Loading...
Search for:
nanotubes
0.008 seconds
Total 721 records
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 ; 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 ; 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 ; 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 ; 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 ; 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 ; 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) ; 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) ; 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) ; 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) ; 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
Comparison of trap-state distribution and carrier transport in nanotubular and nanoparticulate TiO2 electrodes for dye-sensitized solar cells
, Article ChemPhysChem ; Volume 11, Issue 10 , July , 2010 , Pages 2140-2145 ; 14394235 (ISSN) ; Zad, A. I ; Hagfeldt, A ; Boschloo, G ; Sharif University of Technology
2010
Abstract
Dye-sensitized solar cells (DSCs) with nanotubular TiO2 electrodes of varying thicknesses are compared to DSCs based on conventional nanoparticulate electrodes. Despite the higher degree of order in one-dimensional nanotubular electrodes, electron transport times and diffusion coefficients, determined under short-circuit conditions, are comparable to those of nanoparticulate electrodes. The quasi-Fermi level, however, is much lower in the nanotubes, suggesting a lower concentration of conduction band electrons. This provides evidence for a much higher diffusion coefficient for conduction band electrons in nanotubes than in nanoparticulate films. The electron lifetime and the diffusion length...
Vibration and Stability Analysis of DWCNT-Based Spinning Nanobearings
, Article International Journal of Structural Stability and Dynamics ; 2016 ; 02194554 (ISSN) ; Mohammad Khani, H ; Rahmanian, M ; Sharif University of Technology
World Scientific Publishing Co. Pte Ltd
2016
Abstract
This paper aims at investigating free vibrations and stability of double-walled carbon nanotube (DWCNT)-based spinning nanobearings. The so-called nanobearing consists of two coaxial carbon nanotubes (CNTs) where either of the two CNTs can be a rotor while the other takes the role of stator. Euler–Bernoulli beam model along with the Eringen’s nonlocal theory of elasticity are employed to obtain governing equations of transverse vibrations for the CNTs. The coupling of the two CNTs originates from the van-der-Waals (vdW) forcing present in the interface of the two CNTs. The coupling is taken into account as distributed spring foundation with an equivalent elastic stiffness. Based on the...
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) ; 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) ; 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...
Physicomechanical properties of spark plasma sintered carbon nanotube-reinforced metal matrix nanocomposites
, Article Progress in Materials Science ; Volume 90 , 2017 , Pages 276-324 ; 00796425 (ISSN) ; Azarniya, A ; Sovizi, S ; Madaah Hosseini, H. R ; Varol, T ; Kawasaki, A ; Ramakrishna, S ; Sharif University of Technology
Abstract
The technological and industrial needs for development of fully dense nanocomposites have led to significant advances in spark plasma sintering (SPS) technique and its enhanced forms. This technique has opened up a new prospect over carbon nanotube (CNT)-metal matrix nanocomposites (MMNCs) with superior physical or mechanical characteristics. To date, a large number of authentic papers have been published over this ongoing field, but have not been comprehensively reviewed. The pertinent research works cover some significant aspects of CNT-MMNCs requiring a concise review on (i) the potential phase transformations of pure CNTs and microstructure evolution; (ii) the novel approaches for...
Metallurgical challenges in carbon nanotube-reinforced metal matrix nanocomposites
, Article Metals ; Volume 7, Issue 10 , 2017 ; 20754701 (ISSN) ; Safavi, M. S ; Sovizi, S ; Azarniya, A ; Chen, B ; Madaah Hosseini, H. R ; Ramakrishna, S ; Sharif University of Technology
Abstract
The inclusion of carbon nanotubes (CNTs) into metallic systems has been the main focus of recent literature. The aim behind this approach has been the development of a new property or improvement of an inferior one in CNT-dispersed metal matrix nanocomposites. Although it has opened up new possibilities for promising engineering applications, some practical challenges have restricted the full exploitation of CNTs’ unique characteristics. Non-uniform dispersion of CNTs in the metallic matrix, poor interfacial adhesion at the CNT/metal interface, the unfavorable chemical reaction of CNTs with the matrix, and low compactability are the most significant challenges, requiring more examination....
Optimizing carbonaceous nanostructure composition as a substrate to grow co electrocatalysts
, Article Iranian Journal of Physics Research ; Volume 17, Issue 5 , 2018 , Pages 753-760 ; 16826957 (ISSN) ; Naseri, N ; Ghasemi, S ; Sharif University of Technology
Isfahan University of Technology
2018
Abstract
Global warming and other adverse environmental effects of fossil fuels have forced humans to consider clean and renewable energy resources. In this context, hydrogen production from water splitting reaction is a key approach. In order to reduce required overpotential for water oxidation reaction, it is necessary to use low cost and earth abundant electrocatalysts like Co, Cu, Fe, Mn, Ni and Zn nanostructures. Herein, cobalt nanostructures on steel-mesh substrate were applied. Electrochemical method was used for growth of Co nanoflakes because of its simplicity and scalability for commercial approach. On the other hand, using carbonaceous support layers including nanomaterials such as...
Nanostructured ternary composites of PPy/CNT/NiFe2O4 and PPy/CNT/CoFe2O4: Delineating and improving microwave absorption
, Article Comptes Rendus Chimie ; Volume 21, Issue 9 , 2018 , Pages 862-871 ; 16310748 (ISSN) ; Kheirjou, S ; Asgari, S ; Kazerooni, H ; Sharif University of Technology
Elsevier Masson SAS
2018
Abstract
Two different ternary nanocomposites, PPy/CNT/CoFe2O4 and PPy/CNT/NiFe2O4, were synthesized by in situ polymerization method. The resulting composites were characterized using Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction. They were evaluated with the aim of investigating microwave absorption properties. The results showed that the value of microwave reflection decreases as that of prepared nanocomposites increases. This happens with increase in the PPy content and polymerization on the surface. © 2018 Académie des sciences
Investigation of phase diagrams for cylindrical Ising nanotube using cellular automata
, Article Physics Letters, Section A: General, Atomic and Solid State Physics ; Volume 382, Issue 19 , May , 2018 , Pages 1291-1297 ; 03759601 (ISSN) ; Ghaemi, M ; Afzali, K ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Recent developments in the field of applied nanoscience and nanotechnology have heightened the need for categorizing various characteristics of nanostructures. In this regard, this paper establishes a novel method to investigate magnetic properties (phase diagram and spontaneous magnetization) of a cylindrical Ising nanotube. Using a two-layer Ising model and the core-shell concept, the interactions within nanotube has been modelled. In the model, both ferromagnetic and antiferromagnetic cases have been considered. Furthermore, the effect of nanotube's length on the critical temperature is investigated. The model has been simulated using cellular automata approach and phase diagrams were...
Conjugation of amphotericin B to carbon nanotubes via amide-functionalization for drug delivery applications
, Article Engineering Letters ; Volume 17, Issue 4 , 2009 ; 1816093X (ISSN) ; Gojgini, S ; Kazemi, A ; Alemzadeh, I ; Zeinali, M ; Sharif University of Technology
2009
Abstract
Carbon nanotubes are among promising components for a wide range of applications, due to their unique properties; Specifically, They are a new alternative and efficient tool for transporting and translocating therapeutic molecules since they can translocate easily into the cytoplasm or nucleus of a cell through its membrane without generating an immunogenic response and toxic effects. While pristine carbon nanotubes are insoluble in all solvents, the organic functionalisation of carbon nanotubes is the prerequisite for their solubility profiles and their manipulation into biological systems. For this purpose, in this study, we first report the Amide-functionalization of CNTs which a direct...