Search

Abstract: Iron-based nanoparticles, centrifugally classified by size, with variation of subnanometer order, have been used for the growth of diameter-controlled carbon nanotubes (CNTs) for the first time via catalytic chemical vapor deposition. The centrifugal classification of nanoparticles is facilitated by fractional precipitations through the sequential addition of ethanol to a hexane solution containing the nanoparticles. Three different nanoparticle sizes were obtained, which have average diameters and standard deviations of 3.9±0.8nm, 3.3±0.6nm, and 2.8±0.4nm. By the classification process of nanoparticles, the standard deviation of the average diameter of the fractionated nanoparticles decreased by around one half of that of the as-synthesized nanoparticles. In addition, we demonstrate a technique for estimating the average diameter of each classified nanoparticle using conventional low-angle X-ray diffraction, without the need for time-consuming TEM observation and analysis. From the three classified nanoparticle sizes, with average diameters of 2.8, 3.3, and 3.9nm, CNTs with average diameters of 3.1, 3.6, and 4.5nm were obtained by changing growth temperatures, respectively. Therefore, centrifugally classified nanoparticles are one of the most promising ‘seeds’ for use in the diameter-selective growth of CNTs. [Copyright &y& Elsevier]

Abstract: Monodispersed Fe–V–O nanoparticles were prepared by a liquid-phase synthesis to be used as catalysts for carbon nanotube (CNT) growth. Vertically aligned, dense CNTs have been grown from the highly active Fe–V–O nanoparticles by chemical vapor deposition. Diameter distribution of CNTs (3.7±0.6nm) was consistent with that of the original nanoparticles (3.1±0.5nm), and the value was smaller than those of other reported vertically aligned CNTs from as-prepared nanoparticles. TEM study showed that the CNTs consisted mainly of double-walled CNTs (single: 14%, double: 74%, and triple: 12%). The CNT diameter increased to 4.4±0.8nm as the growth temperature was increased from 810 to 870°C. Energy dispersive X-ray spectroscopy of nanoparticles before and after the CNT growth revealed that the V content decreased from 7.2 to 2.7at.%, suggesting that the segregation of Fe and V played an important role for the high activity of the Fe–V–O nanoparticles. [Copyright &y& Elsevier]

We developed a novel anti-agglomeration method that enables preservation of the vertical alignment of carbon nanotubes (CNTs) during desiccation of wet CNTs by utilizing antisolvent precipitation and sublimation of naphthalene (Nap). Moreover, we succeeded in depositing Pt nanoparticles onto CNTs without collapse of the vertically aligned morphology by this method. [ABSTRACT FROM AUTHOR]