Sharif Digital Repository

The size mono-dispersity, saturation magnetization, and surface chemistry of magnetic nanoparticles (NPs) are recognized as critical factors for efficient biomedical applications. Here, we performed modified water-in-oil inverse nano-emulsion procedure for preparation of stable colloidal superparamagnetic iron oxide NPs (SPIONs) with high saturation magnetization. To achieve mono-dispersed SPIONs, optimization process was probed on several important factors including molar ratio of iron salts [Fe3+ and Fe2+], the  

The microstructure and mechanical properties of the ultra-fine grained (UFG) Al6063 alloy reinforced with nanometric aluminum oxide nanoparticles (25 nm) were investigated and compared with the coarse-grained (CG) Al6063 alloy (~2 μm). The UFG materials were prepared by mechanical alloying (MA) under high-purity Ar and Ar-5 vol pct O2 atmospheres followed by hot powder extrusion (HPE). The CG alloy was produced by HPE of the gas-atomized Al6063 powder without applying MA. Electron backscatter diffraction under scanning electron microscopy together with transmission electron microscopy studies revealed that the microstructure of the milled powders after HPE consisted of ultra-fine grains... 

In recent years, polysilicon nanoparticles are used to enhance the oil recovery through the water injection process in oilfields. The contributing mechanisms are the reduction of interfacial tension and wettability alteration which lead to improving or decreasing the oil phase relative permeability and can be traced by change of relative permeability curves. However, profound understanding of the effect of dispersed nano-silica particles on the hysteretic behavior of relative permeability curves remains a controversy topic in the literature.The current study illustrates the influence of dispersed silica particles on hysteretic trend of two-phase curves of oil-water relative permeability.... 

During miscible displacements in fractured porous media, one of the most important factors that plays a significant role in oil production is the matrix-fracture interaction. In this work, a series of hydrocarbon injection experiments have been performed on a fractured glass micromodel that was designed specifically to study matrix-fracture interaction. A high quality image analysis method was used to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that in the case of unit viscosity ratio, the injection rate increased the slope of recovery curve and consequently improved the final... 

Finger initiation/development at fluid-fluid interface during miscible floods can cause poor displacement efficiency, which is undesirable in enhanced oil recovery processes. In this work, a series of hydrocarbon injection experiments performed on 5-spot glass micromodels that were initially saturated with the heavy crude oil. The fractured micromodels with different fracture geometrical characteristics were used in the tests. High quality image analysis was applied to determine the fluid flow behavior, solvent front movement, and viscous fingering associated with solvent movement in matrix and fractures. Observations showed that higher solvent dispersion in the fractures rather than matrix... 

It has been shown that one kind of poly silicon particles with sizes ranging from 10-500 nm, can be used in oilfields to enhance the oil recovery of water injection by 15-20%. The contributing mechanism might be reducing the interfacial tension which appears through improving relative permeability of the oil-phase. However, fundamental understanding of how hysteretic behavior of relative permeability curves affected by nanosilica particles remains a topic of debate in the literature. In this study, water as well as water dispersed nanosilica particles floods was performed on sandstone rock sample saturated by light crude oil supplied from one of Iranian oil reservoir, and the relative... 

It is well known that the displacement efficiency of EOR processes is mainly affected by wettability of porous medium; however, the role of nanoparticles on wettability alteration of pores surfaces remains a topic of debate in the literature. Furthermore, a little is known about how the dispersed silica nanoparticles affect the microscopic/macroscopic recovery efficiency of heavy oils during common immiscible EOR processes such as water flooding. In this study, a series of injection experiments was performed on five-spot glass micromodel which is initially saturated with the heavy oil. Distilled water and dispersed silica nanoparticles in water (DSNW) at different values of weight percent... 

In this study a new iterative algorithm is developed to evaluate dispersivity in fracture and matrix, distinctly. The novelty of proposed algorithm is using mathematical model of solute transport in fractured porous media coupled with experimental data iteratively. A fractured glass micromodel has been designed to visualize the interaction between fracture and matrix during displacement of n-Decane by n-Octane at constant rate. The similarity between numerical and experimental model has been enhanced by reducing the assumptions which were applied in previous related studies. The iteration is performed on velocity components of solute transport and longitudinal as well as transversal... 

Respiratory drug delivery has been under the research spotlight for the past few decades, mainly due to the high incidence of pulmonary diseases and the fact that this type of delivery offers the highest efficiency for treatment. Despite its invaluable benefits, there are some major drawbacks to respiratory drug delivery, the most important of which being poor delivery efficiency and relatively high drug deposition in undesirable regions, such as the mouth cavity. One way to improve the efficiency of respiratory drug delivery with metered-dose inhalers is placing a respiratory spacer between the inhaler exit and the mouth. It is argued that high drug deposition in the immediate airways of... 

A new photocatalyst (Ag-S/PEG/TiO2) was synthesized by adding polyethylene glycol (PEG) to an efficient Ag-S/TiO2 photocatalyst, to obtain a photocatalyst that is highly active under visible light. In addition to Ag-S/PEG/TiO2, Ag-S/TiO2 and pure TiO2 were prepared to compare their properties and activities. Specifically, the morphologies and microstructures of the nanophotocatalysts were characterized by means of powder X-ray diffraction (XRD), N2 adsorption-desorption measurements, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (DRS), photoluminescence (PL) spectroscopy,... 

In this study, the influences of different concentrations of SiO 2 nano sized particles in the bath on deposition rate, surface morphology and corrosion behavior of Ni-P-SiO2 Composite coatings were investigated. The deposition rate of coating was influenced by incorporation of SiO2 particles. The microstructure was investigated with field emission scanning electron microscopy (FESEM). The amount of SiO 2 was examined by Energy Dispersive Analysis of X-Ray (EDX) and amount of SiO2 nanoparticles co-deposited reached a maximum value at 4.5 %wt. Corrosion behavior of coated aluminum was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques. The results... 

The effect of temperature, pressure and bonding time on microstructure of temperature gradient transient liquid phase (TGTLP) diffusion bonded Al7075 alloy using liquid gallium interlayer was investigated. The selected bonding method relies on using the minimum amount of liquid gallium on faying surfaces, using a very fast heating rate to reach the joining temperature and imposing a temperature gradient across the bond region. The microstructure of the diffusion bonded joints was evaluated by light optical microscopy, scanning electron microscopy and energy dispersive spectroscopy (EDS). Results show that by increasing the temperature, pressure and time of joining, a more uniform... 

A novel ultrasensitive modified electrode was fabricated with a graphene nanosheets and carbon nanospheres (GNS-CNS)-based nanocomposite film as a powerful platform. Pt nanoparticles (PtNPs) were simply electrodeposited onto the GNS-CNS-coated glassy carbon electrode creating a PtNPs/GNS-CNS hybrid nanocomposite modified electrode. Scanning electron microscopy, energy dispersive X-ray spectroscopy and linear sweep voltammetry (LSV) techniques were used for the characterization of the prepared modified electrode. The results of investigation of electrochemical response characteristics of cefepime (CP) revealed a considerable improvement in the oxidation peak current of CP on PtNPs/GNS-CNS/GCE... 

Ag and Ni are immiscible, mainly due to their large lattice mismatch. This paper reports on their nanoscale formation of solid solution at room temperature by simple reduction reactions which lead to the amorphous Ag-Ni alloy nanoparticles (ANPs) with mono-disperse distribution. Microscopic and spectroscopic studies confirmed dependence of the alloy composition on size of nanoparticles. In the presence of different ligands such as sodium citrate, polyvinyl alcohol and potassium carbonate a mixture of silver oxide and Ag-Ni ANPs was achieved. Stoichiometry of the Ag-Ni ANPs was also found to be strongly dependent on ligands of the reduction reaction and further study shows without any ligand... 

Since in a highly filled polymer, a major problem arises from non-uniformity of properties due to the poor dispersion of filler, the application of coupling agents have been directed to overcome this problem and also to enhance the mechanical performance of the composites by improving the adhesion at the interface. In this study, a comparison between two major coupling approaches is conducted: 1) Using PPgMA as a kind of compatibilizer which changes the nature of the matrix, 2) Using titanate coupling agent which takes action at the interface and reacts with hydroxyl groups at the inorganic filler surface, resulting in the formation of monomolecular layer on the inorganic surface to increase... 

We use the Fokker-Planck equation and its moment equations to study the collective behavior of interacting particles in unsteady one-dimensional flows. Particles interact according to a longrange attractive and a short-range repulsive potential field known as Morse potential. We assume Stokesian drag force between particles and their carrier fluid and find analytic single-peaked traveling solutions for the spatial density of particles in the catastrophic phase. In steady flow conditions the streaming velocity of particles is identical to their carrier fluid, but we show that particle streaming is asynchronous with an unsteady carrier fluid. Using linear perturbation analysis, the stability... 

X-ray diffraction and rheological measurements were used to characterize nanoparticle dispersion in LDPE/LLDPE/nanoclay hybrid nanocomposites. XRD patterns were interpreted with a novel distribution formula and rheological measurements were used to confirm the results. Results of these two methods indicated that increasing clay in all the prepared nanocomposites exhibited a significant improvement in filler-matrix interaction because of increasing the probability of polymer diffusion but further exfoliation need more compatibilizing situations. It seems that this mathematical method could be used for predicting the overall change in clay gallery d-spacing and the extent of... 

We study the thermal properties of ultra-narrow silicon nanowires (NW) with diameters from 3 nm to 12 nm. We use the modified valence-force-field method for computation of phononic dispersion and the Boltzmann transport equation for calculation of phonon transport. Phonon dispersion in ultra-narrow 1D structures differs from dispersion in the bulk and dispersion in thicker NWs, which leads to different thermal properties. We show that as the diameter of the NW is reduced the density of long-wavelength phonons per cross section area increases, which increases their relative importance in carrying heat compared with the rest of the phonon spectrum. This effect, together with the fact that... 

A Brillouin probing method is proposed to extract the distribution of signal power along phase-sensitive parametric amplifiers. Operation near the zero-dispersion-wavelength shows enhanced sensitivity to dispersion fluctuations, allowing effective extraction of the dispersion map  

Asphaltenes are a polydisperse fraction of the crude oil, the phase behavior of which is significantly affected by the changes in pressure, temperature and composition. The focus of this study is to model the polydisperse asphaltenes' precipitation onset condition and the amount of precipitate from solvent-diluted crude oils using the Perturbed Chain form of the Statistical Associating Fluid Theory (PC-SAFT) over a wide range of crude oil density. Heavy oil and bitumen production can involve diluting with paraffinic solvents. Different fractions of the polydisperse asphaltenes thus precipitated are predicted and when compared to the experimental data show a remarkable matching for different...