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Wyświetlanie 1-9 z 9
Tytuł:
Nonlocal Timoshenko Beam for Vibrations of Magnetically Affected Inclined Single-Walled Carbon Nanotubes as Nanofluidic Conveyors
Autorzy:
Kiani, K.
Tematy:
61.46.Fg
83.50.Lh
43.28.Ra
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1030231.pdf  Link otwiera się w nowym oknie
Opis:
This work displays both longitudinal and transverse vibrations of magnetically affected inclined single-walled carbon nanotubes for conveying fluid flow. By employing an equivalent continuum structure on the basis of the nonlocal Timoshenko beam model as well as plug-like model for the nanofluidic flow inside the pore, the nonlocal governing equations are obtained accounting for nonlocality, frictionless nature of the inside wall, the Knudsen number, and full longitudinal and transverse interactions of the fluid flow with the single-walled carbon nanotubes. By implementing Galerkin-based assumed mode method, the equations of motion are discretized appropriately and then solved for the unknown dynamical deformation fields. The roles of nanofluidic flow velocity, small-scale parameter, inclination angle of single-walled carbon nanotube, and magnetic field strength on maximum values of longitudinal and transverse displacements are explained and discussed. The results show that the maximum dynamic deflection of the inclined nanotube would lessen by increase of the magnetic field strength. This fact is also more apparent for higher levels of fluid flow velocity. Additionally, variation of the longitudinal magnetic field has a trivial influence on the variation of longitudinal displacement. The predicted results reveal that application of the longitudinal magnetic field could be used as an efficient methodology to reduce the lateral vibrations of single-walled carbon nanotubes as nanofluidic conveyors.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Resonance Raman Study on Carbon Nanotubes Formation
Autorzy:
Steplewska, A.
Borowiak-Palen, E.
Tematy:
61.46.Fg
61.46.Np
81.07.De
78.30.-j
61.46.+w
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1807842.pdf  Link otwiera się w nowym oknie
Opis:
Carbon nanotubes can be obtained from variety of the molecular precursors in chemical vapor deposition processes. The low growth temperatures strongly increase the compatibility of carbon nanotubes growth with current complementary metal-oxide-silicon technology for carbon nanotubes-based electronics. Here, we show the low temperature growth of multiwalled carbon nanotubes in acetylene chemical vapor deposition with Fe-Co/MgO. The catalyst mix was active already at 450°C. The higher temperatures growth (500°C and 550°C) were also tested in order to estimate the best thermal condition in respect of the sample quality (via thermogravimetric analyzer) and the sample relative purity (via resonance Raman spectroscopy). High resolution transmission electron microscope was used to determine the morphology of the samples.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Experimental Evaluation of $CO_2//N_2$ Mixture Separation by Multi-multi-walled Carbon Nanotube
Autorzy:
Khalili, S.
Ghoreyshi, A.
Jahanshahi, M.
Davoodi, M.
Tematy:
61.46.Fg
64.75.Jk
66.30.Pa
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1399700.pdf  Link otwiera się w nowym oknie
Opis:
In order to examine the ability of multi-multi-walled carbon nanotube for $CO_2$ separation from flue gas, uptakes of $CO_2$ and $N_2$ were measured at temperatures of 288 K, 298 K and 308 K over the pressure range 1 to 40 bar using volumetric method. The experimental data was fitted by the Langmuir and Frendlich model isotherms. The same shape of isotherms introduced a common mechanism of adsorption but the amount of $CO_2$ adsorbed on multi-multi-walled carbon nanotube was 2.5 times higher than $N_2$ adsorption which indicated the possibility of $CO_2$ removal from flue gases using adsorption process with multi-multi-walled carbon nanotube as the adsorbent. Isosteric heat of adsorption was evaluated from a set of isotherms based on the Clausius-Clapeyron equation.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Annihilation in Carbon Nanotubes Studied by Coincidence Doppler Broadening Spectroscopy
Autorzy:
Murakami, H.
Sato, K.
Kanazawa, I.
Sano, M.
Tematy:
61.46.Fg
78.70.Bj
36.10.Dr
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1812544.pdf  Link otwiera się w nowym oknie
Opis:
In order to assign the sites of positron annihilation, coincidence Doppler broadening spectra were measured for a highly oriented pyrolytic graphite crystal, graphite powder, multi-walled carbon nanotubes (MNTs) and cup-stacked carbon nanotubes (CNTs). The spectrum for graphite powder normalized to that for highly oriented pyrolytic graphite (HOPG) is almost flat in the momentum region from $7×10^{-3}$ to $13×10^{-3} m_{e}c$, having a ratio close to unity. The flat spectrum demonstrates that positrons injected into graphite powder annihilate in the interlayer spaces of piled graphite sheets, in the same manner as positrons in highly oriented pyrolytic graphite annihilate in the bulk. The coincidence Doppler broadening spectra for MNTs and CNTs are quite different from that for highly oriented pyrolytic graphite, which indicates that positrons injected into MNTs and CYTs annihilate not in the bulk, but on surface. The positron lifetime spectrum for multi-walled carbon nanotubes is analyzed in terms of a single component due to surface-trapped positrons, while that for CNTs is decomposed into three components attributable to para-positronium surface-trapped positrons and ortho-positronium. The difference between the coincidence Doppler broadening spectrum for CNTs and that for MNTs is explained in terms of positron annihilation on zigzag surfaces of CNTs which are composed of both graphite-sheet and graphite-edge planes.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Dispersive Micro Raman Backscattering Spectroscopy Investigation of Arc Discharge Synthesized CNTs Doped by Boron and Nitrogen
Autorzy:
Babanejad, S.
Malekfar, R.
Seyyed Hosseini, S.
Tematy:
61.46.Fg
63.22.Gh
78.67.Ch
81.07.De
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1807785.pdf  Link otwiera się w nowym oknie
Opis:
Raman scattering studies reveal the remarkable structure and the unusual electronic and phonon properties of carbon nanotubes. In this study, we directly produced boron, B, and nitrogen doped carbon nanotubes by using DC-arc discharge method which normally can be employed for producing carbon nanotubes. We performed experiments without using catalysts and in the presence of Ar gas for producing boron doped carbon nanotubes. At the second and third stages and in the presence of $Al_{2}O_{3}$ and MgO nanopowders as catalysts and nitrogen gas were used for producing nitrogen doped carbon nanotubes. In general, our investigation revealed that some major changes caused by B and N dopants can be observed in the related recorded Raman spectra.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An ab initio Study of a Model of Single Wall GaN Nanotubes with Oxygen and Zinc as Impurities: Structural and Electronic Properties
Autorzy:
Rezouali, K.
Belkhir, M.
Tematy:
61.46.Fg
61.72.Bb
73.61.Ey
73.61.Wp
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Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1813497.pdf  Link otwiera się w nowym oknie
Opis:
We report a comprehensive theoretical study of structural and electronic properties of substitutional oxygen and zinc contaminations in a model of single wall GaN nanotubes by means of ab initio supercell calculations. Our investigation yields many interesting results. The following ones deserve to be developed. Oxygen forms a shallow donor in the single wall GaN nanotubes as in bulk GaN polytypes. Its ionization energy is deeper than its counterpart in the bulk wurtzite GaN, so it can be a suitable n-type dopant in high temperature applications. Zinc is a relatively shallow acceptor at gallium site. It behaves as charge carrier trap at nitrogen site. The site preference of zinc impurity depends on the stoichiometry. Zinc at gallium site has small ionization energy, thus it would be an efficient p-dopant in GaN nanotubes unlike in bulk GaN polytypes.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Phase Analysis of Magnetic Inclusions in Nanomaterials Based on Multiwall Carbon Nanotubes
Autorzy:
Brzózka, K.
Krajewski, M.
Małolepszy, A.
Stobiński, L.
Szumiata, T.
Górka, B.
Gawroński, M.
Wasik, D.
Tematy:
61.05.Qr
61.46.Fg
61.48.De
75.50.Tt
75.75.Cd
81.07.De
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1032146.pdf  Link otwiera się w nowym oknie
Opis:
Functionalized multiwall carbon nanotubes as well as nanocomposite based on that material covered by nanoparticles composed of iron oxides were the subject of investigations. In order to identify all iron-bearing phases including those reported on the base of previous X-ray diffraction measurements, the transmission Mössbauer spectroscopy was utilized. The experiments were carried out both at room temperature and also at low temperatures. It was stated that in the investigated nanotubes some impurities were present, originating from the catalyst remains, in form of Fe-C and α -Fe nanoparticles. The Mössbauer spectra collected for the nanocomposite showed a complex shape characteristic of temperature relaxations. The following subspectra related to iron-based phases were identified: sextet attributed to hematite, with hyperfine magnetic field reduced due to the temperature relaxations, sextet corresponding to iron carbide as well as two doublets linked to superparamagnetic hematite and ferrihydrites.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ab Initio Study of Functionalized Carbon Nanotubes
Autorzy:
Milowska, K.
Birowska, M.
Majewski, J.
Tematy:
31.15.ae
31.15.E-
61.46.Fg
61.48.De
73.22.-f
81.07.De
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1791295.pdf  Link otwiera się w nowym oknie
Opis:
In the present paper, we study the stability of (9, 0), (10, 0), (11, 0) carbon nanotubes functionalized with simple organic molecules $-CH_{n}$ (for n = 2, 3, 4). Our studies are based on ab initio calculations within the framework of the density functional theory. We determine binding energies of the functionalized carbon nanotubes and the changes in the geometry and electronic structure caused by the functionalization. We observe the characteristic effects such as rehybridization of the bonds induced by fragments attached to carbon nanotubes and pentagon/heptagon (5/7) defects in $-CH_{2}$ functionalized carbon nanotubes. We study also dependence of the binding energies of the functionalized carbon nanotubes on the density of the adsorbed molecules and diameter of the single-wall carbon nanotubes. Our calculations reveal that the $-CH_{2}$ fragments exhibit the strongest cohesion and we determine the critical density of the $-CH_{2}$ fragments which could be adsorbed.
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Manipulations with Atoms and Clusters
Autorzy:
Czajka, R.
Tematy:
81.15.Fg
61.16.Ch
85.42.+m
61.46.+w
Pokaż więcej
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Powiązania:
https://bibliotekanauki.pl/articles/1933857.pdf  Link otwiera się w nowym oknie
Opis:
The investigation and fabrication of nanometer-scale structures becomes a reality due to the development of scanning tunneling microscopy and related techniques. The final goal, manipulations with the individual atoms and molecules, has been achieved. D.M. Eigler used the scanning tunneling microscope (working at low temperatures ca. 4 K) to position individual xenon atoms on a single-crystal nickel surface with atomic precision. Mesoscopic systems composed of metallic or non-metallic clusters are intensively studied because of their new and interesting properties, and perspectives of subsequent application in nanolithography in order to create various structures of a very high degree of miniaturization. In this review, (i) the potential of scanning probe microscopes for revealing subtle details of surfaces down to atomic resolution is presented, (ii) a variety of different atomic manipulations processes and other surface modifications are reviewed against the background of different, more or less universal approaches, and finally (iii) a few examples of cluster surface structures created and/or modified by means of scanning tunneling microscope are demonstrated.
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-9 z 9

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