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Unformatted text preview: Effect of single-walled carbon nanotube purity on the thermal conductivity of carbon nanotube-based composites Aiping Yu, Mikhail E. Itkis, Elena Bekyarova, and Robert C. Haddon a ! Center for Nanoscale Science and Engineering, University of California, Riverside, California 92521-0403; Department of Chemistry, University of California, Riverside, California 92521-0403; and Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521-0403 s Received 6 July 2006; accepted 4 August 2006; published online 25 September 2006 d Raw f as-prepared s AP dg and purified single-walled carbon nanotubes s SWNTs d were utilized for the preparation of SWNT-epoxy composites. Purified functionalized SWNTs provide a significantly greater enhancement of the thermal conductivity, whereas AP-SWNTs allow the best electrical properties because of their ability to form efficient percolating network. A series of SWNT samples of varying purity but identical chemical functionality was prepared to delineate the effect of SWNT purity on the thermal conductivity of SWNT-epoxy composites. The authors found that purified SWNTs provide approximately five times greater enhancement of the thermal conductivity than the impure SWNT fraction demonstrating the significance of SWNT quality for thermal management. © 2006 American Institute of Physics . f DOI: 10.1063/1.2357580 g The outstanding thermal and mechanical properties of carbon nanotubes s CNTs d offer the possibility of a new gen- eration of thermal interface materials s TIMs d for thermal management of high density electronics. The thermal con- ductivity of individual CNTs s up to 3000 W/mK d 1 is signifi- cantly higher than that of traditionally utilized fillers, such as alumina, silver, copper, carbon black, and carbon fibers. Moreover, CNTs provide a more efficient network for heat flow inside the polymer matrix because of their high aspect ratio. 2 Several groups have studied the thermal properties of single-walled carbon nanotube s SWNTs d-based composite materials 3–8 and some of the publications report an enhance- ment of the thermal conductivity of over 100% per 1 wt % of CNT loading, 3,4,7 although in some cases no enhancement was observed. 6 Intrinsic to the performance of SWNT-based composites are the quality of dispersion of SWNTs in the polymer matrix, SWNT loading, conformation and align- ment, and the thermal resistance of the SWNT/matrix interface. 3–11 While these intrinsic variables are extremely important, we found that an extrinsic factor—the SWNT purity—remains critical in defining the thermal performance of SWNT/epoxy composites. In this letter we present a sys- tematic study of the effect of the purity of the SWNT mate- rial on the thermal performance of SWNT-based composites....
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