Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Synthesis of composite filling materials for non-scratch paints and coatings(01. Izmir Institute of Technology, 2024) Paker, Hazal; Polat, HürriyetModern boyalar ve kaplamaların mekanik ve fiziksel özelliklerinin geliştirilmesi, otomotiv, inşaat ve denizcilik gibi belirli endüstriyel uygulamalar için oldukça önemlidir. Bu araştırma, dayanıklılığı ve çizilme direncini artırmayı hedefleyen, boya ve kaplamalarda kullanılmak üzere silika (SiO₂) ve bor-silika kompozitleri (Boron-SiO₂) içeren kompozit dolgu malzemelerinin geliştirilmesine odaklanmaktadır. Çalışma, bu dolguların diğer katkı maddeleriyle birlikte koruyucu kaplamaların mekanik ve işlevsel özelliklerini nasıl geliştirebileceğini incelemektedir. Silika nanoparçacıklarının iyi bilinen kimyasal stabilitesi, sertliği ve yüksek yüzey alanından yola çıkarak, bu çalışmada kullanılan üretim tekniği Stöber sentez yöntemidir. Bu teknik, partikül boyutu, morfolojisi ve dağılımı üzerinde hassas kontrol sağlar ve kaplama özelliklerinin yüksek bir doğrulukla ayarlanmasına olanak tanır. Ayrıca, boyalar/kaplamalar için çizilme direncini daha da geliştirmek amacıyla Boron-SiO₂ kompozitlerinin sentezi gerçekleştirilmiştir. Silika matrisine bor eklenmesi, malzemenin mekanik dayanımını ve dayanıklılığını artırmış, böylece onu koruyucu uygulamalar için son derece uygun hale getirmiştir. Boron-SiO₂ parçacıklarının özelliklerini optimize etmek için kontrollü içerik ekleme yöntemleri dahil olmak üzere çeşitli sentez teknikleri incelenmiştir. Elde edilen kompozit nanoparçacıklar, SEM, STEM, TEM, FTIR ve ICP-MS gibi karakterizasyon teknikleriyle birlikte parçacık yapısını incelemek için ek testlere tabi tutulmuştur. Çizilme direnci performans testleri, Boron-SiO₂ kompozitleri ile doldurulmuş kaplamaların, üretim yöntemine bağlı olarak geleneksel silika dolgulu kaplamalara göre önemli ölçüde daha iyi performans gösterdiğini ortaya koymuştur.Master Thesis Synthesis of Carbon-Based Flexible Temperature-Controlled Semiconductive Composites(01. Izmir Institute of Technology, 2024) Gündüz, Esra Sıla; Polat, Mehmet; Polat, HürriyetGünümüzde, yarı iletken polimer matrisli kompozitler ve kullanım alanları araştırmacıların ilgisini çekmektedir. Ayarlanabilir sıcaklık profillerine sahip yarı iletken esnek polimer matrisli kompozitler, robotik, havacılık ve enerji sektörlerinde kullanım alanı bulmaktadır. Ancak karbon nanotüpler, grafen veya metal nanopartiküller gibi pahalı iletken fazlarlara duyulan ihtiyaç nedeniyle üretim maliyeti yüksektir. Bu çalışma, bu tür kompozitlerin üretimi için polidimetilsiloksan matrisinde karbon siyahı ve doğal grafit gibi ucuz iletken malzemelerin kullanılmasını amaçlamaktadır. Kompozitler 'Çözelti karıştırma' yöntemiyle (%10 ila %35 metanolde) hazırlandı ve dağılabilirlik, elektriksel iletkenlik, termal tepki ve mekanik ve morfolojik özellikler açısından test edildi. Bu substratların yüzeylerinin ıslanmayan, düşük enerjili yüzeyler (Fowke teorisine göre 26 J/m2) olduğu bulundu; bu nedenle parçacıklar daha yüksek konsantrasyonlarda (>%30) topaklanma eğilimliydiler. Aglomerasyonun olumsuz sonuçlarını ortadan kaldırmak için yüzey aktif madde ilavesi kullanıldı. Karbon içeriğinin ayarlanması iletkenliği 0 ile 10,79 S/m arasında modüle edilmesini sağlamıştır. 3,17 S/m iletkenliğe sahip tipik bir kompozit, 30 V yük altında 49,7°C yüzey sıcaklığı göstermiştir. PDMS ile karşılaştırıldığında kompozitlerin mekanik özellikler olumluydu; optimum iletkenliğe ve sıcaklık tepkisine sahip bir kompozit, çekme mukavemetinde %50'lik bir düşüşe rağmen elastik modülde %97,8 ve yırtılma mukavemetinde %197 artış gösterdi. Çalışma, istenen sıcaklık profillerine sahip yarı iletken esnek kompozitlerin üretiminde önemli ekonomik potansiyelin altını çiziyor.Master Thesis Development of Doxorubicin-Loaded Liposomes Self-Assembled With Polysaccharides for Breast Cancer Therapy(01. Izmir Institute of Technology, 2023) Önol, Ayşenur Başar; Kılıç Özdemir, Sevgi; Polat, HürriyetThis thesis aimed to develop Tariquidar and Doxorubicin-loaded liposomes decorated by Fucoidan coating for breast cancer treatment. Fucoidan is a negatively charged polysaccharide with a special affinity to p-selectins expressed on MDA-MB-231 breast cancer cells and, at the same time, possesses anti-cancer activity. Different liposomes were prepared by extrusion method from the DSPC, Cholesterol, and cationic lipid DSTAP mixtures for coating negatively charged Fucoidan. The most stable liposomes with a size of 200 nm were obtained at a molar ratio of DSPC/Cholesterol/DSTAP:55/30/15, exhibiting a zeta potential above +30 mV. Tariquidar was encapsulated into the liposome bilayer by passive loading, and Doxorubicin into the core of the liposome by active loading. In the final step, liposomes were coated with Fucoidan by electrostatic interaction. Tariquidar loading was determined by UV-Vis spectrophotometry, indicating an optimum TRQ/Lipid molar ratio of 0.012 with encapsulation and loading efficiencies of 50% and 20%, respectively. Fluorescence spectrophotometry determined Doxorubicin loading, showing insignificant encapsulation efficiency change (exhibiting around 70%) by neither Tariquidar content in the bilayer nor DSTAP% in the formulation. An optimum amount of Fucoidan was determined by incubating the liposomes with varying amounts of fucoidan at different dilutions. Size and zeta potential measurements monitored the coating of liposomes with Fucoidan. Our finding showed that zeta potentials of liposomes go from positive to negative with increasing fucoidan, while no trend was observed in the size of liposomes. However, smaller sizes were observed when incubation was performed in diluted solutions.Master Thesis Use of Snps With Controlled Size & Shape for Enhanced Surface Hydrophobicity & Hardness for Coil Coating Applications(01. Izmir Institute of Technology, 2023) Sulubaş, Şevval; Polat, Mehmet; Polat, HürriyetIncreasing the hardness of surface while improving hydrophobicity simultaneously has important implications in coating applications. The use of nano sized particles for this purpose is an interesting area of research. SNPs with mono and multi size distributions in a wide size range were successfully synthesized using the Stöber Method directly or after proper modifications such as utilizing seed particles as in Stöber growth solutions. The synthesized monosize and bi-modal silica particles were then employed in coating studies. The silica nanoparticles were added to a clear coat without pigments and fillers, followed by the introduction of a pigmented topcoat. The addition of 25% monosize silica nanoparticles led to a contact angle (CA) of 92°, while an equal amount of bi-modal silica particles increased the CA to 106°. Notably, the highest CA value of 116.7° was achieved with a 40% addition of bi-modal silica particles. When measured CA was converted to actual CA by incorporating the roughness parameter, the maximum effective CA was calculated as 140°. In terms of mechanical properties, loading monosize silica nanoparticles up to 35% resulted in a surface hardness of 2H. Further increasing the loading to 45% improved the surface hardness to 3H. While a 40% addition of monosize silica was necessary to achieve a pencil hardness of 3H, 20% addition of bi-modal sample was sufficient. The findings above demonstrate that addition of nanosized silica particles simultaneously improve hardness and surface hydrophobicity and that a bi-modal particle size distribution results in a superior performance compared to mono-modal particle size distribution.Master Thesis Design of Micelle Embedded Chitosan Nanocomposites for Targeted Delivery of Hydrophobic Drugs(Izmir Institute of Technology, 2016) Cihan, Esra; Polat, HürriyetWhen successed to synthesize in a nanoparticulate form, chitosan has found to be a very effective biomaterial for drug delivery purposes owing to its extremely attractive characteristics such as its positive charge and pH sensitivity in aqueous medium. However, its structure as it is, is not suitable for oil soluble drugs. Even a close control on the size and shape of chitosan particles alone becomes a state of art and the production of chitosan nanoparticles is very difficult. Therefore, in this study, several methods were designed and used for synthesis of chitosan nanoparticles (<100 nm) with a hydrophobic core that are suitable for oil soluble drugs. Characterization of these nanoparticles were done by Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Scanning Transmission Microscope (STEM), Transmission Electron Microscope (TEM), surface tension and zeta potential measurements. It was concluded that the best method was the coupling of drug loading with simple ionic gelation method among all the others. Hydrophobic drug loaded micelle embedded chitosan nano particles were able to manufactured successfully. The sizes of chitosan particles that embed Pluronic-123 micelles were larger (<100 nm) than the sizes of Pluronic-123 micelles (20 nm) alone. It was also possible to obtain smaller chitosan nanoparticles (<50 nm) that embed drug loaded Pluronic-123 micelles when their structure is modified by Sodiumdodecylsulfate.Master Thesis An Investigation of Morphology of Polymeric Micellar Structures in the Presence of Protein for Drung Delivery Purposes(Izmir Institute of Technology, 2016) Kutluay, Gülistan; Polat, HürriyetPolymeric micellar structures are becoming increasingly important in drug delivery applications. Morphology of these structures is a factor determining the form and the amount of the drug to be enveloped as well as how the release mechanisms will function. Though there are numerous work on micelles in the literature in aqueous media, understanding is lacking with respect to the specifics of the micelle formation and the exact morphology of the micelles produced within simulated body fluids (SBF) that also contains protein. In this work, the well-defined micellar structures with and without bovine serum albumin (BSA) in SBF using some selected polymeric surface active agents (PEO-PPO-PEO tri-block copolymer, P-123) were studied. The forms of P-123 molecules in distilled water (DW) and SBF (studied by surface tension measurements), micelle size distributions (studied by AFM, DLS, STEM, TEM), and electro kinetic potentials (studied by DLS) were the main parameters studied. DLS results showed that the average size of P-123 micelles did not change much in the presence of BSA in DW or SBF. In the cases of AFM, STEM and TEM, the sizes of P-123 micelles in the absence of BSA were comparable to the results of DLS. In the presence of BSA, on the other hand, the micelle structures come together to form large and loose aggregates in both DW and SBF. When P-123 micelles loaded with drug, DLS results showed that the presence of drug in micelles does not change the size of micelles much in both water and SBF. But STEM results show a considerable increase in the sizes of P-123 micelles. The drug loaded micelles seem to aggregate in water and SBF in the absence of BSA and in water in the presence of BSA. But they seem to disperse in SBF in the presence of BSA.Master Thesis An Investigation of Dye-Surfactant Intetactions in Aqueous Solutions for Elucidating the Mechanisms of Ultrafiltration(Izmir Institute of Technology, 2014) Olcay, Aybike Nil; Polat, Mehmet; Polat, HürriyetLow Molecular Weight Contaminants (LMWCs) in waters are serious environmental concern due to removal problems with classical techniques such as chemical coagulation, biological treatments and adsorption. LMWCs are usually copresent with surface active agents in contaminated waters. Though such advanced removal techniques as ultrafiltration and micelle enhanced ultrafiltration are said to perform better, no systematic study is present for elucidating how the contaminantsurfactants interactions affect removal efficiency. In this study, methylene blue (MB), a dye widely employed in textile, paper and chemical industries, was chosen as the model contaminant. Surfactants selected were anionic sodium dodecyl sulfate (SDS), cationic hexadecyltrimethyl ammonium bromide (CTAB) and non-ionic ethoxylated octylphenol (TX-100). Surface tension, size, charge and contact angle measurements were conducted to investigate dye-surfactant interactions. Cellulose nitrate filters were employed to determine the effect of these interactions in filtration efficiency. It was found that significant amount of MB was removed from solution since it attached on the negatively charged cellulose nitrate filter. Though presence of surfactants generally decreased MB removal efficiency, MB-SDS interaction created large-loose aggregates at low SDS concentrations which cannot pass the filter paper. The MB-CTAB/TX-100 interactions created positively charged MB-surfactant pairs which can attach to the filter surface causing a decrease in the removal. At concentrations above Critical Micelle Concentration (CMC), the efficiency of MB removal is low due to the formation of surfactant-micelles that are smaller than the pores of the filter. Detailed size distribution experiments suggest that MB molecules are within the micelles structure, not in the core as believed in literature and do not increase the size of the micelle.Master Thesis Preparation and Characterization of Alumina Powders and Suspensions(01. Izmir Institute of Technology, 2000) Şakar, Aylin M.; Polat, HürriyetThis study involves the preparation of fine alumina powders derived from Bayer gibbsite and also aqueous alumina suspensions by using tri block copolymers. Preparation of alumina powders was performed by decomposition of gibbsite into transition alumina phase followed by controlled transformation to alpha phase. To increase transformation rate.. to a-alumina in transition phase hence influence the nucleation and growth rate of the solid-solid phase transformation ball milling and ultrasonication was applied. Gibbsite was thermally treated at 900°C to reach a transition form of alumina. In some cases a heat treatment at 350 °C was applied to create a network of submicroscopic cracks in the heated gibbsite that may help grinding. Ball milling and ultrasonic treatment before calcination at 1100, 1200 °C and 1450 °C followed these heat treatments. Characterizations of the powders were performed with XRD, FTIR, thermal analysis, density measurements and particle size determinations. According to the XRD patterns, complete transformation to alpha form occurred in powders previously heat treated at 900°C, mechanical treated and then cfllcined at 1200 °C in 8 hours and 1450 °C in 2 hours. Powders that were calcined at 1100 °C and 1200 °C in 1-2 hours contained considerable amount of kappa form together with alpha. The effect of the polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO/PPO/PEO) blockcopolymers on the dispersion behaviour of alumina powder suspensions in water were investigated at <1>.0.125,1.0,14 and 50 vol% solid loadings by rheological and turbidity measurements. To compare the effects of block copolymers with other type of dispersants, measurements of some other well known dispersants were also conducted at 10-7 to 10-3 M. The results indicated that type block copolymers with high EO percentage have a positive effect when they are used with ultrasonic treatment on the agglomerated alumina suspensions. But it was not able to create stable dispersions ll1 the absence of ultrasonic bath application. Turbidity measurements at <1>.0.5 wt% showed that some dispersants gave higher dispersion but the stability was reached after a time period. Ultrasonic treatment created stability but lowered the turbidity values.Master Thesis Determination of the Particle Interactions -Rheology Suface Roughness Relationship for Dental Ceramics(Izmir Institute of Technology, 2007) Kes, Mürşide; Polat, HürriyetIn this study, relationship between particle interactions, rheology and surface roughness for dental ceramics was determined. For this purpose IPS Empress 2 veneer powder was chosen and characterized with XRD, SEM, EDS, Zeta Potential and Particle Size measurements.Particle interactions have been interpreted in the light of DLVO Theory for distilled water and electrolyte solutions at different concentrations (0.1, 0.25, 0.5, 0.75,1 M NaCl and CaCl2). The results indicated that interactions between particles change with electrolyte concentration and valency. Electrical Double Layer Thickness (Debye Length) compresses and Energy Barrier height decreases as electrolyte concentration and valency increase mean that there is agglomeration between particles. In order to understand the rheological properties of the system shear rate versus shear stress and shear rate versus viscosity graphs were interpreted for the same environmental conditions, distilled water and electrolyte solutions at different concentrations. It was obtained that at low electrolyte conditions particles formed agglomerates, however at high electrolyte conditions the system reached equilibrium where particles formed gel structures due to their non-Newtonian behaviour.The results obtained from rheological measurements were compared with the results obtained from AFM, profilometer and SEM measurements for the surfaces prepared with IPS Empress 2 veneer powder and it was concluded that in the presence of electrolytes (Na+ and Ca2+) surface roughness increased at low concentrations due to agglomeration of particles whereas surface roughness decreased at high concentrations most probably due to gelation in the system. Moreover, this situation was supported with contact angle measurements where contact angle mean values are high and ditributions are wide at low electrolyte concentrations while contact angle mean values are small and distributions are narrow at high concentrationsMaster Thesis Characterization and Corrosion Performance of Γ-Glycidoxyropyltrimethoxsilane Modified Epoxy Polymer(Izmir Institute of Technology, 2010) Oturaklı, Şafak; Polat, HürriyetEpoxy polymers have been widely used in a protective coating and adhesive due to its strong adhesion, high chemical resistance, and good processing characterisitics. However; epoxy coatings absorbs moisture easily, and the diffusion of absorbed water into the epoxy.steel interface weakens the interfacial adhesion strength between epoxy and steel in corrosive enviroment, due to the presence of hydrophilic hydroxy group in the cured network (epoxy/amine reaction). In this study, commercial epoxy polymer was chemically modified by γ-glycidoxypropyltrimethoxysilane monomer under the catalysis organotin compound via the reaction between hydroxyl group in epoxy polymer and alkoxy group in silanes, aiming to enhance the corrosion performans of epoxy polymer. Commercial epoxy polymer and silane modifed epoxy polymer were characterized by NMR spectroscopy, FTIR spectroscopy, epoxy equivalent weight measurement, contact angle measurement, surface energy measurement, hardness test and MEK double-rub test. The results showed that γ-glycidoxypropyltrimethoxysilane has been successfully grafted to epoxy polymer. Corrosion performance was evaluated by salt spray test acording to ASTM B117. The results showed that the chemically modified epoxy coating perform an improvement in resistance againts the penetration of water in polymeric resin and beter protectiveness on metalic corrosion.