Sharif Digital Repository

One of the common methods used for treatment of gaseous radioactive wastes in nuclear waste management is adsorption process. Nanoporous materials have found great utility as sorption media because of their large internal surface area and more adsorption sites than other adsorbents, which caused the increasing attention of researchers to use them in the nuclear waste management. Hence in this study, the surface of nanoporous silicates of SBA-15 and MCM-41 modified with d-block elements of the periodic table such as silver, copper, zinc and nickel by wet impregnation method. After characterization by different techniques such as X-ray diffraction, nitrogen gas porosimetry, Fourier... 

Water treatment from industrial and domestic pollutants is one of the most important issues in recent decades. In the present research, simulation of water purification using single-layer graphene membrane were studied. The effects of nanopores diameter, applied pressure, concentration of contaminant ions, and functional groups on the amount of filtered water and ion rejection through the membrane were quantified. Contaminant ions including Na+, K+, Mg2+, Ca2+, and Cl- were dissolved in water. Based on the results, by increasing the pore diameter and applied pressure, more water would pass through the membrane. Also it was concluded that pores with functional groups have better performance... 

The aim of this research is to model the separation and transport of multi-component gas mixture through a nanoporous membrane by using pore network models (PNM).
The first part of this project represents the membrane simulating by means of the PNM. A three-dimensional network is used to represent the membrane’s pore space and it consists of two parts; pore and throat. The pores are the main parts of the network and their diameter is characterized according to the pore size distribution of the membrane. Every throat connects two pores and the number of throats which is connected to each pore is named "coordination number". Using a variety size of pores and throats leads to production of... 

Poly vinylidene fluoride (PVDF) as a fluorine polymer with acceptable thermal, chemical and physical property attractive create attention in membrane technology for water treatment application. However, with differential surface free energy between PVDF and water (∆G_s=30 mJ/m^2) PVDF polymer is divided as a hydrophobic materials, that is one of the basic problem for PVDF polymer. Due to its hydrophobicity the water molecules repulsion away from hydrophobic PVDF membrane surface as a spontaneous process with an entropy increasing and therefore pollutant molecules with hydrophobic functional group have tendency to adsorb onto membrane surface and dominate the boundary layer. In recent years... 

Translocation processes are ubiquitous in biology and biotechnology. Translocation of small molecules, e. g. sugar from maltoporin, metabolites through bacteria and macromolecules like proteins, from channels of cellular organelles and or RNA translocation though
nuclear pores are of vital importance for cellular metabolism. One of the important applications of translocation processes in biotechnology is to sense translocating macromolecules or small molecules by analyzing the current passing through natural or synthesis channels. Improving our knowledge about this process can also help us to develop new methods for designing the appropriate drugs. In this thesis by studying and... 

The advent of nanopore-based sensors based on resitive pulse sensing gave rise to a remarkable breakthrough in the detection and characterization of nanoscale species. The sensors can detect the species’concentration, size, and charge using the resistive pulse characteristics. Some strong correlations have been reported between the resitive pulse characteristics and the particle’s geometrical and physical properties. These correlations are commonly used to obtain information about the particles in commercial devices and research setups. The correlations, however, do not consider the simultaneous effect of influential factors such as particle shape, charge, and off-axis translocation, which... 

The aim of the current research is to study the process of making a solidstate nanopore by molding from PDMS polymer and to make a laboratory sample of a solidstate nanopore manufacturing device using this method. Solid-state nanopores are used to control ion transport in microfluidic channels,lab-on-a-chip detection to study nucleic acids and proteins, desalination, nanofluidic transistors,single-cell sensing tools, and particle classification. In general, the smaller the nanopore, the shorter the length and the higher the mechanical stability, the better the performance. In this research, chips have been made on which there is a blade with a sharpness of 10 nanometers and a height of 10... 

In this study, deactivation of Midrex reforming catalysts is evaluated kinetically by 3.5-year data of Mobarakeh Steel Company direct reduction site. The variation of Midrex catalyst’s structure is characterized by XRD and BET test. Two deactivation mechanism are characterized, methane cracking carbone deposition and sintering. The project results demonstrate that victorious mechanism is carbon deposition. The methane cracking carbone cause layer by layer deactivation of catalyst during 5.5 months. Although, XRD and BET showed pore volume and radius reduction and Ni crystal increasing, approximated constant activity of catalyst were approved by kinetic evaluation  

Outer membrane proteins play the role of molecular machines in the outer membrane of bacteria to regulate their basic functions. These macromolecules have nano-scale dimensions and they are involved in the classifications of nano-machines and nano-pores. Protein structure is constructed of chain of amino acids. Coarse grained elastic network model of the protein introduces a network of selected point masses, which is located on α-carbon of each amino acid, linked together with harmonic springs that represent the interactions between residues, both the chemical (protein backbone) and physical bonds. Using the harmonic network potential and theory of mechanical vibration, normal modes of... 

Resistive pulse sensing (RPS) has proved to be a viable method for detection and characterization of micro and nano particles. This method works based on ionic current variation inside nanopores. Modern fabrication methods have introduced different nanopore geometries for resistive pulse sensors therefore studing the effects of geometry on sensing performance of nanaopores is important. Numerical simulation has been used to study a wide variation of nanopore’s geometry configurations and study the physics behind this phenomena. Based on the results, numerical simulation could be used as a fast and easy tool for size determination for nanopore. To compare the sensing performance of different... 

Nanocomposites are fabricated by incorporating nano-scale particles in polymer, metal, or ceramic matrices. Metal matrix nanocomposites are a new kind of materials which have shown superior mechanical features, such as high strength, stiffness, and hardness. However, they are not sensitive to high temperature, in contrast to the polymer matrix nanocomposites. Nanoporous materials, also, have wide range of applications in different fields, such as geology, biology, biomechanics, and electronic. Carbon Nanotubes (CNTs) have shown wonderful properties like high Young’s modulus, high resonance frequency and unique electrical behavior. Wonderful mechanical and electrical properties make CNTs... 

During the various stages of uranium processing in Uranium Conversion Facility (UCF) in Isfahan, significant amounts of liquid waste stream is produced which is sent to evaporation ponds. In addition to environmental considerations, uranium recovery from existing pools is also economically feasible due to high concentration uranium in liquid waste. Several methods have been evolved over the years to remove dissolved uranium from uranium bearing solution. These methods are: chemical precipitation, liquid-liquid extraction, ion exchange and membrane processes. The purpose of this study is recovery of uranium from liquid waste of Isfahan UCF plant by using ion exchange method. Although this... 

Polymer translocation through the nanopores is one of the fundamental macromolecular processes in life. Some examples are , mRNA translocation through nuclear pores, injection of DNA from a virus head into a host cell, protein translocation across biological membranes through membrane channels. Also some applications are suggested for the process, e.g. DNA sequencing by probing the signals during the translocation, drug delivery and/or gene therapy. During the translocation the polymer should pass entropic barrier of the pore and it can be facilitated by changing the chemical potential, application of eclectic field, flow field, or chemical concentrations. In electrically driven...