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EBSD Analysis of Tungsten-Filament Carburization During the Hot-Wire CVD of Multi-Walled Carbon Nanotubes

Published online by Cambridge University Press:  15 January 2014

Clive J. Oliphant*
Affiliation:
Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa National Metrology Institute of South Africa, Private Bag X34, Lynwood Ridge, Pretoria 0040, South Africa
Christopher J. Arendse
Affiliation:
Department of Physics, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
Sigqibo T. Camagu
Affiliation:
Council for Scientific and Industrial Research, Light Metals, Pretoria 0001, South Africa
Hendrik Swart
Affiliation:
Department of Physics, University of the Free State, Bloemfontein, 9300, South Africa
*
*Corresponding author. E-mail: coliphant@nmisa.org
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Abstract

Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation.

Type
Materials Applications
Copyright
Copyright © Microscopy Society of America 2014 

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