Search for: nanotubes
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    Finite element modeling of single-walled carbon nanotubes with introducing a new wall thickness

    , Article Journal of Physics: Conference Series ; Volume 61, Issue 1 , 2007 , Pages 497-502 ; 17426588 (ISSN) Jalalahmadi, B ; Naghdabadi, R ; Sharif University of Technology
    Institute of Physics Publishing  2007
    A three-dimensional finite element (FE) model for armchair, zigzag and chiral single-walled carbon nanotubes (SWCNTs) is proposed. By considering the covalent bonds as connecting elements between carbon atoms, a nanotube is simulated as a space frame-like structure. Here, the carbon atoms act as joints of the connecting elements. To create the FE models, nodes are placed at the locations of carbon atoms and the bonds between them are modeled using three-dimensional elastic beam elements. Using Morse atomic potential, the elastic moduli of beam elements are obtained via considering a linkage between molecular and continuum mechanics. Also, a new wall thickness (bond diameter) equal to 0.1296... 

    Doping reaction of some nanotubes with aluminium atom: A thermodynamic PM6 and ONIOM investigation

    , Article Oriental Journal of Chemistry ; Volume 33, Issue 1 , 2017 , Pages 329-334 ; 0970020X (ISSN) Zeighami, N ; Gholami, M. R ; Boshra, A ; Sharif University of Technology
    Oriental Scientific Publishing Company  2017
    The doping reaction of boron nitride and carbon nanotubes with aluminium atom was theoretically investigated. ONIOM method and PM6 method have been used to evaluate the thermochemistry of doping reactions of single walled boron nitride nanotubes and carbon nanotubes. The enthalpy changes, Gibbs free energy changes, of studied doping reactions were evaluated at different temperatures. All nanotubes were single-walled and finite length with hydrogen saturation in the terminal atoms. The thermodynamic calculations based on the ONIOM and PM6 levels results showed (8,0)CNT is the best candidate for Al-doping reaction.result suggest the aluminum doped boron nitride nanotubes and carbon nanotubes... 

    Hydrogen storage in single- and multi-walled carbon nanotubes and nanotube bundles

    , Article Australian Journal of Basic and Applied Sciences ; Volume 5, Issue 7 , 2011 , Pages 483-490 ; 19918178 (ISSN) Hamidi, S ; Golnabi, H ; Sharif University of Technology
    This article describes the hydrogen storage capacity in different carbon nanotubes. The hydrogen storage capacities in the armchair, zigzag, and chiral nanotubes are investigated. The hydrogen storing capacities as a function of the carbon nanotube (CNT) diameter are investigated for the single-walled (SWNT), multi-walled (MWNT), and CNT bundles and results are compared. Hydrogen storage capacity in SWNTs is increased by increasing the nanotube diameter. For diameter d=0.3887 nm of (5,0) CNT the hydrogen capacity is 0.99%, while for the (17,17) SWNT with a diameter d=2.289 nm the capacity is increased to 5.06%. In comparison of different MWNTs for a common external diameter d=1.6064 nm the... 

    Effect of surface stresses on elastic behavior of a screw dislocation inside the wall of a nanotube

    , Article Physica Status Solidi (B) Basic Research ; Volume 248, Issue 6 , 2011 , Pages 1437-1441 ; 03701972 (ISSN) Shodja, H. M ; Gutkin, M. Y ; Moeini Ardakani, S. S ; Sharif University of Technology
    Behavior of a screw dislocation inside a nanotube (NT) is considered in the context of surface elasticity. The elastic fields as well as the image force acting over the dislocation are derived and analyzed in detail. In contrast with the result of classical elasticity, the screw dislocation is shown to be repelled by free surfaces and occupy two stable equilibrium positions near them. The image force strongly depends on the NT's inner and outer radii as well as surface elastic characteristics  

    Electrochemical synthesis of doped TNT as a nano photocatalyst for color degradation applications

    , Article Desalination and Water Treatment ; Volume 28, Issue 1-3 , 2011 , Pages 23-27 ; 19443994 (ISSN) Asl, S. K ; Kianpour Rad, M ; Sadrnezhaad, S. K ; Sharif University of Technology
    Taylor and Francis Inc  2011
    The preparation of high aspect-ratio TiO2 nanotubes and their photocatalytic activity were demonstrated in this study. The high aspect-ratio TiO2 nanotube thin films were produced by electrochemical anodic oxidation of Ti in chloride-containing electrolytes. Nanotubes were doped with different concentrations of ZnO particles through anodization. The catalytic behavior was evaluated under batch reactor with photo-degradation test of Red Dye. The experimental results collectively demonstrate the successful ZnO doping of the resultant nanotube layers with significant abundant OH groups on their increased surfaces. The nanotubes doped with high content combined with an anatase as a two phase... 

    Fabrication of gas ionization sensor based on titanium oxide nanotube arrays

    , Article Applied Physics A ; Volume 115, Issue 4 , June , 2014 , pp 1387-1393 ; 1432-0630 Nikfarjam, A. (Alireza) ; Mohammadpour, R. (Raheleh) ; Iraji Zad, A. (Azam) ; Sharif University of Technology
    Gas sensors have been fabricated based on field ionization from titanium oxide nanotubes grown on titanium foil. Ordered nanaotube arrays of titanium oxides were grown by the anodization method. We measured breakdown voltages and discharge currents of the device for various gases. Our gas ionization sensors (GIS) presented good sensitivity, selectivity, and short response time. The GISs based on TiO2 nanotube arrays showed lower breakdown voltage, higher discharge current, and good selectivity. An excellent response observed for Ar compared to other gases. Besides, by introducing 2 % CO and 4 % H2 to N2 flow gas, the amount of breakdown voltage shifts about 20 and 70 volts to the lower... 

    Theoretical study of interaction between tacrine and finite-length Al-doped carbon and boron nitride nanotubes: A semiempirical drug delivery study in thermodynamic view

    , Article Oriental Journal of Chemistry ; Vol. 30, issue. 4 , 2014 , p. 1805-1813 Zeighami, N ; Gholami, M. R ; Aghaie, M ; Boshra, A ; Sharif University of Technology
    In order to extend our previous theoretical calculations that dealt with the thermochemistry of doping the single walled boron nitride nanotubes, BNNTs, and carbon nanotubes, CNTs, with alminium atoms [1], we have used the AM1, PM3, and PM6 semiempirical methods to investigate the interaction of the tacrine molecule (a drug for the treatment of Alzheimer's disease) with the side-walls of aluminum doped boron nitride and carbon nanotubes in thermodynamic views. At first, the frequency calculations were carried out to confirm the stability of the involved structures. In addition, the theoretical thermodynamic study of tacrine adsorption onto the considered nanotubes was performed and the... 

    Size-dependent instability of carbon nanotubes under electrostatic actuation using nonlocal elasticity

    , Article International Journal of Mechanical Sciences ; Vol. 80 , 2014 , pp. 144-152 ; ISSN: 00207403 Seyyed Fakhrabadi, M. M ; Rastgoo, A ; Taghi Ahmadian, M ; Sharif University of Technology
    In this paper, the classical and nonlocal elasticity are applied to investigate the deflection and instability of electrostatically actuated carbon nanotubes. The results are presented for different geometries and boundary conditions. They reveal that increasing radius and gap and decreasing length confine to increasing pull-in voltages of the carbon nanotubes. The results prove that application of the nonlocal elasticity theorem leads to stiffer structures with higher pull-in voltages. Thus, in order to obtain more accurate results about the mechanical and electromechanical behaviors of the carbon nanotubes, one should apply the nonclassical elasticity theories such as that applied in this... 

    Non-linear behaviors of carbon nanotubes under electrostatic actuation based on strain gradient theory

    , Article International Journal of Non-Linear Mechanics ; Vol. 67, issue , 2014 , p. 236-244 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    The paper deals with studying the deflection and pull-in voltages of the carbon nanotubes under electrostatic actuation with various dimensions and boundary conditions. The size-dependent behaviors of the carbon nanotubes (CNTs) are considered via application of the strain gradient theory. The results obtained from the strain gradient theory are compared to those estimated using the classical elasticity. The outcomes reveal that the classical elasticity theory underestimates the pull-in voltages of the carbon nanotubes and strain gradient theorem results in stiffer nano-structures with higher pull-in voltages. Increasing of the deflection due to the higher voltages increases the differences... 

    Rheological and morphological properties of nanocomposites based on PA66/PA6/multi-walled carbon nanotube prepared by melt mixing

    , Article ICCM International Conferences on Composite Materials, 21 August 2011 through 26 August 2011, Jeju ; August , 2011 Hadizadeh, A. M ; Shojaei, A ; Bagheri, R ; Sharif University of Technology

    Photocatalytic properties of mesoporous TiO2 nanocomposites modified with carbon nanotubes and copper

    , Article Ceramics International ; 2016 ; 02728842 (ISSN) Nourbakhsh, A ; Abbaspour, S ; Masood, M ; Mirsattari, S. N ; Vahedi, A ; Mackenzie, K. J. D ; Sharif University of Technology
    Elsevier Ltd  2016
    The photocatalytic activity of mesoporous TiO2 modified by the addition of carbon nanotubes (CNTs) and Cu is reported. Nanocomposites of carbon nanotubes (CNTs) containing varying amounts of Cu were formed by treatment with Cu2+ then reduced to Cu0 using NaBH4 as the reducing agent. The mesoporous TiO2, synthesized by a sol-gel method from titanium isopropoxide, was combined with the CNT/Cu nanocomposites to form the photocatalysts which were characterized by XRD, SEM, TEM, FTIR, XPS and BET surface area analysis. The photocatalytic properties of the mesoporous TiO2 composites were studied by measuring the degradation of methyl orange (MO) which was optimal in the sample containing 20wt% of... 

    Nonlinear dynamic analysis of electrostatically actuated single-walled carbon nanotubes using nonlocal elasticity

    , Article Latin American Journal of Solids and Structures ; Volume 12, Issue 7 , 2015 , Pages 1224-1240 ; 16797817 (ISSN) Seyyed Fakhrabadi, M ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    Brazilian Association of Computational Mechanics  2015
    The paper investigates the effects of application of nonlocal elasticity theory on electromechanical behaviors of single-walled carbon nanotubes under electrostatic actuation. The influences of different dimensions and boundary conditions on the vibration and dynamic instability of the carbon nanotubes are studied, in detail, using this theory. The results reveal that application of the non-local elasticity theory leads to the higher pull-in voltages for the nonlocal model applied for carbon nanotubes. Thus, in order to have more accurate results, one should apply nonclassical theorems such as the nonlocal elasticity theory to scrutinize the mechanical and electromechanical behaviors of the... 

    Application of 3D gold nanotube ensembles in electrochemical sensing of ultra-trace Hg (II) in drinkable water

    , Article Surfaces and Interfaces ; Volume 10 , 2018 , Pages 27-31 ; 24680230 (ISSN) Bahari Mollamahale, Y ; Ghorbani, M ; Dolati, A ; Ghalkhani, M ; Sharif University of Technology
    Elsevier B.V  2018
    As a novel and highly sensitive sensor, three-dimensional gold nanoelectrode ensembles (3D GNE) prepared by gold deposition inside the parallel pores of a porous template have been successfully applied in electrochemical determination experiments. In this study, we report on the fabrication of 3D gold nanotubes (GNT) and their application in determination of Hg (II) in water. The morphology and crystal structure of the 3D GNT were characterized by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), respectively. The sensitivity of the fabricated electrode towards Hg (II) was examined using anodic stripping voltammetry (ASV) as a powerful technique in... 

    Nonlinear charging and transport times in doped nanotubes junctions

    , Article Journal of the Physical Society of Japan ; Volume 74, Issue 2 , 2005 , Pages 515-518 ; 00319015 (ISSN) Esfarjani, K ; Farajian, A. A ; Kawazoe, Y ; Chui, S. T ; Sharif University of Technology
    The nonlinear capacitance in doped nanotube junctions is calculated self consistently. A negative differential capacitance is observed when the applied bias becomes larger than the pseudogap of the metallic armchair nanotube. For this device, one can deduce a relaxation time of approximately 0.1 fs. Because of its negative differential resistance (NDR), a switching time of less than a femtosecond, i.e., at least three orders smaller than present-day switching times, can also be estimated. This effect is important in designing ultrafast nano-electronic components. ©2005 The Physical Society of Japan  

    Finite element model of SWCNT under hydrostatic pressure

    , Article AIP Conference Proceedings, 10 April 2007 through 12 April 2007, Sharjah ; Volume 929 , 2007 , Pages 82-88 ; 0094243X (ISSN) ; 0735404399 (ISBN); 9780735404397 (ISBN) Sakhaee Pour, A ; Ahmadian, M. T ; Sharif University of Technology
    A finite element technique is used to mimic radial deformation of single-walled carbon nanotubes under hydrostatic pressure. The elastic deformation of nanotubes is modeled via elastic beams. Properties of the beam element are evaluated by considering characteristics of the covalent bonds between the carbon atoms in a hexagonal lattice. Applying the beam model in a three dimensional space, the elastic properties of the nanotube in the transverse direction are evaluated. The effects of diameter and wall thickness on the radial and circumferential elastic moduli of zigzag and armchair nanotubes are considered. Results are in good agreement with molecular structural mechanics data in the... 

    An investigation on the structural characteristics and reinforcement of melt processed polyamide 66/multiwalled carbon nanotube composites

    , Article Polymers for Advanced Technologies ; Vol. 25, issue. 4 , 2014 , pp. 406-417 ; ISSN: 10427147 Shojaei, A ; Nourbakhsh, P ; Faghihi, M ; Sharif University of Technology
    Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of... 

    Simulation of biomanipulation using molecular dynamics

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Volume 9, Issue PARTS A AND B , 2012 , Pages 137-143 ; 9780791845257 (ISBN) Pishkenari, H. N ; Mahboobi, S. H ; Mahjour, M. A ; Meghdari, A ; Sharif University of Technology
    In this paper, the simulation of biomolecules manipulation using molecular dynamics (MD) is studied. In order to investigate the manipulation behavior, we have used the ubiquitin as biomolecule, a single-walled carbon nanotube (SWCNT) as manipulation probe, a two-layer graphene sheet as substrate. Along this line, a series of simulations are conducted to study the effects of different conditions on the success of manipulation process. These conditions include tip diameter, vertical gap between the tip and substrate, initial orientation of protein, and the tip position with respect to the biomolecule  

    Vibrational analysis of wavy carbon nanotube-reinforced composites

    , Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011, Washington, DC ; Volume 7 , August , 2011 , Pages 371-377 ; 9780791854846 (ISBN) Motahar, M. S ; Ahmadian, M. T ; Sharif University of Technology
    Characterization and simulation of carbon nanotubereinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNTreinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction... 

    Size tuning of Ag‐decorated TiO2 nanotube arrays for improved bactericidal capacity of orthopedic implants [electronic resource]

    , Article Journal of Biomedical Materials Research Part A ; Auguest 2014, Vol. 102, Issue 8, P.2625-35 Esfandiari, N ; Simchi, A. (Abdolreza) ; Bagheri, R ; Sharif University of Technology
    Surface modification of orthopedic implants using titanium dioxide nanotubes and silver nanoparticles (SNs) is a promising approach to prevent bacteria adhesion, biofilm formation, and implant infection. Herein, we utilized a straightforward and all-solution process to prepare silver-decorated TiO2 nanotube arrays with surface density of 10(3) to 10(4) per µm(2). With controlling the synthesis conditions, hexagonal closed-packed nanotubes with opening diameter of 30-100 nm that are decorated with SNs with varying sizes (12-40 nm) were prepared. Various analytical techniques were utilized to characterize the size, morphology, distribution, valance state, surface roughness, and composition of... 

    Fabrication, characterization and mechanical properties of hybrid composites of copper using the nanoparticulates of SiC and carbon nanotubes [electronic resource]

    , Article Journal of Materials Science and Engineering: A ; 10 June 2013, Volume 572, P.83–90 Akbarpour, M. R ; Salahi, E ; Alikhani Hesari, F ; Simchi, A. (Abdolreza) ; Kim, H. S ; Sharif University of Technology
    Copper based hybrid composites containing nano-sized silicon carbide and carbon nanotubes reinforcements with minimal porosity were fabricated via mechanical milling followed by hot pressing technique. Microstructures of the powders and consolidated materials were studied using scanning electron microscope, X-ray diffraction, Raman spectroscopy, and scanning transmission electron microscope. Microstructural characterization of the materials revealed that the addition of nanosized silicon carbide reinforcement lowered the grain growth rate and enhanced the homogenization during mechanical milling. Microhardness measurements and compression test showed considerable improvements in mechanical...