6,626 research outputs found
Titanium-decorated carbon nanotubes: a potential high-capacity hydrogen storage medium
We report a first-principles study, which demonstrates that a single Ti atom
coated on a single-walled nanotube (SWNT) binds up to four hydrogen molecules.
The first H adsorption is dissociative with no energy barrier while other
three adsorptions are molecular with significantly elongated H-H bonds. At high
Ti coverage we show that a SWNT can strongly adsorb up to 8-wt% hydrogen. The
system is quite stable and exhibits associative desorption upon heating, a
requirement for reversible storage. These results advance our fundamental
understanding of dissociative adsorption of hydrogen in nanostructures and
suggest new routes to better storage and catalyst materials.Comment: 4.2 pages, 3 figures, submitted PRL on Nov. 2004, accepted in March
200
Collisional Damping of Giant Monopole and Quadrupole Resonances
Collisional damping widths of giant monopole and quadrupole excitations for
Sn and Pb at zero and finite temperatures are calculated within
Thomas-Fermi approximation by employing the microscopic in-medium
cross-sections of Li and Machleidt and the phenomenological Skyrme and Gogny
forces, and are compared with each other. The results for the collisional
widths of giant monopole and quadrupole vibrations at zero temperature as a
function of the mass number show that the collisional damping of giant monopole
vibrations accounts for about 30-40% of the observed widths at zero
temperature, while for giant quadrupole vibrations it accounts for only 20-30%
of the observed widths of zero temperature.Comment: RevTex, 12 pages, 6 PS figure
Variable and reversible quantum structures on a single carbon nanotube
The band gap of a semiconducting single wall carbon nanotube decreases and
eventually vanishes leading to metalization as a result of increasing radial
deformation. This sets in a band offset between the undeformed and deformed
regions of a single nanotube. Based on the superlattice calculations, we show
that these features can be exploited to realize various quantum well structures
on a single nanotube with variable and reversible electronic properties. These
quantum structures and nanodevices incorporate mechanics and electronics.Comment: 7 pages, 4 figures, To be appear in PR
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A Preliminary Study on Using Multi-Nozzle Polymer Deposition System to Fabricate Composite Alginate/Carbon Nanotube Tissue Scaffolds
Three-dimensional composite alginate/single wall carbon nanotube (SWCNT) scaffolds
encapsulated with endothelial cells were fabricated by a multi-nozzle biopolymer freeform
deposition system. This system enables the converting of CAD designed scaffold pattern into
process toolpaths and the use of computer control program to guide the nozzle deposition at
spatial position for layered fabrication of 3D tissue scaffolds. The morphological, mechanical,
structural and biological properties of as-fabricated scaffolds were characterized by optical
microscope, SEM, Microtensile testing machine, Alamar Blue Assay, and Live-Dead Assay,
respectively. The multi-nozzle deposition system demonstrated a highly efficient and effective
process to build tissue scaffold or cell embedded constructs. Characterization results showed that
the incorporation of SWCNT into alginate not only enhanced the mechanical strength of the
scaffolds but also improved the cell affinity and the interaction with substrate. Further cell
culture experimental results also showed that the incorporation of SWCNT in alginate enhanced
endothelial cell proliferation compared with pure alginate scaffold.Mechanical Engineerin
Structural, Vibrational and Thermodynamic Properties of AgnCu34-n Nanoparticles
We report results of a systematic study of structural, vibrational and
thermodynamical properties of 34-atom bimetallic nanoparticles from the
AgnCu34-n family using model interaction potentials as derived from the
embedded atom method and in the harmonic approximation of lattice dynamics.
Systematic trends in the bond length and dynamical properties can be explained
largely on arguments based on local coordination and elemental environment.
Thus increase in the number of silver atoms in a given neighborhood introduces
a monotonic increase in bond length while increase of the copper content does
the reverse. Moreover, based on bond lengths of the lowest coordinated (6 and
8) copper atoms with their nearest neighbors (Cu atoms), we find that the
nanoparticles divide into two groups with average bond length either close to
(~ 2.58 A) or smaller (~ 2.48 A) than that in bulk copper, accompanied by
characteristic features in their vibrational density of states. For the entire
set of nanoparticles, vibrational modes are found above the bulk bands of
copper/silver. Furthermore, a blue shift in the high frequency end with
increasing number of copper atoms in the nanoparticles is traced to a shrinkage
of bond lengths from bulk values. The vibrational densities of states at the
low frequency end of the spectrum scale linearly with frequency as for single
element nanoparticles, however, the effect is more pronounced for these
nanoalloys. The Debye temperature was found to be about one third of that of
the bulk for pure copper and silver nanoparticles with a non-linear increase
with increasing number of copper atoms in the nanoalloys.Comment: 37 pages, 12 figure
Comparing the Influence of the Drop Fill and Overflow Rinsing on the Reactive Dyeing Process in a Textile Dye House
Drop/fill rinsing method was used for reducing the high water consumption of overflow rinsing process in textile dye house. However, it is not known whether this drop/fill method has adverse effects on the final fabric properties or not. In this study, the effects of using drop/fill method instead of overflow rinsing process on colorimetric and fastness properties of 100% cotton towel fabrics are investigated. It is found that, skipping to the drop fill rinsing method from the over flow rinsing process and obtained fresh water saving has no negative effect on colorimetric and color fastness values of the processed fabric samples and can be used conveniently in the industrial sized production. © Published under licence by IOP Publishing Ltd
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