Sharif Digital Repository

Nowadays catalytic reforming of naphtha is one of the most important parts of the refining process. The catalyst of this process is mostly Pt-Re on the γ-alumina support. The major cause of deactivation is coke deposition and blockage of the pores as a result. Meanwhile, modeling of the process and the deactivation of catalyst would help refining industries to achieve higher yields. In this study industrial data of the catalytic reforming unit #2 in Isfahan Refinery Plant were used to model the process, optimized parameters have been calculated and the best contribution of the catalyst among the four reactors was presented. Then with using a deactivation function the whole coking... 

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... 

In the present work preparation of Ni-TiO2 films and their microstructural and mechanical properties were studied. For film preparation, DC current mode of electrochemical deposition method was used in Watts Nickel bath with different concentrations of transparent TiO2 sol up to 30 mL/L. It presents a new generation of nano Ni-TiO2 coating as a composite film for corrosion and erosion resistance applications. The best wear volume of 0.0046 mm3 was achieved for 30 mL/L Ni-TiO2 nanocomposite in comparison to 0.0071 mm3 for pure Ni film. Moreover, the coating hardness increased to ~345 HV50 for Ni-TiO2 nanocomposite. Corrosion rate of the coatings improved down to 1.10E-05 mm/year with addition... 

The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better... 

Barium Strontium Titanate (BST) thin films are a promising candidate for dielectric capacitors due to their excellent ferroelectric properties. It is well known that BST has a high dielectric constant, low loss tangent, low leakage current and low Curie temperature. Pulse laser deposition (PLD) has been used extensively as it can maintain the stoichiometry of the target in the deposited film and also has high coverage ability, which both are important in capacitors. In this paper, Ba0.6Sr0.4TiO3 (BST) thin film has been deposited on the SiO2/Si substrate by pulsed laser deposition technique. The effect of post-annealed temperature, oxygen pressure deposition ambience and number of pulses on... 

In the last decade, a great deal of attention has been paid to the study of synthesis of Nanoparticles, because of the widespread use of this material in applications involving Fuel cells and magnetic devices. In this thesis, we report some interesting features in the electrodeposition of metallic nanoparticles. The electrochemical phase formation of rhenium and nickel on the surface of P-Si (100) substrate plus morphological, topographical and fractal aspects of the accumulated surface were investigated in this research by means of chronoamperometry method and by utilization of AFM and SEM. The nucleation and growth mechanisms on silicon electrode are characterized using cyclic voltammetry... 

In this thesis, Silicon nanowires were synthesized using carbothermal method via Vapor-Liquid-Solid mechanism catalyzed by gold nanoparticles deposited on various substrates. Silicon nanowires just grew on (100) and (111)-oriented silicon substrates. For a particular set of process parameters, we observed a critical thickness of the nucleating gold film, that had depened on a kind of various substrates. We studied the dependence of the Au-Si alloy droplet size and size distribution on the starting gold film thickness and the annealing conditions. We used a modified heating sequence that deconvoluted the effect of various substrates consumption and gas-phase silicon supply on the Au-Si alloy...