Electrically conductive composites via infiltration of single-walled carbon nanotube-based aerogels
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Electrically conductive composites via infiltration of single-walled carbon nanotube-based aerogels Marcus A. Worsley*, Joshua D. Kuntz, Sergei O. Kucheyev, Alex V. Hamza, Joe H. Satcher, Jr. and Theodore F. Baumann Physical and Life Sciences Directorate, Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550 AUTHOR EMAIL ADDRESS: [email protected] ABSTRACT Many challenges remain in the effort to realize the exceptional properties of carbon nanotubes (CNT) in composite materials. Here, we report on electrically conductive composites fabricated via infiltration of CNT-based aerogels. The ultra lowdensity, high conductivity, and extraordinary robustness of the CNT aerogels make them ideal scaffolds around which to create conductive composites. Infiltrating the aerogels with various insulating materials (e.g. epoxy and SiO2) resulted in composites with electrical conductivities over 1 Scm-1 with as little as 1 vol% nanotube content. The electrical conductivity observed in the composites was remarkably close to that of the CNT scaffold in all cases. INTRODUCTION Carbon nanotubes (CNTs) possess a number of intrinsic properties that have made them promising candidates for a range of composite materials. CNTs can have electrical conductivities [1] as high as 106 Sm-1, thermal conductivities [2] as high as 3000 Wm-1K-1, elastic moduli [3] on the order of 1 TPa, and are extremely flexible [4]. Unfortunately, the realization of these properties in macroscopic forms such as composites [5-13] has been limited. With polymer/CNT composites, though adding as little as 0.007 wt% CNTs can achieve a measurable increase in electrical conductivity [6], typically to reach conductivities >1 S cm-1 much larger quantities of CNTs (>10 wt%) are required [7-10]. This makes it an expensive endeavor to create polymer composites with conductivities on par with highly conductive semiconductors and metals for applications such as electromagnetic interference shielding [14]. Only recently have loadings of 1 S cm-1 [15]. However, this level of conductivity was achieved with specially-prepared multi-walled CNTs, and attaining high conductivity composites with commercial single-walled CNTs (SWNTs) remains a serious challenge. An additional obstacle to fabricating composites is that the method for dispersing CNTs tends to vary greatly depending on the matrix material [12, 13, 16-19]. With a mechanically robust, electrically conductive CNT foam, one could imagine simply infiltrating this low-density CNT scaffold with the matrix material of choice, yielding a conductive composite. This would generalize the fabrication process for making CNT composites and keep the amount of CNTs used to a minimum.
We recently reported the synthesis of ultralow-density SWNT-based aerogel nanofoam (SWNT-CA) monoliths with exceptional electrical and mechanical properties [20]. These SWNT-CAs simultaneously exhibited increased stiffness, and high electrical conductivity even at densities approaching 10 mg cm-3 without reinforcem
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