Sharif Digital Repository

Fractured carbonate reservoirs are mostly oil-wet to intermediate-wet. Due to the negative capillary pressure of the matrix poor spontaneous imbibition of reservoir brine occurs in such reservoirs, and water flooding leads into early break through due to the high conductivity of the fracture network. Some surfactants have the ability to change the wettability of rock matrix toward water-wet state by adsorbing onto the rock surface. The phenomenon can result in spontaneous imbibition improvement and thereby increasing water flooding efficiency and recovery from fractured carbonate reservoirs. In this thesis the effect of some surfactants on the wettability of Iranian carbonate reservoir rocks... 

Highly active unsupported MoO3 and (Co) MoO3 catalysts were synthesized utilizing the solution combustion method where the Ammonium molybdate powder and an organic additive were used as precursors. Different organic materials including Ethylene Diamin Tetra-acetic acid (EDTA), Polyethylene Glycol 200 (PEG 200), Sorbitol and Urea were used as additive in order to investigate the effect of additive structure on morphology and particle size of products. Also various reaction parameters such as the additive/Mo molar ratio, concentration of metal ion in solution, pH of the reaction and temperature of the synthesis media were changed to study effects on product morphology and size. Outcomes were... 

In this work, carbon nanotubes (CNTs) were synthesized via arc discharge in an aqueous solution. The role of iron catalyst in CNTs formation was investigated utilizing arc discharge in iron salts solution (Fe2(SO4)3 and FeCl3). Thermogarvimetric (TG) analysis showed the presence of multi-layered structures including multi-walled carbon nanotubes (MWCNTs) and multi-shelled graphite particles when processing was performed in DI-water. In the presence of iron ions, single-walled carbon nanotubes (SWCNTs) and double-walled carbon nanotubes (DWCNTs) were formed. The effect of iron ions (Fe3+) concentration on CNTs yield was investigated by Raman spectroscopy. The highest yield was obtained when... 

In this work, multi-walled carbon nanotubes (MWCNTs) and single-walled carbon nanotubes (SWCNTs) were synthesized in an aqueous solution of iron chloride and solfate via arc discharge. Thermogravimetric (TG) analysis showed that the multi layer structures including carbon nanotubes (CNTs) and multi-shell graphite particles were formed when DI-water was used. SWCNTs were synthezied in the presence of the iron ions. The effect of [Fe3+]/[Fe2+] ratio on the CNTs yield were investigated. Raman spectroscopy investigations showed that the highest yield was obtained when the ferric to ferro ratio was one. When the concentration of Fe3+ ion was higher than that of Fe2+, many short tubes were... 

Thermodynamic modeling is a useful method for predicting of asphaltene precipitation due to various reasons, such as CO2 injection, mixing of different oils in oil storage and pressure changes. However, the application of solid model and thermodynamic micellization model, for prediction of asphaltene precipitation under gas injection condition, hasnot been improved. In this work, two computer codes which are based on two different asphaltene precipitation thermodynamic models, 1-Thermodynamic Micellization Model and 2- Solid Model, have been developed, and, used for predicting of asphaltene precipitation data reported in the literature as well as the experimental data obtained from high... 

n the present study, the optimal design of feeding system in steel sand-mold castings is considered. The first part of this research includes fundamental studies on the physics of shrinkage defect formation during the casting process. The results of these studies lead to new findings on the mechanism of shrinkage defect formation, effect of melt quality on the distribution of defects within the castings and the connection between shrinkage and gases defects. The theoretical analysis of thermal criterion functions for the prediction of shrinkage defects in castings and introducing new criterion function with fewer shortcomings can be accounted as the other finding of this part. A new model... 

High-strength low alloy (HSLA) E275 developed specifically for automotive application. Also St12 Steel is used in autobodies. On the other hand the resistance spot weld of dissimilar materials is generally more challenging than that of similar materials due to differences in the physical, chemical and mechanical properties of the base metals. The influence of the primary welding parameters affecting the heat input such as; current and time on the morphology, fracture mode, microhardness, and tensile shear load bearing capacity of dissimilar welds between HSLA E275 steel and St12 steel in two different thicknesses (1,2 mm) has been investigated in this study which consisted six group. The... 

Hydrogen fuel cell is one important choice to supply energy for vehicles in near future. The lack of a safe but inexpensive technology to store hydrogen in a vehicle tank is a serious challenge to commercialize the application of fuel cells. Past experiments have shown that carbon nanostructures, especially single walled carbon nanotubes, have considerable capacity to boost up hydrogen storage. Therefore, many studies have been performed to investigate the possibility of higher hydrogen storage capability using nanostructures for the past decade. Molecular dynamics method which is considered as one of the most important tools in studying nanostructures has shown vast applications in these... 

Purified RIPI–CNT was used as support material for the preparation of cobalt FTS catalysts. Carbon nanotubes supported catalysts (S1–S4) were prepared with loadings of 15, 20, 30 and 40 wt.%. The FT synthesis was carried out in a fixed-bed micro reactor. Deactivation factors of cobalt catalysts supported on carbon nanotubes in FT synthesis is investigated. Using carbon nanotubes as cobalt catalyst support was found to cause the reduction temperature of cobalt oxide species to shift to lower temperatures. The strong metal-support interactions are reduced to a large extent and the reducibility of the catalysts improved significantly. Then, the main reason for the catalyst deactivation will be... 

Homo-polymer of Polypropylene is a commodity thermoplastic with good physical and mechanical properties along with fair recyclability and cost. However, its application is limited in some cases, especially in automotive industry, due to a lack of toughness. One of the approaches for PP toughening is the copolymerization of PP with some ethylene co-monomers. However, existence of elastomers in this kind of polymers causes a decrease in tensile properties. Besides, glass fibers improve tensile properties of homo-and co-PP and decrease toughness of co-polymers but result in an increase for homo-polymers. A rise in expenditure of energy due to increasing the processing temperature and... 

Polyamides have found great attraction in the wide variety of application due to their desireable and tribological properties and appropriate processability. Due to their low mechanical strength reinforcing of these types of polymers has always been one of the important academic and industrial issues. In order to improve mechanical properties of such polymers, different kinds of reinforcement particles such as titaniom diaoxide, Nano clay, glass fibers (Short or long glass fiber), etc were used. Carbon nano tubes have high thermal and electrical conduction and mechanical properties; they are widely used as a reinforcement particle for polymer matrix. In this study, carbon nano tube and... 

In this investigation, hydroxyapatite-carbon nanotube nano composite coatings were applied on the 316L stainless steel implants. After polishing with 1200 sand paper, stainless steel implants were coated via dip coating method. The specimens were heat treated at 350˚C after being coated with HAP and HAP-CNTs composite. In vitro test was done in simulated body fluid (SBF) in 1 to 4 weeks periods. XRD evaluation of powder obtained from sol-gel process, showed the presence of HAP and CNTs in the powders. Comparison of XRD results of HAP and HAP-CNTs powders showed the better crystalinity of composite hydroxyapatite. After in vitro tests, specimens were studied with atomic force microscope (AFM)... 

For the sake of decrease in energy and force of earthquake, seismic isolators are used. Regular seismic isolators are too heavy and damaged by chemical materials, therefore in this research a new approach is used that steel shim plates replaced by carbon and polyamide fibers. The aim of this research is to obtain the dynamic and mechanical properties of carbon and polyamide fiber reinforced isolators in comparison with steel reinforced isolators. In this approach, firstly some specimens have been designed and manufactured, then compresional and cyclic shear tests were carried out on them. All three type isolators are cylindrical and have identical diameter and height. The steel, carbon fiber... 

Nanotechnology is the knowledge of future. Some people Compare the initialization of nanotechnology to the beginning of the industrial revolution. Experimental modeling of nano-materials can be so expensive, but, with the aid of computational nanomechanics, we can perform less experiments and more numerical simulation. In the past decades, applications of nanotubes in medicine, electrical engineering, mechanical engineering, building nano sensors, nano engines and etc caused a pervasive study on the mechanics of carbon nanotubes. In this Thesis, the writer has implemented the Tersoff interatomic potential to perform molecular dynamics simulations of carbon nanotubes. In this work, tensile... 

In this research UHMWPE/MWCNT nanocomposites with different concentrations of nanotubes (0.5, 1.5, 2.5, 3.5 wt %) were prepared via in situ polymerization using a novel Bi-supported Ziegler-Natta catalytic systems. Magnesium etoxide and Multi wall carbon nanotubes functionalized by hydroxyl groups were used as supports of catalyst. TiCl4 accompanied by triethylaluminum constituted Ziegler-Natta catalytic system. Preparation of catalyst and polymerization were done in slurry phase under the argon atmosphere. Support of catalyst on MWCNT was investigated using Fourier Transform Infrared Spectroscopy (FTIR). The results confirmed interaction between catalyst and hydroxyl groups on the surface... 

We studied porous silicon as a resistive gas sensor at room temperature. Meso- and macro- porous silicon were formed by electrochemical etching of single crystal silicon wafers in different conditions. For Meso porous Si we used p+-type wafers as substrate and for macro porous Si formation n- and p-type wafers were used. The mechanism of methanol vapor sensing was studied by Scanning tunneling spectroscopy and Fourier transform infrared spectroscopy. The results showed that methanol increases partial oxidation of surface and causes increase of defect density. These defects play important role to trap electrons and create “acceptor surface states”. These acceptor surface states in p+-type... 

First, we peruse the intraction between a quantized light and a two level atom which has been described by Janes-Cummings-Paul Hamiltonian. By solving Heisenberg equations in Fourier space and describing electric field by a generalized-transverse Green function, we obtain spectral density for a quantum dot which is in the strong coupling to a slab photonic crystal cavity. Afterward, by solving Shrouding equations precisely we demonstrate when quantum dot is in a very strong coupling to cavity, rotate wave approximation is not reliable anymore. It means that if coupling constant gets comparable to cavity mode frequency then the prevalent approach to solve this Hamiltonian will not be correct.... 

Relative permeability is an important factor that controls the two phase fluid flow in porous media. The use of carbon dioxide in enhanced oil recovery methods is common. But the question is, how does the carbon dioxide affect the relative permeability curves? In this thesis, the CO2-oil relative permeability is measured in CO2 flooding process with unsteady state method. For this purpose, the core flooding apparatus is used and the results are compared with N2-oil relative permeability in N2 flooding. The results of comparison show that oil relative permeability in CO2 flooding is higher than N2 flooding. Reduction of Interfacial tension and oil viscosity, solubility of CO2 in oil and oil... 

Considering that automobile weigth reduction in industry is important, improvement the strength of low carbon steel sheets is important. These sheets can be supported the service condition in lower thicknesses. Bulk nano-structured materials have been mostly attracted in materials science due to their unique physical and mechanical properties. Severe plastic deformation (SPD) is one of the most efficient methods to produce ultra fine grained or nano-structured materials. Materials produced by SPD are of great importance because of (1) non-porous structure, (2) great mechanical properties such as high strength and toughness and (3) proper dimension for mechanical and physical testing. ... 

In this project, two multiscale modeling procedures have been implemented to study the mechanical behavior of SWCNT/polymer composites. First, a new three-phase molecular structural mechanics/ finite element (MSM/FE) multiscale model has been introduced which consists of three components, i.e. a carbon nanotube, an interphase layer and outer polymer matrix. The nanotube is modeled at the atomistic scale using MSM, whereas the interphase layer and polymer matrix are analyzed by the FE method. Using this model, we have investigated the macroscopic material properties of nanocomposite with and without considering the interphase and compared the results with molecular dynamics (MD) simulations....