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Structural Characterization of Nanocrystalline Mo and W Carbide and Nitride Catalysts Produced by Co2 Laser Pyrolysis

Published online by Cambridge University Press:  15 February 2011

Xiang-Xin Bi ,
K. Das Chowdhury ,
R. Ochoa ,
W. T. Lee ,
S. Bandow ,
M. S. Dresselhaus  and
P. C. Eklund
Xiang-Xin Bi
Affiliation:
Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA 01239
K. Das Chowdhury
Affiliation:
Department of Materials Science and Engineering, MIT, Cambridge, MA 01239
R. Ochoa
Affiliation:
Center for Applied Energy Research, University of Kentucky, Lexington, KY40511–8433
W. T. Lee
Affiliation:
Center for Applied Energy Research, University of Kentucky, Lexington, KY40511–8433
S. Bandow
Affiliation:
Instrument Center, Institute for Molecular Science, Myodaiji, Okazaki, 444 Japan
M. S. Dresselhaus
Affiliation:
Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA 01239 Department of Physics, MIT, Cambridge, MA 02139
P. C. Eklund
Affiliation:
Center for Applied Energy Research, University of Kentucky, Lexington, KY40511–8433
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Abstract

Using both XRD and HRTEM lattice imaging, we have shown that CO2 laser pyrolysis (LP) produces nanoscale transition metal carbide and nitride catalysts, including cubic Mo2C, Mo2N, and W2N, which possess highly crystalline structures in their as-synthesized form In contrast, LP-produced W2C in its hexagonal phase is disordered. Clear lattice expansion, induced by the small crystallite size of the nanoparticles has been observed for LP-produced Mo2C particles, which have a typical crystallite size of 2 nm. No carbon coating was observed in HRTEM for LP-produced Mo2C particles. Furthermore, Mo=N and Mo=C bonding in Mo2N and Mo2C, respectively, were identified by an XPS measurement, which also reveals the presence of a thin oxide layer formed on the particle surface during the passivation process. Finally, the average crystallite sizes determined from HRTEM and XRD are in good agreement, indicating that the line broadening observed in XRD is due to the small crystallite size of the nanoparticles.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 368: Symposium T – Synthesis and Properties of Advanced Catalytic Materials , 1994 , 69
Copyright
Copyright © Materials Research Society 1995

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References

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