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    Finite Element Formulation for Thermo-elastic Analysis of Functionally Graded Coating on Axisymmetric Shell Structures

    , M.Sc. Thesis Sharif University of Technology Ahmadi Kazemabadi, Abolfazl (Author) ; Hosseini Kordkheili, Ali (Supervisor) ; Zabihollah, Abolghasem (Co-Advisor)
    In this paper, a finite element formulation is presented to study the thermoelastic behavior of Functionally Graded (FG) axisymmetric coating in shell structures. The power law distribution model is assumed for the composition of the constituent materials in thickness direction. The Plasma Spray with multi steps coating method is considered for coating method. The procedure adopted to derive the finite element formulation contains the analytical through-the-thickness integration inherently. So the explicit through-the-thickness integration becomes possible after defining a two-noded, three parameters degenerated axisymmetric FG element. The nonlinear heat transfer equation is used for... 

    Investigation and Optimization of Ni-P-Zn Electroless Alloy Coatings

    , M.Sc. Thesis Sharif University of Technology Kordijazi, Amir (Author) ; karam, SaeedAllah (Supervisor) ; Dolati, Abolghasem (Supervisor)
    An optimization condition for obtaining Ni-Zn-P electroless alloy coating has been developed. The sulphate bath with sodium hypophosphate as a reducer and sodium citrate and ammonium chloride as complexing agents were used. The effect of variation in the pH level , temperature , time of deposition and reactants concentration on stability of bath, coating composition, microstructure, microhardness and corrosion resistance of coatings was investigated. The composition of coatings was obtained by using the EDAX analysis. To investigate coating morphology, SEM images were taken and to study the corrosion behavior of coatings potentidynamic polarization, Electrochemical Impedance Spectroscopy... 

    Surface Treatment Effects on Fretting Fatigue Map of a Titanium Alloy

    , M.Sc. Thesis Sharif University of Technology Shariati Nejad, Ali (Author) ; Adib Nazari, Saeed (Supervisor)
    In contacts, the presence of both variable loading and low-amplitude movements causes a kind of fatigue in these components called FRETTING FATIGUE. fretting fatigue has reduced the life of parts. Due to the high cost of replacing some parts in case of failure, it is necessary to take effective measures to delay this exhaustion. One of the effective solutions that can be applied is the use of coating and surface treatments in the contact areas. In this research, first, the fretting fatigue maps of Ti-6Al-4V alloy have been calculated and drawn according to the recommendations of the ASTM standard by using finite element methods. In the next step, by using experimental experiments, the damage... 

    Investigation and Analysis of the Coating Effect on the Contact Pressure and Slip Amplitude in Fretting Fatigue of a Compressor Blade Root

    , M.Sc. Thesis Sharif University of Technology Amini Chehragh, Hassan (Author) ; Adib Nazari, Saeed (Supervisor)
    In many industrial devices and machines, variable loading is applied to the parts, which will lead to fatigue in these parts. Most of these components are in contact with other components, and when the device is operating, low-amplitude movements occur at the contact point. Variable loading conditions and low-amplitude movements at the point of contact can cause failure on parts called FRETTING FATIGUE. This type of failure occurs in many aerospace components, such as where the compressor blade roots connect to the disc. In recent years, many failures due to fretting fatigue has been reported, which has made the need to take solution to prevent this type of failure more and more obvious. One... 

    Estimation of Chitgar Lake Evaporation and the Impact of Chemical Coverings on its Reduction

    , M.Sc. Thesis Sharif University of Technology Nejatian, Amir (Author) ; Tajrishy, Masoud (Supervisor) ; Irajizad, Azam (Supervisor)
    Reducing water evaporation is one of the ways to overcome the low precipitation and drought conditions in water reservoirs. For this purpose, extensive studies have been investigated on physical and chemical coatings on lakes and reservoirs. Physical methods often involve the use of floating covers on the water surface to block evaporation by shading, most of which are only suitable for reservoirs with surface areas smaller than 5 hectares. In chemical methods, the evaporation can be decreased by nanomaterial coating, usually, containing long-chain molecules, which by spraying them on the surface, molecular monolayers are formed. In this study, the effect of nanometer coatings on the surface... 

    Improving Mechanical and Biological Behavior of Mg-2ag Alloy: Effects of Y Addition, Heat Treatment and Coating

    , M.Sc. Thesis Sharif University of Technology Mohammadi Zerankeshi, Meysam (Author) ; Alizadeh, Reza (Supervisor)
    Biodegradable Mg-Ag alloys are promising implants for bone tissue regeneration due to their unique ability to reduce inflammation and infection after implantation with the presence of silver. However, their biological performance, including biodegradability, needs further improvement. In this regard, the effects of adding yttrium element, solution heat treatment and coating on the microstructure, biodegradability behavior, mechanical properties and biological characteristics of a cast Mg-2Ag alloy were studied. Addition of 1 wt% of yttrium caused grain refinement in the microstructure and solid solution heat treatment led to a significant decrease in the volume fraction of secondary phases.... 

    Deposition and Properties of ZIF-8/SiO2 Hydrophobi Anti-Corrosion Coating

    , M.Sc. Thesis Sharif University of Technology Tajaslan, Parisa (Author) ; Dolati, Abolghasem (Supervisor)
    In this research, a coating was created on the steel surface using the network structure of zeolite imidazolate-8 (ZIF-8) and its effect on the corrosion behavior of steel was investigated. Then, the effect of two coupling agents, mercaptopropyltriethoxysilane (MPTES) and aminopropyltriethoxysilane (APTES) on the coating and its anti-corrosion properties was investigated. Then, in order to make a hydrophobic coating, the substrate was first coated with ZIF-8 and then a combination of silica nanoparticles plus hexamethyldisilazane (HMDS) and polymethylhydrogensiloxane (PMHS) was added to the initial solution and then coating was done. As a result of this process, the contact angle of water... 

    Investigating the Microstructure, Mechanical Properties and Corrosion Resistance of Biodegradable Mg-Li-Zn Alloys

    , M.Sc. Thesis Sharif University of Technology Zohrevand, Mohammad (Author) ; Alizadeh, Reza (Supervisor) ; Tavakoli, Rouhollah (Co-Supervisor)
    Due to its biodegradability, magnesium can be a good option for making degradable medical implants that disappear in the body over time and thus there would be no need for secondary surgery. However, high rate of corrosion of magnesium in the body environment and low formability at room temperature are the two main problems of magnesium, which lead to rapid destruction of the sample in a short time and serious problems. For these reasons, much research is currently being done to improve the corrosion behavior and mechanical properties of magnesium alloys through microstructure modification. In this regard, special attention has been paid to Mg-Li alloys as the lightest magnesium alloys. The... 

    Investigation into the Effect of Adding Sr on Microstructure, Mechanical Properties and Biodegradability Behavior of Biodegradable Mg-Zn-Sr Alloys

    , M.Sc. Thesis Sharif University of Technology Gerashi, Ehsan (Author) ; Alizadeh, Reza (Supervisor)
    Biodegradable implants are new generation of implants that require no secondary surgery for their removal. Mg exhibits a great potential to be used as the biodegradable implant. However, mechanical properties and biocorrosion behavior of Mg are not suitable for being used as biodegradable implants. In this study, effects of Sr additions, heat treatments (T4 and T6), and multi-directional forging on the microstructural evolution, mechanical properties and biocorrosion behavior of Mg-4Zn-xSr alloys, and also the effect of hydrothermal coating on the biocorrosion behavior of Mg-4Zn-0.3Sr alloy were investigated. Potentiodynamic polarization and hydrogen evolution methods were used to... 

    Super Hydrophobic Ni Coating on Steel by Electrodeposition Method

    , M.Sc. Thesis Sharif University of Technology Nakhaei Niya, Hamzeh (Author) ; Dolati, Abolghasem (Supervisor)
    In this study, the properties of super-hydrophobic Ni coating on carbon steel including wetting behavior and corrosion resistance of Nickel coatings deposited on the steel substrate were investigated. For this purpose, Nickel coatings deposited by electrodeposition method in deferent current density (10,20,30,50, 70 mA /cm2) in bath containing 1.5 mol of ethylene de-ammonium de-chloride, 0.5 mol H3BO3, 1 mol Nicl2.6H2o and then immersed in a bath containing 0.01 mol per liter myristic acid and ethanol for 24 hours and then placed in the room temperature for 14 days. Deferent tests were used for characterization, wettability properties, corrosion behavior and morphology of Ni coatings. The... 

    Cathodic Disbonding in Steel Structures and the Effect of Paint Type and Environment

    , M.Sc. Thesis Sharif University of Technology Sharbatdar, Meghdad (Author) ; Ghorbani, Mohammad (Supervisor)
    Although using cathodic protection in addition to coating with paint will extend the life of pipelines drastically, it can also accelerate disbondment of coating at coating defects. In this research four usual pipeline coating systems have been examined from applicational aspects and the best coating system among them has been introduced. The four coating systems were consisted of: epoxy coal tar 212 with epoxy 155 primer, solvent free polyamine epoxy 474HG without primer, glasscote 440 witout primer and glasscote 440 with epoxy 155 primer. According to ASTM G8, cathodic disbondment test was accomplished for eight samples simultaneously. During the tests cathodic protection current and... 

    Growth of Perovskite Film based on Lead Iodide by Controlling Deposition Parameters for Solar Cells Application

    , M.Sc. Thesis Sharif University of Technology Tafazoli, Saeedeh (Author) ; Mohammadi, Mohammad Reza (Supervisor) ; Seyed Reihani, Morteza (Supervisor) ; Riahi, Nastaran (Co-Advisor)
    Perovskite solar cells, with high efficiency operation, have been candidated as a cost-effective and environmentally friendly technology. Despite the great progress, there are some primarily issues remained regarding to the perovskite film and its fabrication methods. A very common perovskite cell structure is FTO/TiO2/CH3NH3PbI3/Spiro-OMeTAD/Au. Although, this structure has some advantages, lack of full surface coverage of perovskite film leads researchers to put much effort on finding other constructions. This surface inhomogeneity reduces the amount of light absorption and therefore efficiency. One way to produce a complete and uniform film is applying mixed-halide composition; such as... 

    Preparation and Characterization of ZrO2 Antistatic Coatings on Glass

    , M.Sc. Thesis Sharif University of Technology Naderi, Armaghan (Author) ; Dolati, Abolghasem (Supervisor) ; Afshar, Abdollah (Supervisor)
    In this study, the zirconia antistatic coating was synthesized by dip coating sol-gel route on glass substrate. The solution contains ZrCl4 as precursor and isopropanol as solvent to synthesize zirconium oxide. The effects of environmental humidity and solution concentration on the coating characterization were analyzed. MPTS and primer binder were added as binding agents in the solution to observe the effect of binding agents on the coating adhesion. Solution stability and antistatic coating characterization were analyzed by zita potential test, FTIR spectroscopy, EDX analysis, FESEM and AFM microscopy, pencil hardness test, thickness test, antidust ability and spectrophotometer. The... 

    Creating a Protective Coating Against Corrosion and Erosion on the Surface of the Parts using in Sour Environments

    , M.Sc. Thesis Sharif University of Technology Ghasemi Tabasi, Hossein (Author) ; Kokabi, Amir Hossein (Supervisor)
    A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of... 

    Formation and Investigation of Zinc-Nickel Two Cathionic Electrophospahte Coating Properties on Galvanized Steel

    , M.Sc. Thesis Sharif University of Technology Barati Darband, Ghasem (Author) ; Afshar, Abdollah (Supervisor)
    By using electrophoaphating treatment in the metal coating process, the operating temperature of chemical phosphating bath is decrease and also difficulties with the use of high temperature bath is eliminated. The aim of this study is investigate the effect of operating parameter on coating properties and also investigation the deposition mechanism of Zn-Ni electrophosphate coating. Coating properties such as morphology, corrosion resistance and porosity of the coating characterized using SEM, polarization test and electrochemical method respectively. The values used for pH effect was 1.6,1.8,2 and 2.2 results indicated that by increasing the pH value from 1.6 to 1.8 the icorr decrease from... 

    Effect of Fluorine Addition on Properties of Electrodeposited Fluorine-doped Hydroxyapatite Coating on AZ31 alloy

    , M.Sc. Thesis Sharif University of Technology Amirloo, Hossein (Author) ; Afshar, Abdollah (Supervisor)
    Magnesium and its alloys are potentialy biodegradable implant materials due to their attractive biological properties. But their poor corrosion resistance may result in sudden failure of the implants. Recently, many researchers have focused on applications of fluorine-doped hydroxyapatiteCa10(PO4)6(OH)2−xFx (FHA, x is the degree of fluoridation) as a bioactive coating to provide early stability and long-term performance. In comparison with pure HA coating,FHA coating could provide significant dissolution-resistant property, better apatite-like layer deposition, better protein adsorption, better cell attachment and improved alkaline phosphatase activity in cell culture. In this... 

    An investigation on the Microstructure and Properties of Alumina-Carbon Nanotube (CNT) Nanocomposite Produced by Conventional and Microwave Sintering

    , M.Sc. Thesis Sharif University of Technology Ghobadi, Hossein (Author) ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor) ; Ebadzadeh, Toraj ($item.subfieldsMap.e)
    Carbon nanotubes were coated with boehmite nanoparticles by sol gel method. According to the TGA analysis, formation of gamma-alumina from boehmite was at 500 . SEM investigation revealed the uniform coverage of gamma-alumina nanoparticles on the surface of CNTs. Composite powders containing 1, 2 and 3vol% of coated CNTs were produced by mixing the coated CNTs with alumina suspension. Phase analysis of composite powder calcined at 500 showed the complete decomposition of boehmite and formation of gamma-alumina. Samples were shaped by cold isostatic pressing at the pressure of 180MPa and sintering was performed using two different methods of conventional and microwave. Existance of the CNTs... 

    Preparation and Characterisation of Titania-hydroxyapatite-carbon
    Nanotube Nanostructured Bioceramics by Sol-gel Process

    , M.Sc. Thesis Sharif University of Technology Majidnia, Elahe (Author) ; Mohammadi, Mohammad Reza (Supervisor)
    Hydroxyapatite (HA) is an attractive biomaterial due to its close chemical composition to bone and teeth. However, HA is brittle and has low strength under bearing loads, resulting in limition for orthopedic and dental applications. Two creative approaches have been developed to overcome this problem, using bioactive HA as coatings on metallic implants or as ceramic/metal composites. Carbon nanotubes (CNT) possess excellent mechanical properties to play the role as reinforcement for imparting strength and toughness to brittle hydroxyapatite (HA) bioceramic coating. Moreover, The addition of TiO2 to HA coatings has attracted considerable attention, since TiO2 is capable of increasing the... 

    Lanthanum Chromite Coating on Stainless Steel by sol–Gel Dip Coating Technique

    , M.Sc. Thesis Sharif University of Technology Rashtchi, Hamed (Author) ; Faghihi Sani, Mohammad Ali (Supervisor)
    Because of the high operating temperature, interconnect surface tends to be oxidized and Cr2O3 oxide layer will be created on the surface. This phenomenon is undesirable due to decreasing electrical conductivity, so a preservative coating is needed to improve the interconnect properties. In this paper, a dense perovskite thin film was successfully synthesized on a ferritic stainless steel (type 430) substrate by a sol-gel dip coating method. This coating improved chemical stability, oxidation behavior of the substrate and decreased cathode poisoning. The lanthanum chromite was coated on the substrate by sol-gel dip coating process. First, during a hydrolyze process, a stable sol was made up... 

    Characterization of Nanohydroxyapatite-Carbon Nanotube on Stainless Steel 316L Produced by Sol-Gel Method

    , M.Sc. Thesis Sharif University of Technology Mohamadi, Pouya (Author) ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor)
    In this investigation, hydroxyapatite-carbon nanotube nano composite coatings were applied on the 316L stainless steel implants. After polishing with 1200 sand paper, stainless steel implants were coated via dip coating method. The specimens were heat treated at 350˚C after being coated with HAP and HAP-CNTs composite. In vitro test was done in simulated body fluid (SBF) in 1 to 4 weeks periods. XRD evaluation of powder obtained from sol-gel process, showed the presence of HAP and CNTs in the powders. Comparison of XRD results of HAP and HAP-CNTs powders showed the better crystalinity of composite hydroxyapatite. After in vitro tests, specimens were studied with atomic force microscope (AFM)...