In-plane strain of electro-active paper under electric fields

Electro-active papers (EAPap) made with cellulose have been known as a biomimetic actuator material according to their merits in terms of large bending deformation, low actuation voltage, ultra-lightweight, and biodegradability. This out-of-plane bending deformation is useful for achieving flapping wings, micro-insect robots, and smart wallpapers. On the other hand, in-plane strains, such as extension and contraction of EAPap materials are also promising for artificial muscle applications since the Young's modulus of EAPap materials is large. This paper first reports the experimental investigation of the in-plane strain of EAPap materials in the presence of electric fields. The EAPap samples preparation and the in-plane strain measurement system are explained. The test results are shown in terms of electric field, frequency and the orientation of the samples. The power consumption and the strain energy of EAPap samples are discussed. Although there are still unknown facts in EAPap materials, this in-plane strain may be useful for artificial muscle applications.     

Charge-tunable insertion process of carbon nanotubes into DNA nanotubes

Control over interactions with biomolecules holds the key of the applications of carbon nanotubes (CNTs) in biotechnology. Here we report a molecule dynamics study on the encapsulation process of different charged CNTs into DNA nanotubes. Our results demonstrated that insertion process of CNTs into DNA nanotubes are charge-tunable. The positive charged CNTs could spontaneously encapsulate and confined in the hollow of DNA nanotubes under the combination of electrostatic and vdW interaction in our ns scale simulation. The conformation of DNA nanotubes is very stable even after the insertion of CNTs. For pristine CNTs, it could not entirely encapsulated by DNA nanotubes in simulation scale in this study. The encapsulation time of pristine CNTs into DNA nanotubes was estimated about 21.9 s based on the potential of mean force along the reaction coordination of encapsulation process of CNTs into DNA nanotubes. In addition, the encapsulation process was also affected by the diameter of CNTs. These findings highlight the charge-tunable self-assembly process of nanomaterials and biomolecules. Our study suggests that the encapsulated CNTs-DNA nanotubes could be used as building blocks for constructing organic–inorganic hybrid materials and has the potential applications in the field of biosensor, drug delivery system and biomaterials etc.     

纳米碳管的若干动力学问题

以单壁纳米碳管为例,建立了其分子动力学模型,并对(5,5)和(10,10)扶手椅型纳米碳管与刚性壁的正碰撞过程和简谐纵波传播过程进行了模拟.在此基础上,探讨如何用弹性杆模型来研究纳米碳管的动力学问题。研究表明,弹性杆模型可以描述单壁扶手椅型纳米碳管与刚性壁高速碰撞的动力学行为;对于纵波传播中的色散描述,则需在弹性杆模型中计入纳米碳管微结构引起的非局部弹性效应.     

Contact dynamics of nanodroplets in carbon nanotubes: effects of electric field,tube radius,and salt ions

We report contact dynamics of nanodroplets in carbon nanotubes using molecular dynamics simulations. The effects of electric field, nanotube radius, and salt ions included in the nanodroplets are explored in more detail. For the cases without applied electric field, the droplet fills the cross section of carbon nanotubes with small radius completely. When the tube radius becomes larger, the droplet retracts towards the surface of the nanotube to minimize the surface tension of the droplet and shows wider extension along the axial direction. When an electric field perpendicular to the axial direction of the carbon nanotubes is applied, the position and shape of the droplets are changed which is also related to the tube radius and whether the droplet contains salt ions. Unlike a planar surface, the nanotube limits spreading of the droplets along the radial direction. The variation of the center of mass of the droplets indicates a significant confinement to the position of the droplets in the electric field. For the salty water droplets, a strong electric field induces ejection of small water clusters from the droplet in a nanotube with large radius. As a consequence, the droplet and water clusters are separated and moved to two opposite sides of the nanotube by the electric field.     

Nonlocal free dynamic analysis of periodic arrays of single-walled carbon nanotubes in the presence of longitudinal thermal and magnetic fields

This paper deals with transverse vibrations of three-dimensional vertically aligned periodic arrays of single-walled carbon nanotubes acted upon by both longitudinal magnetic and thermal fields. For this purpose, a nonlocal higher-order beam theory is employed for modeling of the nanosystem. Accounting for the intertube van der Waals forces, a discrete-based model as well as a continuous-based model is established. For various geometries of the nanosystem and under various applied thermal and magnetic fields, the results of the continuous model are successfully checked with those of the discrete model. Through a comprehensive parametric study, the effects of the nanotube’s radius, slenderness ratio, nonlocality, ensemble’s population, temperature change, and strength of magnetic field on fundamental frequencies of the nanosystem are addressed and displayed.     

On radial breathing vibration of carbon nanotubes

The study aims at exploring the RBM (radial breathing mode) frequencies and mode shapes of various carbon nanotubes (CNTs) using a modified molecular structural mechanics (MSM) model. The focus of the work is placed upon studying the characteristics of the RBM-like modes of the CNTs resulted from their large diameter-length aspect ratio and/or asymmetric atomic configuration. By the approach, their dependence on the layer number, aspect ratio and chirality of the CNTs and temperature is also assessed. The validity of these calculated results is extensively confirmed through comparison with the literature theoretical and experimental data. Simulation results show that an additional layer of CNTs would not have significant impact on the associated RBM frequencies. In addition, asymmetric, non-purely radial RBM modes are observed in the chiral CNTs mainly because of their non-axisymmetric atomic structure. Besides, as the aspect ratio becomes larger than about 1.25, the original, standard RBM mode would be transformed into an RBM-like mode.     

Platinated ultrathin films made of carbon nanotubes

In this study a promising approach for a novel fuel cell catalyst layer is shown using films of carbon nanotubes (CNTs) formed by the layer-by-layer (LbL) method. A special focus is on the dispensing procedure of CNTs in water what is one of the most essential steps to realize monolayers in a reproducible way as targeted in LbL. Furthermore, the platination of the tubes is demonstrated using the reduction of platinum salt in ethylene glycol resulting in a sufficient distribution of nanosized particles. Finally, ultrathin films based on the functionalized nanotubes are investigated with atomic force microscopy, showing promising results for the future use as catalyst layer.     

Decomposition of nitrous oxide on carbon nanotubes

In this work, we have suggested the possibility of using carbon nanotubes to remove toxic gas. By taking an advantage of the density functional theory, we have investigated the decomposition of nitrous oxide (N(2)O) on the sidewalls of the perfect and the Stone-Wales defect armchair (5,5)-SWNTs at the B3LYP/6-31G(d) level of theory. There are two reaction mechanisms proposed: stepwise and concerted pathways. Our calculations predict that the former route is kinetically favored on both the perfect and defect SWNTs with barrier heights of the rate-determining steps of 37.23 and 34.38 kcal/mol for the perfect and the defect systems, respectively. In the second pathway, the decomposition of nitrous oxide gas takes place in a single step with higher reaction barriers of 48.60 and 40.27 kcal/mol on the sidewalls of the perfect and the defect SWNTs, respectively. Moreover, we also demonstrated that an encapsulation of electron rich species, such as chloride anion, inside the channel of the SWNT can boost up the reaction rate of the N(2)O decomposition on the SWNT. The chloride ion supplies excess electrons to the SWNT for transferring to the N(2)O molecule causing lower reaction barriers in the reaction pathways.     

Development of an accurate molecular mechanics model for buckling behavior of multi-walled carbon nanotubes under axial compression

In the present paper, an analytical solution based on a molecular mechanics model is developed to evaluate the elastic critical axial buckling strain of chiral multi-walled carbon nanotubes (MWCNTs). To this end, the total potential energy of the system is calculated with the consideration of the both bond stretching and bond angular variations. Density functional theory (DFT) in the form of generalized gradient approximation (GGA) is implemented to evaluate force constants used in the molecular mechanics model. After that, based on the principle of molecular mechanics, explicit expressions are proposed to obtain elastic surface Young’s modulus and Poisson’s ratio of the single-walled carbon nanotubes corresponding to different types of chirality. Selected numerical results are presented to indicate the influence of the type of chirality, tube diameter, and number of tube walls in detailed. An excellent agreement is found between the present numerical results and those found in the literature which confirms the validity as well as the accuracy of the present closed-form solution. It is found that the value of critical axial buckling strain exhibit significant dependency on the type of chirality and number of tube walls.     

Dielectrophoretic separation of carbon nanotubes and polystyrene microparticles

The separation of multi-walled carbon nanotubes (MWCNTs) and polystyrene microparticles using a dielectrophoresis (DEP) system is presented. The DEP system consists of arrays of parallel microelectrodes patterned on a glass substrate. The performance of the system is evaluated by means of numerical simulations. The MWCNTs demonstrate a positive DEP behaviour and can be trapped at the regions of high electric field. However, the polystyrene microparticles demonstrate a negative DEP behaviour at a certain range of frequencies and migrate to the regions of low electric field. Experiments are performed on the microparticles at the frequencies between 100 Hz and 1 MHz to estimate their crossover frequency and select the range of separation frequencies. Further, experiments are conducted at the obtained range of separation frequencies to separate the MWCNTs and polystyrene microparticles.     

Improving jet reactor configuration for production of carbon nanotubes

The jet mixing reactor has been proposed for the industrial production of fullerence carbon nanotubes. The goal is to obtain a uniformly high temperature of a catalyst. The mixing flowfield is studied using the semi-implicit method for pressure-linked equations revised algorithm. Hot peripheral jets are used to enhance heating of the central jet by mixing with the ambience of the reactor. Numerous configurations of peripheral jets with various numbers of jets, distance between nozzles, angles between the central jet and a peripheral jet, and twisted configuration of nozzles are considered. Unlike the previous studies of jet mixing, the optimal configuration of peripheral jets produces strong stretching of a cross-section of the central jet that enhances the mixing of the central jet with the reactor ambience.     

碳纳米管在高电压设备在线监测领域的应用

阐述了高压电气设备绝缘故障在线检测的一些方法,介绍了碳纳米管气体传感器近期的研究动向和取得的成果。应用碳纳米管气体传感器监测电气设备绝缘故障特征气体时,重点介绍了纯SF6,SF6/N2混合气体中局部放电产生的气体分解组分在电压、气体压强、温度等因素下对气体传感器的影响。并提出了碳纳米管气体传感器在高电压设备在线检测领域研究中所存在的问题和未来的研究发展方向。     

Chemo-sensitivity of latex-based films containing segregated networks of carbon nanotubes

In contrast to conventional hydrophobic Conductive Polymer nanoComposites (CPCs) used to design vapor sensors, which are mostly soluble in organic solvents, monodispersed acrylate copolymer latexes present the double advantage of being more sensitive and selective towards polar vapors such as water. A hierarchically structured latex based CPC film was obtained by co-dispersion of an aqueous acrylic emulsion with multiwalled carbon nanotubes (CNTs), followed by spray layer by layer (sLbL) assembly. The analysis of CPC films morphology by AFM and TEM show that a segregated network of CNT as been achieved by partial coalescence of latex nanoparticles and homogeneously assembled in 3D. Transducer sensitivity was investigated as a function of CNT content, latex glass transition temperature (T_g), organic vapor nature and vapor concentration. The source of the high sensitivity and selectivity observed for these latex-based composites towards water vapor is assumed to mainly result from ionic interaction of SDS with water molecules offering interesting perspectives of development. The different diffusion regimes through the CPC transducer are visualized, modeled and interpreted with the Langmuir-Henry-Clustering (LHC) model, showing that only water is reaching a clustering mode at high vapor concentration. Finally it is believed that the unique hierarchical architecture of BA latex-CNT sensors is responsible for their quick, stable and reproducible responses to vapors.     

Simulation of the flow of aqueous solutions through carbon nanotubes

The flow of aqueous NaCl and NaI solutions through carbon nanotubes is treated by extensive molecular dynamics simulations. The dependence of diverse transport features on the solute specificity, the nanotube geometry, and the various atomic models employed, including polarizability, is addressed in detail. The interpretations are developed in conjunction with the structural details of the solution and the energy barriers the solute components have to overcome.     

Progress of synthesizing methods and properties of fluorinated carbon nanotubes

In this paper,the recent development of fluorinated carbon nanotubes(F-CNTs) was introduced.The synthesizing methods of F-CNTs,including direct fluorination and plasma treatment,were discussed in detail,and the effects of factors,such as the temperature and pressure in fluorination as well as the kind of fluorine source and carbon nanotubes,on the structures and properties of F-CNTs were also summarized.In the mean time,the special physical and chemical properties of F-CNTs and the relevant applied fields w...     

Prediction of the viscosity of water confined in carbon nanotubes

In this paper, the viscosity of water confined in single-walled carbon nanotubes (SWCNTs) with the diameter ranging from 8 to 54 ? is evaluated, which is crucial for the research on the nanoflow but difficult to be obtained. An “Eyring-MD” (molecular dynamics) method combining the Eyring theory of viscosity with the MD simulations is proposed to tackle the particular problems. For the critical energy which is a parameter in the “Eyring-MD” method, the numerical experiment is adopted to explore its dependence on the temperature and the potential energy. To demonstrate the feasibility of the proposed method, the viscosity of water at high pressure is computed and the results are in reasonable agreement with the experimental results. The computational results indicate that the viscosity of water inside SWCNTs increases nonlinearly with enlarging diameter of SWCNTs, which can reflect the size effect on the transports capability of the SWCNTs. The trend of the viscosity is well explained by the variation of the hydrogen bond of the water inside SWCNTs. A fitting equation of the viscosity of the confined water is given, which should be significant for recognizing and studying the transport behavior of fluid through the nanochannels.     

The influence of electric fields on nanostructures—Simulation and control

Macroscopic electric fields may be used to influence or even control the shape evolution of single layer islands on a crystalline surface. We validate a phase-field approach to simulate such shape evolutions by comparison with simulations based on a sharp interface approach. The phase-field model is then used to formulate and discretize the control problem of finding an electric field which drives an island to a predefined shape. Some first results of this approach are presented.     

Directed transport and location-designated rotation of nanowires using ac electric fields

The motion control of individual nanowires is essential for effective nanowire manipulation strategies. In this paper, we demonstrate a simple and general method to dynamically control the motion of a chemically untreated nanowire in a quadrupole electrode structure. The motion of single nanowires was determined by positive dielectrophoresis and orientational torque, which were induced by optionally exerting ac signals onto specific electrodes for regulating the electric field distribution in real time. A silver nanowire was guided to transform postures and transport directionally in a working regime of about 115 μm × 115 μm. The selected nanowire was then transported to a region of weak gradients and forced to rotate at the designated location subsequently. The behavior of the nanowires, including their posture, cornering time, linear displacement and location-designated rotation, was dynamically monitored and regulated. A simple analytical model was developed to derive the driving forces and torques on the nanowire.     

Computational study on bonding of carbon nanotubes onto metallic substrates

Mechanism of carbon nanotube bonding onto the metal substrate is investigated using molecular dynamics in this study. Different temperatures and types of the metal atoms to the carbon nanotube surface are considered. It is shown that there is close relationship between surface melting and contact length of the bonding. The melting firstly occurs on the surface of the metal and the contact length increases with the melting propagating from the open surface to the interior of the metal as the temperature rising. In addition, the wetting property of the metal atoms plays an important role during the bonding of the carbon nanotube onto the metal. The carbon nanotube will be easily welded onto the metal with excellent wetting property. The results indicate that the bonding process of the carbon nanotube onto the metal can be controlled by two ways. First, concentrating energy on the metal surface to enhance the surface melting. Second, selecting the metal with excellent wetting property or effective method is utilized to enhance the wetting property of the metal atoms to the carbon nanotube surface.