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    The effect of oxidation of macroporous silicon on carbon nanotubes growth by TCVD method

    , Article Synthesis and Reactivity in Inorganic, Metal-Organic and Nano-Metal Chemistry ; Volume 37, Issue 6 , 2007 , Pages 489-492 ; 15533174 (ISSN) Mortazavi, S. Z ; Iraji zad, A ; Taghavi, N. S ; Reyhani, A ; Sharif University of Technology
    Carbon nanotubes (CNTs) were grown on deposited Ni on macroporous silicon by thermal chemical vapor deposition (TCVD) method using CH4 as the reaction gas. Macroporous silicon was fabricated by electrochemical etching of P-type silicon in organic electrolytes. The effect of oxidation of porous silicon (PS) on growth rate, morphology and structure of CNTs has been studied. The SEM micrographs and Raman spectra indicated that the nanotubes grown on the oxidized PS are more homogeneous and regular than those grown on the pristine PS and growth rate of CNTs grown on oxidized PS higher than those grown on pristine PS. In addition, the CNTs grown on the non-oxidized PS have different morphology... 

    Synthesis and Characterization of Grapheme Foams Fabricated by Chemical Vaporization Deposition

    , M.Sc. Thesis Sharif University of Technology Mahboubi, Sajad (Author) ; Akhavan, Omid (Supervisor) ; Azimirad, Rouhollah (Co-Advisor)
    The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better... 

    Decorated CNT based on porous silicon for hydrogen gas sensing at room temperature

    , Article RSC Advances ; Volume 6, Issue 50 , 2016 , Pages 44410-44414 ; 20462069 (ISSN) Ghorbani Shiraz, H ; Razi Astaraei, F ; Fardindoost, S ; Hosseini, Z. S ; Sharif University of Technology
    Royal Society of Chemistry  2016
    A new triple-component sensor for detection of H2 was developed based on porous silicon and CNTs. An increase in deposition of CVD catalysis was shown to promote a high and fast response. Also, it was shown that the composite system exhibited good selectivity  

    Comparison of synthesis and purification of carbon nanotubes by thermal chemical vapor deposition on the nickel-based catalysts: NiSio2 and 304-type stainless steel

    , Article Journal of Applied Sciences ; Volume 10, Issue 9 , 2010 , Pages 716-723 ; 18125654 (ISSN) Fekri, L ; Jafari, A ; Fekri, S ; Shafikhani, A ; Vesaghi, M ; Behzadi, G ; Sharif University of Technology
    In this study by Thermal Chemical Vapor Deposition (TCVD) method, the synthesis of carbon nanotubes (CNTs) and temperature affects on the grown CNTs on the NiSio2 catalyst and 304-type stainless steel was investigated. The purification of the grown CNTs on the 304-type stainless steel was also investigated in this study. The synthesis and purification of the samples were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), termogravimetric analysis (TGA) and Raman spectroscopy. Our obtained result by SEM and TEM shows that densities of CNTs growth on the 304-type stainless steel are more than the CNTs growth on the NiSio2 catalyst and both of them have... 

    The effect of Pd addition to Fe as catalysts on growth of carbon nanotubes by TCVD method

    , Article Applied Surface Science ; Volume 254, Issue 20 , 15 August , 2008 , Pages 6416-6421 ; 01694332 (ISSN) Mortazavi, S. Z ; Reyhani, A ; Iraji zad, A ; Sharif University of Technology
    Elsevier  2008
    The effects of Pd addition to Fe (Pd/Fe = 0, 2.5/7.5, 5/5, 7.5/2.5 and 1) and growth temperatures (920 and 970 °C) on density, diameter and growth mode of carbon nanotubes (CNTs) have been studied. SEM observations and TG analyses confirmed that the CNT yields depend on Pd/Fe ratios as (7.5/2.5) > (5/5) > Pd > (2.5/7.5) > Fe at both growth temperatures. TEM data showed that addition of Pd results in tip growth mode. From Raman spectroscopy data, the order of samples' structural quality (I G /I D ratio) are Fe > Pd/Fe (2.5/7.5) > (5/5) > (7.5/2.5) > Pd and the I G /I D ratios increase by decreasing the growth temperature. Films with higher concentration of Fe (Pd/Fe = 0, 2.5/7.5) contain some... 

    Synthesis of Titanium Nanoparticles from Titanium Tetrachloride and Potassium Vapors Via Chemical Vapor Condensation Process

    , M.Sc. Thesis Sharif University of Technology Kookhaee, Hamed (Author) ; Halali, Mohammad (Supervisor)
    Titanium nanoparticles were synthesized by chemical vapor condensation (CVC) process. Titanium tetrachloride (TiCl4) as titanium’s precursor reacted with potassium as reductant, in vapor phase and the products were titanium nanoparticles encapsulated in potassium chloride. Dried Argon gas was employed as carrier gas. Resulting powders gathered in ethanol bath. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and atomic adsorption spectroscopy (AAS) analysis were used to characterizing the products. The effect of Argon gas flow on nanoparticles size was investigated in this research. The particle size decreases with increasing Argon gas flow. The size of nanoparticles was under... 

    Design and Implement of Gas Distribution and Control System for Deposition of Nano-Structure through NFCVD

    , M.Sc. Thesis Sharif University of Technology Ahmadi, Zabihollah (Author) ; Rashidian, Bizhan (Supervisor)
    For realization of nanosale photonic device required by the future system, electron beams, and scanning probe microscopes have been used to control the site on the subtrate. However, these techniques have a fatal disadvantage because they cannot deal with insulators and Diffraction of light, limiting their application.To overcome this difficulties, we design and implement near-field optical chemical vapor deposition, which enables the fabrication of nanometer-scale structure, while controlling their position. To guarantee that an optical near field is generated sufficiently, we fabricated a sharped W-tip by electrochemical etching. The separation between the W-tip and the substrate was kept... 

    Control of Size of Graphene Domain Synthesized by Chemical Vapor Deposition

    , M.Sc. Thesis Sharif University of Technology Amini, Negar (Author) ; Ghotbi, Sirus (Supervisor) ; Karimi Sabet, Javad (Supervisor)
    The chemical vapor deposition (CVD) of graphene from methane on a copper substrate is the most promising method for production of large-area graphene films. There have been long-standing challenges in this field such as controlling the graphene coverage, film quality, the number of layers, and the nucleation density of graphene domain. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. The main aim of this study is to control nucleation density of graphene domains. Chemical vapor deposition (CVD) graphene is polycrystalline, and grain boundaries in graphene film have been identified to degrade the properties of graphene as a membrane... 

    The role of reactants and droplet interfaces on nucleation and growth of ZnO nanorods synthesized by vapor-liquid-solid (VLS) mechanism

    , Article Journal of Alloys and Compounds ; Volume 455, Issue 1-2 , 2008 , Pages 353-357 ; 09258388 (ISSN) Hejazi, S. R ; Madaah Hossein, H. R ; Ghamsari, M. S ; Sharif University of Technology
    Short ZnO nanorods and long ZnO nanowires have been produced on SiO2 and Si substrates by VLS and VS mechanisms via a double tube chemical vapor transport and condensation (CVTC) process. The role of reactants and droplet interfaces on the nucleation and growth of ZnO nanorods have been investigated. A conceptual model for nucleation of ZnO nanorods has been proposed by describing the half-oxidation and reduction reactions at the growth front. The importance of Zn vapor in the nucleation phenomena has been studied by changing starting materials. Atomic force microscopy (AFM), scanning electron microscopy (SEM), and EDX analysis have been used to characterize ZnO nanorods and investigate the... 

    Molecular dynamics of single wall carbon nanotube growth on nickel surface

    , Article Computational Materials Science ; Volume 36, Issue 1-2 , 2006 , Pages 117-120 ; 09270256 (ISSN) Esfarjani, K ; Gorjizadeh, N ; Nasrollahi, Z ; Sharif University of Technology
    Growth mechanism of a single wall carbon nanotube on the surface of a nickel nanoparticle in the CVD method has been investigated by classical molecular dynamics method. Using first principles methods, we have first constructed a classical potential to describe the interaction between a carbon atom and the nickel surface. The important ingredient in this potential is its coordination number dependence, which also provides the key to the growth mechanism of the nanotube. From the simulations, it is proposed that the growth of an armchair nanotube takes place via attachment of dimers to its end which is in contact with the nickel surface. The effect of nickel nanoparticle's radius on the... 

    Fabrication and characterization and biosensor application of gold nanoparticles on the carbon nanotubes

    , Article Applied Surface Science ; Volume 355 , November , 2015 , Pages 1175-1179 ; 01694332 (ISSN) Ghodselahi, T ; Aghababaie, N ; Mobasheri, H ; Zand Salimi, K ; Akbarzadeh Pasha, M ; Vesaghi, M. A ; Sharif University of Technology
    Elsevier  2015
    Gold nanoparticles (Au NPs) were synthesized by co-deposition of RF-sputtering and RF-PECVD from acetylene gas and Au target on the carbon nanotubes (CNTs). The CNTs were prepared by thermal chemical vapor deposition (TCVD) and Pd nanoparticles catalyst. TEM image shows that high-density and uniform distribution of Au NPs were grown on the CNTs. XRD analysis indicates that Au NPs have fcc crystal structure and CNTs have a good graphite structure. Raman spectroscopy results suggest that our sample includes double-walled CNTs. It is resulted that intensity of D-band reduces and G-band intensity raises and radial breathing mode (RBM) is changed by immobilizing of Au NPs on the CNTs. Raman... 

    On the performance of vertical MoS2 nanoflakes as a gas sensor

    , Article Vacuum ; Volume 167 , 2019 , Pages 90-97 ; 0042207X (ISSN) Barzegar, M ; Iraji zad, A ; Tiwari, A ; Sharif University of Technology
    Elsevier Ltd  2019
    Despite their potential applications, a limited number of studies for synthesizing vertical MoS2 nanoflakes especially via CVD have been reported so far, which generally involve tedious complex- and/or multi-step growth processes. In this study, direct synthesis of vertical MoS2 nanoflakes grown on the SiO2/Si substrate during a rapid sulfidation process by CVD method has been reported. Material characterization was performed using Raman spectroscopy, XRD and FE-SEM. The XRD results indicated the dominant phase of 2H–MoS2 within the synthesized layers. The characteristic distance between the two dominant peaks of E1 2g and A1g in the Raman spectra confirms the multi-layered structure for... 

    Catalytic activity of the spinel ferrite nanocrystals on the growth of carbon nanotubes

    , Article Journal of Superconductivity and Novel Magnetism ; Volume 26, Issue 2 , 2013 , Pages 429-435 ; 15571939 (ISSN) Hosseini Akbarnejad, R ; Daadmehr, V ; Rezakhani, A. T ; Shahbaz Tehrani, F ; Aghakhani, F ; Gholipour, S ; Sharif University of Technology
    We prepared three ferrite nanocatalysts: (i) copper ferrite (CuFe 2O4) (ii) ferrite where cobalt was substituted by nickel (Nix Co1-x Fe2O4, with x=0, 0.2, 0.4, 0.6), and (iii) ferrite where nickel was substituted by zinc (Zn y Ni1-y Fe2O4 with y=1, 0.7, 0.5, 0.3), by the sol-gel method. The X-ray diffraction patterns show that the ferrite samples have been crystallized in the cubic spinel structural phase. We obtained the size of grains by field emission scanning electron microscopy images and their magnetic properties by vibrating sample magnetometer. Next, carbon nanotubes were grown on these nanocatalysts by the catalytic chemical vapor deposition method. We show that the catalytic... 

    Synthesis and Evaluation of Carbon based Catalyst for HDS Process of Refinery Products

    , Ph.D. Dissertation Sharif University of Technology Hajjar, Zeinab (Author) ; Kazemini, Mohammad (Supervisor) ; Rashidi, Alimorad (Supervisor) ; Bazmi, Mansour (Co-Advisor)
    One of the most important world issues is environmental constraints regarding the pollutants released by transportation fuels and refinery products, sulfur reduction being one of the most significant objectives. Deep hydrodesulfurization processes result in great sulfur reduction in refinery streams. However, such harsh process conditions increase undesired side reactions and facilitate coke formation as well as affecting the surfaces. More effective alternatives for hard process conditions are highly active and selective hydrodesulfurization catalysts, which enable the process to be performed at milder pressure and reaction conditions. Catalyst bases play a very important role in hydrogen... 

    Synthesis and Biocompatibility Evaluation of TiO2/Pyrolytic Carbon Core/Shell

    , M.Sc. Thesis Sharif University of Technology Behzadi, Shahed (Author) ; Simchi, Abdolreza (Supervisor) ; Imani, Mohammad (Supervisor)
    Carbon-based thin films possess low friction coefficient, low surface roughness, chemical inertness and outstanding biocompatibility. In the present work, TiO2 nanoparticles were covered by a thin film of pyrolytic carbon (PyC) to provide a core-shell morphology. The PyC film was deposited by dehydrogenation of methane in a fluidized bed chemical vapour deposition (FBCVD) reactor at 1100 °C. The prepared specimens were characterized by various analytical methods including XRD, SEM, TEM, AFM, TGA and contact angle measurement techniques. Biocompatibility profiles of the resulting materials were evaluated using MTT and cell cycle assay. The results showed that the thin carbon film strongly... 

    Transport Properties in Heterostructures of 2D Layers of Graphene with WS2 and hBN Quantum Dots

    , M.Sc. Thesis Sharif University of Technology Razzaghi, Zahra (Author) ; Simchi, Abdolreza (Supervisor)
    Graphene based photodetectors which are modified with quantum dots, are the new generation of detectors. In these supplies an integration of graphene’s unique characteristics like high conductivity and mobility and the high light absorption of quantum dots, are used.In this research graphene by chemical vapor deposition in centimetric large scales, tungsten disulfide quantum dots, boron nitride and graphene quantum dots and 2D tungsten disulfide have been synthesized. In the next step each of them were characterized to modify the quality of used layers in heterostructure.Based on the characteristic tests, quantum dots aspect ratios were 1 to 5 nanometers. Also tungsten disulfide was obtained... 

    Design and Fabrication of Electronic Subsystems for NFCVD

    , M.Sc. Thesis Sharif University of Technology Ghaderi, Erfan (Author) ; Rashidian, Bizhan (Supervisor)
    The fabrication of future electronic and optical devices will require advanced nanofabrication techniques that realize high spatial resolution and high precision in controlling size and position, and that are applicable to various materials. Near-field CVD (NF-CVD) was proposed to solve these problems with no need to perform nanolithography prcesses. NFCVD system has two major subsystems, first vacuum chamber and gas distribution system for delivering parent gases to the chamber and second, a nanopositiong system to keep the probe and the sample in the constant systems.In this dissertation we have set up a piezoelectric nanopositiong system and its driver modules. The positioning accuracy... 

    The Effects of Catalyst Preparation Parameters on Carbon Nanotube Growth

    , Ph.D. Dissertation Sharif University of Technology Akbarzadeh Pasha, Mohammad (Author) ; Vessaghi, Mohammad Ali (Supervisor) ; Taghavinia, Nima (Co-Advisor) ; Shafiekhani, Azizollah (Co-Advisor)
    In this study three different methods; hot filament chemical vapor deposition (HFCVD), pulsed laser ablation (PLA) and electrochemical deposition were utilized to prepare catalyst thin films or nanoparticles and thermal chemical vapor deposition (TCVD) was used to grow multiwall carbon nanotubes (MWCNTs). We found that even though the three mentioned techniques have been rarely applied by researchers, they are appropriate and efficient methods to produce catalytic basis for CNT growth. In the TCVD step, liquid petroleum gas (LPG) was applied as carbon source. Although, this gas is a mixture of different hydrocarbons and further contains some sulfur, our results verify that utilizing of LPG... 

    Fabrication and Investigation of Silicon Based Nanostructures Surface Properties

    , M.Sc. Thesis Sharif University of Technology Bashirpour, Mohammad (Author) ; Rashidian, Bijan (Supervisor)
    Nowadays, silicon based devices especially carbon nanotubes received lots of attentions and advancement from researchers and industries. Because of amazing electrical and mechanical properties and wide range of applications, CNTs are received a lot of attention from nanoelectronics experts. There are lots of CNT growth methods such as: Arc Discharge, Laser Ablation, Surface Decomposition, CVD and PECVD.
    In this thesis, we are going to use PECVD method to synthesis CNT. A typical PECVD system includes two parallel electrodes that have been packed in vacuum chamber and gases like argon, hydrogen and NH3 are introduced to chamber as a reactant gas.
    In this thesis, firs we had fixed... 

    Modification of Vertically Aligned Carbon Nanotubes with RuO2 for a Solid-State pH Sensor

    , M.Sc. Thesis Sharif University of Technology Kahram, Mohaddeseh (Author) ; Dolati, Abolghasem (Supervisor)
    In this work, a novel type electrode based on RuO2 nanoparticles-modified vertically aligned carbon nanotubes (RuO2/MWCNTs) was investigated. ThisRuO2/MWCNTs electrode not only shows a high capacity nature,but also possesses a good response to the pH value. In order to develope this sensor, aligned carbon nanotubes were synthesized by the chemical vapor deposition at first and then modified with RuO2 nanopartcles by sol-gel method. Various parameters affecting the growth of nanotubes, such as substrate type, surface finishing, surface roughness, the growth temperature and carbon feed rate was studiedand and optimal conditions for growth were obtained. At last, aligned nanotubes with a...