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    Formation & Properties of Zn–Ca– Mn Tri – Cation’s Phosphate Coating on St37 Steels

    , M.Sc. Thesis Sharif University of Technology Rasouli, Hassanali (Author) ; Afshar, Abdollah (Supervisor) ; Ghorbani, Mohammad (Supervisor)
    Addition of heavy metal cations such as manganese and nickel in low zinc phosphating bath increases the corrosion resistance of coatings and provides more suitable substrates for painting (especially electrophoretic painting). In addition, due to accelerating property and low cost availability of heavy metal cations such as Mn, multi– cationic phosphating is cost effective. In the present study, chemical composition and operating parameters of zinc - calcium - manganese Tri- cationic phosphating solution were optimized. Then the effects of various parameters such as phosphating time, bath temperature and pH on properties of coating were investigated. According to the results, about 1 g/L was... 

    Enhanced Photocatalytic Activity of Nano-scaled TiO2 Co-doped with N and Ag by Sol-gel Method

    , M.Sc. Thesis Sharif University of Technology Azimi, Zahra (Author) ; Dolati, Abolghasem (Supervisor)
    Transparent coatings with self-cleaning property in visible light spectrum, UV radiation resistance and antimicrobial are highly desirable. Titanium dioxide (TiO2) is used in this research has been widely studied as an efficient photocatalyst by researchers. In this research enhanced visible-light photocatalytic activity is gained with N and Ag co-doped titania. All samples were annealed at 450℃. Finally AgI was loaded TiO2 coating and the results were investigated. Peaks of XRD pattern wereattributed to different diffraction planes of anatase TiO2. Morphology of coatings were analyzed with using FE-SEM. Nano granis size of TiO2 and AgI loaded TiO2 were observed in FE-SEMimages. Nitrogen... 

    Overall electroelastic moduli of particulate piezocomposites with non-dilute BCC microstructure

    , Article International Journal of Mechanical Sciences ; Volume 53, Issue 9 , 2011 , Pages 777-785 ; 00207403 (ISSN) Hashemi, R ; Kargarnovin, M. H ; Sharif University of Technology
    The present paper addresses an analytical method to determine the overall behavior of piezocomposite materials containing body centered cubic (BCC) distribution of arbitrary oriented ellipsoidal heterogeneities. This approach is based on the extension of the electromechanical equivalent inclusion method (EMEIM) to interacting multi-inhomogeneities. In this treatment the short and long range interactions of the piezoelectric particles are appropriately incorporated through the homogenizing eigenstrainelectric field. The periodicity of the microstructure of the medium suggests representing the eigenfields in terms of Fourier series, accounting for the matrixparticle, interparticle and... 

    Investigation of morphology and bioactive properties of composite coating of HA/vinyl acetate on pure titanium

    , Article Materials Science and Engineering B: Solid-State Materials for Advanced Technology ; Volume 128, Issue 1-3 , 2006 , Pages 243-249 ; 09215107 (ISSN) Afshar, A ; Yousefpour, M ; Xiudong, Y ; Li, X ; Yang, B ; Wu, Y ; Chen, J ; Xingdong, Z ; Sharif University of Technology
    Electrochemical co-deposition approach was expanded to prepare composite bio-ceramic coating of hydroxyapatite (HA)/polyvinyl acetate on the surface of titanium. The role is to improve the bioactive and crystallization properties. The results of XRD, XPS, SEM and TEM characterization showed that by increasing amount of vinyl acetate in the composite bio-ceramic coating before and after immersing in the simulated body fluid (SBF), an oriented growth of HA planes on the (0 0 2) direction had been observed on titanium substrate. Also significant surface morphology changes were obtained  

    Optimization of air plasma sprayed thermal barrier coating parameters in diesel engine applications

    , Article Journal of Materials Engineering and Performance ; Volume 22, Issue 11 , 2013 , Pages 3530-3538 ; 10599495 (ISSN) Azadi, M ; Farrahi, G. H ; Moridi, A ; Sharif University of Technology
    In the present paper, an optimization of thermal barrier coating parameters is performed for diesel engine applications. The substrate is A356.0-T7, a cast aluminum alloy which has a vast application in diesel engines, and the alloy is coated by plasma sprayed ZrO2-8 wt.% Y2O3. Parameters including the feed rate of coating powders, the nozzle distance to specimen surfaces, and the coating thickness are optimized by thermal shock fatigue tests and bending tests. Optimum values of the feed rate and the nozzle distance are 30 g/min and 80 mm, respectively, when the objective is considered as maximizing the bending strength. Thermal shock tests demonstrate that lower thickness of coating layers... 

    Wear and corrosion properties of electroless nickel composite coatings with PTFE and/or MoS 2 particles

    , Article Journal of Coatings Technology Research ; Volume 8, Issue 4 , 2011 , Pages 527-533 ; 15470091 (ISSN) Mohammadi, M ; Ghorbani, M ; Sharif University of Technology
    This study focuses on the effect of co-deposition of PTFE and/or MoS 2 particles on the morphology, wear, and corrosion properties of electroless nickel coating. The composite coating of EN-PTFE-MoS 2 was heat treated at different temperatures for hardness investigations. The surface morphology of coatings was characterized by scanning electron microscopy. Pin-on-disk and potentiodynamic polarization tests were used to study the tribological and corrosion properties of the coatings, respectively. Results of hardness analysis revealed that the hardness of electroless nickel coatings was increased by the heat treatment, and its maximum was gained at 400°C. Wear investigations showed that... 

    Characterisation of Ni-Ti intermetallic coatings formed on Cp titanium by diffusion treatment

    , Article International Journal of Surface Science and Engineering ; Volume 9, Issue 1 , 2015 , Pages 43-54 ; 1749785X (ISSN) Khosravi, G ; Sohi, M. H ; Ghasemi, H. M ; Vafadar, A. Kh ; Sharif University of Technology
    Inderscience Enterprises Ltd  2015
    In order to produce a thick near equi-atomic NiTi intermetallic layer on the surface of titanium plate, layers of nickel with thicknesses of 30 μm and 60 μm were electroplated on commercial pure (Cp) titanium and subsequently were heat treated at 850°C and 900°C. The effects of heat treating temperature and the thickness of electroplated nickel on the evolution of the microstructure and mechanical properties were studied. The results confirm the formation of various intermetallic layers in the coatings that substantially affect their hardness. The optimum condition for the formation of a thick NiTi intermetallic layer on the outer surface of the titanium was diffusion treatment of the sample... 

    Experimental investigation and artificial neural network modeling of warm galvanization and hardened chromium coatings thickness effects on fatigue life of AISI 1045 carbon steel

    , Article Journal of Failure Analysis and Prevention ; Volume 17, Issue 6 , 2017 , Pages 1276-1287 ; 15477029 (ISSN) Kashyzadeh, K. R ; Maleki, E ; Sharif University of Technology
    In the present study, the main purpose is investigation of the coatings thickness effect on the fatigue life of AISI 1045 steel. Herein, two different coatings of warm galvanization and hardened chromium have been used on the specimens. Fatigue tests were performed on specimens with different coating thicknesses of 13 and 19 µm. In the high-cycle level, S–N curves are extracted with 13 points for each sample. The results show that the galvanized coating is the most appropriate coating with low thickness, but with significant increasing of coating thickness, the best choice is hardened chromium coating. However, artificial neural network (ANN) has been used as an efficient approach instead of... 

    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... 

    Experimental investigation of viscous drag reduction of superhydrophobic nano-coating in laminar and turbulent flows

    , Article Experimental Thermal and Fluid Science ; Volume 51 , 2013 , Pages 239-243 ; 08941777 (ISSN) Moaven, K ; Rad, M ; Taeibi Rahni, M ; Sharif University of Technology
    In this research, effects of superhydrophobic nano-coating on frictional drag force have been investigated. The result of this study could be considered to be used as a method in applications concerned with fuel consumption reduction, less CO2 emission and environmental problems as well as speed increase; while, its significance can also be of great use in marine applications. A rotating disc apparatus was used as the experimental set-up to compare the frictional drag force on an aluminum disc with TiO2 superhydrophobic nano-coating and a smooth coatless aluminum disc. The superhydrophobic nano-coating was prepared using sol-gel method and was shown to be able to produce a contact angle of... 

    Fabrication and high-temperature corrosion of sol-gel Mn/Co oxide spinel coating on AISI 430

    , Article Surface and Coatings Technology ; Volume 223 , 2013 , Pages 110-114 ; 02578972 (ISSN) Dayaghi, A. M ; Askari, M ; Rashtchi, H ; Gannon, P ; Sharif University of Technology
    MnCo oxide spinels have received recent interest as surface coatings on ferritic stainless steel (FSS) interconnects in solid oxide fuel cell (SOFC) stacks, where they provide relatively stable electrical conductivity and reduced Cr volatility compared to uncoated FSS interconnects. In this study, sol-gel deposited MnCo surface coatings on FSS, with post-deposition treatments, were investigated in laboratory air at up to 750°C for up to 750h. The protective coating formed and evolved isomorphic crystallites, (Mn,Co,Fe,Cr)3O4, following fifteen (15) fifty hour (50h) cycles in air up to 750°C. Relative to the surface oxide on the uncoated FSS, the coating was dense, crack-free and exhibited... 

    Crystallization of hydroxyapatite during hydrothermal treatment on amorphous calcium phosphate layer coated by PEO technique

    , Article Ceramics International ; Volume 39, Issue 2 , 2013 , Pages 1793-1798 ; 02728842 (ISSN) Faghihi Sani, M. A ; Arbabi, A ; Mehdinezhad Roshan, A ; Sharif University of Technology
    Surface modification of titanium implants is recently considered by several researchers. In this study, PEO was performed over commercially Ti-6Al-4V alloy pellets in an aqueous electrolyte containing calcium acetate (C.A.) and calcium glycerphosphate (Ca-GP) with a Ca/P molar ratio of 6.8, and applying current density of 0.212 A/cm2, frequency of 100 Hz and duty ratio of 60% for 4 min. In the next step, hydrothermal treatments were carried out for various durations and at different temperatures inside an autoclave chamber containing a NaOH solution with pH of 11.5. XRD and SEM results confirmed formation of needle-shaped HAp after all hydrothermal conditions. Maximum intensity of HAp peaks... 

    Protection of titanium metal by nanohydroxyapatite coating with zirconia and alumina second phases

    , Article Protection of Metals and Physical Chemistry of Surfaces ; Volume 48, Issue 6 , 2012 , Pages 688-691 ; 20702051 (ISSN) Family, R ; Solati Hashjin, M ; Nik, S. N ; Nemati, A ; Sharif Universty of Technology
    In this study hydroxyapatite (HA)/zirconia/alumina composite coatings on titanium metal was carried out using Sol-Gel dip coating and calcination process. Hydroxyapatite-Alumina-Zirconia sol, coated samples in three processes by changing final sol stirring time, aging time, calcination temperature of synthesized powder and prepared coating and rate of coating. Some parts of prepared sol were also synthesized and became powder in all three processes. Scanning electron microscopy was used to estimate the particle size of the surface and for morphological analysis. The functional group and crystallization characteristics of the powders were analyzed using (FTIR) and X-Ray diffraction (XRD).... 

    Pre-treatment and oxidation behavior of sol-gel Co coating on 430 steel in 750°C air with thermal cycling

    , Article Surface and Coatings Technology ; Volume 206, Issue 16 , 2012 , Pages 3495-3500 ; 02578972 (ISSN) Dayaghi, A. M ; Askari, M ; Gannon, P ; Sharif University of Technology
    Research and development efforts continue to improve oxidation resistance and electrical conductivity of solid oxide fuel cell (SOFC) interconnects. This research evaluates the performance of a ferritic stainless steel (AISI 430 - a candidate SOFC interconnect material) with and without a Co coating (via sol-gel dip coating technique) with various pre-treatments, during cyclic oxidation exposures up to 750°C in laboratory air. A pre-treatment exposure of Co coated samples to a 750°C reducing atmosphere (prior to oxidation exposures) led to the formation of an effective Co-based spinel oxide coating that lowers oxidation rates by more than 40 times, and substantially lowers area specific... 

    A comparison between the corrosion resistances of High Velocity Oxy Fuel (HVOF) sprayed coatings and hard chromium coatings

    , Article Materials Science Forum, 1 September 2010 through 3 September 2010, Seoul ; Volume 673 , 2011 , Pages 173-178 ; 02555476 (ISSN) ; 9783037850183 (ISBN) Saghi Beyragh, M. R ; Khameneh Asl, S ; Vasfpour, R ; Tazesh, F ; Khallagi, P ; Sharif University of Technology
    HVOF-sprayed coatings (WC-17%Co) and hard chromium coatings corrosion resistances have been compared through electrochemical polarization test in 3.5% NaCl solution. WC-17%Co alloy coatings were deposited on mild steel substrates by High Velocity Oxy-Fuel (HVOF) spray process. The layers of standard and crack free hard chromium coatings were prepared by using Direct Current (DC) and Pulse Current (PC) electroplating process on the mild steel substrates. Hard chromium coatings was characterized as a reference material, to verify whether HVOF-sprayed coatings are suitable as a hard chromium coatings replacement. The microstructure of the coatings was examined by OM, SEM and XRD. Standard hard... 

    Damage prediction for un-coated and coated aluminum alloys under thermal and mechanical fatigue loadings based on a modified plastic strain energy approach

    , Article Materials and Design ; Volume 66, Issue PB , 2015 , Pages 587-595 ; 02613069 (ISSN) Azadi, M ; Farrahi, G. H ; Winter, G ; Huter, P ; Eichlseder, W ; Sharif University of Technology
    In this article, a novel energy-based lifetime prediction model has been presented for uncoated and coated aluminum alloys, subjected to thermal and mechanical fatigue loadings. For this objective, isothermal and thermo-mechanical fatigue tests were performed on the A356.0 alloy, with and without thermal barrier coating systems. This model, which was based on the plastic strain energy, had three correction factors including temperature, strain and mean stress effects. The predicted lifetime showed a proper agreement with experimental data. By the present model, higher accuracy was obtained in comparison to other existed approaches. Besides, the present model had lower number of material... 

    PH-responsive nanostructured polyaniline capsules for self-healing corrosion protection: the influence of capsule concentration

    , Article Scientia Iranica ; Volume 24, Issue 6 , 2017 , Pages 3512-3520 ; 10263098 (ISSN) Tavandashti, N. P ; Ghorbani, M ; Shojaei, A ; Mol, J. M. C ; Terryn, H ; Gonzalez Garcia, Y ; Sharif University of Technology
    Nanostructured hollow polyaniline (PANI) capsules are good candidates for encapsulation of corrosion inhibitors and pH-responsive release when incorporated into organic coatings. In previous studies, the corrosion protection performance of PANI capsules, containing organic inhibitor 2-Mercaptobenzothiazole (MBT), was demonstrated. The present work studies the influence of capsule concentrations (i.e., 0.3, 1, and 2 wt%) on the corrosion protection properties of the coating system. Anti-corrosion properties of different coatings were compared by means of Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). MBT loaded PANI capsules in epoxy ester... 

    Effects of chemical, electrochemical, and electrospun deposition of polyaniline coatings on surface of anode electrodes for evaluation of MFCs' performance

    , Article Journal of Environmental Chemical Engineering ; Volume 8, Issue 5 , 2020 Ghasemi, B ; Yaghmaei, S ; Ghaderi, S ; Bayat, A ; Mardanpour, M. M ; Sharif University of Technology
    Elsevier Ltd  2020
    In this research, different coating methods of polyaniline (PANI) on the anode electrodes and their performance in microbial fuel cells (MFCs) were investigated. The performance of systems in a discontinuous state was studied using the high energy content dairy industry wastewater. The phase enrichment assessment was conducted under open circuit potential (OCP) and the performance of MFCs coated with PANI through three methods was evaluated via chemical oxygen demand (COD), polarization, power density, energy coulombic efficiency (ECE), coulombic efficiency (CE), and potential efficiency (PE) values. The results showed the maximum value for the power density of 28Wm-3, CE of 17%, and COD of... 

    Investigating Effect of Nano Ceramic Coating of Combustion Chamber on the Performance of Internal Combustion Engines

    , M.Sc. Thesis Sharif University of Technology Sharifi, Masoud (Author) ; Naghdabadi, Reza (Supervisor)
    Thermal barrier coatings (TBCs) are used for increasing the efficiency and reducing pollutants of internal combustion engines (ICEs). In this paper, an optimization framework is developed in order to obtain the optimal dimensions for conventional coat, and the optimal dimensions and material property for functionally graded (FG) coat of a partially coated piston. A thermo mechanical analysis is investigated for Nano coat by finite element method. The conventional and Nano coats are made of MgZrO_3 as the insulating ceramic overlay and NiCrAl as the metallic bond-coat. The properties of the FG coat is assumed to vary according to power law through the thickness. For all tree conventional, FG... 

    Preparation and corrosion resistance of pulse electrodeposited Zn and Zn-SiC nanocomposite coatings

    , Article Applied Surface Science ; Vol. 300 , May , 2014 , pp. 1-7 ; ISSN: 01694332 Sajjadnejad, M ; Mozafari, A ; Omidvar, H ; Javanbakht, M ; Sharif University of Technology
    Pure Zn and Zn matrix composite coatings containing nano-sized SiC particles with an average size of 50 nm were prepared from the zinc sulfate bath. The effects of the pulse frequency, maximum current density and duty cycle on the amount of particles embedded were examined. Electron microscopic studies revealed that the coating morphology was modified by the presence of SiC nanoparticles. In the presence of SiC nanoparticles deposit grows in outgrowth mode resulting in a very rough and porous microstructure. However, at very low and very high duty cycles a smooth and pore free microstructure was obtained. Corrosion resistance properties of the coatings were studied using potentiodynamic...