862 research outputs found
Low frequency excitations of C60 chains inserted inside single-walled carbon nanotubes
The low frequency excitations of C60 chains inserted inside single-walled
carbon nanotubes (SWNTs) have been studied by inelastic neutron scattering
(INS) on a high quality sample of peapods. The comparison of the
neutron-derived generalized phonon density of states (GDOS) of the peapods
sample with that of a raw SWNTs allows the vibrational properties of the C60
chains encapsulated in the hollow core of the SWNTs to be probed. Lattice
dynamical models are used to calculate the GDOS of chains of monomers, dimers
and polymers inserted into SWNTs, which are compared to the experimental data.
The presence of strong interactions between C60 cages inside the nanotube is
clearly demonstrated by an excess of mode density in the frequency range around
10 meV. However, the presence of a quasi-elastic signal indicates that some of
the C60\'s undergo rotational motion. This suggests that peapods are made from
a mixture of C60 monomers and C60 n-mer (dimer, trimer ... polymer) structures
Logic Ciucuits Using Solution-processed Single-walled Carbon Nanotue Transistors
This letter reports on the realization of logic circuits employing
solution-processed networks of single-walled carbon nanotubes. We constructed
basic logic gates (inverter, NAND and NOR) with n- and p-type field-effect
transistors fabricated by solution-based chemical doping. Complementary
metal-oxide-semiconductor inverters exhibited voltage gains of up to 20, which
illustrates the great potential of carbon nanotube networks for printable
flexible electronics.Comment: 12 PAGES, 3 FIGURE
On the diffraction pattern of C60 peapods
We present detailed calculations of the diffraction pattern of a powder of
bundles of C peapods. The influence of all pertinent structural
parameters of the bundles on the diffraction diagram is discussed, which should
lead to a better interpretation of X-ray and neutron diffraction diagrams. We
illustrate our formalism for X-ray scattering experiments performed on peapod
samples synthesized from 2 different technics, which present different
structural parameters. We propose and test different criteria to solve the
difficult problem of the filling rate determination.Comment: Sumitted 19 May 200
Constitutional Diagram of Ternary Fe-Ca-Si Alloys
Microstructural observations, thermal analyses, chemical analyses and X-ray diffractions have been made of the alloys melted with arc or high-frequency induction in argon atmosphere, the compositions of which lie in the field of two-liquid immiscibility and one-liquid phase. The results may be summarized as follows : With increasing content of silicon or of aluminium, the miscible gap of the field of the Fe (Mn)-Ca system became narrow and had a critical point at nearly 33% Fe (Mn)-33%Ca-34%Si(Al), at which the two-liquid phase became indistinguishable. Above 35% silicon or aluminium content, only one liquid solution existed over the entire composition range of the alloy system. It was assumed that a quasi-binary eutectic point should appear in the vicinity of 23%Fe-38.5%Ca-38.5%Si for a quasi-binary system existing between the binary intermediate compounds CaSi and FeSi. Freezing of alloys involving ternary three-phase equilibrium was completed at 1030℃ and the composition of this ternary non-variant point lay upon 5%Fe-35%Ca-60%Si. In the field of only one liquid solution there were four primary phase regions of Si, CaSi, FeSi and FeSi_2. As morphological features, Si appeared in rectangular form, FeSi in dendritic or spherical form, and CaSi and FeSi_2 in band or plate-like form
Pressure screening in the interior of primary shells in double-wall carbon nanotubes
The pressure response of double-wall carbon nanotubes has been investigated
by means of Raman spectroscopy up to 10 GPa. The intensity of the radial
breathing modes of the outer tubes decreases rapidly but remain observable up
to 9 GPa, exhibiting a behavior similar (but less pronounced) to that of
single-wall carbon nanotubes, which undergo a shape distortion at higher
pressures. In addition, the tangential band of the external tubes broadens and
decreases in amplitude. The corresponding Raman features of the internal tubes
appear to be considerably less sensitive to pressure. All findings lead to the
conclusion that the outer tubes act as a protection shield for the inner tubes
whereas the latter increase the structural stability of the outer tubes upon
pressure application.Comment: PDF with 15 pages, 3 figures, 1 table; submitted to Physical Review
Interaction between concentric Tubes in DWCNTs
A detailed investigation of the Raman response of the inner tube radial
breathing modes (RBMs) in double-wall carbon nanotubes is reported. It revealed
that the number of observed RBMs is two to three times larger than the number
of possible tubes in the studied frequency range. This unexpected increase in
Raman lines is attributed to a splitting of the inner tube response. It is
shown to originate from the possibility that one type of inner tube may form in
different types of outer tubes and the fact that the inner tube RBM frequency
depends on the diameter of the enclosing tube. Finally, a comparison of the
inner tube RBMs and the RBMs of tubes in bundles gave clear evidence that the
interaction in a bundle is stronger than the interaction between inner and
outer tubes.Comment: 6 pages, 7 figures, submitted to Eur. Phys. J.
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