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    Preparation and Study of Microstructural and Mechanical Properties of Ni-Tio2 Based Nanocomposite by Electrochemical Deposition Method

    , M.Sc. Thesis Sharif University of Technology Sariri, Farshid (Author) ; Mohammadi, Mohammad Reza (Supervisor) ; Ekrami, Ali Akbar (Co-Advisor)
    In the present work preparation of Ni-TiO2 films and their microstructural and mechanical properties were studied. For film preparation, DC current mode of electrochemical deposition method was used in Watts Nickel bath with different concentrations of transparent TiO2 sol up to 30 mL/L. It presents a new generation of nano Ni-TiO2 coating as a composite film for corrosion and erosion resistance applications. The best wear volume of 0.0046 mm3 was achieved for 30 mL/L Ni-TiO2 nanocomposite in comparison to 0.0071 mm3 for pure Ni film. Moreover, the coating hardness increased to ~345 HV50 for Ni-TiO2 nanocomposite. Corrosion rate of the coatings improved down to 1.10E-05 mm/year with addition... 

    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... 

    Investigation On Microstructure And Properties Of Barium Strontium Titanate Thin Films Grown By Pulsed Laser Deposition

    , M.Sc. Thesis Sharif University of Technology Saroukhani, Zahra (Author) ; Nemati, Ali (Supervisor) ; Mahdavi, Mohammad (Supervisor)
    Barium Strontium Titanate (BST) thin films are a promising candidate for dielectric capacitors due to their excellent ferroelectric properties. It is well known that BST has a high dielectric constant, low loss tangent, low leakage current and low Curie temperature. Pulse laser deposition (PLD) has been used extensively as it can maintain the stoichiometry of the target in the deposited film and also has high coverage ability, which both are important in capacitors. In this paper, Ba0.6Sr0.4TiO3 (BST) thin film has been deposited on the SiO2/Si substrate by pulsed laser deposition technique. The effect of post-annealed temperature, oxygen pressure deposition ambience and number of pulses on... 

    Electrodeposition of Rhenium and Nickel Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Ataee, Hamed (Author) ; Sadrnezhad, Khatiboleslam (Supervisor)
    In the last decade, a great deal of attention has been paid to the study of synthesis of Nanoparticles, because of the widespread use of this material in applications involving Fuel cells and magnetic devices. In this thesis, we report some interesting features in the electrodeposition of metallic nanoparticles. The electrochemical phase formation of rhenium and nickel on the surface of P-Si (100) substrate plus morphological, topographical and fractal aspects of the accumulated surface were investigated in this research by means of chronoamperometry method and by utilization of AFM and SEM. The nucleation and growth mechanisms on silicon electrode are characterized using cyclic voltammetry... 

    Fabrication of Silicon Nanowires with various Silicon Substrates and Investigation of the structural Properties and their Behavior

    , M.Sc. Thesis Sharif University of Technology Teymouri, Arastoo (Author) ; Askari, Masoud (Supervisor)
    In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy... 

    Electrophoretic deposition of Ni/SiO2 nanocomposite coating: Fabrication process and tribological and corrosion properties

    , Article Journal of Nano Research ; Volume 26 , 6 January , 2014 , Pages 45-51 ; ISSN: 16625250 Isfahani, A. G ; Ghorbani, M ; Sharif University of Technology
    To the best of our knowledge, this work presents the first successful effort to fabricate and study nanostructured Ni-based composite coatings using the electrophoretic deposition method with nanostructured SiO2 particles. In this work, Ni/SiO2 nanoparticle composite coatings were prepared by electrophoretic deposition (EPD) [1] and their hardness, wear and corrosion resistances [2] were examined. After studying the morphology of the coatings and finding the optimum conditions for uniform coating, in order to improve the mechanical properties as well as resistance to corrosion, sintering was performed. The Ni/SiO2 nanocomposite coatings show excellent hardness (∼376 HV), reduced Young's... 

    An experimental investigation of permeability impairment under dynamic flow conditions due to natural depletion in an Iranian oilfield

    , Article Petroleum Science and Technology ; Volume 31, Issue 3 , 2013 , Pages 250-261 ; 10916466 (ISSN) Khalifeh, M ; Bagherzadeh, H ; Bolouri, H ; Sharif University of Technology
    Asphaltene deposition is an issue that has received much attention since it has been shown to be the cause of major production problems. It leads to permeability reduction under the processes of natural depletion as well as hydrocarbon gas/CO2 injection. Though a great deal of researches have focused on studying permeability impairment in reservoir rocks, little is known about the asphaltene deposition mechanisms that control the permeability reduction for Iranian reservoirs. In this work, an experimental effort is made to investigate the permeability impairment of core samples of Iranian oil reservoirs. The experiments are performed on both sandstone and carbonate rock types at reservoir... 

    Optimization assisted asphaltene deposition modeling in porous media during a natural depletion scheme

    , Article Petroleum Science and Technology ; Volume 30, Issue 9 , Mar , 2012 , Pages 958-965 ; 10916466 (ISSN) Hematfar, V ; Bagheri, M ; Kharrat, R ; Ghazanfari, M ; Ghotbi, C ; Sharif University of Technology
    Changes in thermodynamic properties such as pressure, temperature, and composition may result in asphaltene precipitation and deposition in porous media. In addition, asphaltene deposition can cause wettability alteration, permeability reduction, and ultimately a decrease in the productivity of a reservoir. Natural depletion is one of the most common processes of asphaltene deposition in which pressure changes destabilize the dissolved asphaltene in the oil and settle them onto the rock surface. In this work, natural depletion experiments in consolidated core samples were performed under simulated reservoir conditions to obtain reliable data and analyze the asphaltene deposition mechanisms.... 

    Physical properties of sputtered amorphous carbon coating

    , Article Journal of Alloys and Compounds ; Volume 513 , 2012 , Pages 135-138 ; 09258388 (ISSN) Yari, M ; Larijani, M. M ; Afshar, A ; Eshghabadi, M ; Shokouhy, A ; Sharif University of Technology
    In this study the effect of deposition temperature and thickness on the physical properties of carbon films deposited by magnetron sputtering PVD was investigated. The results of Raman spectra and grazing incidence XRD (GIXRD) patterns show that the graphitization increases by increasing the deposition temperature. There is a change in deposition mechanism at 400 °C from amorphous carbon deposition to nano-structured graphite deposition. Also by increasing substrate temperature the electrical resistance of carbon films reduces significantly up to 300 °C and then remains largely constant. High intrinsic compressive stress in low temperature deposited carbon films causes cracks and... 

    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... 

    A study of the electrophoretic deposition of Bioglass® suspensions using the Taguchi experimental design approach

    , Article Journal of the European Ceramic Society ; Volume 30, Issue 14 , October , 2010 , Pages 2963-2970 ; 09552219 (ISSN) Pishbin, F ; Simchi, A ; Ryan, M. P ; Boccaccini, A. R ; Sharif University of Technology
    This paper presents a study of the Taguchi design method to optimise the rate of electrophoretic deposition (EPD) of Bioglass® particles from aqueous suspensions. The effect of Bioglass® concentration, pH and electric field was investigated. An orthogonal array of L16 type with mixed levels of the control factors was utilized. Multivariate analysis of variance (MANOVA) and regression analysis based on the partial least-square method were used to identify the significant factors affecting the deposition rate and its stability during constant-voltage EPD. It was found that the pH of the suspension significantly influences the deposition rate whereas the applied electric field has the smallest... 

    Role of cooling rate in selective synthesis of graphene and carbon nanotube on Fe foil using hot filament chemical vapor deposition

    , Article 2016 IEEE 7th Annual Ubiquitous Computing, Electronics and Mobile Communication Conference, UEMCON 2016, 20 October 2016 through 22 October 2016 ; 2016 ; 9781509014965 (ISBN) Abdolahi, M ; Kaminska, B ; Akhavan, O ; Talebi, S ; Ghoranneviss, M ; Arab, Z ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2016
    In this study, graphene sheets and carbon nanotubes (CNTs) were selectively grown on Fe foil at a relatively low growth temperature and varying cooling rates using a hot filament chemical vapor deposition (HFCVD) apparatus with C2H2 as the precursor. The results of the scanning electron microscopy and Raman spectroscopy revealed that the increase of the cooling rate from 7 to 10 or 20 °C/min provoked a structure transition from CNT to graphene. The optimum crystal quality of the graphene sheets (Iq/Id ∼1.1) was achieved at the cooling rate of 20 °C/min. According to the AFM analysis, the thickness of the stacked graphene sheets was found to be ∼2.9-3.8 nm containing ∼8-11 monolayers. The XRD... 

    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  

    Mixed-Halide CH3NH3PbI3−xXx (X=Cl, Br, I) perovskites: vapor-assisted solution deposition and application as solar cell absorbers

    , Article ChemPhysChem ; 2016 , Pages 2382-2388 ; 14394235 (ISSN) Sedighi, R ; Tajabadi, F ; Shahbazi, S ; Gholipour, S ; Taghavinia, N ; Sharif University of Technology
    Wiley-VCH Verlag 
    There have been recent reports on the formation of single-halide perovskites, CH3NH3PbX3 (X=Cl, Br, I), by means of vapor-assisted solution processing. Herein, the successful formation of mixed-halide perovskites (CH3NH3PbI3−xXx) by means of a vapor-assisted solution method at ambient atmosphere is reported. The perovskite films are synthesized by exposing PbI2 film to CH3NH3X (X=I, Br, or Cl) vapor. The prepared perovskite films have uniform surfaces with good coverage, as confirmed by SEM images. The inclusion of chlorine and bromine into the structure leads to a lower temperature and shorter reaction time for optimum perovskite film formation. In the case of CH3NH3PbI3−xClx, the optimum... 

    Electrochemical deposition of Ni-TiN nanocomposite coatings and the effect of sodium dodecyl sulphate surfactant on the coating properties

    , Article Bulletin of Materials Science ; Volume 39, Issue 4 , 2016 , Pages 1021-1027 ; 02504707 (ISSN) Parhizkar, N ; Dolati, A ; Aghababazadeh, R ; Lalegani, Z ; Sharif University of Technology
    Indian Academy of Sciences  2016
    Ni-TiN nanocomposite coatings were prepared by using electrochemical deposition in a Watt's bath containing TiN particles to increase the hardness of Ni. The effects of deposition current density, electrolyte agitation speed and the number of particles in the solution on the amount of incorporated particles in the coating process were investigated. The optimum deposition current density of 4 A dm-2 and agitation speed of 450 rpm were obtained. The effect of sodium dodecyl sulphate (SDS) anionic surfactant on the amount of particles in the coatings was investigated. It was observed that the maximum amount of incorporated particles, with a value of 7.5% by volume, was created in the current... 

    Self-limited growth of large-area monolayer graphene films by low pressure chemical vapor deposition for graphene-based field effect transistors

    , Article Ceramics International ; Volume 43, Issue 17 , 2017 , Pages 15010-15017 ; 02728842 (ISSN) Kiani, F ; Razzaghi, Z ; Ghadiani, B ; Tamizifar, M ; Mohmmadi, M. H ; Simchi, A ; Sharif University of Technology
    During the last decade, fabrication of high-quality graphene films by chemical vapor deposition (CVD) for nanoelectronics and optoelectronic applications has attracted increasing attention. However, processing of large-area monolayer and defect-free graphene films is still challenging. In this work, we have studied the effect of processing conditions on the self-limited growth of graphene monolayers on copper foils during low pressure CVD both experimentally and theoretically based on thermokinetics and kinetics of Langmuir adsorption. The effect of copper pre-treatment, growth time, and carbon potential of the atmosphere (indicated by the methane-to-hydrogen gas ratio, r) on the quality of... 

    Electrophoretic deposition of nano-zirconia coating on AZ91D magnesium alloy for bio-corrosion control purposes

    , Article Surface and Coatings Technology ; Volume 311 , 2017 , Pages 182-190 ; 02578972 (ISSN) Amiri, H ; Mohammadi, I ; Afshar, A ; Sharif University of Technology
    Elsevier B.V  2017
    Magnesium alloys are considered as potential biodegradable biomaterials in hard tissue implants. However, the fast degradation rate of these alloys in the biological environment causes failure of the implant just prior to the desirable time. In the present work, in order to decrease and curb the bio-corrosion rate of AZ91D Magnesium alloy, zirconia, which is classified as a biocompatible ceramic, was coated on the alloy surface through electrophoretic deposition (EPD) technique. The effects of alterations in the EPD parameters such as current density, duration time and ZrO2 particles concentration on coating properties including thickness, morphology and adhesion were then characterized.... 

    Ni-P/Zn-Ni compositionally modulated multilayer coatings – part 1: electrodeposition and growth mechanism, composition, morphology, roughness and structure

    , Article Applied Surface Science ; Volume 442 , 2018 , Pages 275-287 ; 01694332 (ISSN) Bahadormanesh, B ; Ghorbani, M ; Sharif University of Technology
    Elsevier B.V  2018
    The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current... 

    An investigation into the effects of green space on air quality of an urban area using CFD modeling

    , Article Urban Climate ; Volume 34 , December , 2020 Moradpour, M ; Hosseini, V ; Sharif University of Technology
    Elsevier B.V  2020
    Tehran, the capital of Iran, is one of the most polluted cities in the Middle East. However, there is no clear evidence of the effects of Tehran green spaces on reducing air pollution because there are still challenges to application of vegetation for improving air quality. The current study investigates the effects of a large volume of green space with 275 ha area in the vicinity of major highways on nearby air quality. Similar environments are often seen in many cities around the world. A computational fluid dynamics model containing aerodynamics and deposition effects of vegetation was used to simulate pollutant dispersion for eight wind directions and three different foliage densities.... 

    Conformal curves on the WO3 surface

    , Article Physical Review Letters ; Volume 100, Issue 4 , 2008 ; 00319007 (ISSN) Saberi, A. A ; Rajabpour, M. A ; Rouhani, S ; Sharif University of Technology
    We have studied the isoheight lines on the WO3 surface as a physical candidate for conformally invariant curves. We have shown that these lines are conformally invariant with the same statistics of domain walls in the critical Ising model. They belong to the family of conformal invariant curves called Schramm-Loewner evolution (or SLEκ), with diffusivity of κ∼3. This can be regarded as the first experimental observation of SLE curves. We have also argued that Ballistic Deposition (BD) can serve as a growth model giving rise to contours with similar statistics at large scales. © 2008 The American Physical Society