Stability Of Double-walled Carbon Nanotubes Research Articles

Dynamics and Stability of Double-Walled Carbon Nanotube Cantilevers Conveying Fluid in an Elastic Medium

The paper concerns the dynamics and stability of double-walled carbon nanotubes conveying fluid. The equations of motion adopted in the current study to describe the dynamics of such nano-pipes stem from the classical Bernoulli–Euler beam theory. Several additional terms are included in the basic equations in order to take into account the influence of the conveyed fluid, the impact of the surrounding medium and the effect of the van der Waals interaction between the inner and outer single-walled carbon nanotubes constituting a double-walled one. In the present work, the flow-induced vibrations of the considered nano-pipes are studied for different values of the length of the pipe, its inner radius, the characteristics of the ambient medium and the velocity of the fluid flow, which is assumed to be constant. The critical fluid flow velocities are obtained at which such a cantilevered double-walled carbon nanotube embedded in an elastic medium loses stability.

Nonlocal Dynamic Stability of DWCNTs Containing Pulsating Viscous Fluid Including Surface Stress and Thermal Effects Based on Sinusoidal Higher Order Shear Deformation Shell Theory

AbstractIn this study, the dynamic stability of double-walled carbon nanotubes (DWCNTs) conveying pulsating viscous fluid located on visco-Pasternak medium is investigated. The effects of small scale are considered using Eringen's non-local theory. The surrounding medium of DWCNT is anticipated as a visco-Pasternak foundation including the normal, shear, and damping forces. The van der Waals (vdWs) force is considered among the inner and outer layers of DWCNT. Three types of temperature changes, i.e. uniform, linear and sinusoidal temperature rise, through the thickness are studied. The equations of motion are obtained using higher order sinusoidal shear deformation shell theory (SSDT), in which the surface effects are included. Dynamical equations of DWCNT are extracted using the energy method and Hamilton's principle. Due to orthogonal conditions, the governing equations are solved based on Bolotin method. The effects of different parameters such as surface stress, non-local parameter, fluid velocity, Knudsen's number, fluid density, dimensions ratio and various temperature loadings on the dynamic stability regions of DWCNTs are discussed.

Stability of Double-Walled Carbon Nanotubes Revisited

An approach to the stability analysis of orthotropic two-layer shells with mechanical and electrical properties of carbon nanotubes is proposed. Van der Waals forces act between the layers. The parameters of the continuum between the layers are obtained using the Lennard-Jones potential. The governing system of equations is written for rates of sixteen variables. The loading and boundary conditions are specified for each layer separately. Numerical results are obtained using the discrete orthogonalization method. The stability of single- and double-walled nanotubes is analyzed. Numerical results are summarized in tables and analyzed

Nonlocal vibration and instability analysis of embedded DWCNT conveying fluid under magnetic field with slip conditions consideration

In this study, vibration of double-walled carbon nanotubes (DWCNTs) conveying fluid placed in uniform magnetic field is carried out based on nonlocal elasticity theory. DWCNT is embedded in Pasternak foundation and is simulated as a Timoshenko beam (TB) model which includes rotary inertia and transverse shear deformation in the formulation. Considering slip boundary conditions and van der Waals (vdW) forces between inner and the outer nanotubes, the governing equations of motion are discretized and differential quadrature method (DQM) is applied to obtain the frequency of DWCNTs for clamped–clamped boundary condition. The detailed parametric study is conducted, focusing on the remarkable effects of small scale, Knudsen number, elastic medium, magnetic field, density, and velocity of conveying fluid on the stability of DWCNT. Results indicate that considering slip boundary conditions has significant effect on stability of DWCNTs. Also, it is found that trend of figures have good agreement with the previous researches. Results of this investigation could be applied for optimum design of nano/micro mechanical devices for controlling stability of DWCNTs conveying fluid under magnetic fields.

Probing structural stability of double-walled carbon nanotubes at high non-hydrostatic pressure by Raman spectroscopy

Theoretical calculations predict that the collapse pressure for double-walled carbon nanotubes (DWCNTs) is proportional to 1/R 3, where R is the effective or average radius of a DWCNT. In order to address the problem of CNT stability at high pressure and stress, we performed a resonance Raman study of DWCNTs dispersed in sodium cholate using 532 and 633 nm laser excitation. Raman spectra of the recovered samples show minor versus irreversible changes with increasing I D/I G ratio after exposure to high non-hydrostatic pressure of 23 and 35 GPa, respectively. The system exhibits nearly 70% pressure hysteresis in radial breathing vibrational mode signals recovery on pressure release which is twice that predicted by theory.

Buckling of functionally graded circular columns including shear deformation

An analysis of the stability of circular cylindrical columns/beams composed of functionally graded materials is made where shear deformation is taken into account. In this study, a new approach is carried out. Different from the assumption of uniform shear stress at the cross-section adopted in the Timoshenko beam theory, proposed model provides a new approach for treating the problem. Based on the traction-free surface condition, two coupled governing equations for the deflection and rotation are derived, and a single governing equation is further obtained. A comparison of buckling loads derived from the proposed circular column model and the Timoshenko and Euler–Bernoulli theories of beams is made. Moreover, the effects of radial gradient on buckling loads of elastic columns with circular cross-section made of functionally graded materials are elucidated. Finally, the stability of double-walled carbon nanotubes is considered and critical stress is determined and compared with existing results. The results obtained by the proposed model show very good agreement with the results of the Timoshenko beam theory or Reddy–Bickford beam theory.

Synthesis and High Thermal Stability of Double-Walled Carbon Nanotubes Using Nickel Formate Dihydrate as Catalyst Precursor

Nickel formate dihydrate is demonstrated to be an effective catalyst precursor for selectively synthesizing double-walled carbon nanotubes (DWNTs) with high thermal stability by using a hydrogen arc discharge technique. High-resolution transmission electron microscopy (HRTEM) observations show that the assynthesized DWNTs are of high quality with good structural integrity and narrow diameter distribution (1.983.47 nm and 1.32-2.81 nm, respectively, for the outer and inner diameter). Thermogravimetric analysis (TGA) in air indicates that the DWNTs have excellent oxidation resistance up to 800 °C, approaching to that of graphitized multiwalled carbon nanotubes and higher than that of DWNTs prepared by other routes or methods. Moreover, Raman analysis and HRTEM observations reveal that these DWNTs can keep good structural stability and other carbon species are removed after oxidation at 650 °C in air flow. The formation of DWNTs with high thermal stability is attributed to the cleaning effect of active radicals such as hydrogen and oxygen originated from the decomposition of nickel formate dihydrate and the in situ defect-healing effect induced by high arc current in the arc growth process. This approach opens various application possibilities for DWNTs with high thermal stability to be used in high-temperature composites, nanoelectronic devices, and electron filed emitters operating at high currents, etc.

Synthesis and High Thermal Stability of Double-Walled Carbon Nanotubes Using Nickel Formate Dihydrate as Catalyst Precursor

Nickel formate dihydrate is demonstrated to be an effective catalyst precursor for selectively synthesizing double-walled carbon nanotubes (DWNTs) with high thermal stability by using a hydrogen arc discharge technique. High-resolution transmission electron microscopy (HRTEM) observations show that the as-synthesized DWNTs are of high quality with good structural integrity and narrow diameter distribution (1.98−3.47 nm and 1.32−2.81 nm, respectively, for the outer and inner diameter). Thermogravimetric analysis (TGA) in air indicates that the DWNTs have excellent oxidation resistance up to ∼800 °C, approaching to that of graphitized multiwalled carbon nanotubes and higher than that of DWNTs prepared by other routes or methods. Moreover, Raman analysis and HRTEM observations reveal that these DWNTs can keep good structural stability and other carbon species are removed after oxidation at 650 °C in air flow. The formation of DWNTs with high thermal stability is attributed to the cleaning effect of active radicals such as hydrogen and oxygen originated from the decomposition of nickel formate dihydrate and the in situ defect-healing effect induced by high arc current in the arc growth process. This approach opens various application possibilities for DWNTs with high thermal stability to be used in high-temperature composites, nanoelectronic devices, and electron filed emitters operating at high currents, etc.