Sharif Digital Repository

In this study a systematic effort was made to study and compare electrochemical oxidation behavior of iodide on Pt, carbon and carbon supported polyorthoaminophenol film electrodes. All of the electrochemical experiments were performed in acidic, basic and nuteral aqueous solutions and the applied electrochemical techniques included Chronoamperometry (CA) and Cyclic voltammetry (CV). Effects of concentration and scan rate of potential on the cyclic voltammetry of KI was studied at the previously mentioned electrodes. Current-time and log current-potential curves were analyezed quantitavely in order to determine kinetic parameters. Carbon supported polyorthoaminophenol electrode was prepared... 

Nanotechnology is an efficient method suitable for fabrication and production of minimal single dimensional nanometric structures. Such materials and systems can be logically designed that lead to new and optimized biological, chemical and physical properties and characteristics due to their size. Nucleation and growth –appearance of a new phase out of an old phase – is a ubiquitous phenomenon in nature. Fundamental understanding of nanoparticles nucleation and growth mechanism allows more control on form, size and composition and allows tuning of the above said properties easily with use of different reactive conditions as a result of this ability . Nanoparticles of titania are one of... 

The purpose of the present project is to construct and improve the quality of an absorbable membrane using a supercritical process and study the effects of the operative parameters. Today, usage of biodegradable polymers is intensively increasing and these kinds of polymers are used as drug delivery carrier and tissue engineering medium. A biodegradable membrane is suitable for this goal. In this study Poly Ethylene Glycol (PEG) is used as the biodegradable polymer. Gas anti-solvent (GAS) method was applied for the production of the membrane. The used anti-solvent was Supercritical Carbon Dioxide. In order to study the effects of the operative parameters on the structure of the produced... 

Fretting fatigue damage occurs in contacting components while they are subjected to fluctuating loads and relatively small movement at the same time. In this condition some micro-cracks are created in these components. These micro-cracks will be propagated and cause sudden failure which is accompanied by great human and economic loss. There are many practical applications that are subjected to fretting fatigue, such as bolted and riveted connections, bearing shafts, blade-disk attachment in gas turbines, aero-engine splined couplings, cable connections and etc. Fretting fatigue failure process can be divided into two portions of crack initiation and propagation. It is very difficult, to... 

Aluminum sulfate is widely used in water treatment as a polyelectrolyte. Its dissolution and recrystallization into nanoparticles directly affects the working conditions. This study concerns determination of the metastable zone and induction time in nucleation of aluminum sulfate nanoparticles in aqueous media and in presence of acetone as anti-solvent. Later the effect of SDS on the metastable zone and induction time are also studied.. The study also shows if the presence of anti-solvents and surface active agents can vary this phenomenon. The study also adds to our understanding of the media in creation and stabilization of nanoparticles. This project has a special focus on the changes... 

The chemical vapor deposition (CVD) of graphene from methane on a copper substrate is the most promising method for production of large-area graphene films. There have been long-standing challenges in this field such as controlling the graphene coverage, film quality, the number of layers, and the nucleation density of graphene domain. These challenges can be overcome by developing a fundamental understanding of the graphene growth process. The main aim of this study is to control nucleation density of graphene domains. Chemical vapor deposition (CVD) graphene is polycrystalline, and grain boundaries in graphene film have been identified to degrade the properties of graphene as a membrane... 

The goal of the present study is to analyze the effect of CaF2 and nano-TiO2 as additives on formulation and properties of common dental glass-ceramics. To achieve the goal, a glass system based on SiO2-Al2O3-Li2O-K2O-P2O5-ZnO-ZrO2 was considered to produce glass-ceramic samples and the additives, nano-TiO2 and CaF2, with the 0.5, 1, and 1.5 %Wt was added to the system. After the melting process, the glass samples poured in the water and ferrite was produced. In the next step, the ferrite was milled and pressed. In the heat treatment step, the samples were treated in the temperature range of 650-850°C in order to gain lithium disilicate glass-ceramics. In the last step, the chemical... 

Crystallization of Aluminum Hydroxide is the most important section of the Alumina production processes as the product yield and crystal size distribution (CSD) of this stage strongly affects the whole Alumina production process. In this work to simulate the crystallization in industrial steady precipitation tanks two Population Balance based models developed. First one is the Coupled CFD-Population Balance Model which considers the effects of flow hydrodynamics on crystallization kinetics and CSD. For development of this model the computational fluid dynamics software ANSYS FLUENT has been used. The two phase flow field has been simulated using Eulerian granular multiphase model coupled... 

The aim of this project is electrodeposition of Cu/Ni-P multi-layer coating and investigating the nucleation and growth mechanisms of the deposits. To evaluate the effect of the selected bath on the kinetics of the process and deposition, cyclic voltammetry and chronoamperometry studies were conducted and electrodeposition mechanism was obtained three-dimensional instantaneous nucleation and growth controlled by diffusion. Potentiostatic pulse-deposition method with potential steps -0.3 and -1.1 V vs SCE was selected for deposition of Cu/Ni-P multi-layers. In order to demonstrate the effect of monolayer thickness on the properties of the final coating, multiple layers with various monolayers... 

The use of renewable energy sources has received much attention due to the increasing need for energy, limited energy resources and the pollution of fossil fuels. Among all types of solar energy conversion technology, photovoltaics has the highest technical potential and Iran’s geographical location is very suitable for benefiting from this energy. So, in this thesis, the fabrication and characterization of nanostructured solar cells based on organic-inorganic perovskites have been investigated. Many research goups have tried to increase the efficiency of perovskite solar cells. The efficiency of this kind of solar cells depends mainly on the light-absorbing layer (perovskite) and its...