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Surface Treatment Effects on Fretting Fatigue Map of a Titanium Alloy
, M.Sc. Thesis Sharif University of Technology ; Adib Nazari, Saeed (Supervisor)
Abstract
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 Optimization of Ni-P-Zn Electroless Alloy Coatings
, M.Sc. Thesis Sharif University of Technology ; karam, SaeedAllah (Supervisor) ; Dolati, Abolghasem (Supervisor)
Abstract
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...
Investigation And Fabrication Super Hydrophobic Coating On Building Facades
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdullah (Supervisor)
Abstract
According to the creation of high-rise buildings and structures due to the increase in urbanization and population concentration in cities and attention to the beauty of these structures and the impact of this beauty on the morale of urban people, owners or municipalities costs a lot of money for cleaning the building facade every year. On the other hand, removing contaminants from high-rise buildings facades is difficult and lifethreatening. Today, with the advancement of science and the use of self-cleaning super hydrophobic coatings, many of these costs, as well as threats to life, can be prevented. On the other hand, protection of ancient structures as a cultural capital of a country,...
A Study on Mechanical, Electrical Properties and Morphology of Ps/Eoc/Cnt Nanocomposite Blends
, M.Sc. Thesis Sharif University of Technology ; Pircheraghi, Gholamreza (Supervisor) ; Seyed Reyhani, Morteza (Supervisor)
Abstract
Nowadays, the development of different polymer blend nanocomposites is of great importance for achieving electrical and antistatic properties for various applications such as auto parts and the packaging industry. Immiscible polymer blends with conductive nanoparticles such as carbon nanotube, graphene, etc. can reach the conductivity threshold with low amounts of nanoparticles and produce desired electrical properties. In the present study, we have attempted to develop a polystyrene(PS)/ethylene-octene copolymer(EOC)/carbon nanotube(CNT) blend nanocomposite with suitable electrical conductivity. The compounding was performed by melt mixing at two weight percent of 80/20 and 50/50 (PS/EOC)...
The Investigation of Effective Parameters in Coating on Aluminized Steel by Plasma Electrolytic Oxidation Process
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Plasma electrolytic oxidation process (PEO) is now recognized as a relatively new method in surface engineering. In this process, formation of micro arcs resulted from electric discharges on the surface of the specimen in the appropriate electrolyte, is used to ionize the gas layer which has enshrouded the specimen. In the present study, ceramic coating on aluminized steel was produced by PEO process and the effects of the influential parameters were comprehensively investigated. For this purpose, coating on the aluminized steel with dimension of 25×30 mm² was produced under different condition of processing time from 1 to 15 minutes, current density from 10 to 20 A/dm², frequency from 50 to...
Investigation on Effective Parameters in Ceramic Coating on Titanium Substrate by PEO Method in Galvano Static Condition
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
During this research, ceramic coatings on titanium substrate were prepared by plasma electrolytic oxidation process at a constant current density. Effect of different parameters such as frequency, current density, additives and time on the characteristics of the coated samples was studied. Composition, structure and elemental distribution of the coatings were studied by XRD, SEM and wave-length dispersive spectroscopy (WDS), respectively. Various tests were carried out to calculate the amount of coatings porosity. Pin-On-Disk method was used to evaluate erosion resistance of coatings. Corrosion and erosion-corrosion behaviors of the coatings were studied in 3.5wt% sodium chloride aqueous...
Investigation of Nanocellulose Performance on the Corrosion Control in Polymeric Coating
, M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar (Supervisor)
Abstract
Cellulose nanocrystals as a reinforcement in polymer nanocomposites are part of current research for reasons such as source renewable, biocompatibility, nanoscale dimensions, high specific surface area, and surface chemistry. This research used cellulose nanocrystals as a corrosion inhibitor carrier in epoxy-based composite with 1% by weight. In order to load the corrosion inhibitor, firstly, cellulose nanocrystals were surface modified by aniline so that they can spread well in the hydrophobic epoxy matrix. Different corrosion inhibitors were tested for adsorption on the surface of cellulose nanocrystals modified with polyaniline, but finally the acidic agent of phosphoric acid showed...
Investigation on Synthesis and Properties of TiO2-CNT Nanocomposites Coating on Al Substrate
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor)
Abstract
The aim of this project is investigation on synthesis and characterization of the TiO2-CNT nanocomposite films on aluminum substrate by sol-gel dip coating method. The pure TiO2 and TiO2-CNT nanocomposite layers were coated on aluminum substrate and heat treated in 400 C. In this work Ti-tetra isopropxide and different amounts of CNTs (5,10,15 %wt), were used for obtain the composites. The coatings were characterized by X-Ray diffraction (XRD) and the crystallite size of TiO2 was calculated by Scherrer formula. The corrosion properties of coating were examined by polarization test, and corrosion resistance of pure TiO2 was compared with TiO2-CNT coatings, and It showed that the composite...
The Structure and Corrosion Behavior of Synthesized Zn-SiO2 Nano-composite Coating by Sol-Gel Method
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Zinc–silicanano-composite coatings were produced by successive dip coatand sintering procedure from different sol-gel solutions. The surface and cross-sectional morphologies of Zn-SiO2 nano-particles (NPs) were examined using field emission scanning electron microscopy (FE-SEM). Corrosion resistance evaluated by means of polarization and electrochemical impedance spectroscopy showed that even thin films of Zn-SiO2 in orders of 200 nm can have corrosion rates as low as conventional hot dip galvanized steels. Multi-layers coatings have been studied and showed that 10 layers coating with the thickness of 2m has the lowest corrosion rate with the passive region in anodic branch. Corrosion...
Investigating Bio-Capability of HA-ZrO2-TiO2 Nano-Composite Coating by EPD on St. St 316 in Physiologic Solution
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
Metallic implants are useful in dental and orthopedic applications. Bio coating is necessary to improve bio-compatibility and bio-activation of metallic implants. For this goal, HA is the most important material. In this research, the goal is to improve bio-compatibility of St. St 316 by coating HA, HA-ZrO2, HA-TiO2, HA-ZrO2-TiO2 using combination of electrodeposition and electrophoretic methods. To form HA, calcium and phosphor salt solution was used then ZrO2- TiO2 nanoparticles was added to solution. In order to analyst the coatings different tests were done. Thickness analysis, XRD, FT-IR, FE-SEM and EDS, bonding Strength, Polarization test, bio-compatibility and surface roughness...
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 ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor) ; Ebadzadeh, Toraj ($item.subfieldsMap.e)
Abstract
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...
Study of Microstructure and Wear behavior of In-Situ Al/Al3Ti Composite Coating on Commercial Pure Al Produced by Aluminum Cored Wires and TIG Process
, M.Sc. Thesis Sharif University of Technology ; Kokabi, Amir Hosein (Supervisor) ; Madaah Hoseini, Hamid Reza (Supervisor)
Abstract
Recently, Aluminum alloys have been the materials of choice for both military aircraft and automotive industries due to their high strength-to-weight ratio, high electrical and thermal conductivities and excellent corrosive resistance. However, their applications have been limited due to the low yield stress and wear resistance. In order to improve the surface wear resistance, structural and chemical surface modifications such as producing composite coatings could be applied. Gas Tungsten Arc welding (GTAW) process can be used to produce alloy and composite surface layers on different substrates. In this research, GTAW process and aluminum cored wires were used for coating of Al/Al3Ti...
Investigating the Microstructure, Mechanical Properties and Corrosion Resistance of Biodegradable Mg-Li-Zn Alloys
, M.Sc. Thesis Sharif University of Technology ; Alizadeh, Reza (Supervisor) ; Tavakoli, Rouhollah (Co-Supervisor)
Abstract
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...
Investigating Different Methods of Coating the Polyaniline on Anode Electrode and its Effect on Microbial Fuel Cell Performance
, M.Sc. Thesis Sharif University of Technology ; Yaghmaei, Soheila (Supervisor)
Abstract
In this research, different methods of coating polyaniline on the anode electrode and its performance in a microbial fuel cell, and a chemical method for making polyaniline / graphene catalyst on a cathode electrode and its performance in microbial electrolysis cell electrode were investigated. There are two main goals in this study. First, the production of polyaniline and the comparison of the surface morphology of this fiber with other forms of polyaniline on the surface of the electrode and its effect on the performance of the microbial fuel cell and the second, the production of polyaniline / graphene catalyst in the cathode electrode and its comparison with the platinum catalyst in the...
Behavior of Composites Containing Multi-coated Nano-fibers with Interfacial Damage in Couple Stress Theory
, Ph.D. Dissertation Sharif University of Technology ; Mohammadi Shodja, Hossein (Supervisor)
Abstract
It is well-known that classical continuum theory has certain deficiencies in capturing the size effects and predicting the nanoscopic behavior of materials in the vicinity of nano-inhomogeneities and nano-defects with reasonable accuracy. Couple stress theory which is associated with an internal length scale for the medium is one of the higher order continuum theories capable of overcoming such difficulties. Since most reinforcements may not be perfectly bonded to their surrounding matrix, the perfect bonding condition is often inadequate in describing the physical and mechanical behavior of real composite materials. In this work, the problem of a nano-size fiber embedded in an unbounded...
An Investigation on Photocatalytic Behavior of N-doped and N-V-doped TiO2 Thin Film, Coated on Glass Surface by Sol-gel Dip Coating Method
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
In this study, the photocatalytic activity and hydrophilicity of coat improved using Nitrogen and Vanadium elements as dopant in TiO2 coating. By using vanadium and nitrogen elements and silica prelayer, a titania coating was deposited on the soda-lime glass substrate by sol-gel dip coating method to produce self-cleaning surface. XRD and FTIR analyses were done on the powders after heat treating at in 450˚C for 30 min. XPS analysis was done for investigation of N replacement in titania structure. The band-gap energy of formed anatase was derived using UV-Vis analysis. The coating morphology and thickness were also investigated by SEM. Hydrophilicity of coatings was determined by measuring...
The Corrosion Behavior of Zinc and SiO2 Composite Coating
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Main aim of this work was to obtain the harder zinc coating and increasing the anti corrosive properties by mean of adding SiO2 particles by electrophoretic method.
The coating was applied on the substrate surface by mean of electro co-deposition technique in three different electrolytes ethanol, methanol and water. The morphology of the coating in each electrolyte studied by scanning electron microscope (SEM).For the Zn/SiO2 coatings achieved in ethanol solvent the polarization and EIS tests was took place and found that for the Zn/SiO2 coating contain less than 10% SiO2 the corrosion rate decreased but for the coatings contains more than 10% SiO2 the paradox occurred because of the...
The coating was applied on the substrate surface by mean of electro co-deposition technique in three different electrolytes ethanol, methanol and water. The morphology of the coating in each electrolyte studied by scanning electron microscope (SEM).For the Zn/SiO2 coatings achieved in ethanol solvent the polarization and EIS tests was took place and found that for the Zn/SiO2 coating contain less than 10% SiO2 the corrosion rate decreased but for the coatings contains more than 10% SiO2 the paradox occurred because of the...
A Study on Properties of Composite Coating with Al2O3 Base Prepared by Hard Anodizing with ZrO2 Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; Afshar, Abdollah (Supervisor)
Abstract
In this study anodized none composite and composite film containing ZrO2 nanoparticles were prepared on 1050 Al Alloy using hard anodizing method in sulfuric and oxalic acid mixed solution by pulse Currents. The microstructure and properties of the film were studied by field emission scanning electron microscopy with EDS analyzer and XRD diffraction and friction wear test were performed to evaluate the mechanical properties of coating . Results indicate that the composite film with ZrO2 nanoparticles have reduced friction coefficient with high micro hardness friction coefficient of composite film can be small as 0.16 which is much smaller than that 0.39 of none composite film. Micro hardness...
Characterization of Nanohydroxyapatite-Carbon Nanotube on Stainless Steel 316L Produced by Sol-Gel Method
, M.Sc. Thesis Sharif University of Technology ; Nemati, Ali (Supervisor) ; Sadeghian, Zahra (Supervisor)
Abstract
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)...
Characterization of Ceramic Coating Synthesized on Magnesium Alloy Substrate by Plasma Electrolytic Oxidation Process
, M.Sc. Thesis Sharif University of Technology ; Faghihi Sani, Mohammad Ali (Supervisor)
Abstract
Plasma electrolytic oxidation (PEO) is currently recognized as an effective coating method on active metals such as magnesium. In this method, through occurrence of strong electric discharges on the surface of the anode accompanied by electrochemical and thermo-chemical reactions at plasma environment, a relatively thick ceramic coating with complex compounds grows on the metal surface which significantly improves its properties. Regarding the influence of PEO electrical parameters on the morphology and other properties of the coating, the objective of the present study is to prepare a quality ceramic coating on AZ31 magnesium alloy substrate via setting the process parameters, such as...