Abstract
We report on a growth technique of carbon nanotubes (CNTs) whose core and interlayer spaces were filled with Ni fine particles using discharge pyrolysis at gas/solid interface with optical-parametric-oscillation (OPO) laser beam assist. Transmission electron microscope observation reveals that CNTs were grown at around a cathode spot and, in most cases, Ni fine particles had 3–4 nm diameters. With decreasing the wavelength of OPO laser, G/D ratios obtained from Raman spectrum analysis increased gradually and, in fact, the structures of CNTs were improved from amorphous-like structures to the long and straight CNTs. For longer wavelengths (593 nm, 650 nm) of OPO laser, diameters of CNTs became thicker (typically 10 ~ 100 nm) and therefore, Ni nanowires were formed in the core spaces of CNTs. However, for shorter wavelength (456 nm, 507 nm), diameters of CNTs were significantly reduced and Ni fine particles were embedded in between CNT layers. It was found that the structures of CNTs strongly depend on both...
Highlights
Recent progress on synthesis of nanoscale objects has attracted much attention because their new functionalities have been expected to be potential candidates for the next-generation devices in the wide area ranging from the biotechnology to the nanoscale electron devices
The authors have developed a growth method in which the arc discharge at the liquid/solid interface has been utilized, and have achieved to synthesize Carbon nanotubes (CNTs) with single-crystalline Ni nanowires in their cores.[6]. Using such a discharge pyrolysis process, the diameter and the chirality of resulting CNTs was not well-controllable and not even reproducible due in part to the difficulties of the systematic control of the liquid/solid interfacial discharge processes because of unstable air bubbles are reacted from liquid to gas
We found that the structures of CNTs strongly depend on both the magnitude of discharge current and the wavelength of OPO laser beam during the CNT growth
Summary
Recent progress on synthesis of nanoscale objects has attracted much attention because their new functionalities have been expected to be potential candidates for the next-generation devices in the wide area ranging from the biotechnology to the nanoscale electron devices. The magnetic and electronic properties of metal-encapsulated CNTs have been investigated, which exhibits single wall nanotubes (SWNTs) filled with 3d transition metals change the electrical conductivity as compared to unfilled CNTs.[3,4] Such structures were firstly synthesized using the arc discharge method, and metals used as catalyst became accidentally incorporated into the CNTs.[5] Recently the authors have developed a growth method in which the arc discharge at the liquid/solid interface has been utilized, and have achieved to synthesize CNTs with single-crystalline Ni nanowires in their cores.[6] using such a discharge pyrolysis process, the diameter and the chirality of resulting CNTs was not well-controllable and not even reproducible due in part to the difficulties of the systematic control of the liquid/solid interfacial discharge processes because of unstable air bubbles are reacted from liquid to gas. We found that the structures of CNTs strongly depend on both the magnitude of discharge current and the wavelength of OPO laser beam during the CNT growth
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