Loading...
Search for:
hydrophobicity
0.007 seconds
Total 177 records
Effect of Superhydrophobic Materials Application on the Car Body to Reduce Drag
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor) ; Khodaygan, Saeed ($item.subfieldsMap.e)
Abstract
Considering the importance of environmental issues and the limitation of fuel supplies in the world, car issues have become one of the most important debates of the day. The methods used to reduce fuel consumption and emissions of greenhouse gases are primarily aimed at changing vehicle structure to reduce drag. An external body shape has been developed to reduce drag forces over the years. Due to the existence of limitations in the actual conditions of the theory, such as the beauty and convenience production, other methods should be examined. In this study, the structure of superhydrophobic properties materials with the emphasis on innovation has been considered. In order to investigate...
Development of Particulate Zinc-Iron/PTFE Composite and Nanocomposite Coatings Using Electrodeposition
, M.Sc. Thesis Sharif University of Technology ; Ghorbani, Mohammad (Supervisor)
Abstract
Electrodeposition is an old, well known and conventional science surface modification method to improve the surface characteristics, decorative and functional, of a wide variety of materials. This science is considered in nanotechnology as a bottom-up method for fabrication of one, two and three-dimensional nanomaterials. A great variety of secondary components can be added to plating baths resulting in metallic matrix composite and nanocomposite coatings production. Low amounts of iron addition for alloying zinc coatings, significantly increases the corrosion resistance of this generally used metal economically. Superhydrophobic coatings on metallic substrates have shown, during the past...
Numerical Modeling of Electroosmotic Flow of Viscoelastic Fluids in Hydrophobic Microducts
, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Hassan (Supervisor) ; Kazemzadeh Hannani, Siamak (Co-Advisor)
Abstract
The integrated development of small-scale electronic and mechanical systems has drawn attention, since they lead to increase in speed and decrease in volume of industry dimensions in the manufacturing sector. That is why microelectromechanical systems are highly considered. MEMS are widely used in Microfluidic systems that can be used in medicine, biology and drug injection. Due to the fact that consistent fluid velocity is necessary in biological applications, electroosmotic flow is more important than ever. To investigate the behavior of biofluids, Newtonian models cannot be used and it is required to use models that predict the behavior of these fluids accurately. In this research...
, M.Sc. Thesis Sharif University of Technology ; Mosavi, Abbas (Supervisor) ; Shojaei, Akbar (Co-Advisor)
Abstract
In this work nanocomposite CNT/polysulfone and CNT/polyethersulfone membranes for membrane contactor application in gas separation were fabricated. The two types of CNTs used for chemical and physical separation of H2S from a mixture of CH4 an H2S, had the outer diameter of 20-30nm and 50-100nm. One of the greatest concerns about using membrane contactors for gas separation applications is the wetting of membranes which consequently leads to decrease in separation performance. The aim of this study is to enhance the hydrophobicity of membranes by mixing hydrophobic carbon nanotubes in the polymeric matrix. The effect of factors like type of the polymer, diameter of the carbon nanotube and...
Modeling of a glucose sensitive composite membrane for closed-loop insulin delivery
, Article Journal of Membrane Science ; Volume 335, Issue 1-2 , 2009 , Pages 21-31 ; 03767388 (ISSN) ; Wu, X. Y ; Sharif University of Technology
2009
Abstract
A theoretical model was developed to describe a dynamic process involving an enzymatic reaction and diffusion of reactants and product inside glucose sensitive composite membrane. The composite membrane consisted of nanoparticles of a weakly acidic polymer, glucose oxidase and catalase embedded in a hydrophobic polymer. Time- and position-dependent diffusivity of involved species was considered in the model. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of pH, species concentrations, volume fraction of swollen gel, polymer and water-filled space, as well as solute diffusivity inside the membrane were predicted by the model as a function...
Drag Reduction Using Geometrically Structured Surfaces for Non-newtonian Multi-phase Fluids
, M.Sc. Thesis Sharif University of Technology ; Moosavi, Ali (Supervisor)
Abstract
With the advancement of the industry, microscale devices use due to its unique characteristics. On the other hand, it is essential to find ways to reduce drag inside microchannels because of The importance of energy. One of the methods is to optimize the contact surface using structured geometric surfaces. These hydrophobic surfaces reduce drag by trapping the air in roughness and creating a two-phase flow. The purpose of this project is to reduce the drag within the microchannel using structured geometric surfaces for non-Newtonian and multiphase flows. In most previous studies, with simplification, Newtonian and two-phase flows have been investigated. While most industrial fluids show...
In Situ Preparation of Acrylamide-Styrene- Maleic Anhydride Nano Hydrogels and Investigation of their Properties
, M.Sc. Thesis Sharif University of Technology ; Ramazani Saadatabadi, Ahmad (Supervisor)
Abstract
Among the methods for increasing chemical oil extraction,the polymeric flood method has the most commercialization capability.However,most commonly used polymers such as Hydrolyzed Polyacrylamide (HPAM) are not able to withstand high levels of salinity and high temperatures.To overcome these problems,in this project,new types of polymer nanostructures were synthesized with hydrophobic groups consisting of styrene (hydrophilic monomer) and malic anhydride (hydrophilic monomer) acrylamide (hydrophilic monomer). These polymers were synthesized by reversible mini-emulsion by adjusting the synthesis conditions for the purpose of producing the terpolymer with suitable conditions for tolerating...
Preparation of Hydrophobically Modified Copolymer Nanostructures as Viscosity Increasing Agents for Enhanced Oil Recovery
, Ph.D. Dissertation Sharif University of Technology ; Ramazani Saadatabadi, Ahmad (Supervisor) ; Ahadian, Mohammad Mahdi (Supervisor)
Abstract
Among chemical enhanced oil recovery (CEOR) methods, polymer flooding has the highest commercial potential. However, the most widely used conventional polymers such as partially hydrolyzed polyacrylamide (HPAM) are not applicable for high temperature and high-salinity reservoirs. To overcome above mentioned problems, in this work, a series of water- soluble hydrophobically modified polymers (HMPs) nanostructures comprising styrene (hydrophobic monomer) and acrylamide (hydrophilic monomer) have been produced. The copolymers have been synthesized using inverse miniemulsion synthesis method by adjusting synthesis conditions to optimize solution characteristic of copolymers for applying under...
The Effect of Hydrophobic Mismatch and Rigidity of Protein on the Cluster Formation of Transmembrane Proteins in Biomembranes
, M.Sc. Thesis Sharif University of Technology ; Ahmadiyan, Mohammad Taghi (Supervisor) ; Jalali, Mir Abbas (Co-Advisor) ; Khoshnood, Atefeh (Co-Advisor)
Abstract
Membrane proteins aggregation is a very important biological phenomenon in a variety of cell functions. It has been suggested that aggregation behavior of membrane proteins is influenced by the shape of the hydrophobic domain of the proteins, proteins hydrophobic mismatch and bilayer curvature. However, in this study by means of coarse grained membrane simulations it has been found that in thermal equilibrium, protein-protein interactions also depend on protein rigidity and structural strength. Based on simulation results, we have observed stable large clusters even in the absence of hydrophobic mismatch between lipids and proteins. Interestingly, our results also indicate that proteins with...
PVDF/SiO2 Nanocomposite Coating with Different Wettability in Contact with Oil and Water for phase Separation Propose
, M.Sc. Thesis Sharif University of Technology ; Dolati, Abolghasem (Supervisor)
Abstract
increased cohesion up to 4H pencil. Results of immersion test in water showed stability of coatings. Polarization test in naphtha and water mixture for stainless steel, copper and aluminum meshes demonstrated 98.89%, 86.25% and 66.6% protection efficiency respectively. In order to study of oil and water separation efficiency, mixtures of water and naphtha with different content of naphtha were used. Separation test for 200μm St.St mesh in different slopes demonstrated that changing of slop increase separation efficiency up to 95.5% for water and up to 100% for naphtha. Separation test for meshes with different pore size demonstrated that meshes with small pore size are more appropriate for...
Identification of a novel multifunctional ligand for simultaneous inhibition of amyloid-beta (aβ42) and chelation of zinc metal ion
, Article ACS Chemical Neuroscience ; Volume 10, Issue 11 , 2019 , Pages 4619-4632 ; 19487193 (ISSN) ; Shamloo, A ; Sharif University of Technology
American Chemical Society
2019
Abstract
Zinc binding to β-amyloid structure could promote amyloid-β aggregation, as well as reactive oxygen species (ROS) production, as suggested in many experimental and theoretical studies. Therefore, the introduction of multifunctional drugs capable of chelating zinc metal ion and inhibiting Aβ aggregation is a promising strategy in the development of AD treatment. The present study has evaluated the efficacy of a new bifunctional peptide drug using molecular docking and molecular dynamics (MD) simulations. This drug comprises two different domains, an inhibitor domain, obtained from the C-terminal hydrophobic region of Aβ, and a Zn2+ chelating domain, derived from rapeseed meal, merge with a...
A new approach for preparation of semi-transparent superhydrophobic coatings by ultrasonic spray hydrolysis of methyltrimethoxysilane
, Article Progress in Organic Coatings ; Volume 135 , 2019 , Pages 248-254 ; 03009440 (ISSN) ; Sabour Rouh Aghdam, A ; Nazari, M ; Bayat, A ; Saievar Iranizad, E ; Sharif University of Technology
Elsevier B.V
2019
Abstract
A novel nebulizing spray hydrolysis approach was used for preparation of semi-transparent superhydrophobic coatings. Methyltrimethoxysilane was dissolved in water:ethanol mixture and ultrasonically sprayed on different substrates. Superhydrophobic coatings with a contact angle (CA) as high as 164° and a sliding angle below 5° were obtained. FESEM and AFM revealed a hierarchical micro-nano binary structure with nanometric roughness of the coatings. The coated glass substrate exhibited transmittance close to 80%. The prepared coating showed great self-cleaning and water jet repellency behaviors. The superhydrophobicity of the samples was remained after subjecting to ambient conditions for 50...
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) ; Ramazani S. A., A ; Tamsilian, Y ; Shirazi, M ; Sharif University of Technology
John Wiley and Sons Inc
2019
Abstract
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...
Pressure drop reduction of power-law fluids in hydrophobic microgrooved channels
, Article Physics of Fluids ; Volume 31, Issue 7 , 2019 ; 10706631 (ISSN) ; Moosavi, A ; Sharif University of Technology
American Institute of Physics Inc
2019
Abstract
Using hydrophobic surfaces is one of the efficient methods to preserve energy in fluid transfer systems. However, the studies have been concentrated on Newtonian fluids despite the wide applications of non-Newtonian fluids in daily life and many industries such as the biological, foodstuff, chemical, petroleum, cosmetic, and lab on a chip fields. In this study, we consider power-law fluids as a typical example of non-Newtonian fluids and investigate the effect of hydrophobic microgrooves on the pressure drop in channels by utilizing the phase field method. We demonstrate that the optimum size of the rectangular microgrooves in which the maximum pressure drop reduction (PDR) happens for both...
Investigation of the impact of synthesized hydrophobic magnetite nanoparticles on mass transfer and hydrodynamics of stagnant and stirred liquid–liquid extraction systems
, Article Chemical Engineering Research and Design ; Volume 147 , 2019 , Pages 305-318 ; 02638762 (ISSN) ; Azizi, Z ; Bastani, D ; Sharif University of Technology
Institution of Chemical Engineers
2019
Abstract
The impact of modified magnetite nanoparticles (MMNPs)on hydrodynamics and mass transfer in liquid–liquid extraction process was assessed using a ternary chemical system of toluene-acetic acid–water. The organic phase which contained toluene and acetic acid was dispersed through water, and the mass transfer of acetic acid between two phases was investigated. The hydrophobic modified magnetite nanoparticles (MMNPs)prepared through an optimized in-situ method were added to the dispersed phase at different concentrations (0.001−0.005 wt%). Two separate conditions were provided in the experiments, i.e. stagnant and stirred continuous phase. The latter case was provided by a rotor at two...
Electrowetting-induced droplet jumping over topographically structured surfaces
, Article Materials Research Express ; Volume 6, Issue 8 , 2019 ; 20531591 (ISSN) ; Moosavi, A ; Shafii, M. B ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
We analyze the process of electrowetting-induced jumping of droplets away from a substrate with a geometric heterogeneity in the form of a cone and compare the results with those of a flat substrate in different wettabilities and hydrophobicities. Our results reveal that the droplet dynamics can be enhanced through applying a topographic heterogeneity. However, increasing the height of the cones does not always provide a better condition for the jumping and there is an optimum value for the height of the cones. The enhancement is due to the fact that more liquid flowing affects the pressure gradient within the droplet leading to a higher jumping velocity. It is shown that for the flat...
Experimental investigation on asphaltene biodegradability using microorganism: cell surface properties’ approach
, Article Journal of Petroleum Exploration and Production Technology ; Volume 9, Issue 2 , 2019 , Pages 1413-1422 ; 21900558 (ISSN) ; Ayatollahi, S ; Sharif University of Technology
Springer Verlag
2019
Abstract
Asphaltene precipitation is known to be responsible for serious challenges in oil industry such as wellbore damage, oil flow reduction, and plugging of transportation lines. The traditional methods to remove asphaltene deposition are mostly based on chemical solvent. One of the recent proposed green and cost–effect remedial methods is the application of microorganisms capable of consuming the heavy hydrocarbon chains. The cell surface hydrophobicity among others effectively manipulates the efficiency of the microorganism for asphaltene degradation. Besides, surface active agents would affect the microorganism adhesion and cell surface properties, and alters its hydrophobicity. Investigating...
Impact of ionic composition on modulating wetting preference of calcite surface: Implication for chemically tuned water flooding
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 568 , 2019 , Pages 470-480 ; 09277757 (ISSN) ; Badizad, M. H ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Despite previous researches on ion-engineered waterflooding (IEWF), its underlying mechanisms are not fully understood, particularly in presence of additives, like surfactants. This paper concerned with the contribution of Ca 2+ , Mg 2+ , SO 4 2- and Na + into altering wettability of oil-wet carbonate minerals towards water preferred state. As a mechanistic study, an experiment workflow was conducted to probe the impact of ions' concentrations in SW, either with or without sodium dodecylbenzene sulfonate (SDBS) which is an anionic surfactant. At first, contact angle (CA) measurement was carried out to evaluate the degree of wettability reversal upon treating the oil-aged calcite slabs with...
Droplet condensation and jumping on structured superhydrophobic surfaces
, Article International Journal of Heat and Mass Transfer ; Volume 134 , 2019 , Pages 680-693 ; 00179310 (ISSN) ; Moosavi, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
A complete cycle of droplet nucleation, growth, coalescence and jumping on different textured hydrophobic and superhydrophobic surfaces is studied for the first time, using a 2-D double distribution function thermal lattice Boltzmann method. First, droplet nucleation mechanism on smooth and rough surfaces is studied in detail. The results reveal the presence of cooled vapor layer instability in the condensation on completely smooth surfaces. However, on the rough surfaces and near the roughness a completely different mechanism is observed and the nucleation occurs on the roughness wedges. Also, the condensation on different textured surfaces with nominal contact angles θa=90°,120°,155° is...
Bilayered heparinized vascular graft fabricated by combining electrospinning and freeze drying methods
, Article Materials Science and Engineering C ; Volume 94 , 2019 , Pages 1067-1076 ; 09284931 (ISSN) ; Shamloo, A ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Small diameter vascular grafts (<6 mm) are highly demanded for patients suffering from severe occluded arteries to be used as a bypass or substituted conduit. Fabricating a graft with appropriate structural, mechanical and cell growth properties which has simultaneously anti-thrombogenic trait is a challenge nowadays. Here, we proposed a bilayer heparinized vascular graft that can mimic the structural and mechanical characteristics close to those of the native coronary artery by combining electrospinning and freeze drying methods. In this study, the inner layer was made by co-electrospinning of synthetic polymer, poly-caprolactone (PCL) and the natural polymer, gelatin (Gel). Also, heparin...