Sharif Digital Repository

Electrocatalytic oxidation of L-ascorbic acid (L-AA) on silver electrode in alkaline solutions was studied employing cyclic voltammetry, chronoamperometry and impedance spectroscopy techniques. In comparison to Pt, the onset potential for L-AA electro-oxidation process on Ag, in a solution containg 0.02 M L-AA and 0.5 M NaOH, was 0.1 V more negative. Also, L-AA oxidation current increased more than 900% at -0.26 V/SCE. According to voltammety and impedance spectropy findings, although hydroxide anion presence was vital for L-AA oxidation to occur, at potentials more positive than -0.2 V/SCE, hydroxide ion tends to inhibit the oxidation process. Studies on the L-AA oxidation process on Ag in... 

In this research, for optimization of repair welding of control valve and flange that use in East Oil& Gas Company, effect of chemical composition, microstructure, hardness and stress relive on sulfide stress cracking (SSC) investigated with select of four electrodes. All welds were prepared by shielded metal arc welding (SMAW) and investigated with optical microscope, hardness test, tensile test and SSC test. The results showed that increase of nickel content in the range of 0.032–1.58 wt. % in weld metals, decrease of acicular ferrite and increase of side plate ferrite, grain boundary ferrite and M/A micro constituent in microstructure. Ni3S2 decrease SSC resistance and (FeCu).S increase... 

In this project, we have studied the geometric and electronic structures of CdS nano-particles. The bulk CdS is known to be a semiconductor with the experimental energy gap of 2.42eV which is more than twice the theoretical resuls based on LDA or GGA energy functionals used in the density functional theory. However the calculations based on Kohn-Sham formalism used in DFT (KS-DFT) predicts the geometric structure of bulk semiconductors fairly well. Therefore, we have employed the KS-DFT formalism for our CdS nano-particles and have used the Gaussian as well as SIESTA computer codes to predict the geometric structures of these nano-semiconductor-particles. For calculating their electronic... 

With considering the existence of carbonyl sulfide in natural gas and crude oil, we need to study the absorption of this gas in aqueous alkanolamine solutions. In this project the solubility of carbonyl sulfide in different pressures and two temperatures of 313.15 and 348.06 K have been measured.The absoption of carbonyl sulfide in aqueous alkanolamine solutions is a very slow process. In this study we used different methods for measuring the required data. Befor the experiments we calibrated the set up with reliable data. Finaly the results simulated with Deshmakh-Mather thermodynamic model, numerically. The simulation results show a good agreement with experimental data  

During recent years, thin-film solar cells based on chalcogenide light absorbers with CuInxGa1-xS(Se)2 compound have attracted considerable attraction due to their desirable band gaps and demonstrated high power conversion efficiencies. These solar cells are fabricated under two categories named as ‘substrate’ and ‘superstrate’, generally. The best reported energy conversion efficiency belongs to substrate type (sodalime glass/Mo/absorber layer/buffer layer/window layer) CIGS solar cells, most have been fabricated with vacuum processes. In spite of this, superstrate solar cells (transparent conducting oxide/blocking layer/buffer layer/absorber layer/back contact) provide easier and cheaper... 

Recently separation technology has been developed and engineers are trying to find more rapid and more economic ways in order to reach pure materials. One of the most important needs of human being is natural gas which has some impurities. Acid gases such as carbon dioxide and hydrogen sulfide must be separated from methane. This operation is called gas sweetening. Membrane contactors are equipments recently developed and may be used instead of packed towers for gas sweetening in the future. In this project we designed and made a membrane contacting unit to separate carbon dioxide and hydrogen sulfide from methane. This unit lets you to study the effect of many parameters such as gas and... 

The present research describes sensing behavior of modified aligned carbon nanotubes toward detection of hydrogen sulfide. Aligned carbon nanotubes were grown on etched stainless steel by thermal chemical vapor deposition. Obtained CNTs have curved closed tips and bamboo like structure. Purification of carbon nanotubes were performed by electrochemical oxidation of CNTs. Potential cycling was applied on grown CNTs in different acid solutions and 0.2 M sulfuric acid was chosen to oxidize the CNTs. Carboxylic functional groups were produced by electrochemical oxidation of CNTs and can be observed in FTIR studies. These groups enhanced the electrochemical properties of electrodes and may act as... 

The aim of this research is preparation of tungsten trioxide nanoparticles film for hydrogen sulfide gas sensing. These nanoparticles were made by simple and inexpensive sol-gel method. To improve gas sensing properties, various precursors of copper and copper oxides were added to the sol. This solution was coated on alumina substrate by spin coating method. After annealing, sensing properties of samples were studied by measuring the electrical resistance. Best precursor and its molar percentage of copper to tungsten were selected (WO3-Cu2O (1%)). All tests for this sample were done in temperatures below 100 °C and gas concentration lower than 10 ppm. Sensitivity of WO3-Cu2O (1%) to 1 ppm... 

Zeolite membranes are of interest due to their special properties; thermal and mechanical resistances and non-plasticization property in gas separations. Therefore, separation of H2S from natural gas by these membranes is the main goal of this thesis which is not investigated in the world. After some theoretical investigations including diffusion mechanisms of gases in the zeolites and adsorption mechanism of H2S on the zeolites, pure silica CHA-type (Si-CHA) zeolite was selected. After successful synthesis of Si-CHA zeolite, adsorption isotherms of H2S, CO2, and CH4 on the Si-CHA zeolite were measured over pressure range of 0-190 kPa and temperatures of 25 °C, 50 °C, and 75 °C. Acid gases... 

A concern in the production sour oil and gas is the corrosion caused by the acid gas H2S. Even though corrosion resistant alloys (CRA) have long been available as a material selection option that mitigates H2S corrosion, the carbon steel is in general more cost-effective for oil and gas facilities. The aim of this study is to investigate the mechanical properties of 410NiMo cladding on a low alloy steel substrate. In this investigation, two successive layers of ER410NiMo were clad on low alloy steel substrates. To reduce the likelihood of Hydrogen Induced Cracking (HIC) and producing stable hydrogen traps, Post Weld Heat Treatment (PWHT) was used. To characterize the mechanical properties of... 

Due to the presence of carbon dioxide and hydrogen sulfide in natural gas outlet of wells, it cannot be sent directly to the municipal pipelines. This study was trying to be select and made membranes for separation of CO2 and H2S from methane. Permeability of methane and carbon dioxide gases through the polyurethane membranes were studied. For this purpose, two commercial polyurethane and synthesized polyurethane with different formulations of the compounds that have been studied so far in the literature were used. Synthesized polyurethane and nano-composite membranes were characterized by using Scanning Electron Microscopy (SEM), Differential Scanning Calorimetry (DSC) and Fourier Transfer... 

In the first part, we report a new and simple procedure for preparing reduced graphene oxide /nickel, cobalt hydroxide composite (Ni,Co-OH/rGO/NF via a fast and simple two-step electrochemical method including potentiostatic routes in the presence of Cetyl trimethyl ammonium bromide )CTAB( as a cationic surfactant. In the first step, a piece of nickel foam (NF) is sonicated in a suspension of graphene oxide (GO, 6 mg/L) after dried in an oven, reduced by electrochemically. After that, Ni, Co LDH were co-deposited on the surface of rGO/NF. The resulting modified electrode afforded extremely high specific capacitance of 2133.3 F/g at a current density of 4 A g-1. FE-SEM results showed that... 

In this study, four parameters were investigated including temperature, inlet flow rate, gas composition (oxygen) and particle size on the roasting of Bama company zinc sulfide concentrate in Fluidized bed reactor. Initially, primary sample was heated in electric furnace at 125℃ for 24 hours until the moisture content dried. Then roasting operation was done at 700 and 900℃. The operation was carried out on three range of particle size including 300-500, 500-700 and 700-1000 microns and flow rate was greater than the minimum flow rate of Fluencing. To investigate the effect of flow rate and gas composition input, 500-700 micron particle size range was selected. The effect of 155, 172 and 188... 

Solution-processed quantum dots (QDs) have attracted significant attention for the low-cost fabrication of optoelectronic devices. Here, we synthesized PbS QDs via hot injection method and passivated the trap states by using short thiols and dopant elements for photovoltaic application. In order to study the effect of dopants on photovoltaic application, PbS QDs were doped by using three different cations: Cadmium, Calcium, and Zinc. The results showed that Cd dopant has a better improvement than Ca and Zn dopants in order to increase the efficiency of the PbS QDs solar cells. We achieved solar power conversion efficiencies of 5.81% using Cd therapy. Recently, hybrid nanocomposites... 

In this project, The cadmium sulfide nanoparticles were formed on a nanostructured and meso-porous titanium dioxide layer and its properties were characterized. Deposition process of titanium dioxide and cadmium sulfide has been performed respectively in one stage and two stages of dipcoating. In order to probing effects of temperature and dipcoating time, samples have been prepared in various times and temperatures. Also, some of the samples have been annealed. Thickness of titanium dioxide and cadmium sulfide coatings were approximately measured 1 μm and between 3-5 μm, respectively. As expected, XRD results disclosed that cadmium sulfide and titanium dioxide were formed in the form of... 

The optimization of CdS photoluminescence nanoparticles which has been considered as one of the most important II-VI semiconductors has been studied here. As the first step, synthesis parameters effect on CdS:Mn photoluminescence intensity has been regarded by thermochemical method. Effect of parameters like pH solution, heating time and capping agent concentration on photoluminescence of these materials has been experimented. What seemed so important was reaching nanoparticles with suitable nano size and nano structure and having highly photoluminescence intensity. Observing the good effect of Oxygen on photoluminescence of CdS nanoparticles leaded us to concentrate on synthesizing CdS:O... 

One-dimensional (1D) cadmium sulfide (CdS), nanostructures have significant potential applications in solar cells, photocatalysts and many electronic devices. There are many experimental approaches to synthesis 1D CdS nanostructures. Among them solvothermal method has many advantage such as controllable and inexpensive method. 1D CdS nanostructures with different properties in morphology, crystal structure, band gap energy and etc can be obtained by controlling solvothermal processing parameters. In the present work the effect of solvothermal processing parameters including reaction temperature (120ºC ,160ºC and 200ºC), process time (12h, 48h and 72h), sulfur source (S powder, Thiourea and... 

Over the past two decades, several studies have been investigated on synthesis and properties of semi-conductor quantum dots because of their applications in sensors, LEDs, detectors, solar cells, etc. One of challenging issues in synthesizing these nano-particles is their size distribution. In this study, Cadmium Selenide was synthesized by the method of colloidal synthesis. X-ray diffraction showed that the crystalline nano-particles have wurtzite structure. For obtaining a uniform size distribution, effect of various parameters such as molar ratio of components and reaction temperature on the growth kinetics of these particles, were studied. Results showed that molar ratio of Selenium to... 

The goal of this study is to synthesise and study the catalytic properties of a Mn-Porphyrin complex fixed on a magnetic nanoparticle bed. This nanocatalyst was used in oxidation of sulfides and epoxylation of olefin. In the multistage synthesis of this catalyst, iron oxide magnetic nanoparticles were first prepared, then, by silanizing these nanoparticles, and then using the 3-chloropropyltrimethoxy methanol reactor, Immobilzation the material on the substrate and immediately react in reaction Substitution of the nucleus of friendship and using a sodium azide reaction, bromide is replaced by azide. Subsequently, by synthesising 4-hydroxy porphyrin and replacing one of its positions with...