Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis A Comparative Study on the Photocatalytic Activity of Dye-Sensitized and Non-Sensitized Graphene Oxide-Ti̇o2 Composites Under Simulated and Direct Sunlight(01. Izmir Institute of Technology, 2019) İlhan, Hatice; Varlıklı, Canan; Demir, Mustafa MuammerAmine modified graphene oxide (mGO) and TiO2 composite was synthesized by low temperature hydrothermal method. Characterization of the synthesized material was carried out by using X-ray diffraction, X-ray photoelectron spectroscopy, and BET analysis techniques. The films of mGO:TiO2 and formerly synthesized TiO2, N-TiO2, GO-TiO2 and GO:N-TiO2 were fabricated by doctor blade method and employed as photocatalysts for the photodegradation of Rhodamine-B (RhB) dye under simulated (Xe lamb) and direct sun-light. P25 was also used as reference photocatalyst for all of the synthesized ones. Photodegradation of RhB was monitored by UV-Vis spectroscopy. Among all the catalysts, GO:N-TiO2, the composite of GO and N-doped TiO2, presented the best photocatalytic activity and although the activity of mGO:TiO2 was better than the activities of P25 and TiO2, it presented lower degradation rate constant even than that of the N-TiO2. It is proposed that increased abundance of C-C bonds and decreased number of oxygenated functional groups on mGO:TiO2, in addition to the morphological difference between GO (sheet like) and mGO (dot like) has great influence on their photocatalytic activities. Among the GO containing photocatalysts including mGO:TiO2, specific surface area (SSA) and number of RhB molecules per film volume were the lowest and particle size was the highest for mGO:TiO2. Although the number of RhB molecules per film volume was higher in mGO:TiO2 than that of the N-TiO2, it is thought that approximately 2 folds higher SSA of N-TiO2 allowed better photocatalytic performance. Additionally, the films were sensitized with PTE dye to obtain effective catalysts in visible region and reusability of the films were also tested. Degradation rate constants of all fabricated films have increased under both of the irradiation media and no significant change in rate constants were detected after the reusability tests.Master Thesis A Case Study on Settlement Analysis of Geothermal Power Plant Foundation(01. Izmir Institute of Technology, 2018) Elmas, Hakan; Ecemiş Zeren, NurhanFoundation settlement criteria are highly sensisitive for geothermal power plants. In geotechnical literature there are several settlement analyses which can be done by using elastic approaches, in-situ test results or numerical methods. Unfortunately, all these methods cannot give close results with each other. As a result, the unrepresentative analyses influence the safety, economy and time of the projects. In this study, the settlement of the geothermal power plant located in Aydın / İncirliova which constructed on a raft foundation was investigated. According to soil investigations, the raft foundation is located on multilayer soil profile and a compacted high qualified fill layer is placed under the raft foundation. Soil parameters were obtained from in-situ tests (standard penetration tests, cone penetration tests, pressuremeter tests and plate load test and) and laboratory experiments. Settlement results were obtained by 1D stress – strain analyses and 3D continuum numerical analyses (Hardening Soil Model with Small Strain Stiffness and Mohr Coulomb Soil Model) using the commercially available Settle 3D and Plaxis 3D software, respectively. The results of these analysis were also compared with the field monitoring data. The results show that Hardening Soil Model with Small Strain Stiffness gave more accurate result than other models due to the representation of real soil behavior, obtaining non-uniform stress distribution of foundation and obtaining effective stress depth accurately for settlement.Master Thesis Conservation and Presentation of Greco-Roman Temple Remains in Western Anatolia: a Critical Assessment on Selected Examples Through the Concept of Anastelosis(01. Izmir Institute of Technology, 2018) Toköz, Özge Deniz; İpekoğlu, BaşakAnastelosis, a conservation and presentation technique in archaeological sites, is the practice of reassembling the scattered original parts of the structures. It can be stated that anastelosis ensures a better protection of the architectural fragments by re-placing them in their original places and contributes to the necessity of conservation practice by providing three-dimensional information about the structures. The aim of this study was, to contribute to the conservation and presentation of the structures in archaeological sites and to determine the basic principles to be considered during the implementations by analysing and evaluating the anastelosis implementations in Western Anatolia. Accordingly, anastelosis examples of Ancient Greek and Roman period temple structures that had significance in polis and sanctuaries were selected from Western Anatolia. Method of the study was on-site examination of the implementations, archive and literature research and evaluation of the information obtained from excavation reports prepared by the excavation team. In the evaluation, anastelosis principles, within the framework of international conservation documents and publications, were determined as emphasis of the structure within site scale and in original state, structural and visual integrity of the monument, authenticity, reliability, distinguishability, visual and material compatibility, reversibility and re-treatability. It can be stated that the implementations examined, in line with these principles, emphasized the importance of the temples in ancient times, contributed to better conservation of the scattered structure elements and transfer of information concerning the constructions. However, in some cases, the implementation has transformed to restoration or reconstruction as the authenticity principle could not be met; the temple became dominant than its original due to the inability to emphasize the structure within site principle; the mass of the temple could not be perceived due to lack of integrity principle; and the implementations that need to be redone have been identified as the use of new materials damaged the original elements.Master Thesis Development of protective nano-coatings for electro-optical systems(01. Izmir Institute of Technology, 2016) Karabıyık, Merve; Ebil, ÖzgençElectro-optical (EO) systems have wide range of applications and in recent years, especially the use of EO imaging systems in military and civil aviation applications have substantially increased. In these applications, EO systems are exposed to quite harsh and unstable operating conditions like sudden changes in temperature and humidity, dust, fog, physical shock, vibration and radiation. If their optical surfaces such as prisms, lenses and mirrors are damaged due to these conditions, their repair usually is not possible. To overcome these problems, it is necessary to develop special protective coating layers for optical surfaces. The main goal of this study is to produce protective, self-cleaning and super-hydrophobic polymeric thin films for optical surfaces of the electro-optical (EO) systems. Initiated chemical vapor deposition (iCVD) is a novel method for the fabrication of thin film coatings and it has many advantages such as low production cost, very low deposition temperature, 3D geometry coating performance and high deposition rate. Therefore, iCVD was employed to fabricate homopolymers of poly (glycidyl methacrylate) (PGMA) and poly (1H, 1H, 2H, 2H-Perfluorodecyl acrylate) (PPFDA) and P(GMA-PFDA) copolymer thin-films as protective coatings for EO systems. Optical modeling and simulations were performed to determine the effect of film thickness and refractive index on optical performance of substrates to be coated. Optical performance of fabricated coatings was also measured between 400 and 1000 nm range to confirm that protective coatings do not have any measureable impact on optical performance provided that the protective film thickness is kept between 50 nm to 1 μm. The surface morphology of the protective coatings was evaluated using a variety of analytical tools such as Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Contact Angle measurements. Optical tests were performed by following MIL-F-48616 Military Standard (MIL-STD). The best protective coatings were obtained by using P(GMA-PFDA) copolymer which yields good mechanical properties due to epoxy pendant group and super hydrophobicity due to incorporation of fluoro monomer.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 Characterization of Ion Implanted Surfaces by Laser Induced Breakdown Spectroscopy, Libs(01. Izmir Institute of Technology, 2008) Örer, Sabiha; Yalçın, ŞerifeLaser Induced Breakdown Spectroscopy, LIBS, is a versatile atomic emission spectrometric technique for the determination of the elemental composition of solids, liquids, gases and aerosols with the need for little or no sample preparation.In this study, an optical LIBS system from its conventional parts was designed, constructed and optimized for spectrochemical analysis of solid materials. Specifically, the 2-D elemental distribution of Ge ions on silicon oxide surfaces, prepared by the method of ion implantation, with differing atomic concentrations between 1016 - 1017 ions/cm2 have been investigated by LIBS. For this purpose a Nd: YAG laser operating at the second harmonic wavelength, 532 nm, was used to create a plasma on the material surfaces. Spatially and temporally resolved atomic emission from the luminous plasma was detected by an Echelle spectroctrograph and Intensified Charged Coupled Device (ICCD) detector combination. Spectral emission intensity from the LIBS measurements has been optimized with respect to time, crater size, ablation depth and laser energy. Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) coupled with Energy Dispersive X-Ray Spectroscopy (EDX) have been utilized to obtain crater depth, morphology and elemental composition of the sample material, respectively. LIBS spectral data revealed the possibility of performing 2-D distribution analysis of Ge ions over the silicon oxide substrate at Ge ion concentrations lower than 0.5% (atomic). LIBS as a fast semi-quantitative analysis method with 50.m lateral and 800 nm depth resolutions has been evaluated. In this wok, elemental analysis of some metal surfaces, such as Al and Cu, was also performed by LIBS.Keywords: LIBS, surface analysis, Ge ion implantation, lateral resolution,Master Thesis Preparation and Characterization of Inorganic Membranes by Using Sol-Gel Techniques(01. Izmir Institute of Technology, 2000) Yelken, Gülnihal; Çiftçioğlu, MuhsinIn this research the preparation of ceramIC membranes for gas separation applications by using sol-gel techniques were investigated. The effects of water/alkoxide ratio, H+/alkoxide ratio on the catalysis of the hydrolysis-condensation reactions and the peptization process were investigated by using N2 adsorptiondesorption isotherms, thermogravimetric analysis and FfIR (Fourier Transform Infra Red). The performance and the potential use of these materials in gas separation applications depend mainly on the ability in controlling-designing the microstructurepore network in these materials.The alumina and silica sols were prepared by using aluminium isopropoxide and tetraethylorthosilicate. Sols with different H+/ AI+3 and H20 / AI+3 ratios were prepared.These peptized clear boehmite sols were used for the preparation of unsupported Ah03 membranes at 600°C. The similar ratios were varied for the preparation of clear silica sols and these sols were further dried and heat treated at 400 C.The thermogravimetric analjsis has shown that the weights of the unsupported membranes were stable at the above temperatures. The boehmite was observed to decompose to the y-Alz03 phase at about 425°C. The FfIR analysis have proved the formation of boehmite in the sols and all the organic solvent peaks disappeared upon heat treatment.The y-Alz03 membranes all displayed Type IV isothems typical of mesoporous materials. Hysteresis loops were present in all these isotherms and fast desorption took place in the 0.4-0.6 PlPo range. The BJH pore size distributions were sharp for all the samples.The desorption pore size distributions were found to become wider at an intermediate acid content membrane which also had the lowest BET surface area. The BET particle sizes of these membranes were estimated to be in the 70-100 A0 range.The throat and pore cavity sizes of monosize sphere packings for this particle size range were observed to be in close agreement with the experimentallly determined adsorptiondesorption pore sizes.The silica samples all displayed Type I isotherms with no hysteresis typical of microporous materials. The HK (Horvoath Kawazoe) pore sizes were in the 4-5 AO range. An effect of the water content of these acid-catalyzed sols on the pore size were also detected.Master Thesis Preparation and Characterization of Polymer-Zeolite Composite Membranes(01. Izmir Institute of Technology, 1999) Ebil, Özgenç; Çiftçioğlu, MuhsinThis thesis is on the investigation of polymer-zeolite composite membranes for gas separation and the effects of a number of parameters such as solvent and zeolite type, zeolite content, polymer/solvent ratio and preparation temperature on the microstructure of the final membrane. Although there is an increasing interest in polymeric composite membranes, most of the previous work concentrated on the synthesis and performance measurements of new membrane materials rather than the effects of different methods and parameters on processmg.In this study polymer-zeolite composite membranes were prepared by a phase inversion technique. Polysulfone, natural zeolite and synthetic zeolite 13X were used as polymer and second phases respectively. Dichloromethane and dimethylformamide were used as solvents. Four experimental sets of membranes containing the same polymer but different solvents and zeolites with increasing zeolite loadings were prepared and characterized by thermo gravimetric analysis, infrared spectroscopy, optical microscopy and scanning electron microscopy.It has been found that the types of the solvent and zeolite directly affect the final microstructure of the membranes. Solvent removal rate and distribution of zeolite particles are important and have strong effects on the mechanical performance of the membranes.Membranes prepared by using synthetic zeolite 13X and dichloromethane were determined to be the best zeolite distributions in the microstructure by optical microscopy and thermogravimetric analysis. Uniform and mechanically strong membranes with 20-60 % synthetic zeolite contents were prepared. Mechanically weak and relatively nonuniform membranes were prepared by using natural zeolite clinoptilolite. The incorporation of an ultrasonic treatment of the zeolite dispersion most likely contributed in the successful deagglomeration of the second phase in the polymer matrix.Master Thesis The Preparation Characterization and Sintering of Nanocrystalline Ceramics(01. Izmir Institute of Technology, 1999) Çağlar, Özlem; Çiftçioğlu, MuhsinNanocrystalline Titania was prepared by a chemical synthesis technique commonly known as sol-gel method. In the sol gel method, Titanium (IV) Isopropoxide was mixed with Isopropanol and Nitric Acid solution in predetermined ratios. A rapid hydrolysis reaction occurs between Titanium (IV) Isopropoxide and water in the Nitric Acid solution resulting in the formation of Titan oxide (Titania). The sols were clear sols and then gelled without any change in its clarity.Nanocrystalline Titania were tried to prepare by two different techniques in this work. The first technique involved the drying of the gel and subsequent sintering of the dried gel. A number of organic additives (oxalic acid, acetic acid, polyacrylic acid and stearic acid) were mixed into the sol before gelation in order to control drying (drying control chemical addives-DCCAs). Powders was prepared from sols and gels by several processes and a solid form was obtained by dry pressing and subsequently sintered in second technique. Oxalic acid was the most efficient DCCA among the others.The dried gels and powder compacts were sintered at 650, 700, 750, 800, and 850C. The sintering behaviors of them were examined. Relative densities of the dried gels were between 79-99% depending on the sintering temperature. The green body density of the pellets were varied between 41-52%. Their relative densities after sintering were varied between 55-83% depending on the sintering temperature. The pellets were pressed at different pressures to observe the pressure effect on the densification. Increase in pressure improve the densification behavior. The best route for the nanocrystalline powder preparation was the Route 4. This powder had smaller size of agglomerate most probably the agglomerates were broken during the ultrasonic radiation.The pore size analyses showed the pore structure of the gel. The pore size of the gels are about 35 nm. FTIR Spectra gave the crystal structure of the sols gels and powders. As a result, the sintering behavior of the dried gels is better than the powder compacts. The pellets can be densified to higher densities by appropriate forming technique. Although, the dried gels have significantly high densities, the shape and the weight of the gels can not be controlled.Master Thesis Engineering Concepts in Industrial Product Desing With a Case Study of Bicycle Desing(01. Izmir Institute of Technology, 2004) Kocabıyık, Elif; Günaydın, Hüsnü Murat; Özcan, A. CanIndustrial product design, as a field of design discipline, borrows concepts and methods from other disciplines, one of which is engineering, in order to develop its own knowledge in research and industry contexts. In the means of strengthening its place among other disciplines, a concentration on .designerly. ways of knowing, thinking and acting should be provided. Therefore, in this study, the intersection between industrial product design field and engineering discipline is searched for revealing the engineering concepts and non-intuitive design methods within intuitive design methods used in industrial product design. Engineering design field is stated, since its being close to industrial product design, and a comparison is made between industrial product design and some engineering fields through their approach to design problems and the tools they use. Engineering design methods are stated and their advantages in design activity are revealed. This study is a part of design systems area, with formal approaches to models of design processes and knowledge. Finally, a case study of bicycles is carried out in order to prove the design approaches and the priorities of engineering and industrial product design on a product.Keywords: industrial product design, design criteria, engineering design, design methods, bicycle.