Cylindrical Graphene Research Articles

Numerical modelling of the surface plasmon modes of a circular cylindrical three-layer graphene waveguide

Numerical modelling of the surface plasmon modes of a circular cylindrical three-layer graphene waveguide

Field emission from cylindrical graphene cathodes prepared by chemical vapor deposition and cold rolling

We report field emission (FE) properties of cold cathodes made by a scalable chemical vapor deposition synthesis of three-dimensional graphene (3DG) from a cast catalyst followed by cold rolling. This process leads to an increase in mechanical strength and electrical conductivity of the tested material. For a given distance between the tip of the cathode and the anode, it is found that the FE current from the edge of a single sheet of cold-rolled 3DG-based cathode can be increased by over one order of magnitude when rolling the 3DG sheet in the shape of a cylinder with several turns. A FE current in the order of 4.5 mA was measured from a 3 mm diameter cold-rolled 3DG cylinder with six turns at a bias of 2400 V for a separation of 0.5 mm between the tip of the cylindrical cathode and the anode. The FE data of all cold-rolled 3DG-based cathodes are well fitted by the expression proposed by Abbot, Henderson, Forbes, and Popov [Filippov et al., R. Soc. Open Sci. 9, 220748 (2022)], Im=CVmκexp(−B/Vm), where Im is the FE current, Vm is the bias applied between the cathode and anode, and B and C are fitting parameters. It is found that κ=1 and 3/2 for FE from the surface and edge of the cold-rolled based cathodes, respectively.

Modulation of hybrid plasmon phonon polaritons mode in circular cylindrical three-layer graphene waveguide

In this present research article, we have investigated analytically the characteristics of the fundamental mode of hybrid surface plasmon phonon polariton (HSPPhPs) mode in a circular cylindrical three-layer graphene (CTLG) waveguide structure. The dispersion equation of HSPPhPs is derived by using Maxwell’s equations and continuity conditions of tangential components of electric and magnetic fields in cylindrical geometry. The dispersion curve has been illustrated and thoroughly examined in relation to the effects of temperature and chemical potential (μc) of graphene, as well as variations in the thickness of silicon dioxide (SiO2) and hexagonal boron nitride (hBN) layers, and found that in the presence of hBN, the effective mode index exhibits hyperbolic behavior with wave number. Up to the first Reststrahlen band (∼830.57 cm⁻¹), it varies slightly with graphene temperature; increasing graphene's (μc) lowers the index, while a thicker hBN layer reduces it, whereas the index increases with SiO₂ layer thickness. Also, we looked at how the CTLG waveguide structure is affected by the electric field distribution, phase speed, and propagation length.

Nonlinear electro-thermo-mechanical dynamic behavior of complexly curved GPL-reinforced panels with auxetic core

This research aims to study the nonlinear electro-thermo-mechanical dynamic responses of cylindrical, sine, and parabolic graphene platelets reinforced panels with auxetic cores and piezoelectric layers. By applying the higher-order shear deformation theory, viscoelastic foundation model, approximate technique for stress function, Rayleigh dissipation function, and energy method, the governing formulations are established. The natural frequency is determined explicitly, and the Runge-Kutta method is used to acquire the time amplitude responses of panels numerically. The noticeable effects of piezoelectrical layers, auxetic core, and GPL parameters on the mechanical and thermal dynamic buckling and vibration responses are recognized from the numerical investigations.

Hydrodynamic Model for Particle Beam-Driven Wakefield in Carbon Nanotubes

The charged particles moving through a carbon nanotube (CNT) may be used to excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell that makes up a nanotube wall. This effect has recently been proposed as a potential novel method of short-wavelength-high-gradient particle acceleration. In this contribution, the existing theory based on a linearized hydrodynamic model for a localized point-charge propagating in a single wall nanotube (SWNT) is reviewed. In this model, the electron gas is treated as a plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. The governing set of differential equations is formed by the continuity and momentum equations for the involved species. These equations are then coupled by Maxwell’s equations. The differential equation system is solved applying a modified Fourier-Bessel transform. An analysis has been realized to determine the plasma modes able to excite a longitudinal electrical wakefield component in the SWNT to accelerate test charges. Numerical results are obtained showing the influence of the damping factor, the velocity of the driver, the nanotube radius, and the particle position on the excited wakefields. A discussion is presented on the suitability and possible limitations of using this method for modelling CNT-based particle acceleration.

Excitation of wakefields in carbon nanotubes: a hydrodynamic model approach

The interactions of charged particles with carbon nanotubes (CNTs) may excite electromagnetic modes in the electron gas produced in the cylindrical graphene shell constituting the nanotube wall. This wake effect has recently been proposed as a potential novel method of short-wavelength high-gradient particle acceleration. In this work, the excitation of these wakefields is studied by means of the linearized hydrodynamic model. In this model, the electronic excitations on the nanotube surface are described treating the electron gas as a 2D plasma with additional contributions to the fluid momentum equation from specific solid-state properties of the gas. General expressions are derived for the excited longitudinal and transverse wakefields. Numerical results are obtained for a charged particle moving within a CNT, paraxially to its axis, showing how the wakefield is affected by parameters such as the particle velocity and its radial position, the nanotube radius, and a friction factor, which can be used as a phenomenological parameter to describe effects from the ionic lattice. Assuming a particle driver propagating on axis at a given velocity, optimal parameters were obtained to maximize the longitudinal wakefield amplitude.

Extended Method of Lines to Model Cylindrical Graphene-Based Multilayer Structures

In this article, the method of lines (MoL) is extended to analyze 2-D multilayer structures loaded with graphene plates in cylindrical coordinates. Accordingly, the admittance transformation matrices through a 2-D interface are derived taking into account the tensor-form conductivity of the magnetized graphene plate. The transformations determine the admittance matrices on all the planes of the multilayer structure. Furthermore, a technique to obtain the characteristic equation and hence the propagation constant of the structure is proposed by matching the fields at the interfaces loaded with graphene. As a result, the proposed method is able to analyze a generic graphene-loaded multilayer structure in cylindrical coordinates. As a proof of concept, the MoL is exploited to analyze 2-D cylindrical graphene microstrip and stripline transmission lines. The proposed method is validated by comparing the results with COMSOL simulations exhibiting a good agreement. Tuning the chemical potential of the graphene plate has potential applications in tunable microwave attenuators and phase shifters.

Insight into Darcy flow of ternary‐hybrid nanofluid on horizontal surfaces: Exploration of the effects of convective and unsteady acceleration

AbstractThe transport phenomenon of water conveying spherical carbon nanotubes, cylindrical graphene, and platelet aluminum oxide nanoparticles exhibits a linear relationship between the pressure gradient causing the dynamics of ternary‐hybrid nanofluid and the velocity. However, it is essential to note that little is known about the computation of roughness at the surface transition zone during the early stages of accretion. The Darcy flow of ternary‐hybrid nanofluid was investigated and reported in this paper with the intention to provide insight into the convective and unstable acceleration related to leading‐edge accretion. The governing equations roughly represented that the time‐dependent fluid flow were nondimensionalized using the Blasius‐Rayleigh Stokes variable, and the three‐stage Lobatto IIIa integration formula for a finite difference (MATLAB package bvp4c) was used to solve numerically. Based on the analysis of results, it is worth concluding that the velocity decreases significantly due to a growth in the leading‐edge accretion (γ) because the convective acceleration increases while the unsteady acceleration decreases for . As , convective acceleration increases while the unsteady acceleration decreases. As γ enlarges from 90° to 180°, both forms of the acceleration are decreasing properties, but unsteady deceleration is bound to manifest.

Graphene Metamaterial Embedded within Bundt Optenna for Ultra-Broadband Infrared Enhanced Absorption.

Graphene is well-known for its extraordinary physical properties such as broadband optical absorption, high electron mobility, and electrical conductivity. All of these make it an excellent candidate for several infrared applications such as photodetection, optical modulation, and optical sensing. However, a standalone monolayer graphene still suffers from a weak infrared absorption, which is ≅2.3%. In this work, a novel configuration of graphene metamaterial embedded inside Bundt optical-antenna (optenna) is demonstrated. It can leverage the graphene absorption up to 57.7% over an ultra-wide wavelength range from 1.26 to 1.68 µm (i.e., Bandwidth ≅ 420 nm). This range covers the entire optical communication bands of O, E, S, C, L, and U. The configuration mainly consists of a Bundt-shaped plasmonic antenna with a graphene metamaterial stack embedded within its nano-wide waveguide that has a 1.5 µm length. The gold average plasmonic loss is ≅25%. This configuration can enhance graphene ultra-broadband absorption through multiple mechanisms. It can nano-focus the infrared radiation down to a 50 nm spot on the graphene metamaterial, thus yielding an 11.5 gain in optical intensity (i.e., 10.6 dB). The metamaterial itself has seven concentric cylindrical graphene layers separated by silicon dioxide thin films, thus each layer contributes to the overall absorption. The focused infrared propagates tangential to the graphene metamaterial layers (i.e., grazing propagation), and thus maximizes the light–graphene interaction length. In addition, each graphene layer experiences a double-face exposure to the nano-focused propagating spot, which increases each layer’s absorption. This configuration is compact and polarization-insensitive. The estimated maximum absorption enhancement compared to the standalone monolayer graphene was 25.1 times (i.e., ≅4 dB). The estimated maximum absorption coefficient of the graphene stack was 5700 cm−1, which is considered as one of the record-high reported coefficients up to date.

Reconfigurable multiband nano-antenna design for photonic applications

The Antenna that comprises metal patches set on the Dielectric which is given by coplanar transmission line is known to be a patch antenna. It can also be known as Microstrip patch antenna. The foremost downside is the efficiency of the antenna. A M-patch antenna includes a patch i.e a radiating patch, ground plane on one side and a thin flat metallic region on the other side of dielectric substrate. There are various feed methods such as offset feed, centre feed, inset feed and quarter wave line feed. Microstrip patch antennas have better advantages over conventional antennas. In this paper we develop Multiband Antenna for photonic application. The proposed antenna is designed in a patch model. And in the patch, a cylindrical shape graphene is placed over the patch in which we use this for photonic application. And this antenna is designed in flexible material such as copper tape, Kaptonmaterial and nano materials. Nano based cylindrical antenna was not done previously.In this, we have achieved a gain of 8dB which is comparatively better with other antenna after many implementation.

Simulation of the dynamics of colloidal mixture of water with various nanoparticles at different levels of partial slip: Ternary-hybrid nanofluid

Some of the fundamental properties of nanofluids capable of influencing not only the transport phenomena, but also mass and heat transfer within the boundary layer and throughout the domain are thermo-migration and random mobility of nanoparticles in the based fluid. In such a case mentioned above, nothing is known on a comparative ternary-hybrid nanofluid flows induced by forced convection, free convection, and mixed convection when radiative heat flux is substantially regulated by temperature difference as in the case of non-linear thermal radiation, and partial slip. This report presents the similarity solutions of the governing equations that models the dynamics of colloidal mixture of water with spherical carbon nanotubes, cylindrical graphene, and platelet alumina nanoparticles at different levels of partial slip considering the cases of forced, free and mixed convection. The shooting approach was used in conjunction with the conventional Runge-Kutta integration scheme and MATLAB bvp4c to get solutions of the emerged boundary value problems. The outcome of the study shows that the friction at the wall decreases with partial slip but the most minimum decreasing rate manifests at the higher level of buoyancy forces when the transport phenomenon was induced by free convection. Optimal increasing transfer rates of mass/species is achievable due to rising haphazard motion of the three kinds of nanoparticles when the ternary-hybrid nanofluid was induced by mixed convection. Rising thermo-migration of spherical carbon nanotubes, cylindrical graphene, and platelet alumina nanoparticles causes the transfer of species and heat across the ternary-hybrid nanofluid to diminish.

Influence of CNT Diameter and Annealing on the Tensile Property of CNT by Using Untwisted CNT Yarn

Carbon nanotube (CNT) is tubular nanofibers made of cylindrical graphene sheets. CNT is thought to have higher tensile strength and elastic modulus than those of conventional carbon fibers. Its ideal mechanical properties are estimated to be about 1 TPa for Young's modulus and 10 GPa or more for tensile strength. However, intrinsic excellent mechanical properties of CNTs have not been fully utilized owing to defects of graphene, catalysts left in the core of CNTs and kinks of graphene layers. Decreasing the diameter of CNT and annealing of CNT at high temperature are thought to be useful to improve the tensile properties of CNT. In this study, we investigated the effects of annealing and diameter of CNTs on the tensile properties of CNTs by conducting tensile tests of as-produced and annealed CNT untwisted yarns.

A Sensor Based on One-Dimensional Cylindrical Photonic Crystals and Graphene Elements With a Higher Quality Factor and a Wider Measurement Range

In this paper, a new structure for the sensing and detection of refractive index (RI) based on the one-dimensional cylindrical photonic crystals containing the graphene elements with a higher quality factor (QF) and a wider measurement range are theoretically investigated by the transfer matrix method. The sensing function of the presented structure is that, under impedance matching conditions, the defect cavity captures the tunnel optical Tamm state, and then generates high absorption through electromagnetic resonance. The obtained results show that it is almost unaffected for the sensor in measuring by minor chemical potential, core radius, loss tangent value, and smaller manufacturing roughness. Consequently, it is very tolerant of the working environment and the production industry. However, it is angle-sensitive. As the incident angle ( θ) increases, the sensitivity (S) is enlarged obviously, but the linear area of the sensor shrinks by a large margin. So, the choice of θ should be considered comprehensively. The proposed sensor provides relatively higher performance, ranging from 1.0 ~ 2.8, the S is equivalent to 117.639 nm/RIU, and the average figure of merit is 2707.804. In addition, the average QF arrives at 29906.059. The average detection limit (DL) is 0.0001688 nm, and the lowest DL reaches 0.000006715 nm. In overall sensors, owing to the much-needed to identify substances in the fields of biology, chemistry, environmental monitoring, food safety biological analysis, engineering, and military, the RI sensors are demanded desperately, and it is so far more than other sensor types to research.

Plasmonic leaky wave antenna based on modulated radius of cylindrical graphene waveguide

In this paper, the concept, analysis, and synthesis of a novel plasmonic leaky wave antenna (LWA) based on the modulated radius of a cylindrical graphene waveguide (CGW) at the terahertz band are presented. Devices based on the planar graphene waveguide (PGW) suffer from high attenuations, which significantly limit the radiation efficiency and beam width of LWAs. It is shown here that the LWA based on CGW compared to PGW can decrease the beam width from 55° to 12° and increase the radiation efficiency from 20% to 50%. A sinusoidally modulated graphene surface is employed to excite the leaky wave antenna. A sinusoidally modulated reactance surface is realized by the modulation of the radius of the cylindrical waveguide. In comparison to other structures, the proposed antenna can be implemented by applying a single voltage to graphene sheets. As a result, the antenna beam direction can be readily changed by varying the applied voltage.

Calcium metaborate induced thin walled carbon nanotube syntheses from CO2 by molten carbonate electrolysis

An electrosynthesis is presented to transform the greenhouse gas CO2 into an unusually thin walled, smaller diameter morphology of Carbon Nanotubes (CNTs). The transformation occurs at high yield and coulombic efficiency of the 4-electron CO2 reduction in a molten carbonate electrolyte. The electrosynthesis is driven by an unexpected synergy between calcium and metaborate. In a pure molten lithium carbonate electrolyte, thicker walled CNTs (100–160 nm diameter) are synthesized during a 4 h CO2 electrolysis at 0.1 A cm−2. At this low current density, CO2 without pre-concentration is directly absorbed by the air (direct air capture) to renew and sustain the carbonate electrolyte. The addition of 2 wt% Li2O to the electrolyte produces thinner, highly uniform (50–80 nm diameter) walled CNTs, consisting of ~ 75 concentric, cylindrical graphene walls. The product is produced at high yield (the cathode product consists of > 98% CNTs). It had previously been demonstrated that the addition of 5–10 wt% lithium metaborate to the lithium carbonate electrolyte boron dopes the CNTs increasing their electrical conductivity tenfold, and that the addition of calcium carbonate to a molten lithium carbonate supports the electrosynthesis of thinner walled CNTs, but at low yield (only ~ 15% of the product are CNTs). Here it is shown that the same electrolysis conditions, but with the addition of 7.7 wt% calcium metaborate to lithium carbonate, produces unusually thin walled CNTs uniform (22–42 nm diameter) CNTs consisting of ~ 25 concentric, cylindrical graphene walls at a high yield of > 90% CNTs.

Carbon Nanotube Photoluminescence Modulation by Local Chemical and Supramolecular Chemical Functionalization.

ConspectusCarbon nanotubes (CNTs) have been central materials in nanoscience and nanotechnologies. Single-walled CNTs (SWCNTs) consisting of a cylindrical graphene show a metallic (met) or semiconducting (sc) property depending on their rolling up manner (chirality). The sc-SWCNTs show characteristic chirality-dependent optical properties of their absorption and photoluminescence (PL) in the near-infrared (NIR) region. These are derived from their highly π-conjugated structures having semiconducting crystalline sp2 carbon networks with defined nanoarchitectures that afford a strong quantum confinement and weak dielectric screening. Consequently, photoirradiation of the SWCNTs produces a stable and mobile exciton (excited electron-hole pair) even at room temperature, and the exciton properties dominate such optical phenomena in the SWCNTs. However, the mobile excitons decrease the PL efficiency due to nonradiative relaxation including collision with tube edges and relaxation to lower-lying dark states. A breakthrough regarding the efficient use of the mobile exciton for PL has recently been achieved by local chemical functionalization of the SWCNTs, in which the chemical reactions introduce local defects of oxygen and sp3 carbon atoms in the tube structures. The defect doping creates new emissive doped sites that have narrower band gaps and trap the mobile excitons, which provides locally functionalized SWCNTs (lf-SWCNTs). As a result, the localized exciton produces E11* PL with red-shifted wavelengths and enhanced PL quantum yields compared to the original E11 PL of the nonmodified SWCNTs.In this Account, we describe recently revealed fundamental properties of the lf-SWCNTs based on the analyses by photophysics, theoretical calculations, and electrochemistry combined with in situ PL spectroscopy. The new insight allows us to expand the wavelength regions of the NIR E11* PL derived from the localized exciton, in which upconversion generates a higher energy PL through thermal activation and proximal doped site formation using bis-aryldiazonium modifiers provides a much lower energy PL than typical E11* PL. Moreover, owing to the chemical reaction-dominant doping process, the molecular structure design of modifiers succeeds in producing functionalized lf-SWCNTs; namely, molecular functions are incorporated into the doped sites for their PL modulation. The wavelength changes/switching in the E11* PL selectively occurs by a supramolecular approach using molecular recognition and imine chemistry. Therefore, the local chemical functionalization of the SWCNTs is a key to designing the properties and creating their new functions of the lf-SWCNTs. Fundamental understanding of the doped site properties of the lf-SWCNTs and molecularly driven approaches for exciton and defect engineering would unveil the intrinsic natures of these materials, which is crucial for elevating the SWCNT-based nanotechnologies to the next stage. The resulting materials are of interest in the fields of high performance NIR-II imaging and sensing for bio/medical analyses and single-photon emitters in quantum information technology.

On the use of Chebyshev polynomials in the Rayleigh-Ritz method for vibration and buckling analyses of circular cylindrical three-dimensional graphene foam shells

This study aims to perform free vibration and buckling analyses of circular cylindrical shells made of three-dimensional (3D) graphene foam. Three kinds of porosity distribution are considered including two kinds of symmetrical distribution and uniform distribution. The Kirchhoff-Love shell theory is utilized to establish the mathematical model of 3D graphene foam (3D-GF) shells. Natural frequencies and buckling loads of the shells under various boundary conditions are obtained via the Rayleigh-Ritz method in conjunction with Chebyshev polynomials. Results show that the mechanical characteristics of the 3D-GF shells are significantly affected by the porosity coefficient and porosity distribution. Moreover, the effect of porosity coefficient is closely related to boundary conditions of the shells. It is also shown that as the porosity coefficient increases, the porosity distribution effect on the mechanical characteristics of 3D-GF shells becomes increasingly significant.

Sinusoidally modulated leaky wave antenna based on cylindrical graphene waveguide

Based on the cylindrical graphene waveguide, the concept and analysis of a leaky wave antenna (LWA) at terahertz band are presented. The proposed structure overcomes the limitations of planar LWA characteristics, such as radiation efficiency and beam width. The values of attenuation and leakage constants can lead to the maximum radiation efficiency and beam width in the planar LWA equal to about 20% and 57°, but in cylindrical LWA equal to about 50% and 12°, respectively. The leaky wave is excited by a sinusoidally modulated graphene surface. A sinusoidally modulated reactance surface (SMRS) allows for a nearly independent control of the phase and leakage constants and thus adjusts the scan angle and radiation efficiency simultaneously. An SMRS was first realized by applying various bias voltages to different gating pads underneath the graphene sheet. Another desirable feature of an antenna is the high value of input impedance, so it can easily be matched to a photomixer.

Graphene properties from curved space Dirac equation

A mathematical formulation for particle states and electronic properties of a curved graphene sheet is provided, exploiting a massless Dirac spectrum description for charge carriers living in a curved bidimensional background. In particular, we study how the new description affects the characteristics of the sample, writing an appropriate conductivity Kubo formula for the modified background. Finally, we provide a theoretical analysis for the particular case of a cylindrical graphene sample.

Mechanism of Hydrogen Adsorption in Graphene Nanostructures Synthesized in Membrane Pores and on Zeolites

The mechanism of hydrogen adsorption in mono- and multilayer oriented carbon nanotubes with graphene walls (OCNTGs) synthesized in the pores of TRUMEM membranes is studied. A comparative analysis of these results and data obtained earlier on hydrogen adsorption in cylindrical and planar graphene nanostructures (CPGNSes) formed on TsVM and TsVN zeolites is conducted. The OCNTGs and CPGNSes are synthesized at a temperature of 800°C using methane as a pyrolyzed reagent and saturated with hydrogen at pressures of 9.0–12.0 MPa. Using thermogravimetric analysis (TGA) combined with mass spectrometry analysis, it is found that hydrogen is desorbed from the OCNTGs at a temperature of 175°C and from the CPGNSes at 250 and 450°C; this finding indicates the existence of two hydrogen adsorption mechanisms. Using Raman spectroscopy and transmission electron microscopy (TEM), it is shown that the OCNTGs are graphene structures. Studies of changes in the electrophysical characteristics (ξ-potential and pore surface charge) of the original membranes, membranes with OCNTGs, and membranes with OCNTGs with accumulated hydrogen and studies of the morphology of the OCNTGs suggest that hydrogen adsorption occurs according to a dissociative mechanism. In addition, it is found that the ability of OCNTGs to adsorb hydrogen disappears when they cease to be a cylindrical structure closed along the circumference of a pore. It is concluded that hydrogen diffuses across the OCNTG surface and the earlier studied noncatalytic hydrogenation of decene-1 and naphthalene involving hydrogen occurs according to a spillover mechanism. A comparative analysis of the mechanisms of hydrogen adsorption in OCNTGs and CPGNSes is conducted, and the effect the physicochemical properties of the surface of substrates have on this process is determined.