We demonstrate a class of model nano-electromechanical systems (NEMS) based on multiwalled carbon nanotubes (MWNTs) which has longer inner cores coaxially oscillating inside their respective shorter outer shell holders and can operate at continuously controllable frequencies up to the gigahertz range when fuelled by AC electric fields. Its additional attributes include much larger oscillation amplitudes and forces and much lower rates of thermal dissipation (Q-factor = 10^5) and air damping (Q-factor = 10^4~10^5) than those of nano-beam based NEMS. A crucial feature of the conceived model NEMS is that after having tuned the electric field frequency to any prescribed value within a permitted range, the NEMS will respond quickly (in sub-nanoseconds) at the same oscillation frequency. These merits, when contrasted with the nano-beam resonators developed so far, make it a better potential candidate for the ongoing miniaturization progress from micro- to nano-electromechanical systems.
The synthesis of Ni filled multiwalled carbon nanotubes was performed by atmospheric pressure chemical vapor deposition with propane on Si at 850 C using a simple mixture of Ni(salen), and a conventional photoresist. Analysis of the carbon nanotubes using scanning electron microscopy together with high resolution transmission electron microscopy show that the nanotubes have grown by a tip growth mechanism and exhibit a multi walled structure with partial Ni filling. The high quality of the Ni filled nanotubes is evidenced by Raman spectroscopy. The magnetic properties of Ni filled nanotubes we…
The effect of Fe and Ni catalysts on the synthesis of carbon nanotubes (CNTs) using atmospheric pressure chemical vapor deposition (APCVD) was investigated. Field emission scanning electron microscopy (FESEM) analysis suggests that the samples grow through a tip growth mechanism. High-resolution transmission electron microscopy (HRTEM) measurements show multiwalled carbon nanotubes (MWCNTs) with bamboo structure for Ni catalyst while iron filled straight tubes were obtained with the Fe catalyst. The X-ray diffraction (XRD) pattern indicates that nanotubes are graphitic in nature and there is n…
In this work, a novel electrospun conductive polymer nanocomposite made of polycaprolactone with an exohedral complex made of multiwalled carbon nanotubes and fullerene C60 was prepared and characterized. The preparation was straightforward and the complexes self-assembled within the nanocomposite fibers. The nanocomposite showed electrical switching behavior due to charge accumulation of fullerene C60 upon electrical stimulation. Write-once read-many memory devices were fabricated by electrospinning a nanocomposite with 0.8%wt. fullerene C60 onto interdigitated coplanar electrodes. The device…
In the present work, multiwalled carbon nanotubes were decorated with rhodium nanoparticles using a colloidal solution in the post-discharge of an RF atmospheric plasma of argon (Ar) or argon/oxygen (Ar:O$_2$). The properties of these hybrid materials towards the room temperature detection of NO$_2$, C$_2$H$_4$, CO, C$_6$H$_6$ and moisture were investigated and discussed in view of compositional and morphological studies. It was found that the presence of oxygen in the plasma treatment is essential to significantly enhance the gas response of Rh-decorated multiwalled carbon nanotubes and to av…
Self-organized composites of multiwalled carbon nanotubes and nematic liquid crystal 5CB: Optical singularities and percolation behavior in electrical conductivity
Experiments with multiwalled carbon nanotubes and graphite as targets in a source of negative ions with cesium sputtering have shown that nanotubes with nanometer radii and micrometer length can be compared with micrometer size graphite grains to understand the irradiation effects that include the formation, sputtering of carbon clusters and the resulting structural changes. The simultaneous adsorption of cesium on the surface and bombardment by energetic cesium ions is shown to play its role in the cluster formation and sputtering of carbon atoms and clusters and the cesium substituted carbon…
Polydimethylsiloxane (PDMS) is an insulator and it is commonly used in fabrication of micro-structures but there is a need of electrical conductive PDMS. Therefore, this research is mainly focused on producing PDMS nanocomposites with high electrical conductivity. Thus, we produced highly conductive PDMS nanocomposites which were filled with multiwalled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs). Due to the synergistic effect between CNTs and GNPs inside a polymeric matrix, we expected to obtain more conductive nanocomposites than PDMS nanocomposite filled with only CNTs. Addi…
This investigation deals with the effect of growth temperature on the growth behavior of Fe filled multiwalled carbon nanotubes (MWCNTs). Carbon nanotube (CNT) synthesis was carried out in a thermal chemical vapor deposition (CVD) reactor in the temperature range 650 to 950 1C using propane as the carbon source, Fe as the catalyst material, and Si as the catalyst support. Atomic force microscopy (AFM) analysis of the catalyst exhibits that at elevated temperature clusters of catalyst coalesce and form macroscopic islands. Field emission scanning electron microscopy (FESEM) results show that wi…
Diameter-dependent conductance oscillations in carbon nanotubes upon torsion
我们将机电测量与{ \em ab initio}密度泛函计算相结合，解决了多壁碳纳米管中扭转诱导电导振荡起源的争议。根据我们的观察，振荡周期与纳米管直径的平方成反比，正如相同直径的单壁纳米管所预期的那样。这是支持我们的理论发现，微分扭转有效地使费米能级附近的多壁纳米管的壁，并移动量子线的费米动量。我们排除了与壁之间的配准变化相关的另一种解释，因为它会导致振荡周期的不同直径依赖性。
The surface reconstruction of the Fe catalyst films due to high temperature processing in hydrogen prior to nanotube nucleation and its effect on the growth morphologies of partially filled carbon nanotubes (CNTs) synthesized using atmospheric pressure chemical vapor deposition (APCVD) of propane was investigated. Results show that pre-heating of the catalyst film deeply influences the particle size distribution, which governs the growth morphologies of the corresponding CNTs. The distribution of the catalyst particles over the Si substrate was analyzed before and after the heat treatment by a…
Here we present graphene-based nanoelectromechanical switch with the vertical carbon nanotube electrode via classical molecular dynamics simulations. The carbon nanotube is grown in the center of the square hole and the graphene covers on the hole. The potential difference between the bottom of the hole and the graphene is applied to deflect the graphene. By performing classical molecular dynamic simulations, we investigate the electromechanical properties of graphene-based nanoelectro- mechanical switch with carbon nanotube electrode, which can be switched by the externally applied force. Thi…
The effects of charge doping on the structural deformation and on the electronic structure of armchair single wall carbon nanotube (SWNT) bundles are investigated through first-principles calculations. In particular, we select a (6; 6) SWNT as an example and we calculate a mechanical deformation in the SWNT bundles as a function of gate voltage, which could serve as a basis of the electromechanical actuators in an artificial muscle. We find that the magnitudes of the actuation responses such as strain and stress of the (6; 6) SWNT bundle in the case of hole doping are substantially larger than…
We present a novel computational framework to simulate the electromechanical response of self-sensing carbon nanotube (CNT)-based composites experiencing fracture. The computational framework combines electrical-deformation-fracture finite element modelling with a mixed micromechanics formulation. The latter is used to estimate the constitutive properties of CNT-based composites, including the elastic tensor, fracture energy, electrical conductivity, and linear piezoresistive coefficients. These properties are inputted into a coupled electro-structural finite element model, which simulates the…
Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-…
