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    Electroosmotic Flow in Microchannels

    , M.Sc. Thesis Sharif University of Technology Lesani, Mostafa (Author) ; Saeedi, Mohammad Saeed (Supervisor)
    The present study examines both Direct Current (DC) and Alternating Current (AC) electroosmotic flows in a parallel plate microchannel. The method consists of a central finite difference scheme for spatial terms and a forward difference scheme for the temporal term. Asymmetric boundary conditions are assumed for Poison-Boltzmann equation used to determine the electric double layer (EDL) potential distribution. The potential distribution is then used to evaluate the velocity distribution for both DC and AC electroosmotic flows. The velocity distributions are obtained by applying slip boundary conditions on the walls to account for probable hydrophobicity of the surfaces. After determining the... 

    LBM simulation of electro-osmotic flow (EOF) in nano/micro scales porous media with an inclusive parameters study

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) ; Vol. 7 , November , 2014 ; ISBN: 9780791849545 Zakeri, R ; Lee, E. S ; Salimi, M. R ; Sharif University of Technology
    In this paper, we present our results about simulation of 2D-EOF in Nano/Micro scales porous media using lattice Boltzmann method (LBM) in micro-channel for EOF. The high efficient numerical code use strongly high nonlinear Poisson Boltzmann equation to predicate behavior of EOF in complex geometry. The results are developed with precisely investigation of several effective parameters on permeability of EOF, such as geometry (channel height and number and location of charge), external electric field, thickness of Debye length (ionic concentration), and zeta potential. Our results are in excellent agreement with available analytical results. Our results show that for certain external electric... 

    Numerical simulation of heat transfer in mixed electroosmotic pressure-driven flow in straight microchannels

    , Article Journal of Thermal Science and Engineering Applications ; Volume 8, Issue 2 , 2016 ; 19485085 (ISSN) Shamloo, A ; Merdasi, A ; Vatankhah, P ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2016
    This paper investigates two-dimensional, time-independent elecroosmotic pressuredriven flow generated by a direct current electric potential with asymmetrical and symmetrical zeta potential distributions along the microchannel walls. Fluid flow through the horizontal microchannel is simulated using a numerical method. Two different cases are proposed to study the effect of electric potential on the flow field. First, negative electric potential is applied on the microchannel walls. In this case, large segments with negative electric potential are initially placed on the first half of the microchannel walls with two different arrangements. Afterward, smaller segments with negative electric... 

    Experimental Investigation of Effective Parameters on Lead Ion Removal by Nanofiltration

    , M.Sc. Thesis Sharif University of Technology Mehdipour Zareh, Saber (Author) ; Kariminia, Hamidreza (Supervisor) ; Vatanpoor, Vahid ($item.subfieldsMap.e)
    In this study, the effects of parameters such as operation pressure, concentration of Pb2+ ion, nature of associated anion, pH of initial feed and composition of feed was investigated by commercial polyamide nanofilter membrane. One-salt solution nanofiltration experiments was performed by using Pb(NO3)2, PbCl2 and PbSO4 and the binary-salt solution experiments was conducted by using Cu(NO3)2, Cd(NO3)2, Zn(NO3)2, NaNO3 and NH4NO3 together with Pb(NO3)2. The binary-salt experiments in presence of monovalent and divalent cations (together with Pb2+) were performed successively. At first the surface charge of membrane in contact with 1mM KCl solution at pH range of 3-7 was measured. The pH of... 

    Wettability Altration Determination by Using Streaming Potential

    , M.Sc. Thesis Sharif University of Technology Esmaeili, Sajjad (Author) ; Massihi, Mohsen (Supervisor) ; Ayatollahi, Shahabodin (Supervisor)
    The assessment of fluid transport in porous media is the main subject in oil reservoirs to understand the oil recovery efficiency. The efficiency of Enhanced oil recovery (EOR) processes depends on the surface properties and wetting behavior of oil reservoir rocks which are also affected by the electrokinetic behavior of solid part of the porous rock. Streaming potential measurement is one of the techniques to determine the electrokinetic properties. The streaming potential measurements using electrodes have recently been introduced in oil field applications and there are still significant uncertainties during the measurements and interpretation of streaming potential results. The Primarily... 

    An Investigation to the Effect of Heterogeneity of Surface’s Potential on Mass Transport and Surface Reaction Kinetics in Microreactors

    , M.Sc. Thesis Sharif University of Technology Abodllahzadeh, Mojtaba (Author) ; Saeedi, Mohammad Saeed (Supervisor)
    Nowadays, technology has facilitate the miniaturization of laboratory systems, medical and drug delivery tools. As a result, researchers are interested to miniaturize these tools. The extensive research in this field led to invention of lab-on-a-chips, which with the size of a few µm to a few mm, can do multiple tasks in human body. One of most important components of these devices, is microreactor. A wide range of measurements and reactions in microreactors, need to bind with the receptors at the surface of the cylindrical microchannels. For this purpose, this study, investigates the effects of surface heterogeneity on microreactors performance. In this Thesis, the governing equations were... 

    Deposition of Ceramic Nanoparticles on Aluminum Sheet by Air Gun Spraying for ARB Processing of Nanocomposite Sheets

    , M.Sc. Thesis Sharif University of Technology Keramat, Ehsan (Author) ; Akbarzadeh, Abbas (Supervisor)
    Particle reinforced aluminum matrix composites have considerable attraction in automotive and aerospace industries due to their special properties as light weight, high ratio of strength/density, improved elastic modulus, low coefficient of thermal expansion and high wear and corrosion resistance. Among the production processes of metal matrix composites, accumulative roll bonding process has particular importance due to producing ultrafine grained composite sheets. However, uncontrolled and undesired agglomeration of particles is the main problem in producing these composites. In this research, the Al2O3 and SiC nanoparticles were electrostatically stabilized against agglomeration by... 

    On The Weil Conjectures

    , M.Sc. Thesis Sharif University of Technology Rezaee, Fatemeh (Author) ; Jafari, Amir (Supervisor)
    ” The story of the "Weil conjectures" is a marvelous example of mathematical imagination, and one of the most striking instances exhibiting the fundamental unity of mathematics.”In 1949,Andre Weil stated some conjectures on the zeta function of Algebraic varieties over finite fields .These conjectures were analogue of the properties of Riemann zeta function ,in particular Riemann hypothesis.In fact ,Weil built a bridge between Diophantine structure on varieties over finite fields (Counting of rational points on varieties) and cohomological structure of them over the field of complex numbers(topology of variety).In this thesis, first we state Weil’s motivations for these conjectures and state... 

    Design and physicochemical characterization of lysozyme loaded niosomal formulations as a new controlled delivery system

    , Article Pharmaceutical Chemistry Journal ; Volume 53, Issue 10 , 2020 , Pages 921-930 Sadeghi, S ; Ehsani, P ; Cohan, R. A ; Sardari, S ; Akbarzadeh, I ; Bakhshandeh, H ; Norouzian, D ; Sharif University of Technology
    Springer  2020
    Lysozyme loaded niosomes containing various molar ratios of two kinds of surfactants were prepared and the properties of these niosomal formulations were studied. The results revealed that the size of niosomes varied between 240.06 ± 32.41 and 895.2 ± 20.84 nm. Formulations with the lowest size and no precipitation had entrapment efficiencies ranging from 60.644 ± 3.310 to 66.333 ± 1.98%. Their controlled release profiles after 48 h were 15.67, 20.67 and 31.50%. After 2 months, the most stable formulation in terms of size, PDI, zeta potential, and entrapment efficiency was used to study the secondary structures of lysozyme in niosomal and free forms. Lysozyme loaded niosome and lysozyme... 

    Remedial effects of metal oxide nanoparticles to treat suspension transport in saturated porous media

    , Article SPE - European Formation Damage Conference, Proceedings, EFDC ; Volume 1 , 2013 , Pages 478-488 ; 9781627486101 (ISBN) Arab, D ; Pourafshary, P ; Ayatollahi, S ; Habibi, A ; Sharif University of Technology
    Hydrocarbon production decline as a result of formation damage caused by fines migration has been widely observed in laboratory corefloods and natural flows in porous media. Permeability impairment due to fines migration is explained by different capture mechanisms of already released particles at some pore sites. Preventing detachment of in-situ particles from the rock surface during enhanced oil recovery (EOR) agent injection into the porous media has been reported recently. In this experimental study, the effect of five types of metal oxide nanoparticles; γ-AI2O3, ZnO, CuO, MgO and SiO: to adsorb the fine particles existing in the flowing suspension has been investigated. In each test,... 

    Electrophoretic velocity of spherical particles in Quemada fluids

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 436 , September , 2013 , Pages 225-230 ; 09277757 (ISSN) Moosavi, S. M ; Sadeghi, A ; Saidi, M. S ; Sharif University of Technology
    The biomicrofluidic devices utilizing electrophoresis for sample manipulation are usually encountered with non-Newtonian behavior of working fluids. Hence, developing theoretical models capable of predicting the electrophoretic velocity of colloidal particles in non-Newtonian fluids is of high importance for accurate design and active control of these devices. The present investigation is dealing with the electrophoresis of a spherical particle in a biofluid obeying the Quemada rheological model. The sphere radius is considered to be significantly larger than the Debye length. Moreover, it is assumed that the particle zeta potential is small so that the Debye-Hückel linearization is... 

    Streaming potential measurement to quantify wetting state of rocks for water based EOR, inhouse novel setup experience

    , Article IOR NORWAY 2017 - 19th European Symposium on Improved Oil Recovery: Sustainable IOR in a Low Oil Price World, 24 April 2017 through 27 April 2017 ; 2017 ; 9789462822092 (ISBN) Rahbar, M ; Jafarlou, A ; Nejadali, M ; Esmaeili, S ; Pahlavanzadeh, H ; Ayatollahi, S ; Sharif University of Technology
    The wetting condition of the reservoir rock is the key to the success of any EOR technique and the ultimate oil recovery. Wettability is dictated by the surface chemistry related to the interactions between the fluids and the rock surface which determines the stability of the water film between the rock and the oil phase. Streaming potential measurement is one of the electrokinetic techniques used to determine the average zeta potential of porous rock which can provide reliable information on fluid-rock interaction and wettability state of the rock surface. Streaming potential measurement has recently been introduced in the oil reservoirs applications and there are still significant... 

    Inclusion of carbon nanotubes in a hydroxyapatite sol-gel matrix

    , Article Ceramics International ; Volume 35, Issue 7 , 2009 , Pages 2987-2991 ; 02728842 (ISSN) Najafi, H ; Nemati, Z. A ; Sadeghian, Z ; Sharif University of Technology
    In this study, the inclusion of multi-walled carbon nanotubes as the second phase in the hydroxyapatite matrix, in order to improve the mechanical strength, has been performed via the sol-gel process. The stability of carbon nanotube sol with the changes of pH and dispersant values (sodium dodecyl sulfate) was evaluated by zeta potential analysis. The results indicated that synthesis of hydroxyapatite particles in the presence of the carbon nanotubes had the best result in homogenization of the carbon nanotube dispersion and faster crystallization of hydroxyapatite. The crystallization of hydroxyapatite phase was investigated with differential scanning calorimetry (DSC) and X-ray diffraction... 

    Super-hydrophilic characteristic of thermochemically prepared CdS nanocrystals

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Vol. 58 , April , 2014 , pp. 146-152 ; ISSN: 13869477 Marandi, M ; Taghavinia, N ; Babaei, A ; Sharif University of Technology
    CdS nanocrystals were thermochemically (thermally activated) synthesized thorough the reaction between CdSO4 and Na2S 2O3 in an aqueous solution. Thioglycolic Acid (TGA) was used as the capping agent and catalyst of the reaction. The method was based on heat activated dissociation of Na2S2O3 and controllable release of S and free electrons in the solution. CdS NCs were formed by heating the sample solution at 96 C for 1 h. The results of optical spectroscopy and transmission electron microscopy demonstrated round shape NCs with sizes about 3.0 nm. The nanocrystals were also luminescent and represented a broad emission with a peak located at 515 nm and FWHM of 160 nm. Several samples were... 

    Mixed pressure and AC electroosmotically driven flow with asymmetric wall zeta potential and hydrophobic surfaces

    , Article ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 ; Volume 1 , 2013 ; 9780791855478 (ISBN) Lesani, M ; Sharif University of Technology
    The present study examines Alternating Current (AC) electroosmotic flows in a parallel plate microchannel subject to constant wall temperature. Numerical method consists of a central finite difference scheme for spatial terms and a forward difference scheme for the temporal term. Asymmetric boundary conditions are assumed for Poison-Boltzmann equation for determining the electric double layer (EDL) potential distribution. The potential distribution is then used to evaluate the velocity distribution. The velocity distribution is obtained by applying slip boundary conditions on the walls which accounts for probable hydrophobicity of surfaces. After determining the velocity distribution... 

    Zeta-potential investigation and experimental study of nanoparticles deposited on rock surface to reduce fines migration

    , Article SPE Journal ; Volume 18, Issue 3 , February , 2013 , Pages 534-544 ; 1086055X (ISSN) Ahmadi, M ; Habibi, A ; Pourafshary, P ; Ayatollahi, S ; Sharif University of Technology
    Finesmigration is a noticeable problem in petroleum-production engineering. Plugging of throats in porous media occurs because of detachment of fine particles from sand surfaces. Thus, the study of interactions between fines and pore surfaces and the investigation of governing forces are important factors to consider when describing the mechanism of the fines-release process. The main types of these forces are electric double-layer repulsion (DLR) and London-van der Waals attraction (LVA). It may be possible to alter these forces with nanoparticles (NPs) as surface coatings. In comparison with repulsion forces, NPs increase the effect of attraction forces. In this paper, we present new... 

    Comparison of different strategies for the assembly of gold colloids onto Fe3O4@SiO2 nanocomposite particles

    , Article Physica E: Low-Dimensional Systems and Nanostructures ; Volume 49 , 2013 , Pages 30-38 ; 13869477 (ISSN) Mohammad Beigi, H ; Yaghmaei, S ; Roostaazad, R ; Arpanaei, A ; Sharif University of Technology
    Three strategies were employed for the assembly of gold nanoparticles on silica-coated magnetite particles (SCMPs). In strategy I, citrate-coated gold nanoparticles were attached on the surface of amine-SCMPs. In strategy II, amine-SCMPs were coated with carboxylated gold nanoparticles via amide bond formation. In strategy III, the thiol-SCMPs surface was coated with gold nanoparticles. Among the above examined strategies, coating amine-SCMPs with gold nanoparticles via strategy I resulted in a better coverage and stronger intensity of absorption bands. Furthermore, results obtained through strategy I showed that decreasing the pH of the solution from 7 to 3 leads to a further red-shift of... 

    Electrophoretic deposition of titania nanoparticles in different alcohols: Kinetics of deposition

    , Article Journal of the American Ceramic Society ; Volume 94, Issue 8 , 2011 , Pages 2354-2361 ; 00027820 (ISSN) Farrokhi Rad, M ; Ghorbani, M ; Sharif University of Technology
    The suspension of titania nanoparticles in different alcohols (methanol, ethanol, and butanol) was prepared and triethanolamine (TEA) was used as a dispersant. The suspensions were characterized by different tests such as sedimentation, zeta potential, and Fourier transform infrared spectroscopy. The electrophoretic deposition (EPD) was performed at various voltages and times. EPD from butanolic suspension (0.8 g/L TEA) showed the slowest kinetics, because of the low electrophoretic mobility of titania nanoparticles in it (2.40 × 10-5 cm2·(V·s)-1). Also, it was observed that at low voltages (5, 10, and 20 V), the EPD kinetics from methanolic suspension (0 g/L TEA) was the fastest; however,... 

    Mixed electroosmotically and pressure-driven flow with temperature- dependent properties

    , Article Journal of Thermophysics and Heat Transfer ; Volume 25, Issue 3 , Sep , 2011 , Pages 432-442 ; 08878722 (ISSN) Sadeghi, A ; Yavari, H ; Saidi, M. H ; Chakraborty, S ; Sharif University of Technology
    The present work reports the outcome of a comprehensive parametric study on mixed electroosmotically and pressure-driven flow in slit microchannels with constant wall heat fluxes. Special attention is given to disclose the applicability ranges of usual assumptions in simplified analyses. The governing equations for fully developed conditions are first made dimensionless and then solved by means of an implicit finite difference method. The results reveal that the assumption of constant thermophysical properties does not leadto significant errors in practical applications. Although the Debye-Huckel linearization may successfully be used to evaluate velocity profiles up to the zeta potentials... 

    Stabilization of the suspension of zirconia microparticle using the nanoparticle halos mechanism: zeta potential effect

    , Article Journal of Dispersion Science and Technology ; Volume 37, Issue 1 , 2016 , Pages 6-13 ; 01932691 (ISSN) Keramati, H ; Saidi, M.H ; Zabetian, M ; Sharif University of Technology
    Taylor and Francis Inc  2016
    An experimental study has been conducted to investigate the effect of silica nanoparticle halos on the stability of the zirconia aqueous suspension. The results of turbidity measurements showed that addition of nanoparticles to the suspension increases the stability of the zirconia suspension for all pH values. The achieved stability refers to the formation of nanoparticle halos around the microparticles that can be observed by scanning electron microscopy (SEM) imaging. The best stabilization is achievable when zirconia microparticles are at the isoelectric point. The minimum stabilization occurs when microparticles have relatively high zeta potential and the force between micro and...