Sharif Digital Repository

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... 

During the past two decades, laminated composite structures have been used for many engineering applications, including aerospace, automotive, sport equipment and pressure vessels.
In spite of the excellent properties of strength to weight ratio, composite structures are vulnerable to failure when subjected to impact and vibration. It is well known that impact damage may severely degrade the strength and stability of laminated composite structures. For this reason the effect of impact on composites has been a subject of extensive research.
There are several ways of decreasing the vibration energy of structures, such as diminishing the source energy, designing structures... 

Laminated composite beams are being widely used in engineering applications, including aerospace and automobile where the structures are highly subjected to non-deterministic random loadings, requiring a reliable technique to ensure the stability of structure during operation. A Novel N-layer model of layerwise theory (LWT) for laminated composite beams incorporated with magnetorheological fluid (MR-laminated beams) is developed. In addition, a finite element model of tapered laminated composite beams incorporated with magnetorheological fluid (MR-tapered beam) based on layerwise theory is developed. The dynamic response of the present model for uniform and tapered beams have been compared... 

Non-uniform laminated beams are being used in many engineering applications as primary elements. Helicopter blades, wind turbine blades and robot arms are examples of applications of these structures, in which the high stiffness-to-weight ratio and the non-uniform geometry are of high importance. Changing the thickness in laminated structures is a big challenge in fabrication view as different tapering configurations may significantly alter the stiffness of the structure. Thus, increasing the stiffness and dynamics characteristics of tapered beams with simple configuration is of high importance. The present work aims to investigate the effect of adding nano particles in resin during the... 

Ni-Co/SiC composite coatings with various contents of SiC nano particles were electrodeposited in a modified watt type of Ni-Co bath containing 20 nm SiC nano particles to be codeposited. The influences of the SiC concentration, current density, stirring rate of the deposition bath on the composition of the coatings were investigated and these parameters optimized for highest amount of SiC codeposition. The optimized deposition parameters were 40 g/l SiC and 480 rpm stirring rate and current density equal to 4 A/dm2. Ni-Co/SiC composite coating was deposited with the maximum particles content of 30.5 volume percent. Linear voltammetry demonstrates addition of the SiC to the Ni-Co deposition... 

Many of the major structure over coastal waters in the Kish Island due to the aggressive condition are showing signs of reinforcement corrosion. Recent advances in the development of anodes make it practical to use zinc galvanic cathodic protection to protect this structure in this area. Five anode systems were tested on several samples as, (1) zinc metal spray applied by arc-spraying on the concrete, (2) a zinc foil with conductive adhesive backing, (3) a system of zinc mesh and grout jacket, (4) a system of zinc mesh and compression panels, and (5) a bulk zinc. These anodes are set up to comparison the effects of potential and current over the zinc galvanic cathodic protection during 4... 

Platinum nanotubes were deposited inside the pores of polycarbonate template with the pore size of 200 nm by electrochemical methods. In this regard a solution containing of 0.05 M H2PtCl6 and 0. 1 M H2SO4 in doubly distilled water was utilized. The electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. It was observed that the process was conducted in several stages including; nucleation and growth in steady state regime. Furthermore, it was concluded that electrodeposition was affected by mass transport restriction and was controlled by a diffusion process. In this regard, all the voltammograms were shifted to more negative... 

Ni-P alloy coatings were electrodeposited using pulse current in a watt type bath in various conditions. The influences of different parameters were investigated and optimized for the highest amount of coating hardness using the Design Of Experiment (DOE) method. The optimized deposition parameters were current density 23.7 A/dm2, duty cycle 75%, frequency equal to 188 Hz, temperature equal to 70ºC and 17.5 gr/l of H3PO3. The DOE prediction of hardness for the optimized coatings was between 700 and 750 the achieved micro-hardness was about 725.8 HV. It was obtained that an increase of the current density will improve micro-hardness, decreases P content and increase deposition rate. Also, the... 

Reinforced concrete is one of the most important structural materials used in the construction industry worldwide. Nevertheless, certain physical and chemical factors in the service environment can contribute to its deterioration and failure. One of the most significant factors is the reinforcing steel bar (rebar) corrosion. In order to minimize the rebars corrosion, different kinds of coatings were investigated and evaluated by scientists. In this investigation comparative studies were performed on two different kinds of coated rebars (zinc-rich epoxy and polyamide epoxy coated rebars) and uncoated rebar. In order to evaluate these reinforced concretes, the adhesion, durability, thickness... 

In this research project, Ni electrodeposition process has been modeled by a 3D coupled continuum-kinetic Monte Carlo simulation. Kinetic Monte Carlo module processes surface reactions along the substrate using electrochemical equations for the relating events. Continuum model also determines concentration of the whole system according to a 3D interpretation of diffusion law in solutions. After running each module, exchange of data between two codes is done and boundary conditions are updated. In fact, the whole simulation time is divided by small time steps relating to time fastest reactions need to proceed. Present model will generate three outputs: current-time curve, surface morphology... 

This research describes a new and relatively general method to grow well-aligned carbon nanotubes (CNTs) on cobalt-deposited stainless steel by thermal chemical vapor deposition (CVD) of ethylenediamine precursor. The CNTs are vertically aligned at high density over large areas on the surface. Different effective parameters in growth of carbon nanotubes, as type of substrate, surface treatment, temperature of growth , feeding carbon supplies have been studied. Finally, aligned carbon nanotubes have been prepared by 100-150 nm diameter and 9µ length. CoOx•nH2O–MWCNTs nanocomposites were successfully synthesized, using a cathodic electrochemical reduction of H2O2 to deposit cobalt... 

In this work, a novel type electrode based on RuO2 nanoparticles-modified vertically aligned carbon nanotubes (RuO2/MWCNTs) was investigated. ThisRuO2/MWCNTs electrode not only shows a high capacity nature,but also possesses a good response to the pH value. In order to develope this sensor, aligned carbon nanotubes were synthesized by the chemical vapor deposition at first and then modified with RuO2 nanopartcles by sol-gel method. Various parameters affecting the growth of nanotubes, such as substrate type, surface finishing, surface roughness, the growth temperature and carbon feed rate was studiedand and optimal conditions for growth were obtained. At last, aligned nanotubes with a... 

In this work, effects of different additives on trivalent Chromium bath and Chromium coating has been investigated. Malonic acid wich had been used as a complexing agent of the bath improved current efficiancy and coating quality obviously. Effects of Magnesum, zinc, Tin, Aluminium sulfates, Molybdic acid, TiO2 nano particles, Sodium hypophospite, formaldehead and mixtures of these compositions on hexavalent Chromium concentration of the bath were also studied. Concentration of Cr6+ ion decreased by 18 ppm due to adding these materials. Using Ti/ TiO2/ RuO2 Anode also could decrease Cr6+ concentration by 78 ppm. Remarkable results had been recorded in current efficiency and coating... 

Metal matrix nanocomposites contains ceramic ultrafine particles in a metal matrix, are used to improve the mechanical properties such as hardness and wear of coatings. For developing metal matrix nanocomposites, there are many methods. Electrochemical deposition process is one of these methods that have some advantages like uniform depositions on substrates with complex shapes, low cost, good repeatability and reducing waste. In this project, for increasing the hardness and wear resistance of nickel, composite coatings of nickel - titanium nitride was created by using electrochemical deposition of Watts bath contained titanium nitride particles. In order to increase the amount of... 

Silver nanoparticles are widely used in different industries because of their antibacterial effects. Many synthesis methods were used to obtain silver nanoparticles. In this study the microwave method is used to synthesize nanosilver. This method is easier and faster in comparison to other methods. The effect of precursors’ concentrations, using different solvents, different remaining time in microwave and microwave power were studied. By increasing the reaction time, microwave power and using different solvents, nanosilver particle size varies from 2 nm up to 300nm. The TEM images, size distribution, XRD patterns and UV-visible spectrum are shown. The obtained nanosilver was used to observe... 

Thin film of Indium oxide doped with tin is used as a transparent electrode for different applications like screening panels, solar cells, touch panels and elechtrochromic tools. Trading thin films of ITO are precipitated using sputtering. However sol gel method can be simple and economic to make transparent electrodes. In this thesis first ITO sols is prepared using Indium nitrate and tin chloride with two or four capacities due to the production of transparent oxides on soda lime glass. Then the effect of tin chloride with two and four capacities is investigated on resistance and optic properties. Results show that tin chloride with four capacities in comparison with tin of two capacities... 

In recent years, different of nanoparticles as oil additives has been investigated in many studies . These research show that nanoparticles are deposited on the surface friction and improve tribology properties of base oil and also significant reduction of wear and friction caused by the nanoparticles. Compared with metal and metal oxide nanoparticles , carbon nanotubes (CNT) due to the high thermal conductivity and high aspect ratio , is an excellent candidate as the nanoparticle is dispersed . For preparing useful oil it is essential to stabilize nanoparticles in fluid that will not settle over long time . Oils containing nanoparticles by increasing the heat transfer coefficient... 

Chromium oxide coatings (Cr2O3) have been widely used due to their remarkable properties in corrosion, wear, optical and mechanical applications. So far, several methods have been used to prepare Cr2O3 thin films. In this study, the chromium oxide was produced by the sol-gel method and dip coated on the low carbon steel and glass substrates. In this context, we encountered with the problem of incoherency of the Cr2O3 ceramic coating to the steel substrates. It is highly likely that this problem be due to causes such as: a) thermal stresses due to the difference between the thermal expansion coefficients of the substrate and the coating, b) incoherent substrate/coating interface due to their... 

Syntheses of coats including nickel nano-particles by electrodeposition have been
investigated for over 10 years. A method of testing according to surface reply was chosen
to reveal the effect of each pulse parameters (including duty cycle, frequency, average
current density, off time (toff) and on time (ton)) and the effect of saccharin concentration
on electroplating cathode efficiency, nanostructure. Pulse electroplating test of nickel was
composed by 30 tests. Pulse electroplating with relatively high peak current density was
employed and saccharine was added to increase deposition and rate of nickel nucleation on
surface. According to the results of cathode...