Synthesis, structure, and superconducting
properties of tantalum carbide nanorods and
nanoparticlesA. Fukunaga, S. Chu, M.E. McHenry
(Carnegie Mellon University)
Tantalum
carbide nanorods and nanoparticles have been synthesized using a
vapor-solid reaction path starting with CVD grown carbon nanotube
precursors. Their structures were studied using XRD, TEM, and HRSEM.
Superconducting properties were characterized using SQUID magnetometer.
For reactions at lower temperatures, carbide nanorods which replicate the
~14 nm diameter of the precursor carbon nanotubes are observed. For higher
temperature reactions, coarsened carbide nanoparticles (100 ~ 250 nm) are
observed which have spherical or cubic-faceted morphologies. A
morphological Rayleigh instability is postulated as initiating the
transition from nanorod to nanoparticle morphologies. Stoichiometric bulk
TaC crystallizes in the rock salt structure and has a superconducting
transition temperature of 9.7 K. In TaC nanorods and nanoparticles, the
superconducting properties correlate with the lattice parameter.
Nanoparticles with a little higher lattice parameter than the ideal one
show higher Tc and higher fields at which the
superconductivity disappears, than stoichiometric bulk TaC.
Order No.:
JA809-018 © 1998 MRS
Go to September 1998 Table of Contents
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