Single-walled nanotubes (SWNTs) possess exceptional mechanical, electrical and thermal properties due to their nanoscale dimension and unique chemical structure. Particularly, SWNTs are considered the most promising reinforcement materials for high performance structural composites and multifunctional materials. However, due to the nanoscale dimension and intensive van der Waals interactions of the nanotubes, nanocomposites made by directly and randomly mixing SWNTs with polymer resin have poor tube dispersion, low tube loading and lack nanotube orientation. Therefore, conventional methods of producing nanocomposites fail to realize anticipated properties. Our research has developed a new technical approach using magnetically aligned nanotube buckypaper and resin infiltration for producing bulk nanostructured composites with desirable in-plane aligned SWNTs. Magnetically aligned nanotube buckypapers are thin membranes of aligned tube networks with a thickness of 15-30µm, which are produced by filtrating well-dispersed SWNT suspensions under high magnetic fields. These buckypapers can be impregnated by epoxy resin, stacked in multiple layers and cured to make nanostructured materials with desirable tube orientation. By using this method, the tube dispersion and alignment in the buckypaper can be successfully transited into final solid and bulk composites. The resultant composites have controlled in-plane tube orientation and high tube loading. In this paper, the effects of surfactant, tube concentration in suspension, dispersion method and strengths of magnetic field on the nanostructures and electrical properties of the resultant buckypapers are presented. Using this technique at the National High Magnetic Field Laboratory has produced buckypapers as large as 387 cm2 (60 in2), which are the world's largest aligned buckypapers. Examining the buckypapers using an atomic force microscope and scanning electronic microscope revealed significant tube alignment and uniform nanostructures. Nanocomposites with controlled in-plane orientation of purified SWNTs have been fabricated in the research. Dynamic mechanical analysis shows the tensile storage modulus of these composites is as high as 40.5 GPa. These results demonstrate that the proposed technical approach is an effective method to produce bulk composites with controlled in-plane SWNT orientation.
Department of Industrial & Manufacturing Engineering
Florida A&M University-Florida State University College of Engineering
2525 POttsdamer St.
Tallahassee, FL 32310-6046 USA
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