Purification of SWNTs Using Microwave Heating
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Purification of SWNTs Using Microwave Heating Avetik R. Harutyunyan1, Bhabendra K. Pradhan1, Gamini U. Sumanasekera, Jiping Chang2, Gugang Chen1, H. Goto3, J. Fujiwara3 Peter C. Eklund1 1 Dept. of Physics, 104 Davey Laboratory, 2Materials Research Laboratory, The Pennsylvania State University, University Park, Pennsylvania 16802, USA 3 Honda R&D Co., Ltd. Wako Research Center, Saitama 351-0193, Japan ABSTRACT A new method for purifying single wall carbon nanotubes (SWNTs) using microwave heating is developed. The microwaves couple to the residual metal catalyst, raising significantly the local temperature leading to both the oxidation and rupturing of the carbon passivation layer over the metal catalyst particles and sintering. With this protective carbon coating weakened or removed, a mild acid treatment in HCl is then sufficient to remove most of the metal in the sample, leaving the nanotubes in tact. Results from transmission and scanning electron microscopy (TEM & SEM), Raman spectroscopy and thermo-gravimetric studies are discussed. INTRODUCTION Single wall carbon nanotubes (SWNTs) were first reported in the products of an electric arc in 1993 by research scientists in NEC-Tsukuba [1] and IBM-Almaden [2], and later produced in much more significant quantities and higher purity by pulsed laser vaporization at Rice University [3]. Most of synthesis methods today produce tubes in the diameter range 0.5-2 nm, and they are arranged in bundles of 10-100s of tubes. SWNTs are often a minority constituent (
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