Sharif Digital Repository

Dissolution modeling of smart core-shell polymer particles (SPP) during polymer flooding is the main purpose of this study. The SPP is used to improve the efficiency of conventional polymer flooding. The smart title comes from selective dissolution of these core-shell particles in porous media, which is related to the hydrophobic-hydrophilic behavior of them. The core of the SPP is a hydrophilic high molecular weight polymer, which is covered by a protective shell layer of low molecular weight hydrophobic polymer. Reaching at the water-oil interface, these particles increases the viscosity of flooding water at neighborhood of the water-oil interface. Considering the analogy between drug... 

Hollow carbon spheres (HCS) are spherical forms of carbon materials that can be used as nanocontainers due to their empty cores. In this work, zinc cations were doped in HCS (Zn@HCS) from an aquatic solution of zinc nitrate salt. Corrosion inhibition of released zinc cations in saline solution on bare mild steel samples was assessed by EIS, polarization, and electrochemical noise measurements. The sample surfaces were characterized through FTIR spectroscopy and grazing incidence XRD analyses after exposure to the test solutions. The results showed improvement in the corrosion resistance in the presence of Zn@HCS in a long immersion period. Zn@HCS were also incorporated in organosilane... 

In this research work, to reduce permeability of polyethylene vinyl acetate) packaging films, organoclay nanocomposites of these thermoplastics were prepared by solution method. Organoclay are mixed with polyethylene vinyl acetate (EVA) with 18 and 28% of vinyl acetate (VA) content in solution phase. Solutions of 3, 5 and 7% of organoclay are prepared under reflux condition and then nanocomposite films are prepared by thermal phase inversion method. Morphological and gas barrier properties of different prepared samples have been investigated. Morphology of prepared nanocomposite films and order of exfoliation of clay were investigated using X-ray diffraction (XRD) and transmission electron... 

The main purposes of this study were to scrutinize experimentally effects of polymer and rock types on the oil recovery using water and polymer flooding processes. Four dynamic flooding experiments were carried out at simulated reservoir condition of temperature and pressure. According to the obtained results, the ultimate oil recovery by water flooding in highly fractured reservoirs was less than reservoirs with the microfractures. The results of polymer flooding showed that in addition the polymer molecular weight, the sulfonation of polymers also affects the oil recovery  

In this work, hybrid of silica nanoparticles (NPs) with sulfonated copolymer has been prepared in order to improve the copolymer properties for Enhanced Oil Recovery (EOR). Some tests are done to find the effectiveness of injecting fluid on Recovery Factor (RF), such as Contact Angle (CA), interfacial tension (IFT), inherent viscosity, and eventually Micro-Model (MM) flooding. In CA test, wettability alteration from Oil-Wet (OW) to Water-Wet (WW) is reached by sedimentation and adsorption of NPs on the rock slice. In addition, IFT reduction is obtained by increasing the NaCl concentration. The viscosity change is investigated for the hybrid and copolymer under simulated high-temperature oil... 

Molybdenum disulfide (MoS2), a 2D layered structure, because of its unique properties has widely attracted many researchers. In this study, by employing physical and chemical methods, not only layers of MoS2 have been intercalated, but also their surface properties enhanced. Low-dimensional and potential properties of intercalated MoS2 nanosheets are the aim of many researches. Here, we report a novel four step method to intercalate the layers of MoS2 nanosheets successfully using acid treatment, sonication, oxidization and thermal shocking. The other goal in this study is to evaluate the cation exchange ability and anticorrosion performance of the Ce3+ doped MoS2 nanosheets. The... 

A family of conformational rheological models for multi-component miscible polymer blends is developed using a modified form of the Poisson bracket formulation. Two conformation tensors called c1 and c2 are introduced to show the orientation of the first and the second components of a blend, respectively. The mobility tensor and the energy function for each blend component are expressed in terms of these conformation tensors. The interaction effects are also included by energy expressions. The predictions of this family of "volume-preserving" models are illustrated for a Hookean-type energy function and several expressions of the modified mobility tensors. The results are illustrated for... 

This research deals with the numerical simulation of two viscoelastic uids ow in an open capillary of a reservoir. Oldroyd-B and Leonov models have been used to describe the rheological behavior of polymer solutions. The finite volume method on a structured and collocated grid has been used for discretization of the governing equations. The discrete elastic viscous stress splitting technique has also been used. The steady state, isothermal and incompressible uids past through a two dimensional micropore have been considered. The numerical method has been validated through the comparison of numerical results by the analytical solutions of Oldroyd-B uid ow through a planar channel. The effects... 

Numerous advantages of application of tailor welded blanks (TWBs) in automobile industry, namely reduction of weight, fuel consumption and air pollution, have made the manufacturers eager to investigate in this field. On the other hand, while experiments generally provide valuable information in regard with mechanical behaviors, but utilization of simulation methods has extended vastly due to time and cost saving issues. One challenging issue in numerically analyzing the forming behavior of transversely welded TWBs, welded by laser welding methods, has been the presence of weld zone. While some researchers believe that during simulation, the weld zone can be neglected due to its minority and... 

In this work, the rheological changes of several crude oil samples exposed to ultrasonic waves for different time intervals in addition to the effect of temperature on viscosity behavior of heavy crude oils were investigated using a series of steady shear flow and oscillatory tests. The colloidal structural evolutions of flocs in oil samples were illustrated by analysis of the size distribution of flocculated asphaltene particles (confocal microscopy tests). The rheological investigations indicate that the ultrasonic irradiation dissolved heavy components in crude oil. After ultrasonic treatment, the Kouh-e-Mond crude oil was found to be pseudoplastic. In addition, confocal microscopy... 

The graphene-based Ziegler-Natta catalyst has been used to prepare ultrahigh molecular weight polyethylene/graphene oxide (UHMWPE/GO) nanocomposite via in situ polymerization. The morphological investigations have been conducted using X-ray diffraction patterns and scanning electron microscopy method. The obtained results indicated that no diffraction peak is detected in a GO pattern, which could be due to the exfoliation of graphene nanosheets in the UHMWPE matrix. Morphological investigations indicated that GO nanosheets are dispersed almost uniformly in polymeric matrix, and that there should exist a good interaction between nanofillers and matrix. The mechanical properties of the... 

Peripheral nervous system in contrary to central one has the potential for regeneration, but its regrowth requires proper environmental conditions and supporting growth factors. The aim of this study is to design and fabricate a conductive polyaniline/graphene nanoparticles incorporated gelatin nanofibrous scaffolds suitable for peripheral nervous system regeneration. The scaffolds were fabricated with electrospinning and the fabrication process was designed with Design-Expert software via response surface methodology. The effect of process parameters including applied voltage (kV), syringe pump flow rate (cm3/h), and PAG concentration (wt%), on the scaffold conductivity, nanofibers diameter,... 

Thermal conductivity and phonon transport properties of graphyne nanotubes (GNTs) and conventional carbon nanotubes (CNTs) are studied using nonequilibrium molecular dynamics simulations. The effect of nanotube length on the thermal conductivity and phonon transport transition from a ballistic to a diffusive regime is investigated. It is found that the thermal conductivity is significantly higher for CNTs in comparison to that of GNTs across the entire ballistic-diffusive transport range. Among GNTs, β- and γ-GNTs demonstrated the lowest and highest thermal conductivities, respectively. In addition, ultralow ballistic to diffusive transition length (4.5-7.6 nm) was observed in GNTs, which... 

In this study, poly (vinylidene fluoride) PVDF/Starch nanofibers with a great potential for tissue engineering applications have been investigated. The electrospun nanofibers were formed by the electrospinning of the PVDF/Starch solutions in various ratios of PVDF to Starch. Characterizations of PVDF/Starch nanofiber were performed using rheometric mechanical spectroscopy (RMS), field emission scanning electron microscope (FE-SEM) and tensile test. The results showed that the addition of more Starch into the PVDF solution increased the viscosity of the prepared PVDF/Starch solutions. In addition, the mechanical properties of PVDF enhanced in the presence of Starch due to the higher... 

A new equation of state based on the Statistical Associating Fluid Theory (SAFT) is presented to study the phase behavior of associating and non-associating fluids. In the new equation of state, the hard sphere contribution to compressibility factor of the simplified version of the SAFT (SSAFT) is replaced with that proposed by Ghotbi and Vera. The Ghotbi-Vera SSAFT (GV-SSAFT) was also extended to study the phase behavior of associating and non-associating mixtures. The GV-SSAFT like the SSAFT equation of state has three adjustable segment parameters for non-associating fluids and five parameters for associating fluids. The experimental data of liquid densities and vapor pressures for pure... 

Understanding the effect of crystallographic orientation on the twinnin/detwinning mechanisms in NiTi shape memory alloys at an atomistic scale can help to control and tune the mechanical properties and failure behavior of such materials. In this work, we employed classical molecular dynamics (MD) and density functional theory (DFT) computational methods to better understand how twinning and detwinning occurs through a combination of slip, twin, and shuffle on 〈0 1 0〉, 〈1 1 0〉, and 〈1 1 1〉 crystallographic orientations under uniaxial tensile test. Elastic constants including Young's Modulus (E), Bulk modulus (B), Poisson's ratio (ν), and Shear Modulus (G) are obtained and computed for... 

Recently, ultrasonic wave technology has received much attention as a method for removal of asphaltene deposits from the near wellbore region. However, very little is known about another feature of this technology on the kinetics of asphaltene molecules aggregation. In this work, the kinetics of asphaltene flocculation in several crude oil samples exposed to ultrasonic waves for different time intervals is studied by confocal microscopy. The colloidal structural evolutions of flocks are described by analysis of size distribution of flocculated asphaltene particles. The results show that for the first 90 min of flocculation time, the size of aggregates increases rapidly, and a... 

In this study, physically cross-linked hydrogels were developed by freezing-thawing method while different concentrations of honey were included into the hydrogels for accelerated wound healing. The hydrogel was composed of chitosan, polyvinyl alcohol (PVA), and gelatin with the ratio of 2:1:1 (v/v), respectively. Further, the effect of honey concentrations on antibacterial properties, and cell behavior was investigated. In vivo studies, including wound healing mechanism using rat model and histological analysis of section tissue samples were performed. The results illustrated that the incorporation of honey in hydrogels increased the ultimate strain of hydrogels approximately two times,... 

In this study, physically cross-linked hydrogels were developed by freezing-thawing method while different concentrations of honey were included into the hydrogels for accelerated wound healing. The hydrogel was composed of chitosan, polyvinyl alcohol (PVA), and gelatin with the ratio of 2:1:1 (v/v), respectively. Further, the effect of honey concentrations on antibacterial properties, and cell behavior was investigated. In vivo studies, including wound healing mechanism using rat model and histological analysis of section tissue samples were performed. The results illustrated that the incorporation of honey in hydrogels increased the ultimate strain of hydrogels approximately two times,...