Nanoscale carbon blacks produced by CO 2 laser pyrolysis
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M. Jagtoyen Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40511-8433
M. Endo Faculty of Engineering, Shinshu University, Nagano-city 380, Japan
K. Das Chowdhuryb) Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
R. Ochoa and F. J. Derbyshire Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40511-8433
M.S. Dresselhaus Department of Electrical Engineering and Computer Science and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
P.C. Eklund Center for Applied Energy Research, University of Kentucky, Lexington, Kentucky 40511-8433 and Department of Physics and Astronomy, University of Kentucky, Lexington, Kentucky 40506 (Received 16 February 1995; accepted 30 June 1995)
CO2 laser pyrolysis has been used to synthesize carbon black (particle diameter —30 nm) via a catalytically driven pyrolysis of benzene vapor. The H: C ratio is found to be ~1 :10, which is unusually high for carbon blacks. Subsequent heat treatment of the "laser black" to temperatures up to —2800 °C produces well-graphitized faceted particles with central polygonal cavities. High resolution TEM lattice imaging, Raman scattering, and x-ray diffraction have been used to characterize the morphological structure of these carbon particles in their as-synthesized and heat-treated forms. Furthermore, KOH treatment at —800 °C has been employed to activate the as-synthesized particles, producing a tenfold increase in the surface area from 50 to 700 m 2 /g. Possible pore structures generated during this activation process have been identified by high resolution TEM imaging.
I. INTRODUCTION Classical carbon blacks represent many morphological forms of finely divided carbon-based particles with diameters in a typical range of 10-100 nm. They are often produced by hydrocarbon dehydrogenation with, or without, the assistance of a catalyst.1 They have been studied, and widely used as a filler to modify the mechanical, electrical, and optical properties of the host material (e.g., rubber tire).2 Different types of industrial carbon blacks have been given names that in many cases are derived from the processes by which they are prepared. For example, "thermal blacks" were proa) Present
address: International Center for Materials Research, 750 Enterprise Dr., Lexington, Kentucky 40511. b) Present address: Intel Corp., 4100 Sara Rd., Rio Rancho, New Mexico 87124. J. Mater. Res., Vol. 10, No. 11, Nov 1995 http://journals.cambridge.org
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duced by thermal decomposition of natural gas, "channel blacks" by partial combustion of natural gas, "acetylene blacks" by exothermic decomposition of acetylene, "furnace blacks" by partial combustion of oil droplets, and "plasma blacks" by decomposition of ethylene in a plasma arc.1 On a laboratory bench scale, carbon blacks have also been prepared by special processes such as laser ablation of graphite,3 CO 2 laser pyrolysis of a
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