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    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
    Abstract
    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
    Abstract
    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
    Abstract
    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
    Abstract
    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... 

    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
    Abstract
    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... 

    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
    2012
    Abstract
    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  

    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
    Abstract
    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... 

    Formation of carbon nanotubes in Iron-catalyzed arcing method: Effect of iron-ion charge in the aqueous medium [electronic resource]

    , Article International Journal of Modern Physics B Condensed Matter Physics; Statistical Physics; Atomic, Molecular and Optical Physics ; 30 December 2011, Volume 25, Issue 32, PP. 4411-4417 Shervin, Sh ; Gheytani, S ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    Abstract
    Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe2+]/[Fe3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism  

    On the formation of SWCNTs and MWCNTs by Arc-discharge in aqueous solutions: the role of iron charge and counter ions [electronic resource]

    , Article Journal of Fullerenes, Nanotubes and Carbon Nanostructures ; 2011, Volume 19, Issue 4, Pages 317-328 Gheytani, S ; Shervin, Sh ; Simchi, A. (Abdolreza) ; Sharif University of Technology
    Abstract
    Single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs) were synthesized in aqueous solutions containing FeCl2, FeCl3, FeSO4 and Fe2(SO4)3. The effects of iron charge and the counter ions on the formation of carbon nanotubes (CNTs) were investigated. Thermogravimetric (TG) analysis indicated that carbon multilayer structures including CNTs and multishell graphite particles were formed in deionized (DI) water without the iron precursor. SWCNTs were also synthesized in the presence of the iron ions. It was also found that the mole ratio of [Fe2+]/[Fe3+] in the solution has a significant influence on the purity of CNTs and the process yield. The highest yield was... 

    Horseradish peroxidase immobilization on amine functionalized carbon nanotubes: direct electrochemistry and bioelectrocatalysis

    , Article Progress in Reaction Kinetics and Mechanism ; Volume 37, Number 2 , 2012 , pp. 161-172 Tasviri, M. (Mahboubeh) ; Ghourchian, H. (Hedayatollah) ; Gholami, M. R. (Mohammad Reza) ; Rafieepour, H. A. (Hossain Ali) ; Sharif University of Technology
    Abstract
    Horseradish peroxidase (HRP) was successfully immobilized on amine functionalized TiO2-coated multiwalled carbon nanotubes (NH2 – TiO2 – CNTs) by a convenient and efficient method. Electrochemical impedance spectroscopy, cyclic voltammetry and amperometry were applied to characterize the HRP/NH2 – TiO2 – CNT nano-composite. These techniques showed that the NH2 – TiO2 – CNTs greatly enhance the electron transfer between HRP and the modified electrode. Owing to the redox reaction of the electroactive centre of HRP, the HRP = NH2 – TiO2 – CNTs modified electrode exhibited a pair of quasi-reversible peaks with a peak-to-peak separation (ΔEp) of 70.6 mV and a formal potential (E 0′) of 367.65 mV... 

    Cytotoxicity of carbon nanotube/polycitric acid hybrid nanomaterials

    , Article Iranian Polymer Journal (English Edition) ; Vol. 23, issue. 3 , 2014 , pp. 195-201 ; ISSN: 10261265 Adeli, M ; Alavidjeh, M. S ; Mohammadifar, E ; Sharif University of Technology
    Abstract
    Polycitric acid was conjugated onto the surface of carbon nanotubes (CNTs), and hybrid nanomaterials containing CNT axis and polycitric acid branches that were highly soluble in aqueous solutions were synthesized. In this work, pristine MWCNTs were opened and functionalized through treatment with acid, then polycitric acid was covalently grafted onto their surface by the "grafting from" approach based on polycondensation of citric acid in the melting state. The chemical structure, morphology, thermal properties and size of MWCNT-g-PCA hybrid materials were investigated by IR, 13C NMR, 1H NMR, TEM, TGA, DSC and DLS. To investigate the biocompatibility of the synthesized hybrid nanomaterials... 

    Carbon nanotube-based nano-fluidic devices

    , Article Journal of Physics D: Applied Physics ; Vol. 47, issue. 8 , 2014 ; ISSN: 00223727 Masoud Seyyed Fakhrabadi, M ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    The paper investigates the influences of fluid flow on static and dynamic behaviours of electrostatically actuated carbon nanotubes (CNTs) using strain gradient theory. This nonclassical elasticity theory is applied in order to obtain more accurate results possessing higher agreement with the experimental data. The effects of various fluid parameters such as the fluid viscosity, velocity, mass and temperature on the pull-in properties of the CNTs with two cantilever and doubly clamped boundary conditions are studied. The results reveal the applicability of the proposed nano-system as nano-valves or nano-fluidic sensors  

    Nonlinear analysis of carbon nanotube-based nanoelectronics devices

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Vol. 228, issue. 13 , 2014 , p. 2426-2439 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    Abstract
    The paper deals with the investigation of nonlinear static and dynamic behaviors of electrostatically actuated carbon nanotubes with different geometries and boundary conditions. The deflection and pull-in properties are studied in detail in the presence of DC and combined DC+AC electrostatic voltages accompanying the interatomic interactions. The considered nano system can be applied in a wide range of nanoelectronics devices such as nano switches, nano resonators, nano transistors, nano capacitors and random access memories. Moreover, a useful mathematical model of the nano sensor application of the studied nano system to sense the stiffness of the nano particles is presented  

    Investigation of the electrochemical behavior of mesalazine on the surface of a glassy carbon electrode modified with CNT/PPY doped by 1,5-naphthalenedisulfonic acid

    , Article Electroanalysis ; Volume 25, Issue 11 , 2013 , Pages 2481-2491 ; 10400397 (ISSN) Shahrokhian, S ; Hosseini, P ; Kamalzadeh, Z ; Sharif University of Technology
    2013
    Abstract
    A glassy carbon electrode (GCE) was modified with a thin layer of multiwalled carbon nanotubes (MWCNTs) and subsequently, electrochemically deposited poly-pyrrole. The electrochemical behavior of mesalazine was studied on the surface of the modified electrode by applying linear sweep voltammetry (LSV). The electropolymerization process and the electrochemical response toward mesalazine were investigated in the presence of different aromatic anion dopants including, benzenesulfonic acid (BSA), 1,3-benzenedisulfonic acid (1,3-BDSA), 1,5-naphthalenedisulfonic acid (1,5-NDSA) and new coccine (NC). By using 1,5-NDSA as dopant, a significant increase (~418 times) in the peak current of mesalazine... 

    Preparation and characterization of Co-Mo catalyst supported on CNT coated cordierite monoliths utilized for naphta HDS process

    , Article Procedia Engineering ; Volume 42 , 2012 , Pages 1484-1492 ; 18777058 (ISSN) Soghrati, E ; Kazemeini, M ; Rashidi, A. M ; Jafari Jozani, Kh ; Sharif University of Technology
    2012
    Abstract
    In the present study, an acid treatment of the cordierite monolith followed by coating of the CNT onto it by means of catalytic chemical-vapor deposition (CCVD) of methane over CoMo catalyst was performed. The resulting material utilized as the supports for the HDS catalyst onto which was deposited Co and Mo species. The as-prepared samples were characterized by the BET, XRD, FESEM and ICP-MS techniques. BET experiments showed that a significant increase in specific surface area and pore volume was observed, and a suitable pore size distribution was obtained after acid pretreatment. The FESEM images of CNT coated monolith showed that CNTs were distributed uniformly on the surface of monolith... 

    Application of glassy carbon electrode modified with a bilayer of multiwalled carbon nanotube and polypyrrole doped with Nitrazine Yellow for voltammetric determination of naltrexone

    , Article Electroanalysis ; Volume 23, Issue 12 , NOV , 2011 , Pages 2925-2934 ; 10400397 (ISSN) Shahrokhian, S ; Kamalzadeh, Z ; Saberi, R. S ; Sharif University of Technology
    2011
    Abstract
    A new sensitive electrochemical sensor was fabricated based on a layer by layer process. In this process the glassy carbon electrode (GCE) is first coated by a thin film of multiwalled carbon nanotubes (MWCNTs). In the next step, the electropolymerization of pyrrole in the presence of Nitrazine Yellow (NY) as a dopant anion is performed on the surface of the MWCNTs precoated electrode. The electrochemical response characteristics of the modified electrode toward naltrexone (NTX) were studied by means of linear sweep voltammetry (LSV). A remarkable increase (~19 times) was observed in the anodic peak current of NTX on the surface of the modified electrode relative to the bare GCE. The effects... 

    Formation of carbon nanotubes in iron-catalyzed liquid arcing method: Effect of iron-ion charge in the aqueous medium

    , Article International Journal of Modern Physics B ; Volume 25, Issue 32 , 2011 , Pages 4411-4417 ; 02179792 (ISSN) Shervin, Sh ; Gheytani, S ; Simchi, A ; Sharif University of Technology
    2011
    Abstract
    Carbon nanotubes (CNTs) were synthesized via arc discharge in aqueous solutions containing ferrous and ferric irons to reveal the effect of iron-charge mole ratio, R = [Fe 2+]/[Fe 3+], on the purity of CNTs and the process yield. Raman spectroscopy and transmission electron microscopy were used to analyze the cathodic deposits. It is shown that the nucleation of multi-walled CNTs is catalyzed by ferric irons while their growth is affected by ferrous ions. Well-graphitized CNTs with a high-yield are obtained at R = 1 and total iron concentration of 0.05 M. The effect of iron charge is described based on the two-stage formation mechanism  

    Effect of carbon nanotube geometries on mechanical properties of nanocomposite via nanoscale representative volume element

    , Article Journal of Solid Mechanics ; Volume 8, Issue 3 , 2016 , Pages 568-577 ; 20083505 (ISSN) Moghaddam, F ; Ghavanloo, E ; Fazelzadeh, S. A ; Sharif University of Technology
    Islamic Azad University  2016
    Abstract
    Predicting the effective elastic properties of carbon nanotube-reinforced nanocomposites is of great interest to many structural designers and engineers for improving material and configuration design in recent years. In this paper, a finite element model of a CNT composite has been developed using the Representative volume element (RVE) to evaluate the effective material properties of nanocomposites. Based on this model, the effects of geometrical characteristics such as the aspect ratio, orientation and volume fraction of the CNTs in conjunction with the interphase behavior on the mechanical properties of the nanocomposites are elucidated and the elastic properties of a complex polymeric... 

    Composites of carbon nanotubes with the blend of poly(vinylidene fluoride)/poly(vinyl acetate)

    , Article Polymer (Korea) ; Volume 40, Issue 2 , 2016 , Pages 232-237 ; 0379153X (ISSN) Davand, R ; Frounchi, M ; Sharif University of Technology
    Polymer Society of Korea  2016
    Abstract
    Poly(vinylidene fluoride)/poly(vinyl acetate)/carbon nanotubes, PVDF/PVAc/CNT, composite films were prepared at various compositions via a solution casting method. The amorphous PVAc formed a miscible blend with PVDF and drastically improved dispersion of CNT in PVDF/CNT composites. Combination of ductile PVAc and rigid CNT had favorable effects on mechanical properties of PVDF. The elongation of PVDF increased from 8% to 300% with addition of 40 wt% PVAc and 0.5 wt% CNT and the modulus at 1.5 wt% CNT was almost 2.3 fold of that of the neat PVDF while retaining high ductility and tensile strength. XRD and FTIR results showed that CNT favored formation of β-crys-talline phase in PVDF. Also...