polymer coaxial nanofibers due to the formation of hydrogen bonding between silica and composite nanofibers and subsequent adsorption of silica on the fiber surface.
