Electrostatic Spinning, Pyrolysis, and Characterization of Boron Carbide Nanofibers Prepared from Poly(norbornenyldecabo
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Electrostatic Spinning, Pyrolysis, and Characterization of Boron Carbide Nanofibers Prepared from Poly(norbornenyldecaborane) - a Polymeric Ceramic Precursor Daniel T. Welna1, Xiaolan Wei2, Jared D. Bender1, Nick R. Krogman1, Larry G. Sneddon2, Harry R. Allcock1* 1 Department of Chemistry, The Pennsylvania State University, University Park, PA 16802, USA 2 Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104, USA ABSTRACT Electrostatic spinning is a well-developed technique for the fabrication of fibers in the nanoscale domain. Novel boron carbide nanofibers were generated by the electrostatic spinning and ceramic conversion of poly(norbornenyldecaborane) (PND) - a polymeric ceramic precursor. The prepyrolyzed fibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. The ceramic fibers were characterized by SEM, X-ray diffraction (XRD), 11B magic-angle spinning nuclear magnetic resonance (MAS NMR) and DRIFT spectroscopy. SEM analysis showed retention of the nanostructure in the pre- and postpyrolyzed fibers. INTRODUCTION Nanostructured materials have received much attention due to their unique properties and superior performance compared to their bulk counterparts [1]. Specifically, nanofibers fibers have become an area of intense research because of their application to ceramic matrix composites (CMCs). By combining the high tensile strengths and strain to failure of fine fibers with the advantageous properties of ceramics, their high heat and wear resistance, hardness and compressive strength, advanced CMCs can be fabricated for aeronautical and space applications [2]. An early method used in the fabrication of ceramic fibers employed chemical vapor deposition (CVD) techniques onto a support substrate, which was typically tungsten or carbon. Applications of CVD are severely limited because of its costly nature and small scale production capabilities. The sintering of sol-gel precursors has also been utilized in the production of titania, alumina, and silica-based oxide ceramic fiber systems. Melt-spinning of polycarbosilane followed by pyrolysis has been shown with great success to generate silicon carbide fibers, known as Nicalon® [3]. Novel templating methods are currently under investigation, which are able to produce nanoscale boron carbide fibers from a polyhexenyldecaborane polymeric ceramic precursor [4]. Recently, electrostatic spinning techniques have been shown to readily yield fine fibers with controlled morphologies and diameters with many different types of polymeric systems on a large scale [5-8]. Electrostatic spinning works by generating a solid fiber from an electrified jet of a highly viscous polymeric solution. The solid fiber is continuously stretched by electrostatic repulsions between the surface charges and the evaporation of the solvent [9]. Electrostatic spinning has recently been utilized to produce materials for composite reinforcement applica
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