2011 Annual Report - Center for Integrated Nanotechnologies - Los ...

Nanoscale Electronics & Mechanics Thrust
Enhanced superconducting properties through integration of NbC with highly aligned CNT forest
Accomplishment: We have successfully integrated superconducting
NbC with highly aligned carbon nanotube (CNT) forests
using a chemical solution approach.1 Fig. 1 shows the schematic
drawing of the processing steps to form the CNT-NbC composites.
The formation of superconducting NbC coating on the CNT
forests does not destroy the microstructure of CNTs. Importantly,
NbC shows much improved superconducting properties such
as higher irreversibility field and upper critical field (the highest
reported for the bulk NbC). Furthermore, the superconducting
properties of the CNT-NbC composite become anisotropic compared
with pure NbC. Fig. 3 show shows the upper critical fields
when the field is parallel and perpendicular to the aligned CNT
forest, respectively. In other words, the highly oriented CNTs
embedded in superconducting NbC can function as defects and
effectively enhance the superconducting properties of the NbC.
Figure 2. Morphology and microstructure of the prepared CNT forest and CNT:NbC
composite. a) SEM image of a highly aligned CNT forest, b) HRTEM image of CNTs,
c) SEM image of as-synthesized CNT:NbC composite, and d) HRTEM image of NbC
coated CNT. Insets show the magnified SEM image of CNT forest (a), the highresolution
electron microscopy image of the as-grown multi-wall CNTs (b), and the
magnified SEM image CNT:NbC composite (c), respectively.
Figure 1. Schematic processing steps for the synthesis of CNT-NbC composites.
Challenge: The growth of ceramic-like NbC with desired functionalities
has been a big challenge because a reaction temperature
above 1000 °C is generally required. Such a high
processing temperature leaves no playground to manipulate the
microstructure and/or defect landscape in NbC and to control the
functionalities desired for specific applications.
Significance: The formation of CNT and superconductor composites
makes it possible to produce new and/or improved functionalities
that the individual material does not possess. Highly
oriented CNTs embedded in superconducting NbC matrix can
function as defects and effectively enhance the superconducting
properties of the NbC.
References:
1. Q. X. Jia, T. M. McCleskey, A. K. Burrell, Y. Lin, G. Collis, H.
Wang, A. D. Q. Li, and S. R. Foltyn, “Polymer-assisted deposition
of metal-oxide films,” Nat. Mater. 3, 529 (2004).
2. G.F. Zou, H.M. Luo, S. Baily, Y.Y. Zhang, N.F. Haberkorn, J.
Xiong, E. Bauer, T.M. McCleskey, A K. Burrell, L. Civale, Y.T. Zhu,
J.L. MacManus-Driscoll, and Q.X. Jia, “Highly aligned carbon
nanotube forests cotaed by superconducting NbC” Nat. Commun.
2, 428 (2011).
CINT Contact: Quanxi Jia
Figure 3. Anisotropic properties of the upper critical magnetic field of a CNT-NbC
composite. Inset shows the angular dependence of the temperature at which ρ/ρn =
80% at an applied field of 3T, where 0⁰ and 90⁰ correspond to the field parallel and
normal to the CNT growth direction, respectively.
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