Polymer modified bitumen is a binder obtained by the incorporation of various types of polymers in bitumen using mechanical mixing or chemical reactions. There are several factors affecting the properties of polymer modified bituminous composites such as / chemical composition of bitumen, kind of polymer and filler, compatibility of bitumen and polymer, amount of bitumen, polymer and filler, particle size of filler and process conditions. The main objective of this study is to determine the effects of polymer type and concentration on mechanical, thermal, properties and morphologies of bitumen based composites. It was also aimed to determine the effect of process temperature on mechanical and thermal properties of bituminous composites. Bituminous composites were prepared by using Brabender Plastic Coder, PLV 151. Mixing was made at two different temperatures (150 &ordm / C and 180 &ordm / C) at 60 rpm for 20 minutes. Three different kinds of polymer and four different polymer concentrations were used to understand the effect of polymer type and polymer concentration on bituminous composites properties. Low density polyethylene (LDPE), styrene-butadiene-styrene copolymer (SBS) and ethylene-vinyl-acetate (EVA) were chosen as polymer. The compositions were adjusted as the polymer volumes were equal to 5%, 10%, 20% and 50% of bitumen volume. According to the test results, addition of polymer increases the mechanical properties, reduces the melt flow index and thermal conductivity values of bituminous composites. Morphological analysis results show that, fibrillation occurs at tensile fractured surfaces of composites which contain LDPE and EVA when the polymer concentration reaches 20% of bitumen volume.

In this work, zeolite Beta was synthesized experimentally in order to be used as filler in fuel cell membranes in order to assess the proton conductivity of composite membranes. Effects of the Si/Al ratio, and synthesis time on yield, relative crystallinity, crystal size, and proton conductivity were investigated. Zeolite Beta with Si/Al ratio between 10 and 30 was synthesized with a batch formulation of 2.2Na2O:1Al2O3:ySiO2:4.6(TEA)2O:tH2O (where TEA&amp / #8801 / tetraethylammonium) at 150&deg / C for 5-15 days of synthesis time. Sodium aluminate, tetraethylammonium hydroxide (TEAOH) solution, sodium hydroxide pellets (NaOH), and deionized water were used for the preparation of the batch solution. Zeolite Na-Beta was calcined and treated with sulfuric acid solution at different concentrations in order to have zeolite H-Beta. Polyetherether ketone (PEEK) was sulfonated in order to have a proton conductive membrane and than zeolite H-Beta was incorporated resulting in a composite or nanocomposite membrane. X-ray diffraction (XRD) analysis helped to understand whether the synthesized material was zeolite Beta or not. The morphology and the crystal size of the crystals were observed as a result of the scanning electron microscopy (SEM) analysis. In order to see the effect of sulfuric acid treatment on the sodium (Na) content of the zeolite Beta, inductively coupled plasma (ICP) analysis was performed. Synthesis results indicate that as Si/Al ratio and synthesis time increased the yield of zeolite Beta increased. It was observed that Si/Al ratio from 10 to 30, and synthesis time between 5 to 15 days did not affect the crystal size significantly. For the sulfonation of PEEK, sulfuric acid was used. Sulfonated polyetherether ketone (SPEEK) was dissolved in a solvent that was dimethyl acetamide (DMAC), incorporated with zeolite Beta, and then solvent was removed in the vacuum oven. The proton conductivity was measured with a 2-probe impedance spectrometer. Initial results indicate that zeolite Beta at 10 and 20 wt % loadings did not affect the proton conductivity of the SPEEK membrane at 100 % relative humidity and room temperature.

The design and development of isolation or backfill materials, which seal the disposal facility, are important for disposing the wastes. The use of compacted bentonite-sand for construction of shaft seals and liners for waste containment structures has been proposed by various studies. Therefore / it is aimed in this study to develop an isolation material to be used in underground waste repositories. For such designs to be effective, their performance need to be assessed and a minimum hydraulic conductivity requirement defined by regulatory agencies should be satisfied (i.e. 1x10-8 m/s in Turkey, 1x10-9 m/s in USA). Therefore / this study assesses the performance of compacted bentonite/sand mixtures in terms of hydrological and mechanical properties. To be able to assess the performance of this material, a variety of laboratory tests were carried out. Engineering geological tests such as compaction, falling head permeability, swelling, unconfined compression and shear strength tests were conducted to select an optimum mixture. Finally, an optimum bentonite-sand mixture possessing 30% bentonite was recommended for the isolation of underground waste disposal facilities.

ABSTRACT BIOSENSOR BASED ON INTERPENETRATED POLYMER NETWORK OF ALGINIC ACID AND POLY (1-VINYLIMIDAZOLE) Kartal, M&uuml / jgan M.S., Department of Chemistry Supervisor : Prof. Dr. Levent Toppare January 2008, 63 pages A new proton conductor polymer was prepared using alginic acid (AA) and poly (1-vinylimidazole) (PVI). The polymer network was obtained by mixing AA and PVI at various stoichiometric ratios, x (molar ratio of the monomer repeat units). The AA/PVI network was characterized by elemental analysis (EA) and FT-IR spectroscopy. Potential use of this network in enzyme immobilization was studied. Enzyme entrapped polymer networks (EEPN) were produced by immobilizing invertase and tyrosinase (PPO) in the AA/PVI network. Additionally, the maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were investigated for the immobilized invertase and enzymes. Also, temperature and pH optimization, operational stability and shelf life of the polymer network were examined.

The aim of this study was to improve electrical properties of conductive polymer composites. For this purpose, various studies were performed using different materials in this dissertation. In order to investigate the effect of alternative composite preparation methods on electrical conductivity, nylon 6/carbon black systems were prepared by both in-situ polymerization and melt-compounding techniques. When compared with melt compounding, in-situ polymerization method provided enhancement in electrical conductivity of nylon 6 composites. Furthermore, it was aimed to improve electrical conductivity of polymer composites by modifying surface chemistry of carbon black. 1 wt. % solutions of 3-Aminopropyltriethoxysilane and formamide were tried as chemical modifier, and treated carbon black was melt mixed with low-density polyethylene (LDPE) and nylon 6. According to electron spectroscopy for chemical analysis (ESCA), chemicals used for surface treatment may have acted as doping agent and improved electrical conductivity of polymer composites more than untreated carbon black did. Formamide was more effective as dopant compared to the silane coupling agent. In order to investigate electromagnetic interference (EMI) shielding effectiveness and dielectric properties of conductive polymer composites, 1, 2 and 3 wt. % solutions of formamide were tried as chemical modifier and treated carbon black was melt mixed with poly(ethylene terephthalate) (PET). Composites containing formamide treated carbon black exhibited enhancement in electrical conductivity, EMI shielding effectiveness and dielectric constant values compared to composites with untreated carbon black. In order to enhance electrical conductivity of polymer composites, the selective localization of conductive particles in multiphase polymeric materials was aimed. For this purpose, carbon nanotubes (CNT) were melt mixed with polypropylene (PP)/PET. Grinding, a type of solid state processing technique, was applied to PP/PET/CNT systems to reduce the average domain size of blend phases and to improve interfacial adhesion between these phases. Grinding technique exhibited improvement in electrical conductivity and mechanical properties of PP/PET/CNT systems at low PET compositions. To investigate application potential of conductive polymer composites, polyaniline (Pani)/carbon nanotubes (CNT) composites were synthesized and electrochemical capacitance performances of these systems, as electrode material in electrochemical capacitors, were studied. Polyaniline/carbon nanotubes composites resulted in a higher specific capacitance than that of the composite constituents. Pseudocapacitance behavior of Pani might contribute to the double layer capacitance behavior of nanotubes. Additionally, as an alternative to Pani/CNT systems, polyaniline films were deposited on treated current collectors and electrochemical capacitance performances of these electrode systems were investigated. The highest specific capacitance of polyaniline/carbon nanotubes composites was 20 F/g and this value increased to 35.5 F/g with polyaniline film deposited on treated current collector.

Magnetic Resonance Electrical Impedance Tomography (MREIT) reconstructs images of electrical conductivity distribution based on magnetic flux density (B) measurements. Magnetic flux density is generated by an externally applied current on the object and measured by a Magnetic Resonance Imaging (MRI) scanner. With the measured data and peripheral voltage measurements, the conductivity distribution of the object can be reconstructed. There are two types of reconstruction algorithms. First type uses current density distributions to reconstruct conductivity distribution. Object must be rotated in MRI scanner to measure three components of magnetic flux density. These types of algorithms are called J-based reconstruction algorithms. The second type of reconstruction algorithms uses only one component of magnetic flux density which is parallel to the main magnetic field of MRI scanner. This eliminates the need of subject rotation. These types of algorithms are called B-based reconstruction algorithms. In this study four of the B-based reconstruction algorithms, proposed by several research groups, are examined. The algorithms are tested by different computer models for noise-free and noisy data. For noise-free data, the algorithms work successfully. System SNR 30, 20 and 13 are used for noisy data. For noisy data the performance of algorithm is not as satisfactory as noise-free data. Twice differentiation of z component of B (Bz) is used for two of the algorithms. These algorithms are very sensitive to noise. One of the algorithms uses only one differentiation of Bz so it is immune to noise. The other algorithm uses sensitivity matrix to reconstruct conductivity distribution.

In this study simultaneously developing single phase, laminar and incompressible flow in a micro gap between parallel plates is numerically analyzed by including the effect of variation in thermal conductivity and viscosity with temperature. Variable property solutions for continuity, momentum and energy equations are performed in a coupled manner, for air as a Newtonian fluid. In these analyses the rarefaction effect, which is important for the slip flow regime, is taken into account by imposing slip velocity and temperature jump boundary conditions to the wall boundaries. Mainly, the influence of viscous dissipation, axial conduction, geometric parameters and rarefaction on the property variation effect is aimed to be discussed in detail. Therefore, the effects of variable thermal conductivity and viscosity are investigated simultaneously with the effects of rarefaction, geometric parameters, viscous dissipation and axial conduction. The difference between constant and variable solutions in terms of heat transfer characteristics is related to the effects of viscous dissipation axial conduction and rarefaction. According to results, property variation is substantially effective in the entrance region where temperature and velocity gradients are high. On the other hand, property variation effects are not significant for fully developed air flows in microchannel.

A nanofluid is the suspension of nanoparticles in a base fluid. Nanofluids are promising for heat transfer enhancement due to their high thermal conductivity. Presently, discrepancy exists in nanofluid thermal conductivity data in the literature, and enhancement mechanisms have not been fully understood yet. In the first part of this study, a literature review of nanofluid thermal conductivity is performed. Experimental studies are discussed through the effects of some parameters such as particle volume fraction, particle size, and temperature on conductivity. Enhancement mechanisms of conductivity are summarized, theoretical models are explained, model predictions are compared with experimental data, and discrepancies are indicated. Nanofluid forced convection research is important for practical application of nanofluids. Recent experiments showed that nanofluid heat transfer enhancement exceeds the associated thermal conductivity enhancement, which might be explained by thermal dispersion, which occurs due to random motion of nanoparticles. In the second part of the study, to examine the validity of a thermal dispersion model, hydrodynamically developed, thermally developing laminar Al2O3/water nanofluid flow inside a circular tube under constant wall temperature and heat flux boundary conditions is analyzed by using finite difference method with Alternating Direction Implicit Scheme. Numerical results are compared with experimental and numerical data in the literature and good agreement is observed especially with experimental data, which indicates the validity of the thermal dispersion model for explaining nanofluid heat transfer. Additionally, a theoretical analysis is performed, which shows that usage of classical correlations for heat transfer analysis of nanofluids is not valid.

Electrical conductivity of biological tissues is a distinctive property which differs among tissues. It also varies according to the physiological and pathological state of tissues. Furthermore, in order to solve the bioelectric field problems accurately, electrical conductivity information is essential. Magnetic Resonance Electrical Impedance Tomography (MREIT) technique is proposed to image this information with high spatial resolution. However, almost all MREIT algorithms proposed to date assumes isotropic conductivity in order to simplify the underlying mathematics. But it is known that most of the tissues in human body have anisotropic conductivity values. The aim of this study is to reconstruct anisotropic conductivity images with MREIT. In the study, five novel anisotropic conductivity reconstruction algorithms are developed and implemented. Proposed algorithms are grouped into two: current density based reconstruction algorithms (Type-I) and magnetic flux density based algorithms (Type-II). Performances of the algorithms are evaluated in several aspects and compared with each other. The technique is experimentally realized using 0.15T METU &ndash / EE MRI System and anisotropic conductivity images of test phantoms are reconstructed using all proposed algorithms.

In this study, Mg, Sn, Cd, Bi and Sb containing, five binary, three ternary and two quaternary different alloys to be used in a Valve-Regulated Lead-Acid (VRLA) batteries have been studied in terms of their mechanical and electrochemical properties. The investigated properties are hardness, passivity, corrosion rate, hydrogen gassing and the conductivity of the passive film. All electrochemical tests were carried out in 3.75 M H2SO4 solution by using open-circuit potential, anodic polarization, polarization resistance measurement and gas collection techniques. The results showed that while the minimum hardness values were observed in Pb and Pb-Bi alloy, Mg containing alloys have the highest hardness values among all alloys. According to corrosion measurements, lowest icritical value was obtained for Pb, Pb-Bi and Pb-Sn, which reached to passivation region earlier than others. Passive film formation was seen for all specimens. The noble Ecorr value and minimum corrosion rates belonged to Pb and Pb-Mg. Pb-Bi and Pb-Cd have the highest gas evolution rate. Besides, there were not seen much difference in the gassing behavior of Pb-Sn and Pb-Sb alloys. Mg is found to have a superior effect on hydrogen gassing. Addition of Sn, as an alloying element, to lead increases the conductivity of the passivation layer. Mg containing alloys did not show good conductivity characteristic. As a result, Mg containing alloy seemed to have an important role because of the desired hardness, corrosion and, gas evolution behavior. However, conductivity of passivation layer of these alloys came up to be low due to the higher tendency of Mg to oxidation. Even so, Mg seems to be a promising alloying element for lead grid alloys in Valve-Regulated Lead-Acid (VRLA) batteries.