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    Wettability alteration properties of fluorinated silica nanoparticles in liquid-loaded pores: An atomistic simulation

    , Article Applied Surface Science ; Volume 371 , 2016 , Pages 349-359 ; 01694332 (ISSN) Sepehrinia, K ; Mohammadi, A ; Sharif University of Technology
    Elsevier  2016
    Abstract
    Control over the wettability of reservoir rocks is of crucial importance for enhancing oil and gas recovery. In order to develop chemicals for controlling the wettability of reservoir rocks, we present a study of functionalized silica nanoparticles as candidates for wettability alteration and improved gas recovery applications. In this paper, properties of fluorinated silica nanoparticles were investigated in water or decane-loaded pores of mineral silica using molecular dynamics simulation. Trifluoromethyl groups as water and oil repellents were placed on the nanoparticles. Simulating a pore in the presence of trapped water or decane molecules leads to liquid bridging for both of the... 

    Increase in the β-sheet character of an amyloidogenic peptide upon adsorption onto gold and silver surfaces

    , Article ChemPhysChem ; Volume 18, Issue 5 , 2017 , Pages 526-536 ; 14394235 (ISSN) Soltani, N ; Gholami, M. R ; Sharif University of Technology
    Wiley-VCH Verlag  2017
    Abstract
    Fibrillation of amyloid beta (Aβ) peptide is the hallmark of Alzheimer's disease. Given that interactions at the bio–nano interface affect the fibrillation tendency of this peptide, an understanding of the interactions at Aβ peptide–inorganic surfaces on the microscopic level can help to determine the possible neurotoxicity of nanoparticles. Here, the interactions between a fibril-forming peptide, Aβ25–35, and (111) and (100) facets of gold and silver surfaces have been studied by conducting atomistic molecular dynamics simulations. The obtained results indicate that the adsorption onto gold and silver surfaces force the peptide into the β-sheet-rich conformations, which is prone to... 

    Increasing the interfacial adhesion in poly(methyl methacrylate)/carbon fibre composites by laser surface treatment

    , Article Polymers and Polymer Composites ; Volume 14, Issue 6 , 2006 , Pages 585-589 ; 09673911 (ISSN) Nematollahzadeh, A ; Mousavi, S. A. S ; Tilaki, R. M ; Frounchi, M ; Sharif University of Technology
    Rapra Technology Ltd  2006
    Abstract
    The impact strength of poly(methyl methacrylate)/caibon (long) fibre composites for denture prosthesis applications was improved by fibre surface treatment. The carbon fibre surfaces were modified by Nd:YAG laser irradiation at 1064 nm wavelength. Laser light intensity was adjusted at 100 mj per pulse that only changed the fibre surface roughness and did not lead to fibre rupture, as verified by scanning electron microscopy. Increased surface roughness of the fibres improved the adhesion of poly(methyl methacrylate) to the fibre surface. Adhesion between the fibres and poly(methyl methacrylate) was evaluated by a tear-off method and by scanning electron microscopy. The results also suggest... 

    Interaction of spherical colloidal particles in nematic media with degenerate planar anchoring

    , Article Soft Matter ; Volume 7, Issue 3 , Nov , 2011 , Pages 1107-1113 ; 1744683X (ISSN) Mozaffari, M. R ; Babadi, M ; Fukuda, J. I ; Ejtehadi, M. R ; Sharif University of Technology
    2011
    Abstract
    The interaction between two spherical colloidal particles with degenerate planar anchoring in a nematic media is studied by numerically minimizing the bulk Landau-de Gennes and surface energy using a finite element method. We find that the energy achieves its global minimum when the particles are in close contact and forming an angle = 28°± 2 with respect to the bulk nematic director, in agreement with the experiments. Although the quadrupolar structure of the director field is preserved in the majority of configurations, we show that for smaller orientation angles and at smaller inter-particle separations, the axial symmetry of the topological defect-pairs is continuously broken, resulting... 

    On the rate of oxidation of co on La2O3 doped NiO/Al2O3 catalysts: An artificial neural network approach

    , Article Reaction Kinetics and Catalysis Letters ; Volume 85, Issue 2 , 2005 , Pages 347-353 ; 01331736 (ISSN) Ardakani, S. J ; Gobal, F ; Sharif University of Technology
    2005
    Abstract
    The rate constants of the oxidation of CO on a number of pure and La 2O3 doped NiO/Al2O3 solid catalysts were correlated with the mole percent of dopant, calcinations temperature, surface area, pore volume and pore mouth diameter by an artificial neural network simulator. The cross validation method had to be used due to the scarcity of the data. A three-layer network with 3 nodes in the hidden layer was found to simulate the system well. © Akadémiai Kiadó, Budapest. All rights reserved  

    Development of injectable hydrogels based on human amniotic membrane and polyethyleneglycol-modified nanosilicates for tissue engineering applications

    , Article European Polymer Journal ; Volume 179 , 2022 ; 00143057 (ISSN) Kafili, G ; Tamjid, E ; Niknejad, H ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    Recently, decellularized amniotic membrane-derived hydrogels (DAMHs) have received significant attention for wound care, ocular surface reconstruction, and chondral healing. Despite the advantages of DAMHs for tissue engineering (TE), the loss of structural components during the decellularization process mitigates their mechanical strength and thus limits their practical application. Herein, we present a method for the surface modification of two-dimensional nanosilicates (laponite) as a rheological modifier to tailor the properties of DAMHs. Results show that after introducing nanosilicates, severe aggregation of the nanoparticles occurs, owing to the shielding effect of ions on the surface... 

    Effect of morphology-based defect structure of ZnO nanostructures in photo-degradation of organic dye

    , Article Materials Research Society Symposium Proceedings ; Vol. 1672 , 2014 ; ISSN: 02729172 Shidpour, R ; Vosoughi, M ; Simchi, A ; Ghanbari, F ; Sharif University of Technology
    Abstract
    The fabrication of strong photocatalysts applied to the degradation of organic pollutants is necessary in environmental applications. In a single-stage method, acetate precursor and poly vinyl pyrolydine are used to produce ZnO nanostructures with various morphologies in annealing temperatures ranging from 300 °C to 900 oC. The physical properties of the prepared nanostructures were characterized by SEM, XRD and PL spectroscopy. The SEM images exhibit a variety of the as-prepared hexagonal zinc oxides including wires, rods, particles and porous network of welded particles of ZnO nanoparticles. The results of the photocatalytic degradation of methylene blue as an organic dye in aqueous... 

    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
    2013
    Abstract
    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... 

    Surface energy effects on the yield strength of nanoporous materials containing nanoscale cylindrical voids

    , Article Mechanics of Materials ; Volume 42, Issue 9 , September , 2010 , Pages 852-862 ; 01676636 (ISSN) Goudarzi, T ; Avazmohammadi, R ; Naghdabadi, R ; Sharif University of Technology
    2010
    Abstract
    Surfaces and interfaces behave differently from their bulk counterparts especially when the dimensions approach small scales. The recent studies have shown that the surface/interface free energy (surface stress) plays an important role in the effective mechanical properties of solids with nanosized inhomogeneities. In this work, within a micromechanical framework, the effect of surface stress is taken into account to obtain a macroscopic yield function for nanoporous materials containing cylindrical nanovoids. Gurtin-Murdoch model of surface elasticity is incorporated in the generalized self-consistent method to obtain a closed-form expression for the transverse shear modulus of transversely... 

    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
    Abstract
    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... 

    Morphological and mechanical properties of polyamide 6/nanodiamond composites prepared by melt mixing: effect of surface functionality of nanodiamond

    , Article Polymer International ; Volume 66, Issue 4 , 2017 , Pages 557-565 ; 09598103 (ISSN) Karami, P ; Shojaei, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2017
    Abstract
    Surface chemistry of as-received nanodiamond (ND) was first tailored by dry thermal oxidation to obtain carboxylated ND (ND-COOH) and by wet chemistry to obtain ethylenediamine-functionalized ND (ND-EDA). Then, the surface-functionalized ND particles were dispersed in polyamide 6 (PA6) using the melt-mixing method. Transmission optical and scanning electron microscopies indicated a fine dispersion at low nanodiamond concentrations, e.g. 0.25 wt%, particularly with ND-EDA. Differential scanning calorimetry revealed that ND-EDA favoured the α-phase crystal and enhanced the degree of crystallinity of PA6. Experimental data indicated that ND-EDA had considerably improved tensile properties at... 

    Application of a free volume model in correlating thermodynamic properties of β-lactam, tetracycline, fluoroquinolone and chloramphenicol antibiotic groups in associating fluids

    , Article Chemical Engineering Research and Design ; Volume 87, Issue 3 , 2009 , Pages 335-342 ; 02638762 (ISSN) Pazuki, G. R ; Taghikhani, V ; Vossoughi, M ; Alemzadeh, I ; Sharif University of Technology
    2009
    Abstract
    In this work, an expression for the free volume Gibbs energy model based on the local composition concept (LCC) has been proposed in correlating the solubility, the partitioning and the surface tension of β-lactam, tetracycline, fluoroquinolone and chloramphenicol antibiotic groups in water, alcohol, ketone, trihalomethane, ether and ester solvent groups. Similar to the LCC models the proposed model has two combinatorial and residual terms. The extended Guggenheim model is used as combinatorial term and a new local composition-based model, which is the extended local area fraction NRTL-NRF model, is proposed for the residual term. The results obtained from the proposed model have been... 

    Condensation enhancement on hydrophobic surfaces using electrophoretic method and hybrid paint coating

    , Article Heat Transfer Engineering ; 26 August , 2020 Najafpour, S ; Moosavi, A ; Najafkhani, H ; Sharif University of Technology
    Taylor and Francis Ltd  2020
    Abstract
    Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle... 

    On thermoelastic fields of a multi-phase inhomogeneity system with perfectly/imperfectly bonded interfaces

    , Article International Journal of Solids and Structures ; Volume 45, Issue 22-23 , 2008 , Pages 5831-5843 ; 00207683 (ISSN) Hatami Marbini, H ; Mohammadi Shodja, H ; Sharif University of Technology
    2008
    Abstract
    The stress fields of cylindrical and spherical multi-phase inhomogeneity systems with perfect or imperfect interfaces under uniform thermal and far-field mechanical loading conditions are investigated by use of the Boussinesq displacement potentials. The radius of the core inhomogeneity and the thickness of its surrounding coatings are arbitrary. The discontinuities in the tangential and normal components of the displacement at the imperfect interfaces are assumed to be proportional to the associated tractions. In this work, for the problems where the phases of the inhomogeneity system are homogeneous, the exact closed-form thermo-elastic solutions are presented. These solutions along with a... 

    Condensation enhancement on hydrophobic surfaces using electrophoretic method and hybrid paint coating

    , Article Heat Transfer Engineering ; Volume 42, Issue 18 , 2021 , Pages 1557-1572 ; 01457632 (ISSN) Najafpour, S ; Moosavi, A ; Najafkhani, H ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    Condensation heat transfer on stainless steel tube utilizing superhydrophobic coatings was investigated. The electrophoretic deposition and spraying methods were employed to coat the tubes’ outer surface. The mixture that was synthesized for spray coating was a hybrid paint. It incorporated polyurethane matrix and a colloidal suspension containing organic nanoparticles. The hybrid paint had a proper adhesion to the substrate which caused more durability compared to the electrophoretic coating. The agglomeration of nanoparticles in the hybrid paint caused the formation of particles with larger size compared to the particles in the electrophoretic coating. Consequently, contact angle... 

    Characterization of etched glass surfaces by wave scattering

    , Article Surface and Interface Analysis ; Volume 37, Issue 7 , 2005 , Pages 641-645 ; 01422421 (ISSN) Jafari, G. R ; Mahdavi, S. M ; Iraji Zad, A ; Kaghazchi, P ; Sharif University of Technology
    2005
    Abstract
    The roughness of glass surfaces after different stages of etching is investigated by reflection measurements with a spectrophotometer, light scattering, atomic force microscopy (AFM, on a small scale) and profilometry (on a large scale). The results suggest that there are three regimes during etching, according to their optical reflectivity and roughness. The first and the second regimes are studied by the Kirchhoff theory and the third one is studied by the optical geometric theory. Also, the roughness obtained by optical scattering is compared with the AFM results. Copyright © 2005 John Wiley & Sons, Ltd  

    Adsorption dynamics of surface-modified silica nanoparticles at solid-liquid interfaces

    , Article Langmuir ; Volume 38, Issue 41 , 2022 , Pages 12421-12431 ; 07437463 (ISSN) Khazaei, M. A ; Bastani, D ; Mohammadi, A ; Kordzadeh, A ; Sharif University of Technology
    American Chemical Society  2022
    Abstract
    Understanding the adsorption dynamics of nanoparticles at solid-liquid interfaces is of paramount importance to engineer nanoparticles for a variety of applications. The nanoparticle surface chemistry is significant for controlling the adsorption dynamics. This study aimed to experimentally examine the adsorption of surface-modified round-shaped silica nanoparticles (with an average diameter of 12 nm), grafted with hydrophobic (propyl chains) and/or hydrophilic (polyethylene glycol chains) agents, at an aqueous solution-silica interface with spherical soda-lime glass beads (diameter of 3 mm) being used as adsorbents. While no measurable adsorption was observed for solely hydrophobic or... 

    Correlation between surface roughness and hydrophobicity of GLAD RF sputtered PTFE/W/Glass nanorod thin films

    , Article Vacuum ; Vol. 101, issue , March , 2014 , p. 279-282 Bayat, A ; Ebrahimi, M ; Moshfegh, A. Z ; Sharif University of Technology
    Abstract
    In this research, we have used glancing angle deposition (GLAD) RF sputtering technique with various angular speeds ranging from 5 to 30 RPM to fabricate polytetrafluoroethylene (PTFE, Teflon) coated Tungsten on glass substrate for producing hydrophobic surface. According to scanning electron microscopy (SEM) observations, Tungsten nanorods were formed on the substrate with average diameter and length of about ∼50 nm and 300 nm, respectively. Hydrophobic property of W/Glass and PTFE/W/Glass systems was investigated by water contact angle measurements and we have found that the contact angle varied with the substrate angular speed. Maximum contact angle of 121 was measured for the... 

    Size-controlled synthesis of superparamagnetic iron oxide nanoparticles and their surface coating by gold for biomedical applications

    , Article Journal of Magnetism and Magnetic Materials ; Volume 324, Issue 23 , November , 2012 , Pages 3997-4005 ; 03048853 (ISSN) Maleki, H ; Simchi, A ; Imani, M ; Costa, B. F. O ; Sharif University of Technology
    2012
    Abstract
    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 [Fe 3 and Fe 2], the concentration of ammonium hydroxide as reducing agent, and molar ratio of water to surfactant. The biocompatibility of the obtained NPs, at various concentrations, was evaluated via... 

    A combined first principles and analytical treatment for determination of the surface elastic constants: Application to Si(001) ideal and reconstructed surfaces

    , Article Philosophical Magazine Letters ; Volume 92, Issue 1 , Sep , 2012 , Pages 7-19 ; 09500839 (ISSN) Ojaghnezhad, F ; Shodja, H. M ; Sharif University of Technology
    2012
    Abstract
    Behavior of nanostructures, which are characterized by a large surface-to-volume ratio, is greatly influenced by their surface parameters, such as surface elastic moduli tensor. Accurate determination of the surface elastic constants by first principles is of particular interest. To this end, through consideration of the fundamental thermodynamic arguments for free solid surfaces, an analytical formulation for the change in specific Helmholtz surface free energy is developed. Relating this formulation to the corresponding energy calculated via first principles leads to the determination of the surface elastic moduli tensor. The surface mechanical properties, namely surface energy, surface...