SiC nanofibers by pyrolysis of electrospun preceramic polymers

Abstract

Silicon carbide (SiC) nanofibers of diameters as low as 20 nm are reported. The fibers were produced through the electrostatic spinning of the preceramic poly(carbomethylsilane) with pyrolysis to ceramic. A new technique was used where the preceramic was blended with polystyrene and, subsequent to electrospinning, was exposed to UV to crosslink the PS and prevent fiber flowing during pyrolysis. Electrospun SiC fibers were characterized by Fourier transform infrared spectroscopy, thermo gravimetric analysis-differential thermal analysis, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and electron diffraction. Fibers were shown to be polycrystalline and nanograined with β-SiC 4H polytype being dominant, where commercial methods produce α-SiC 3C. Pyrolysis of the bulk polymer blend to SiC produced α-SiC 15R as the dominant polytype with larger grains showing that electrospinning nanofibers affects resultant crystallinity. Fibers produced were shown to have a core–shell structure of an oxide scale that was variable by pyrolysis conditions.