Sharif Digital Repository

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... 

Transparent coatings with self-cleaning property in visible light spectrum, UV radiation resistance and antimicrobial are highly desirable. Titanium dioxide (TiO2) is used in this research has been widely studied as an efficient photocatalyst by researchers. In this research enhanced visible-light photocatalytic activity is gained with N and Ag co-doped titania. All samples were annealed at 450℃. Finally AgI was loaded TiO2 coating and the results were investigated. Peaks of XRD pattern wereattributed to different diffraction planes of anatase TiO2. Morphology of coatings were analyzed with using FE-SEM. Nano granis size of TiO2 and AgI loaded TiO2 were observed in FE-SEMimages. Nitrogen... 

Antimony Doped tin oxide as a conductive film has found a wide range of applications and sol-gel method has so advantageous with respect to another methods for preparing ATO thin films. In this study, ATO thin film has been synthesized using a solution containing metal salts of tin chloride and antimony chloride. The microstructure of the obtained films was studied by applying scanning electron microscopy (SEM) and X-ray diffraction patterns (XRD). In diffraction patterns of the acquired ATO layers which was deposited from a sol containing SnCl4.5H2O and SnCl2.2H2O with Sb concentration of 15%mol and layers which was deposited from a sol containing SnCl4.5H2O with Sb concentration of 15%mol... 

The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with... 

The goal of this study is synthesis of nanocoating on basis of ZnO by Sol-Gel method and evaluation of their antibacterial and photocatalyst properties changes by different values of TiO2. For this purpose in both method of synthesis contents of TiO2 hase been changed from 0-25 molar percent. Dip coat method has been used for coating from sol with 1.4 mm/s withdrawal speed and 2 minute immersion time. After each step of coating samples has been dried at 150oC for 10 minute and for increasing thickness this process has been repeated 4 times. In first method zinc acetate dihydrate in 0.1 M final concentration and titanium tetraisopropoxide are sol precursors at in situ way of synthesis. In... 

The purpose of this research is producing one phase silica superhydrophobic coating by sol-gel method and drying temperature less than 200 degrees. For preparing micrometer and nanometer scaled hierarchical structure based on silica, TEOS precursor and Fumed Silica nanoparticles were used by density of 43/30 cc/lit and 6/52 gr/lit in order to provide desired roughness in the range of 40 nm. Moreover, HMDS surface modifying agent was used for reducing the surface energy of coating, which is not a danger to the environment in comparison to the same substances. The best Contact Angle is 155 degree and the best Sliding Angle is less than 5 degree. For instance, it was created with the...