Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Production and Characterization of Composed-Based Friction Materials for Safety Cluthes in Aviation Applications(01. Izmir Institute of Technology, 2024) Karabulut, Orhan; Akkurt, Sedat; Sütçü, MücahitDebriyaj sistemleri, araç hızını kontrol etmede kritik öneme sahiptir. Bu çalışmada, uçak debriyaj sistemleri, yüzey malzemelerinin kimyasal ve mekanik özellikleri, üretim yöntemleri ve kullanım koşulları incelenmiştir. Ticari kompozit esaslı bir uçak fren balatası (Trimat MN2221) malzeme karakterizasyonu, mikro yapısal (OM, SEM-EDS), faz (XRD), kimyasal (XRF), bağ yapısı (FTIR) ve termal (TGA) analizleri ile gerçekleştirilmiştir. Yeni balata formülasyonları geliştirilmiş ve kompozit balata üretim yöntemleri kullanılarak sabit koşullar altında güvenlik debriyaj balataları üretilmiştir. Farklı katkı maddeleri ve karışım oranları ile deneyler yapılarak balata özelliklerindeki farklılıklar analiz edilmiştir. Bu araştırma, fenolik reçine, kuvars, alümina, cam elyafı ve grafit miktarlarının sürtünme kuvveti ve aşınma direnci üzerindeki etkilerini incelemeyi amaçlamaktadır. Farklı oranlarda alümina (Al2O3) ve kuvars (SiO2) içeren üç farklı debriyaj balatası örneği üretilmiş ve sürtünme özellikleri test edilmiştir. Benzer deneyler, fenolik reçine, cam elyafı ve grafit miktarları değiştirilerek tekrar edilmiştir. SAE J661 standardına göre sürtünme-aşınma testleri yapılmış, yoğunluk, yüzey pürüzlülüğü ve sertlik gibi fiziksel özellikler değerlendirilmiştir. Yoğunluk kütle-hacim ilişkisine göre hesaplanmış, sertlik SHORE D cihazı ile ölçülmüştür. TSE 555 standardına göre spesifik aşınma oranları belirlenmiştir. Sonuçlar, alüminanın sürtünme malzemelerini ve debriyaj performansını artırdığını, kuvarsın ise sürtünme katsayısını iyileştirdiğini göstermiştir. Çalışma, debriyaj performansı için en uygun formülasyon ve optimum üretim parametrelerini belirlemiştir.Master Thesis Sintering and Densification Behavior of Nanoparticle-Infiltrated Alumina Scaffolds(Izmir Institute of Technology, 2023) Özbekler, Meti̇n; Akkurt, SedatThis study explores high-purity Alumina's sintering and densification behavior, specifically the CT3000 SG variation, which traditionally requires high temperatures for full densification. The goal is to lower processing costs by achieving densification at lower temperatures through nanoparticle infiltration. The process involves a two-step heat treatment and infiltration technique. Alumina scaffolds are initially bisque-fired at 1100 °C and then infiltrated with a polymer precursor solution containing Al+3 ions, followed by decomposition at 400 °C to precipitate alumina nanoparticles in the scaffold pores. Multiple infiltration cycles are performed to enhance density. The relative density of furnace-sintered pellets increases with decreasing heating rate and increasing sintering temperature in reference samples. Infiltrated samples and "P" pellets (formed by washing CT3000 SG Alumina loose powder with the polymer precursor solution) follow a similar trend, with higher infiltration numbers leading to increased relative density. However, "P" samples have lower relative densities than reference samples. In-depth analysis using a horizontal dilatometer reveals that the 15 times infiltrated scaffolds exhibit better densification due to early activation of nanoparticles, leading to neck formation, reduced porosity, and altered particle shape. On the other hand, "P" pellets fail to achieve sufficient densification compared to reference samples. In summary, this study investigates lowering the sintering temperature of Alumina by nanoparticle infiltration. It involves bisque firing, multiple infiltration cycles, and a polymer precursor solution. Results indicate that 15 times infiltrated scaffolds achieve better densification, while "P" pellets fall short of achieving adequate densification compared to reference samples.Master Thesis Characterization and Recyclability of Pharmaceutical Blisters(01. Izmir Institute of Technology, 2023) Çapkın, İrem Yaren; Gökelma, Mertol; Akkurt, Sedat; Gökelma, Mertol; Akkurt, SedatPackaging is one of the largest industries in the world. Pharmaceutical blister packages are the most preferred packaging type in the pharmaceutical industry. Especially after the COVID-19 pandemic, the use of pharmaceutical packaging has become widespread with the increasing demand for drugs. Pharmaceutical blister packages typically contain thin sheets of plastic and aluminium and generate substantial solid waste. Since these packages have a multi-layered and complex structure, they are difficult to recycle. Before recycling, plastic and aluminium need a separation process. Chemical separation or thermal processes can be used for separation. The aim of this study is to characterize different pharmaceutical blister types with SEM-EDS (Scanning electron microscopy- Energy dispersive X-ray spectroscopy), TGA (Thermogravimetric Analysis), DSC (Differential scanning calorimetry), ICP-MS (Inductively coupled plasma mass spectrometry), and FTIR (Fourier Transform Infrared Spectroscopy) and to review the different reagents used in the pharmaceutical blister layer separation process. In addition to thermal degradation, the parameters and results of the separation processes were evaluated using hydrochloric acid, formic acid, acetic acid, sulfuric acid, ethanol, acetone, and organic solvents. It also evaluates the recyclability of the separated layers (plastic and aluminium). Its recyclability was evaluated by melting the aluminium fraction under salt consisting of a mixture of NaCl-KCl-CaF2. The plastic fraction was obtained in solid and liquid form by thermal degradation and analysed by GC-TCD (Gas Chromatography-Thermal conductivity detector).Master Thesis Remelting Behaviour of Pure and Az63 Magnesium Chips(01. Izmir Institute of Technology, 2023) Yörük, Pınar; Gökelma, Mertol; Akkurt, SedatMagnesium is a widely used light metal in many areas such as the automotive, aerospace, and medical industries. Magnesium has become widely used in industrial applications despite its poor corrosion resistance and high cost. It has great machinability, weldability, and remarkable mechanical properties such as lightweight, strength, and creep resistance. Magnesium is considered by the European Union as a critical raw material. The demand for magnesium has been increasing and it is used as a substitute for other heavy materials in many applications. Thus, recycling magnesium scrap is important due to limited raw material accessibility and environmental concerns. Secondary sources of magnesium should contribute to the economy and the procedure should be as efficient as possible to prevent metal loss. Magnesium is typically remelted under a salt flux (chloride and fluoride mix) which removes the surface oxides and other contaminants from the metal or under a cover gas that covers the surface against oxidation. This research studies the effects of salt composition, different fluorides, and the compaction degree of turnings on the recovery efficiency of pure and AZ63 magnesium alloy chips that were remelted under different chemical compositions of NaF, CaF2, MgCl2, KCl, and NaCl salt fluxes. The purpose is to minimize the metal loss and increase the coalescence ability of the metal. Metal yield and coagulation efficiency were reported XRD, SEM-EDX, XRF, and TGA analysis were performed for the characterization of chips and remelted samples. The melting point and density of the salt fluxes were determined by the FactSage software.Master Thesis Coating of La0.3sr0.7fe0.7cr0.3o3-Δ and La0.3ca0.7fe0.7cr0.3o3-Δ Cathode Layers on Gdc Ceramics by Electrospray Deposition (esd)(01. Izmir Institute of Technology, 2023) Erğen, Emre; Akkurt, Sedat; Ahmetoğlu, Çekdar VakıfHigh temperatures are needed to rapidly transfer of oxygen ions between layers during the chemical energy to electrical energy conversion in solid oxide fuel cells (SOFC). Nevertheless, intermediate-temperature SOFCs are preferred to increase their lifetime and reduce maintenance and production costs. The performance of IT-SOFCs depends particularly on the microstructure and electrochemical properties of the cathode layer. In this study, cobalt-free La0.3Sr0.7Fe0.7Cr0.3O3-δ and La0.3Ca0.7Fe0.7Cr0.3O3-δ cathode layers were coated on GDC ceramic pellets by ESD method. The aim of the thesis was to have better structural and electrochemical properties of coatings than the literature. ESD provides the atomization of liquids with the help of electrical forces. ESD is an effective method for forming coatings with desired compositions. By changing ESD parameters, different structural properties such as reticular, cracked, and dense were obtained. Reticular structures are useful for easier oxygen transfer with increased surface area. Effects of parameters were examined by Plackett-Burman design, and the most effective parameter was found as flow rate. The quality of the coatings was evaluated by quantitative scoring. The 16th sample, which was coated with solution E, got the best score. Parameters of 16th sample were used in the investigation of the effects of different solutions on the coatings. 8 different solutions named A to H were prepared with different solvents and precursor salts. Coating by solution E shows better EIS results than the literature as 0.22 Ω.cm2. Coatings by solution G and A show close values to the literature as 0.29 Ω.cm2, and 0.34 Ω.cm2, respectively.Master Thesis Coating of Spinel Layers on Alumina by Electrostatic Spray Deposition (esd)(01. Izmir Institute of Technology, 2023) Demirkol, İrem; Akkurt, SedatMgAl2O4 spinel layer was coated on dense alumina pellets by advantageous ESD among the other deposition methods in terms of providing a simple, inexpensive setup and good control of the layer morphology. The main goals are successfull deposition of spinel layers on alumina pellets by ESD, to investigate the effect of ESD parameters (working distance, flow rate of precursors, applied voltage) on coating microstructure by conducting full factorial design experiments and to determine the best experimental conditions for a porous layer. Besides, MgCr2O4 layer was coated on dense alumina and MgAl2O4 layer was deposited on bisque-fired alumina pellet to extend the scope of the work. Alumina powders were compressed and sintered, respectively to obtain pellets. MgAl2O4 spinel precursor solution was sprayed on the alumina pellets by changing the parameters accordingly the full factorial design. MgAl2O4 and MgCr2O4 solutions were also sprayed on the bisque-fired and the dense alumina pellets with the parameters given the best porous layer. Elemental analysis of the residues obtained after evaporation of the solutions by energy dispersive X-ray spectroscopy (EDX), both unheated and post-heated residual powders of solutions by X-ray diffraction (XRD) and surface morphologies of coated pellets by scanning electron microscopy (SEM-EDS) were analyzed. Spinel layers on alumina pellets were successfully coated by ESD, which could provide variable surface morphologies. The optimum conditions for a porous layer were obtained as working distance of 15 mm, flow rate of 0.25 mL/h and applied voltage of 6 kV in this study. The coatings on the pellets before further heating were amorphous. Post-heating of the pellets were required to obtain crystalline spinel structure.Master Thesis Comparatic-Ve Energy Performance Assesment of Hemp-Clay as Building Block Material(01. Izmir Institute of Technology, 2022) Ergün, Betül; Durmuş Arsan, Zeynep; Akkurt, SedatBio-based and earthen building materials have recently started to be used again in seeking sustainable materials to combat climate change. Hemp-based building materials stand out as energy-efficient materials due to their favorable thermal properties, although they still have unstandardized features that vary by location. This study aims to investigate the thermal properties and energy performance of hemp-clay building blocks which are produced with local hemp and clay in the western Aegean region of Turkey for today and the future, leading up the research on hemp-based building materials in the Mediterranean region. The methodology of the research consists of laboratory experiments on material and building energy simulations via DesignBuilder software. Building block samples were produced with 27 different hemp-clay mixtures and tested using a quick thermal conductivity meter. Subsequently, the thermal performance of selected hemp-clay block was compared with conventional wall infill materials such as hollow clay brick, autoclaved aerated concrete, and lightweight pumice block via simulations of the annual energy consumption of an existing residential building in Izmir. Simulation scenarios were generated keeping wall thickness and U-value as constant for the climate of 2020, 2050, and 2080. Hemp-clay building blocks reduced the heating and cooling demands of the case building by 21% and 14%, respectively in 2020. Their energy performance outperformed the other materials' performances even if the scenario walls have the same U-value as hemp-clay walls in today's and the future's climate conditions. Consequently, the hemp-clay building blocks are apparent as a promising material to be improved in Turkey.Master Thesis Energy Performance Analysis and Materials Characterization of Aerogel Insulation Blankets(Izmir Institute of Technology, 2022) Alan, Selena; Gökçen Akkurt, Gülden; Akkurt, Sedatİzmir Geothermal Energy Inc. is a geothermal district heating company in İzmirTurkey that circulates hot water throughout the district via a 450 km of piping system and with the help of valves, pipes, and heat exchangers. As the distance traveled by the hot water is excessively long, heat losses are common. Rock wool is used as thermal insulation material, but the performance degraded over time because of water leakage. Instead of rock wool, aerogel insulation blanket use is evaluated in this study. Rock wool and three different aerogel insulation blankets are comparatively studied to assess their structures and thermal performances in two ways: the first is the characterization of materials by various physical and chemical analysis methods in the IZTECH-Integrated Research Center. The second way is to assemble a test setup on-site and make thermal measurements on the test setup for each aerogel insulation material, rock wool, and bare pipe. Heat loss calculations were conducted by EES software. The results are compared based on each characterization and thermal performance calculation. The thermal conductivity values of the insulation materials were calculated. Nonwetting properties were also checked to understand their hygrothermal properties. Compared with bare pipe, with the 10 mm thickness, rock wool decreases heat loss by 48-52%, and with the 10 mm thickness, the aerogel insulation blankets reduce heat loss by 57-61%. Finally, while aerogel insulation blankets have a better performance, they are more expensive than rock wool.Master Thesis Sintering and Densification Behavior of Gdc Infiltrated Porous Gdc Electrolyte(01. Izmir Institute of Technology, 2021) Tekin, Sinem; Akkurt, Sedat; Ebil, ÖzgençIt is desired that the electrolytes used in solid oxide fuel cells have a dense structure. Ceria-based electrolytes require temperatures of 1400-1500oC to densify. High densification temperatures make this material less in demand despite its good ionic conductivity. In this study, it was aimed to sinter and densify porous GDC scaffolds made of GDC (Gd0.10Ce0.90O1.95) material at low temperatures using infiltration technique. A porous GDC scaffold is first produced by sintering the GDC pellet around 1000oC to obtain an intermediate product ready to be infiltrated by a GDC-bearing solution. Multiple infiltration and drying cycles were intended to fill the pores by GDC nanoparticles which are expected to densify at lower temperatures. Two different groups (infiltrated and non-infiltrated) were formed and their densification behaviors with temperature and infiltration repetition cycles were investigated using a vertical dilatometer. The porous GDC scaffold was infiltrated with a polymeric solution prepared from Ce(NO3)3.6H2O and Gd(NO3)3.6H2O. The prepared samples were sintered at 1400oC. As a result of the experiments, it was observed that the densification decreased with the increase in temperature and infiltration cycles. This is thought to be because the porous scaffold could not be completely dried during the infiltration cycles. This led to the formation of a dense outer layer of GDC and porous inner layer. This dense layer inhibited shrinkage of the pellet during dilatometric analysis. Further studies need to be conducted to fully evaporate the solvent during drying of the infiltrated pellets.Master Thesis Microstructural Analysis of the Corrosion of Al2o3 and Zro2 in Frit Melts(Izmir Institute of Technology, 2007) Şenöz, Ceylan; Akkurt, SedatDense alumina and zirconia crucibles manufactured in the laboratory by slip casting were tested for their resistance to corrosive attack by opaque and transparent frits between 1400-1500oC. Interface between the crucible and the frit was investigated by Scanning Electron Microscopy (SEM, Philips XL-30S FEG) equipped with EDS (Energy Dispersive Spectroscopy) unit, X-ray diffraction (XRD, Philips X.Pert Pro), and Optical Microscope (OM, Nikon Eclipse L150). Formation of a continuous band of zinc aluminate (gahnite) crystals was observed at the interface between the alumina crucible wall and the contained opaque and/or transparent frit melt. When opaque frit was used, isolated pockets of zirconia were present adjacent to the zinc aluminate band inside the frit. Deeper inside the frit incompletely dissolved zircon were observed. On the other hand zirconia crucible failed against both of the corrosive frits, resulting in complete penetration of frit species into zirconia crucible wall. Thermodynamic predictions based on the use of phase diagrams also produced similar conclusions with the practically observed results. Crucibles with 50 wt% zirconia and 50 wt% alumina were also manufactured and tested for their corrosion resistance against the frit. It was found that the alumina crucibles could be safely used for corrosion testing with minimal aluminum contribution to the frit melt.
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