Search

Reversed micelles containing metallic ions are used as precursors of novel catalysts for the gas-phase synthesis of single-walled carbon nanotubes (SWNTs) and the results of screening study on catalytic behavior of Fe-Mo binary catalysts are reported. The results suggested that the catalytic ability is closely related to the strain of the crystal structure of Fe-Mo catalysts formed in the reaction and/or the phase transition caused by dissolution of the Mo atoms.

Studies on confined water are important not only from the viewpoint of scientific interest but also for the development of new nanoscale devices. In this work, we aimed to clarify the properties of confined water in the cylindrical pores of single-walled carbon nanotubes (SWCNTs) that had diameters in the range of 1.46 to 2.40 nm. A combination of x-ray diffraction (XRD), nuclear magnetic resonance, and electrical resistance measurements revealed that water inside SWCNTs with diameters between 1.68 and 2.40 nm undergoes a wet-dry type transition with the lowering of temperature; below the transition temperature Twd, water was ejected from the SWCNTs. Twd increased with increasing SWCNT diameter D. For the SWCNTs with D = 1.68, 2.00, 2.18, and 2.40 nm, Twd obtained by the XRD measurements were 218, 225, 236, and 237 K, respectively. We performed a systematic study on finite length SWCNT systems using classical molecular dynamics calculations to clarify the effect of open ends of the SWCNTs and water content on the water structure. It was found that ice structures that were formed at low temperatures were strongly affected by the bore diameter, a = D - σOC, where σOC is gap distance between the SWCNT and oxygen atom in water, and the number of water molecules in the system. In small pores (a < 1.02 nm), tubule ices or the so-called ice nanotubes (ice NTs) were formed irrespective of the water content. On the other hand, in larger pores (a > 1.10 nm) with small water content, filled water clusters were formed leaving some empty space in the SWCNT pore, which grew to fill the pore with increasing water content. For pores with sizes in between these two regimes (1.02 < a < 1.10 nm), tubule ice also appeared with small water content and grew with increasing water content. However, once the tubule ice filled the entire SWCNT pore, further increase in the water content resulted in encapsulation of the additional water molecules inside the tubule ice. Corresponding XRD measurements on SWCNTs with a mean diameter of 1.46 nm strongly suggested the presence of such a filled structure. [ABSTRACT FROM AUTHOR]

A highly selective double-walled carbon nanotube synthesis was performed by using oxygen-containing aromatics to demonstrate the function of water as a growth enhancer to control the structure of the carbon nanotube (CNT). The newly developed method provides an easy and convenient method to grow various kinds of nanotubes from the same catalyst and same growth conditions.

A statistical and macroscopic analysis to estimate the catalyst activity of water-assisted growth of single-walled nanotubes (SWNT) and to characterize SWNT forests is proposed. The catalyst activity is estimated to be 84% (plusmn 6%), the highest ever reported.

Size-controlled Co, Co-Mo, and Fe-Mo nanoparticles is prepared by the reversed micelle method as the catalysts for the gas-phase pyrolytic synthesis of single-walled carbon nanotubes (SWCNTs). Findings reveal that the alkyl groups of the surfactants play a role in controlling the sizes of the nanoparticles.

The compatibility of various catalysts for ethylene and ethanol chemical vapor deposition (CVD) syntheses of single-walled carbon nanotubes (SWNTs) on Si substrates is studied. A strong selectivity between the catalyst elemental species and carbon source is found and SWNT yield for Fe(Co) catalysts is much higher for ethylene (ethanol) CVD than for ethanol (ethylene) CVD.

A highly efficient growth of single walled-carbon nanotube (SWNT) and double-walled carbon nanotube (DWNT) forests on conduction metal foils, is reported. It is found that foils made of Ni-based alloys with Cr or Fe are excellent for SWNT(DWNT) synthesis and DWNTs grown on these substrates showed homogenous field emission throughout the entire cathode grid, thus providing evidence of electric contact between the DWNT's and the metal foils.