Sharif Digital Repository

Due to Reduction of fossil fuels resources and the pollution caused by using them, it seems inevitable to shift to using reproducible energies. Among different resource of reproducible energy, fuel cell is one of suitable technologies for investigation and development. Fuel cell is an electrochemical system to convert chemical energy of fuel directly to electrical energy. Each fuel cell has seven part (two Bipolar Plate, two electrode, two catalyst layer and polymeric Membrane). Oxidation occur in anode of fuel cell and created electron enters external circuit and then riches the cathode. The positive ion created in the anode reaches the cathode through the membrane (electrolyte) and... 

This research investigates the effect of soil-structure interaction on the buckling behavior of an above-ground storage tanks. For this purpose, a steel tank with a height-to-diameter ratio of 0.4 was selected. Four types of support conditions including a fixed-based condition and three soil islands with a depth of 30 meters, assuming a uniform stiff soil and a two-layered soil consisting of stiff and medium soil, and a three-layer soil with stiff, medium, and soft layers. The tank and soil were modeled using the finite element method, and absorbing boundaries were applied around the soil island to simulate the semi-infinite soil domain. After validating the modeling through parametric and... 

In this study, the seismic response of aboveground, anchored cylindrical steel tanks subjected to horizontal and vertical ground acceleration is investigated. The buckling capacity of the steel tanks is estimated using static pushover (SPO) and incremental dynamic analyses (IDA). Finite element models of a broad tank and a tall tank with height to diameter ratios (H/D) of 0.40, 0.80 and with a liquid level of 90% of the height of the cylinder were used in this study. Appropriate load patterns due to the horizontal and vertical components of ground excitations are utilized for SPO analyses. The influence of the vertical component of ground acceleration on buckling capacity curve of the tank... 

In the preceding years, hydroxyapatite (HA)-based coatings and scaffolds have been known as the best biomaterials for dental and orthopedics applications. Biocompatible and bioactive hydroxyapatite-based Coatings on metallic implants is one of the best methods for reaching both suitable mechanical properties and appropriate bioactivity, leading to better osseointegration and osteoblast proliferation. The ultimate goal of this project is characterization as well as mechanical and electrochemical behavior investigation of Hydroxyapatite- Chitosan nanocomposite coating by electrophoretic deposition (EPD) method on Plasma Electrolyte Oxidation (PEO) treated titanium substrates and Magnesium (Mg)... 

Titanium anodes activated by noble metal oxides under the trade name of dimensionally stable anodes (DSAs) are widely used in the electrolytic industry, particularly in chlor – alkali electrolysis. Over 20 years of use, the fundamental aspects of their long – lasting performance are not fully understand and the corrosion mechanisms are still the subject of many investigations. RuO2 – TiO2 coatings on titanium substrate, due to proper electrochemical characteristics and good corrosion resistance, is most applicable as an anode in chlor – alkali systems. In the present investigation, the first layer of Pt – Ir coating is applied via electrodeposition method on the pretreated titanium substrate... 

Ni-SiC composite coatings are widely used in industry (equipment high wear resistance coatings, corrosion resistant coatings, ship and boiler coatings, . . . ). Its unique properties in high wear resistance, corrosion resistance and tribological properties, researchers tend to investigate this coating. This study covers Ni-SiC composite coating under pulsed current using a rotating disk electrode to achieve optimal conditions in synthsis process, increaseing hardness and resistance to corrosion in coatings.waats' bath established for electrodeposition in this research. Bath parameters, current parameters and hydrodynamic of solution is examined. Changing of current type from direct current... 

At the first stage, chitosan-hydroxyapatite-multiwalled carbon nanotube (CH-HA-MWCNT) composite coatings were synthesized by electrophoretic deposition technique (EPD) on Ti6Al4V and 316L stainless steel substrates at different levels of pH and characterized by X-ray diffraction (XRD), Raman spectroscopy, FTIR and field emission scanning electron microscopy (FESEM). A smooth distribution of HA and MWCNT particles in a chitosan matrix with strong interfacial bonding was obtained. At the second stage, effect of pH and MWCNT content of the suspension on corrosion behavior and mechanism of deposition were studied. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS)... 

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... 

In nanometer technologies, the effect of process variation is observed in Multi-Processor System on Chip (MPSoC) in terms of variation in processors‟ frequency and leakage power. Traditionally, only worst case values of the system parameters were concerned and a worst-case optimization algorithm was employed for an application under design. As previous researches have shown these algorithms are not optimal in terms of parametric yield compared with newly employed statistical optimization algorithms. In this project, we have considered the problem of simultaneously selecting MPSoC architecture (which includes type and number of processors and the communication media) and task and... 

This thesis is concerned with the synthesis and characterization of high porous Ti based on thin films and the effect of polymer agents on their photocatalytic properties. Ti films can demonstrate different properties like self -cleaning and treatment of broad range of aqueous pollutants when it is exposed to light of wavelength less than 400 nm. This is due to photocatalytic reaction occurring on film surface which results in film superhydrophilicity and the active oxygen species production. This active sites and radicals will cause oxidize organic pollutants and microbe adherent to the material surface.
In this study Ti thin films have been prepared by the sol-gel method from... 

Composite coatings including self-lubricant particles such as graphite, MoS2, Al2O3 and SiC are extensively used to decrease the coefficient of friction of tribo-surfaces. Adding lubricant particles to an appropriate metallic matrix like copper, nickel, lead and their alloys is a suitable option in severe condition –for instance high temperature and low pressure- which liquid lubricants will be failed. Bronze can give various properties such as wear resistance, corrosion and oxidation protection, However cyanide solutions for electroplating process have environmentally limited for plating of Cu-Sn. In this research, a chloride electrolyte for bronze electroplating was developed and effect of... 

In this thesis, optimal station keeping of spacecraft on the closed-orbits near the Earth-Moon Lagrange points has been investigated. Lagrange points L1 and L2 are unstable equilibrium points of the circular restricted three-body problem (CRTBP), and periodic orbits near them are the destination of modern missions. However, perturbations resulting from the gravitational forces of the Sun and the planets and the eccentricity of the orbit of the Moon around the Earth make the Lagrange point unstable, even L4 and L5, which are stable in CRTBP. The most suitable choice for spacecraft mission near the collinear Lagrange points is the Halo and other closed-orbits around them, which need... 

In this study, biocompatible ceramic coating, containing hydroxyapatite particles (HA), was successfully created by AC anodizing, on the surface of commercially pure titanium grades 2. Coating process basically consisted of three methods. In Method 1, samples were anodized in a salty electrolyte containing calcium – phosphate base and in method 2 samples were anodized as initial process, following cathodic polarisation deposition of HA particles. Finally in method 3, samples were anodized in an electrolyte containing of HA particles suspension.Parameters such as current density and time of anodizing process, in first procedure, and time of cathodic deposition process in second procedure, and... 

The synthesis and usage of nanoscaled TiO2 accompanied by the photocatalytic activity were experimented through a systematic research. The synthesis was based on the sol-gel method at low temperatures and atmospheric pressure. In recent years, many endeavors have been made so as to enhance the efficiency of TiO2 photocatalytic activity. The studies show that the inclusion of SiO2 into the TiO2 can give rise to the photocatalytic activity relevant to the derived composite Nanoparticles with regard to the pure TiO2. In this study, the production of TiO2-SiO2 Nanocomposite layers was proceeded via the sol method and the effect of SiO2 increasing and its amount in the primary solution on the... 

In this study, ternary metal oxide coating consisting of Ti, Ru, Ir were prepared by sol-gel method. In order to achieve optimal conditions, the effect of number of layers, temperature and velocity of the heat treatment, the amount of ruthenium and iridium, polymeric additive on the coating and also, comparisons of binary and ternary oxide coatings were studied. The corrosion behavior was examined by anodic polarization and cyclic voltammetry tests and accelerated stability test (AST), the morphology of coatings was studied by field emission scanning electron microscopy (FESEM), phase and elemental analysis was performed using X-ray diffraction (XRD) and energy dispersive spectroscopy... 

In recent years, magnesium and its alloys have been considered as biodegradable implants, but they corrode in the body before natural process of damaged organs recovery is completed. In this investigation PEO operation was used for corrosion control and effect of different parameter such as number of operation steps, electrolyte type, time and operation voltage on coating properties was studied. Scanning electron microscopy was used for investigating of morphology of coats and to determine chemical composition and phase of coats EDS analysis and X-ray diffraction were used. The corrosion resistance of samples were evaluated by potentiodynamic polarization and electrochemical impedance (EIS)... 

Plasma electrolytic oxidation is the novel surface engineering technology that used as the low cost and eco-friendly method for improvement of corrosion resistance and wear resistance of Mg and Ti alloys. The aim of this investigation is firstly joint the Ti and Mg, then optimization of coating process condition of Ti-Mg couple for achieve the best corrosion and wear resistance of coating. For this purpose, initially Ti and Mg were joint together by friction stir welding treatment and then the effect of coating variable such as type of electrolyte, coating voltage, coating time and the concentration of the bath constitute, on the coating properties were investigated, and then the effect of...