Sharif Digital Repository

Usage of electroless Ni-B coatings as coatings with super hardness and wear resistance has been increased widely, but these coatings have low resistance to corrosion.In this project, in order to increase resistance to corrosion, titania powder of szie 200 to 300 nanometers is added to Ni-B coatings to make a composite coating of Ni-B-TiO2 that has better corrosion properties compared to Ni-B coatings. Ultrasonic use for creating composite coatings of Ni-B-TiO2 and the optimum ultrasonic and electroless bath conditions for creating optimum coating in terms of corrosion resistance are determined. These optimum conditions are as follows: speed of 300 rpm for substrate circulation in bath, 250 W... 

The present work emphasizes on hydrogen resistance- sensing properties of WO3 films prepared by Sol-gel routs. The sol-gel is a simple and low cost rout which makes film with high homogeneity and low processing temperature .To improve Hydrogen sensing we modified WO3 films with Pd catalysts by Sol-gel and Electroless methods. AFM , EDX, SEM , XPS , XRD , were applied to analyze structure, morphology and Chemical composition of the fabricated thin films. We measured resistance sensing behavior of prepared films in exposure to different concentration of Hydrogen. All the films were tested under the same conditions. We measured resistance sensing in exposure to concentration below 10000 ppm... 

Gold coatings due to their unique properties, use in a wide range of applications.Decorative coatings of gold for centuries, has been considered.However, few studies have been done on the properties of this metal, this metal is shown not only in terms of decorating, but in the industry also has a wide range of applications. In this project non-cyanide electroless bath based on binary complex sulfite-thiosulfate was prepared and metal ion concentration of the complex components, temperature, time, pH and addition of amino acids, optimzed bystability, qualityand rate of coating. The main aim of optimizing bathsis optimize the thickness and appearance of the coating.It was found that by... 

In this study Ni-P-Al2O3-SiO2 nano composite coating developed on aluminium alloy 6061 using electroless method. Due to oxidation of aluminium, a double zincate pretreatment performed to obtain proper adhesion of coating on substrate. Effect of solution temperature and heat treatment on thickness and property of nano composite coating was studied. Furthermore, effect of concentration of nano particles in electroless solution on thickness, morphology, micro hardness, wear behavior, corrosion resistance and particle content in coating were investigated. Field emission scanning electron microscopy (FESEM, Hitachi S-4160) with energy dispersive spectroscopy (EDS) was used to evaluate morphology... 

We have studied making and characterization of gasochromic thin films that are used as gas sensors. Gasochromic films consist of an electronchromic layer and a catalyst layer. Addition of palladium to the surface , increased the sensitivity and decreased the working temperature. The used electrochromic layer was tungsten oxide. WO3 films were fabricated by (PLD) method. The substrates were slide glasses. Structure, morphology and composite of tungsten oxide and optical property of films depend on condition of deposition. The pressure of oxygen gas in chamber and temperature of substrate are two factors that can affect in deposition. We can make layers with different morphology by variation... 

Adding solid lubricant particles such as PTFE, Graphite and MoS2, has major influence on electroless composite nickel coatings in order to make low friction surfaces. Among these lubricants, MoS2 has attracted great attention due to its highest stability under wearing condition. In this work Ni-P-MoS2 composite coatings using MoS2 nano-particles have been made and in the next step, we evaluated tribological properties of these coatings. For exploring these coatings different experiments were utilized, like Scanning Electron Microscope study (SEM), chemical composition analysis exploiting AAS and XRF method, and thickness measurements. Two kinds of surfactants, CTAB and PVP, have been applied... 

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... 

Noble metallic nanostructures based on their localized surface plasmon resonance (LSPR) exhibit a phenomenon known as surface-enhanced Raman scattering (SERS) in which the scattering cross sections are dramatically enhanced for molecules adsorbed thereon. The enhancement factor (EF) in typical cases can reach 106 and in recent years, it has been reported that even single-molecule spectroscopy is possible by SERS, suggesting that the EF can be as much as 1014-1015. In this study, we report a simple method to synthesize nanostructures of Ag and Au on metallic wafers and semiconductor via electroless deposition method. This approaches has been demonstrated to deposit metal nanostructures, thin... 

Dye-sensitized solar cells (DSSCs) are emerging as low-cost alternatives to conventional, solid-state, silicon solar cells. A porous network of a nanosize semiconductor material with a wide band-gaps usually TiO2, serves as charge transport medium. A monolayer of dye is chemically adsorbed on this material. Photoexcitation of dye causes injection of electrons into the conduction band of TiO2 from where they diffuse towards a transparent conducting oxide (TCO) substrate. The dye is regenerated through receiving electrons from a redox couple dissolved in the electrolyte. After passing through a desired load, the electrons enter the cell through a counter electrode to reduce the redox ions and...