Search for: hydrophobicity
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    Wettability alteration modeling for oil-wet calcite/silica nanoparticle system using surface forces analysis: contribution of DLVO versus non-DLVO interactions

    , Article Industrial and Engineering Chemistry Research ; Volume 57, Issue 43 , 2018 , Pages 14482-14492 ; 08885885 (ISSN) Dehghan Monfared, A ; Ghazanfari, M. H ; Kazemeini, M ; Jamialahmadi, M ; Helalizadeh, A ; Sharif University of Technology
    American Chemical Society  2018
    In this work, application of silica nanoparticles for wettability alteration of initially oil-wet calcite was investigated through analysis of surface forces and DLVO theory. Doing so, the wettability and zeta potential of calcite surfaces were measured through the sessile drop method and an in-house experimental setup, respectively. Primary evaluation indicated that incorporating DLVO terms in the Frumkin-Derjaguin model was not sufficient to describe the wettability in an oil-wet calcite/nanofluid system. Sensitivity analysis showed that calculating the double-layer interaction using constant potential-constant potential boundaries along with structural hydrophobic forces (non-DLVO... 

    Influence of surface-modified nanoparticles on the hydrodynamics of rising bubbles

    , Article Chemical Engineering and Technology ; Volume 44, Issue 3 , 2021 , Pages 513-520 ; 09307516 (ISSN) Fayzi, P ; Bastani, D ; Lotfi, M ; Miller, R ; Sharif University of Technology
    Wiley-VCH Verlag  2021
    Local velocities of bubbles rising in four different nanosilica solutions were investigated experimentally. Also, the density, viscosity, and surface tension of fumed nanosilica and modified nanosilica solutions were measured. Heat treatment and chemical functionalization were used to modify the properties of silica nanoparticles. It was found that the addition of nanosilica affected the hydrodynamics of the rising bubble by increasing the drag friction at the interface. However, environmentally responsive nanosilica particles behaved like surfactant molecules, due to the interfacial activity of hydrophilic and hydrophobic chains. Silica nanoparticles coated with both hydrophilic and... 

    Corrosion Behavior of Hydrophobic Silane Coating Prepared by Sol–gel Method on Carbon Steel

    , M.Sc. Thesis Sharif University of Technology Vaez Ghasemi, Fariba (Author) ; Dolati, Abolghasem (Supervisor)
    This project aims to study corrosion protection performance of silane coating based on tetraethylorthosilicate (TEOS), (3-Mercaptopropyl) trimethoxysilane (MPTS) and Hexamethyldisilazane (HMDS) on carbon steel substrate. Water contact angle (WCA) were measured to study hydrophobicity. The water contact angle increased from 60 degrees in carbon steel to 134.8 degrees in the sample containing 0.35 MPTS and 1.25 HMDS. Surface morphology was studied using Field emission scanning electron microscopy (FESEM) and chemical analysis was conducted using Fourier Transform Infrared Spectroscopy (FTIR). Corrosion resistance was studied by means of Electrochemical Impedance Spectroscopy (EIS) and tafel... 

    Facile synthesis of cauliflower-like hydrophobically modified polyacrylamide nanospheres by aerosol-photopolymerization

    , Article European Polymer Journal ; Volume 83 , 2016 , Pages 323-336 ; 00143057 (ISSN) Shaban, M ; Ramazani, S. A. A ; Ahadian, M. M ; Tamsilian, Y ; Weber, A. P ; Sharif University of Technology
    Elsevier Ltd  2016
    Amphiphilic copolymers consist of hydrophilic and hydrophobic monomer units have attracted great technological attention recently, owing to their unique properties and their ability to stabilize various interfaces in aqueous systems. This paper presents a novel and facile approach to produce spherical polyacrylamide, polystyrene and hydrophobically modified polyacrylamide (HM-PAM), as one of the most important type of amphiphilic copolymers, using a continuous aerosol-photopolymerization for the first time. To this end, the monomer droplets were generated by an atomizer, then photopolymerization was initiated ‘‘in flight’’ by ultraviolet (UV) irradiation of the aerosol monomer droplets... 

    Electroosmotic flow in hydrophobic microchannels of general cross section

    , Article Journal of Fluids Engineering, Transactions of the ASME ; Volume 138, Issue 3 , 2016 ; 00982202 (ISSN) Sadeghi, M ; Sadeghi, A ; Saidi, M. H ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME)  2016
    Adopting the Navier slip conditions, we analyze the fully developed electroosmotic flow in hydrophobic microducts of general cross section under the Debye-Hückel approximation. The method of analysis includes series solutions which their coefficients are obtained by applying the wall boundary conditions using the least-squares matching method. Although the procedure is general enough to be applied to almost any arbitrary cross section, eight microgeometries including trapezoidal, double-trapezoidal, isosceles triangular, rhombic, elliptical, semi-elliptical, rectangular, and isotropically etched profiles are selected for presentation. We find that the flow rate is a linear increasing... 

    Edge-functionalization of graphene by polyglycerol; A way to change its flat topology

    , Article Polymer (United Kingdom) ; Volume 54, Issue 12 , 2013 , Pages 2917-2925 ; 00323861 (ISSN) Movahedi, S ; Adeli, M ; Fard, A. K ; Maleki, M ; Sadeghizadeh, M ; Bani, F ; Sharif University of Technology
    This work presents a procedure for functionalization of graphene sheets from edges by polyglycerol. Hyperbranched polyglycerol with a bi-dentate aromatic segment in its focal point was synthesized and used to sandwich graphene sheets from the cut-edges. Due to the hydrophobicity of the flat surface of the edge-functionalized graphenes and hydrophilicity of their edges, they changed their conformation from the extended- to the closed-state and formed nanocapsules in aqueous solutions. Spectroscopy and microscopy evaluations showed that the average size for nanocapsules is 300 nm. They were able to encapsulate hydrophobic molecules such as doxorubicin in aqueous solutions with a high loading... 

    Characterization of polymeric membranes for membrane distillation using atomic force microscopy

    , Article Desalination and Water Treatment ; Volume 51, Issue 31-33 , 2013 , Pages 6003-6008 ; 19443994 (ISSN) Shirazi, M. M ; Bastani, D ; Kargari, A ; Tabatabaei, M ; Sharif University of Technology
    Taylor and Francis Inc  2013
    As membrane distillation (MD) is an under-developed separation process, specific membranes for MD applications are not yet commercially available. Therefore, microporous polymeric membranes made of hydrophobic materials fabricated for microfiltration purposes are usually used for MD applications. Characterization of such kind of membranes is important in order to achieve a better in-depth understanding of their performance and to fabricate specific membranes for MD process. One of the emerging characterization methods is atomic force microscopy (AFM) analysis. AFM is a newly developed high-resolution method that is useful for studying the surface topography of various types of membranes, and... 

    An exploratory study on application of various classification models to distinguish switchable-hydrophilicity solvents based on 3D-descriptors

    , Article Separation Science and Technology (Philadelphia) ; Volume 56, Issue 5 , 2021 , Pages 961-969 ; 01496395 (ISSN) Shiri, M ; Shiri, F ; Sharif University of Technology
    Bellwether Publishing, Ltd  2021
    A set of solvents were classified into the switchable-hydrophilicity solvents (SHSs) and non-switchable-hydrophilicity solvents based on forming or not forming a biphasic mixture with water. SHSs have been developed to make the reaction and product separation processes easier. Herein, three classifier algorithms and various feature selection techniques relay on 3D-molecular descriptors to characterize chemicals and forecast their classes were employed. Cfs-SVM method was employed to perform a classification study. The importance of this study helps to understand more about the presence of hydrophobic groups, their position, and their shape in the molecule. © 2020 Taylor & Francis Group, LLC  

    Synthesis and Investigation on the Properties of Silica-Graphene Oxide Nanocomposite Coating

    , M.Sc. Thesis Sharif University of Technology Afzali, Neda (Author) ; Dolati, Abolghasem (Supervisor)
    The investigations on hydrophobic surfaces have attracted lots of intrests in science and technology. Silica sols have been used extensively in the area of producing hydrophobic coatings. On the other hand, carbon-based materials have attracted of a great deal of scientific interest in recent years. The purpose of this research is synthesis and investigation on the properties of Silica- Graphene Oxide nanocomposite coating.Graphene Oxide synthesized by using Hummer’s method. Silica nanoparticles were prepared using sol-gel process and tetraethylorthosilicate (TEOS) as precursor. The surface hydroxyl groups of silica nanoparticles are replaced with Methyl groups by treatment with... 

    Synthesis, Characterization and Hydrophobicity of Teflon Coated Tungsten Nanostructure Thin Films

    , M.Sc. Thesis Sharif University of Technology Bayat, Amir (Author) ; Moshfegh, Ali Reza (Supervisor) ; Azimirad, Rouhollah (Supervisor)
    Hydrophobic and superhydrophobic surfaces find many applications in different fields of science. The aerospace industry is one such field that can take the advantage of superhydrophobicity for anti-icing coatings. In order to make hydrophobic and superhydrophobic surfaces on hydrophilic materials, two-step process is usually need, at first, making a rough surface and then modifying it with hydrophobic coatings with low surface free energy. In this research, we have used glancing angle deposition (GLAD) RF sputtering technique to fabricate Teflon coated tungsten on glass substrate for obtaining hydrophobic surface. GLAD approach is a method to grow structures such as nanorods and zigzag... 

    Vacuum enhanced membrane distillation for trace contaminant removal of heavy metals from water by electrospun PVDF/TiO2 hybrid membranes

    , Article Korean Journal of Chemical Engineering ; Volume 33, Issue 7 , 2016 , Pages 2160-2168 ; 02561115 (ISSN) Moradi, R ; Monfared, S. M ; Amini, Y ; Dastbaz, A ; Sharif University of Technology
    Springer New York LLC 
    Electrospun hybrid membranes were synthesized using electrospinning of Poly (vinylidenefluoride) - titanium tetraisopropoxide (PVDF-TTIP) sol. Asymmetric post-treatment of membrane conducted for deprotonation of titanate and making hydrophilic/hydrophobic dual characteristics. The membranes were characterized by various methods such as wettability, scanning electron microscopy, infrared spectroscopy, X-ray diffraction and liquid entry pressure tests. For evaluating the separation performance, these membranes were applied in the VMD process to treat water heavy metal contaminants. The effects of operating parameters such as flow rate, temperature and membrane properties as porosity, on... 

    Ab initio study of solvent effects on rate of 1,3-dipolar cycloadditions of benzonitrile oxide and various dipolarophiles

    , Article Journal of Chemical Research - Part S ; Issue 2 , 2003 , Pages 91-95 ; 03082342 (ISSN) Rajaeian, E ; Monajjemi, M ; Gholami, M. R ; Sharif University of Technology
    Ab initio molecular orbital calculations have been used to investigate the structures and the transition states of 1,3-dipolar cycloadditions between benzonitrile oxide with ethylene, cyclopentene, acrylonitrile and tetracyanoethylene in heptane and water: calculations reveal enhanced hydrogen bonding of a water molecule to the transition states for the cycloaddition 1,3-dipolar of reaction of benzonitrile oxide with cyclopentene, the optimal interaction energies being 0.7 kcal/mol more favourable for hydrogen bonding to the oxygen atom in the transition states than for the reactants  

    Geometry selects highly designable structures

    , Article Journal of Chemical Physics, Woodbury, NY, United States ; Volume 113, Issue 15 , 2000 , Pages 6437-6442 ; 00219606 (ISSN) Shahrezaei, V ; Ejtehadi, M. R ; Sharif University of Technology
    American Inst of Physics  2000
    The designability of structures in a two-dimensional hydrophobic-polar (HP) pair contact lattice model in a wide range of intermonomer interaction parameters was studied by considering HP constraints. The designability of all structures was clarified by enumerating all sequences of length 20. Results confirm that changing the intermolecular interactions affects the structure designability and also chooses the search space of the native state but the set of HDSs is invariant  

    Efficient biodegradation of naphthalene by a newly characterized indigenous achromobacter sp. FBHYA2 isolated from Tehran oil refinery complex

    , Article Water Science and Technology ; Volume 66, Issue 3 , March , 2012 , Pages 594-602 ; 02731223 (ISSN) Farjadfard, S ; Borghei, S. M ; Hassani, A. H ; Yakhchali, B ; Ardjmand, M ; Zeinali, M ; Sharif University of Technology
    IWA Pub  2012
    A bacterial strain, FBHYA2, capable of degrading naphthalene, was isolated from the American Petroleum Institute (API) separator of the Tehran Oil Refinery Complex (TORC). Strain FBHYA2 was identified as Achromobacter sp. based on physiological and biochemical characteristics and also phylogenetic similarity of 16S rRNA gene sequence. The optimal growth conditions for strain FBHYA2 were pH 6.0, 30°C and 1.0% NaCl. Strain FBHYA2 can utilize naphthalene as the sole source of carbon and energy and was able to degrade naphthalene aerobically very fast, 48 h for 96% removal at 500 mg/L concentration. The physiological response of Achromobacter sp., FBHYA2 to several hydrophobic chemicals... 

    Physiological temperature has a crucial role in amyloid beta in the absence and presence of hydrophobic and hydrophilic nanoparticles

    , Article ACS Chemical Neuroscience ; Volume 4, Issue 3 , December , 2013 , Pages 375-378 ; 19487193 (ISSN) Ghavami, M ; Rezaei, M ; Ejtehadi, R ; Lotfi, M ; Shokrgozar, M. A ; Abd Emamy, B ; Raush, J ; Mahmoudi, M ; Sharif University of Technology
    Amyloid beta fibrillation can lead to major disorder of neurons processes and is associated with several neuronal diseases (e.g., Alzheimer's disease). We report here an importance of slight temperature changes, in the physiological range (35-42 °C), on the amyloid fibrillation process in the presence and absence of hydrophilic (silica) and hydrophobic (polystyrene) nanoparticles (NPs). The results highlight the fact that slight increases in temperature can induce inhibitory and acceleratory effects of hydrophobic and hydrophilic NPs on the fibrillation process, respectively. Using further in vivo considerations, the outcomes of this study can be used for considerable modifications on the... 

    Stimulus-responsive liposomes as smart nanoplatforms for drug delivery applications

    , Article Nanotechnology Reviews ; 2017 ; 21919089 (ISSN) Sahandi Zangabad, P ; Mirkiani, S ; Shahsavari, S ; Masoudi, B ; Masroor, M ; Hamed, H ; Jafari, Z ; Davatgaran Taghipour, Y ; Hashemi, H ; Karimi, M ; Hamblin, M. R ; Sharif University of Technology
    Liposomes are known to be promising nanoparticles (NPs) for drug delivery applications. Among different types of self-assembled NPs, liposomes stand out for their non-toxic nature, and their possession of dual hydrophilic-hydrophobic domains. Advantages of liposomes include the ability to solubilize hydrophobic drugs, the ability to incorporate different hydrophilic and lipophilic drugs at the same time, lessening the exposure of host organs to potentially toxic drugs and allowing modification of the surface by a variety of different chemical groups. This modification of the surface, or of the individual constituents, may be used to achieve two important goals. Firstly, ligands for active... 

    Superhydrophobic surfaces with a dual-layer micro- and nanoparticle coating for drag reduction

    , Article Energy ; Volume 125 , 2017 , Pages 1-10 ; 03605442 (ISSN) Taghvaei, E ; Moosavi, A ; Nouri Borujerdi, A ; Daeian, M. A ; Vafaeinejad, S ; Sharif University of Technology
    Elsevier Ltd  2017
    We propose a facile and cost effective method for fabricating superhydrophobic surfaces with significant drag reduction in a wide velocity range. A dual structure superhydrophobic aluminum surface with a hydrophobic Al2O3micro- and nanoparticle coating and also another superhydrophobic surface with a nanoparticle layer coating are fabricated. Then, the resulted drag from each of these surfaces is measured carefully in different velocities and compared with the drag of the as-received aluminum surface. Our results reveal that the surface with the dual structure experiences drag reduction in a wider velocity range compared with the nanoparticle coated sample. Drag reduction of the dual... 

    Surface wettability effect on the rising of a bubble attached to a vertical wall

    , Article International Journal of Multiphase Flow ; Volume 109 , 2018 , Pages 178-190 ; 03019322 (ISSN) Javadi, K ; Davoudian, S. H ; Sharif University of Technology
    This paper deals with the dynamics of rising bubbles attached to a vertical wall under different wettability conditions. Even though, bubbles rising freely in a liquid have extensively been studied, bubbles attached to a wall have not been fully understood. Therefore, in this work, rising bubbles attached to a vertical wall were numerically investigated by applying the ALE method along with adaptive mesh refinement schemes to properly resolve the bubble interface and its deformation. To consider wall wettability effects, different contact angles of 45° 90° and 105° were considered along with the case of freely rising bubbles. The problem was carried out at different Bond numbers of 0.27,... 

    Stimulus-responsive liposomes as smart nanoplatforms for drug delivery applications

    , Article Nanotechnology Reviews ; Volume 7, Issue 1 , 2018 , Pages 95-122 ; 21919089 (ISSN) Sahandi Zangabad, P ; Mirkiani, S ; Shahsavari, S ; Masoudi, B ; Masroor, M ; Hamed, H ; Jafari, Z ; Davatgaran Taghipour, Y ; Hashemi, H ; Karimi, M ; Hamblin, M. R ; Sharif University of Technology
    Walter de Gruyter GmbH  2018
    Liposomes are known to be promising nanoparticles (NPs) for drug delivery applications. Among the different types of self-assembled NPs, liposomes stand out for their non-toxic nature and their possession of dual hydrophilic-hydrophobic domains. The advantages of liposomes include the ability to solubilize hydrophobic drugs, the ability to incorporate different hydrophilic and lipophilic drugs at the same time, lessening the exposure of host organs to potentially toxic drugs and allowing modification of the surface by a variety of different chemical groups. This modification of the surface, or of the individual constituents, may be used to achieve two important goals. First, ligands for... 

    Inverse emulsion polymerization of triple monomers of acrylamide, maleic anhydride, and styrene to achieve highly hydrophilic–hydrophobic modified polyacrylamide

    , Article Journal of Applied Polymer Science ; Volume 136, Issue 29 , 2019 ; 00218995 (ISSN) Lalehgani, Z ; Ramazani S. A., A ; Tamsilian, Y ; Shirazi, M ; Sharif University of Technology
    John Wiley and Sons Inc  2019
    The purpose of this study was the production of copolymers and terpolymers with highly hydrophilic–hydrophobic properties, using inexpensive and available monomers as potential enhancing oil recovery (EOR) and water production control agents for high-temperature and high-salinity (HTHS) oil reservoirs. For this purpose, several copolymers and terpolymers with different molar percentage of acrylamide/styrene, acrylamide/maleic anhydride, and acrylamide/styrene/maleic anhydride were synthesized by the inverse emulsion polymerization technique. The presence of hydrophobic styrene and hydrophilic maleic anhydride monomers in the copolymer and terpolymer structure, provided some unique properties...