Electrospinning of Carbon Nanotube Reinforced Nanocomposite Fibrils and Yarns
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Electrospinning of Carbon Nanotube Reinforced Nanocomposite Fibrils and Yarns Hoa Lam, Nick Titchenal, Nevin Naguib, Haihui Ye, Yury Gogotsi and Frank Ko Drexel University, Department of Materials Science and Engineering and A. J. Drexel Nanotechnology Institute Philadelphia, PA 19104, U.S.A. ABSTRACT Single wall (SWNT) and multi-wall carbon nanotubes (MWNT) were electrostatically assembled into nanofibers through an electrospinning process in order to increase the strength and toughness of polyacrylonitrile (PAN)-derived carbon fibers. It was found that the effectiveness of carbon nanotubes (CNT) in reinforcing the PAN precursor is highly dependent on the dispersion and the alignment of the CNT. Alignment was achieved during electrospinning by the flow of polymer, electrostatic charge and diameter confinement. Up to 10 wt. % SWNT coelectrospun with PAN was successfully produced with fiber diameters in the range of 40 nm to 400 nm. With the addition of 1 wt. % SWNT, a two-fold increase in strength and modulus was obtained in the as-spun nanofibers mat. These encouraging results show a promising pathway to produce the next generation of high performance carbon fibers that will help bridge dimensional and properties gap between nanoscopic and macroscopic structures. INTRODUCTION With a tensile modulus of close to 1 TPa and a breaking strength of 37 GPa at a breaking elongation of almost 6 % [1, 2], CNTs promise to be an important basic building block for a new class of engineering materials that will have far reaching impact on the next generation of advanced products ranging from aerospace vehicles, to surgical implants, to micro and nanoelectronic components. In spite of these promising characteristics, the translation of these superior properties to the meso and macro structural levels has not yet been achieved [3]. This can be attributed to the unique dimensional and surface characteristics of the CNT that affect, concomitantly, the performance and processability of CNT structures. With a diameter of 1 nm and length of 1-2 µm, the SWNT has a high aspect ratio and an enormous amount of available specific surface area for mechanical bonding to the matrix in a composite. However, the fineness of the SWNT promotes agglomeration and formation of un-oriented ropes which prevents full translation of properties. Attempts have also been made to form aligned CNT composites [4], but no significant translation of the CNT properties has been achieved. This is due, in part, to the inert nature of the CNT surface resulting in a weak interface between the CNT and the matrix, and thus leading to poor translation of strength and modulus from the CNT to the composite structure. In order to maximize the translation of properties to higher order structures, there is a need for a family of processable CNT carrier media, preferably in the form of continuous filaments that will allow for well-controlled alignment and tailored distribution of the CNTs within a structure. Accordingly, our goal is to establish a robust manufacturin
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