Fibers of Carbon Nanotubes
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Fibers of carbon nanotubes
Brigitte Vigolo, Pascale Launois1, Marcel Lucas1, Stéphane Badaire, Patrick Bernier2, Philippe Poulin Centre de Recherche Paul Pascal / CNRS, Université Bordeaux I, Avenue Schweitzer, 33600 Pessac, France 1-Laboratoire de Physique des Solides (UMR CNRS 8502), bât. 510, Université Paris-Sud, 91405 Orsay, France 2-GDPC, Université de Montpellier II, 34095 Montpellier, France ABSTRACT We briefly review some methods recently proposed to make films and fibers of preferentially oriented carbon nanotubes. We discuss in more detail a simple spinning process which consists in dispersing the nanotubes in a surfactant solution, re-condensing the nanotubes in the flow of a coagulating polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. We measure the mechanical properties of the obtained fibers and characterize the nanotube alignment along the fiber axis by X-ray scattering experiments. We show that the alignment can be improved by stretching the fibers under well-defined conditions. This allows the Young’s modulus to be increased by a factor 4, leading thereby to materials forty times stronger than high-quality buckypaper. We believe that these improved fibers can already be potentially useful as functional materials. A simple example of electromechanical actuation is shown. INTRODUCTION Single wall carbon nanotubes (SWNTs) are considered as very promising systems to make functional materials [1-3]. Unfortunately, as produced nanotubes are under the form of a light, fragile and isotropic soot [4,5]. This soot is of rather difficult use and far from being optimized. Processing and assembling nanotubes on macroscopic scales to obtain materials of more practical use is thus an important issue. Thin mat, known as bucky paper, can be obtained by drying SWNTs suspensions onto membrane filters [6]. Although classical bucky papers are almost isotropic, they are widely used to characterize the properties of nanotubes on macroscopic scale and to make functional systems mostly comprised of nanotubes [7]. We do not consider in this paper composite materials that include only a relatively small fraction of nanotubes, generally embedded in polymeric matrices. Recent progresses have shown the possibility to make films of aligned nanotubes by using high magnetic fields [8-10] and to make fibers of aligned nanotubes by using an electrophoretic process [11,12] or by directly spinning an aqueous suspension [13]. We briefly review in this paper the two first processes and focus on the fibers obtained by the last spinning process. This method consists in dispersing the nanotubes in a surfactant solution, re-condensing the nanotubes in the flow of a coagulating polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. We measure the mechanical properties of obtained fibers and characterize the nanotube alignment along the fiber Z1.4.1
axis by X-ray scattering experiments. The alignment can be improved by stretching the fibers under well-defined c
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