Eur. Phys. J. Appl. Phys.
Volume 28, Number 2, November 2004
|Page(s)||173 - 178|
|Section||Nanomaterials and Nanotechnologies|
|Published online||30 August 2004|
Non-uniformity of temperatures along nanotubes in hot reactors and axial growth
National Institute for Materials Science, Advanced Materials Laboratory, Namiki 1-1, Tsukuba, Ibaraki, 305-0044, Japan
Corresponding author: email@example.com
Revised: 12 May 2004
Accepted: 15 June 2004
Published online: 30 August 2004
Non-uniformity of temperatures appears as a general rule in hot nanofiber synthesis reactors, where local variations of the balance between long-range radiative heat exchanges and short-range conductive heat exchanges are driven by size and composition of structures. Metal particles larger than a few tens of nanometer are radiation captors, when fiber bodies thinner than 10 nm are transparent. We note that typical gradient lengths correspond remarkably well to usual length of nanotubes (micron range), and increase with fiber radius. For anisotropically radiating reactors as well as for furnace-type reactors, difference between radiative and conductive environments allows temperature intervals as high as several hundred degrees. Practically, axial thermal gradients arise by fiber attachment to a metallic particle, eventually at each tip (ideally with different sizes or compositions), or by attachment to a hot wall (electrode, supporting substrate, or target). The resulting thermal gradients are unusually stiff, typically 10 K µm−1. We show that local temperature evolution in early stage of nucleation is triggered by dimension of attached particle(s). We show that a diffusion flux of adatoms induced by the axial thermal gradient is quantitatively consistent with a feeding flux, as measured for different reactors. In addition, we notice that the spontaneous minimization of free energy at fiber tip is such that a temperature drop favors axial extension.
PACS: 61.46.+w – Nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals / 82.60.Qr – Thermodynamics of nanoparticles / 81.16.-c – Methods of nanofabrication and processing
© EDP Sciences, 2004
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.