Sharif Digital Repository

Thin liquid films on solid substrates are of considerable relevance in widespread of natural and technological fields. Examples are eye irrigation, biological cell interaction, tertiary oil recovery, coating, painting, lubrication, integrated circuits, micro- and nano-electronic devices, to name just a few. It is well known that liquid films are not always stable and there are verities of factors that may destabilize and expose the film to dynamical processes which leads to removal of the liquid from the substrate, the phenomenon so-called dewetting, either by nucleation or spinodal mechanisms. In many cases dewetting is destructive but there are several situation in which dewetting turns... 

By considering the effect of surface/interface stress, classical problems of the interaction between dislocations and inhomogeneities are addressed. Especifically two distinct problems are solved, the first one is consisted of an edge dislocation located near an elliptical nano-inhomogeneity and the second one hasa screw dislocation laid in the core-shell nanowire. The stress field as well as the image force on the dislocation are calculated and discussed in detail. Results show that by decreasing the dimension of the problem to nano-scale, the differences between classical elasticity and surface approachincrease rapidly. By considering the effect of the surface/interface stress, new... 

Water transportation through carbon nanotubes is key for designing nanodevices. The directed transport of water molecules through a rotating charged carbon nanotube (CNT) is investigated by molecular dynamics simulations. It is found that the net flux of continuous unidirectional water flow depended sensitively on the charge distribution, charge density and rotation of the CNT. we find that for a constant charge density, the water flux increases with the increase of the charge difference. Besides, we find that the water flux shows a nonlinear dependence on the angular velocity of the rotation. The rotation of the CNT with low angular velocities, can not generate a continuous water flux. The... 

In the first part of this thesis, limitations on magnetic field distribution are studied. After that methods of creating high gradient magnetic field and limitations on it is discussed. In the second part, magnetic properties of materials and the effect of particle shape and size on these properties are studied. In this part a comprehensive analysis on demagnetizing field inside magnetic bodies is also conducted and its dependence on material susceptibility and shape is discussed. At the end of this part the effect of particle shape and size on its hysteresis loop is demonstrated theoretically, practically and by computer simulation. In order to ... 

The electro-elastic fields of nano-sized piezoelectric structures are considered based on the non-classical continuum theory. Nowadays because of increasing the application of piezoelectric materials in nano technology and exclusive properties of this kind of materials, they can use as the ingredients of electromechanical systems. Therefore, the determination of induced electro-mechanical fields is important. In this study the constitutive equations based on non-classical continuum theory and general anisotropy for the elastic, piezoelectric and dielectric tensors are considered, and the electromechanical fields are determined using the micromechanical method. Furthermore, the size effects... 

In recent years, the use of mesoporous silica nanoparticles as carriers of biological agents has increased. The use of nanometer dimensions in intra-body applications not only hides the particles from the view of macrophages and the body's immune system, but also causes the particles to enter the cells more easily through endocytosis. Template removal method is the most common method in the synthesis of mesoporous silica. In this method, the orderly arrangement of pattern-forming molecules is used to form pores. Until now, various types of organic materials have been used as pattern materials. The main goal is the synthesis of nanoparticles with the largest size of holes and the largest... 

A theory of gradient elasticity is used and numerically implemented by a meshless method that is called reproducing kernel particle method (RKPM) to model size effects. Some of the problems are modeled under the consideration of gradient elasticity for the first time and all of them are also modeled with classical elasticity to compare with gradient elasticity. First of all, the RKPM formulation and computing the amount of shape functions and requisite derivatives will be explained with details and a mathematical innovation that will decrease the computational cost seriously proposed for the first time. Several 1D and 2D shape functions with first and second derivatives that are resulted... 

Electroless coating is a chemical reduction process which depends on the catalytic reduction. In this study, the influences of different concentrations, stirring rate, pH and heat treatment of Al2O3 and SiO2 Nano sized particles in the bath on deposition rate, hardness, wear resistant, surface morphology and corrosion behavior of the Ni-P-Al2O3-SiO2 composite coatings have been investigated. The microstructure was investigated by field emission scanning electron microscopy (FESEM) and among the nanoparticles SiO2 and Al2O3 have drawn attention due to their high hardness, availability, particles distribution and reduced cost. The amount of Al2O3 and SiO2 was examined by Energy Dispersive... 

The main purpose of this study is simulation of in-situ release of nano-size coated polymer particles at the water-oil interface during the polymer flooding. Reaching at the flooding interface, the hydrophobic coating starts dissolving into the oil phase. Subsequently, the hydrophilic core polymer starts diffusing back and simultaneously solves into the water phase and increase the in-situ viscosity of the flooding interface. Because of the in-situ release of the polymer and consequently the viscosity reduction of the injected fluid, the driving force for injection of the polymer as well as the amount of polymer used in flooding will reduce. In addition, smart coating can decrease the... 

This thesis presents a research on the physical behavior of water inside carbon nanotubes (CNTs). Molecular simulations are carried out using the Monte Carlo method in the canonical and grand canonical ensembles. Due to the difference between the inter-molecular forces in the axial and radial directions, the anisotropic pressure tensor is calculated for water confined inside the CNTs with the diameters of 0.88, 1.08, 1.28, and 1.48 nm at different densities using the Monte Carlo simulations. Using the assumption of effective extended Lennard-Jones interactions between the nearest neighbors, a set of new equations of state for water confined inside the CNTs is derived and shown to be...