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Phononic Casimir corrections for Graphene resonator
摘要： By calculating a Casimir energy for the acoustic phonons of Graphene, we find some temperature-dependent corrections for the pretension of a Graphene sheet suspended on a trench. We obtain values of the order of few mN/m for these corrections in fully as well as doubly clamped Graphene on a narrow trench with one nanometer width, at room temperature. These values are considerable compared to the experimental values, and can increase the fundamental resonance frequency of the Graphene. The values of these corrections increase by increasing the temperature, and so they can be utilized for tuning the Graphene pretension.
关键词： Resonance frequency,Graphene sheet,Casimir energy,Acoustic phonons,Pretension,Nanoelectromechanical systems
更新于2025-09-23 15:23:52
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Elastic constants and phonon dispersion relation analysis of graphene sheet with varied Poisson's ratio
摘要： Through the achievement of elastic parameter equivalence by the structural mechanics method, the beam–truss space frame model for graphene sheet has been simpli?ed; moreover a representative unit cell of the periodic graphene structure has been extracted. On this basis, the Bloch theorem is combined with the ?nite element method to determine the phonon dispersion relation of graphene. For the widely used thickness values of the carbon–carbon (C–C) bond, the aspect ratios (thickness/length) are so large that the shear deformation should be considered such that as a result, the negative Poisson's ratio (NPR) characteristic of the C–C bond is observed. Analytical expressions for the elastic constants of graphene sheet have been obtained with varied C–C bond Poisson's ratios. The reasonable coherence with previous results reveals the e?ectiveness of the structural mechanics method for analysing the mechanical properties of nanostructures. The e?ect of deformation modes on the phonon dispersion relation of graphene sheet is further discussed; it is concluded that the acoustic phonon modes are sensitive to the deformation modes of the C–C bond, whereas these deformation modes negligibly in?uence the optical phonon modes. The numerical results also reveal that the shear deformation and the resulting NPR e?ect play an important role in the mechanical property analysis of graphene sheet. To summarise, the interrelation between NPR materials and nano materials has stimulated a wide ?eld of research; moreover, numerous novel phenomena have been observed.
关键词： Elastic constants,Poisson's ratio,Phonon dispersion relation,Graphene sheet,Structural mechanics method
更新于2025-09-23 15:22:29
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Preparation and characterization of graphene sheet prepared by laser ablation in liquid
摘要： Graphene sheets prepared successfully by Nd: YAG laser ablation of carbon target immersed in deionized water. The structural, optical and morphological properties investigated using Fourier transform infrared spectroscopy, X-ray diffraction, UV–VIS spectrophotometry, photoluminescence spectroscopy, and Transmission electron microscopy. The result of FTIR spectra conform C?C and C@C bonds, which yield to carbon nanoparticles (CNPs) suspend in liquid. After re-irradiation, new peaks appear at 1723 cm(cid:1)1 and 2697 cm(cid:1)1 caused by the disordered arrangement and irregular layer thickness of graphene sheets. The XRD pattern observed sharp peaks at 2h (cid:3) 24(cid:1), 26.6(cid:1), and 43(cid:1) with higher intensity after the re-irradiation process. The absorption result shows a shoulders peaks among 260 and 320 nm relates to transition in C@O and C@C bands. The PL spectra have a peak in the visible region at 597 nm and increased as laser energy increased. TEM images show straight isolated long multiwall carbon nanotubes MWCNT with the hollow core in different dimensions. While graphene sheet it takes the shape of a ?at transparent layer with small wrinkles and folding sheet, appeared after re-irradiation the suspensions with same laser energy.
关键词： Carbon nanoparticles,Carbon nanotubes,Laser ablation,Graphene sheet
更新于2025-09-11 14:15:04