Sharif Digital Repository

In the present study, the surface chemical and depth profile composition of the electrodeposited Ni-Fe base alloy layers on the Cu substrates were investigated with compositions of the Ni80-Fe20 (binary) and Ni77-Fe20.7-Cr1.7-Mo0.6 (quaternary) deposits. Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) results showed the surface accumulation of copper on the surface layers of binary alloy films in the form of Cu 2O. In the quaternary films, addition of Cr and Mo reduced the amount of the Cu accumulation at the surface, while Cu accumulation was enhanced under air-exposed condition for both alloy films. Depth profiles using the secondary ion mass spectroscopy... 

The method of unity bond index-quadratic exponential potential (UBI-QEP) and the computer simulation of the temperature programmed desorption (TPD) patterns are employed to derive the kinetic and thermodynamic parameters associated with the steps of the pathway we propose for the catalytic decomposition of methyl iodide on the Cu(111) surface. Assuming a highly reactive `hot methyl' surface intermediate and on the basis of our calculations it is concluded that the desorption of a part of this species is responsible for the reported methyl radical TPD peak at 140 K, while a part of this surface species is trapped in the three-fold sites of the Cu(111) surface and desorbs to form the reported... 

Patterns formed by the flow of an inhomogeneous fluid (suspension) over a smooth inclined surface were studied. It was observed that fractal patterns are formed. There exists a threshold angle for the inclination above which global fractal patterns are formed. This angle depends on the particle size of the suspension. We observed that there are two fractal dimensions for these patterns, depending on the area from which the pattern is extracted. If the pattern is taken from the top which only consists of the beginning steps of the pattern forming, one finds two fractal dimensions, i.e. 1.35-1.45 and 1.6-1.7, in which the first one is dominant. And if the entire pattern is taken, then fractal... 

Recently, interaction of electromagnetic waves with conducting interfaces has been studied and several applications have been proposed. For instance, new type of photonic crystals similar to Kronig-Penny electronic crystals has been implemented by using these structures. In these structures a free two dimensional interface charge layer is generated at the dielectric interfaces and interesting phenomena are observed. In this manuscript, the effect of finite charge layer thickness and its asymptotic behavior toward conducting interface, where the thin charge layer is modelled via a surface conductivity σs, is numerically studied for the first time. Two different regimes are considered: first,... 

A multiscale FD-KMC model has been developed to simulate the cyclic voltammetry test of a copper electrode in simple copper sulfate bath. In this coupled model, the FD code provides the cupric ion concentration on OHP for KMC code, while the KMC code provides the electrochemical properties of the copper electrode (surface activity and rate constants of redox reactions) as an input data for FD code. The changes in the electrode properties due to the atomistic phenomena (deposition dissolution and surface diffusion) have been studied for the present potentiodynamic system. The results showed that the CV process consists of some distinct stages, so that the electrode exhibits a specific... 

A model for prediction of corrosion of mild steel in aqueous solutions containing carbon dioxide is proposed. In this model, formation of protective corrosion product is not yet considered, species concentration at the surface was calculated by using molecular diffusion phenomena and the diffusion equations were solved using the finite difference method. Calculated electrochemical currents at the steel surface may be used to determine the corrosion rate. The model was verified experimentally under atmospheric pressure and the effect of parameters, such as liquid velocity and pH, was investigated. The model can predict the electrochemical reaction rates when they were controlled by diffusion...