Master Degree / Yüksek Lisans Tezleri

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Access type: Open accessDepartment: search.filters.department.Thesis (Master)--İzmir Institute of Technology, Materials Science and Engineering

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Now showing 1 - 10 of 144
  • 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, Mücahit
    Debriyaj 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
    The Effects of Manganese Concentration on the Mechanical Properties of A356 Aluminum Alloy Wheels Produced by Low Pressure Die Casting
    (01. Izmir Institute of Technology, 2024) Kaya, Ahmet Yiğit; Gökelma, Mertol; Davut, Kemal
    Alüminyum, otomotiv endüstrisinde her geçen gün daha önemli hale gelmektedir. Genellikle alüminyum alaşımından yapılan otomobil jantları, geri dönüşüm verimliliği, yüksek özgül mukavemeti, termal iletkenliği, işlenebilirliği ve korozyon direnci nedeniyle tercih edilmekte ve hafiflikleriyle araçların artan performansına ve yakıt verimliliğine katkıda bulunmaktadır. Alüminyum alaşımlı jantlar belirli mekanik standartları karşılamak zorundadır. Bu konudaki büyük bir endişe, geri dönüştürülmüş alüminyum alaşımlarının bu mekanik gereksinimleri karşılayıp karşılayamayacağıdır. Alüminyum alaşımlarında geri dönüştürülmüş hurda oranı arttıkça, empüritelerin karışması ve birikmesi önemli sorunları beraberinde getirmektedir. Bu çalışmada demir içeriğinin zararlı etkilerini ortadan kaldırmak için Mn kullanılmıştır. Mangan varlığı demir intermeteliklerinin olumsuz etkilerini nötralize eder, böylece ikincil alüminyumun güvenlik açısından kritik uygulamalarda kullanılmasına olanak tanır. Bu amaçla ağırlıkça %0,040 (şarj 1), ağırlıkça %0,069 (şarj 2) ve ağırlıkça %0,14 (şarj 3) Mn içeren A356 alaşımlı otomobil jantları alçak basınçlı döküm yöntemiyle döküldü. İntermetalikler incelenerek Mangan etkilerinin görülebilmesi amacıyla optik mikroskop incelemesi yapılmış ve bu görüntüler ImageJ yazılımı yardımıyla sayısal verilere dönüştürülmüştür. Üretilen jantların mekanik özellikleri sertlik ölçümü, çekme testi ve Charpy darbe testi yapılarak incelenmiştir. Charpy darbe testi sonucunda oluşan kırılma yüzeyleri SEM ve EDX yardımıyla incelenmiştir. Beklendiği gibi, sertlik ve akma dayanımı değerleri tüm numunelerde benzer davranış sergilemiştir. Bölgesel artış ve azalışlar vardır. İstatistiksel analizler sonrasında, Mn konsantrasyonu ile mekanik özellikler arasında güçlü olmayan negatif doğrusal bir korelasyon gözlenmiştir. Dolayısıyla, Mn ilavesi mekanik özelliklerdeki düşüş için tek ve en güçlü parametre değildir. Darbe enerjisi, uzama ve akma dayanımında olduğu gibi en-boy oranı ve tane/mm2 üzerinde güçlü bir etkiye sahiptir. Ancak akma dayanımı ve uzamanın aksine, en-boy oranı tane/mm2'ye göre daha hassastır.
  • Master Thesis
    High-Throughput Selection of Mineralizing Peptides
    (01. Izmir Institute of Technology, 2024) Çulha, Gizem; Toptan, Fatih; Yücesoy, Deniz Tanıl
    3,4 milyar yılı aşkın protein evrimi boyunca Doğa Ana, biyomineral oluşumunu düzenleyen ve kontrol eden moleküler yollar geliştirmiştir. Biyolojik sert dokuların mükemmel hiyerarşik yapıları ve çok işlevli özellikleri uzun süredir malzeme bilimcilerine ve mühendislerine ilham kaynağı olmuştur. Proteinler tarafından sentezlenen bu doğal kompozitler, inorganik katıların çekirdeklenmesini ve büyümesini kolaylaştırır ve böylece organizmalarda mineral oluşumunu yönlendirir. Biyomineralizasyon yaşam için gerekli olmasına rağmen; düzensizliği önemli sağlık sorunlarına yol açabilir. Bu nedenle, bu mekanizmayı anlamak anormal mineral birikimiyle ilişkili hastalıklara yönelik tedavilerin geliştirilmesi açısından çok önemlidir. Nano ölçekte biyolojiden ilham alan bu tezin amacı, derin yönelimli evrim yaklaşımıyla doğal proteinlere benzer şekilde hidroksiapatit (HAp) mineralizasyonunu yönetebilen kısa katalitik peptitleri tanımlamaktır. Sonuçlarımız, benzersiz dizilere sahip peptitlerin tanımlandığını gösterdi. XRD ve FTIR analizleri yoluyla yapılan yapısal karakterizasyon, bu peptitlerin varlığında hidroksiapatit oluşumunu doğruladı. Bununla birlikte, kinetik ölçümler bu peptitlerin fizyolojik koşullar altında kalsiyum fosfat mineralizasyonunu on beş kat daha hızlı katalize ettiğini ortaya çıkardı. Bu peptitlerin, kalsiyum ve fosfat ile desteklenmiş sulu ortamda sergilediği hızlı mineralizasyon kinetiği, demineralize olmuş dokuların onarılması ve patolojik biyomineralizasyon ile ilişkili hastalıkların tedavisi için güçlü bir potansiyele işaret etmektedir. Aynı zamanda, bu peptit dizileri, diş jelleri ve diş macunu formülasyonları dahil olmak üzere klinik ürünlerin geliştirilmesinde, kemik rejenerasyonu tedavilerinde ve kontrollü mineralizasyonun önemli olduğu diğer tıbbi uygulamalarda temel unsurlar olarak hizmet edebilir
  • Master Thesis
    Electrocaloric Properties of the Zr-Substituted Batio3 – Na0.5bi0.5tio3 Ceramics
    (2023) Akkaşoğlu, Oğuz; Adem, Umut
    The aim of this study is to investigate electrocaloric properties and thermodynamic behaviour, obtaining high adiabatic temperature change (ΔT) values with a broad temperature span of zirconium doped barium titanate-sodium bismuth titanate by substitution of Zr into B-site (titanium). Ceramics are synthesized in a pellet form by solid-state reactions. Chemical composition was Ba0.7Na0.15Bi0.15TixZr1-xO3 (abbreviated as BT-NBT) where x= 0.00, 0.01, 0.02, 0.03, 0.035, 0.04 and 0.05. Phase analysis was conducted by X-ray diffraction method. Microstructural analysis and average grain size determination was performed by Scanning Electron Microscopy. To understand phase transitions and physical behaviours, dielectric measurements are performed. Ferroelectric properties are investigated by using temperature dependent polarization, strain and current-electric field relationships. Electrocaloric measurements are done by using temperature dependent polarization-electric field data. Maxwell relations are used to calculate temperature dependent electrocaloric temperature change, ΔT, and from this data, temperature span, Tspan, was calculated. It was observed even though Zr substitution into the Ti-site rapidly decreases the Curie temperature and introduces relaxor ferroelectric character to the samples. However, the 1st order like nature of the ferroelectric-paraelectric phase transition at the Curie temperature and, consequently significant ΔT is maintained even for 4 % Zr substituted sample close to room temperature. Temperature span, on the other hand, has a lower value compared to previous works related to barium titanate systems. Electrocaloric efficiency is comparable to other works on Pb-free sytems and these results showed that BT-NBT systems have promising features for electrocaloric cooling technologies.
  • Master Thesis
    Synthesis of Drug Loaded Ph Sensitive Albumin Nanoparticles
    (2023) Argıtekin, Eda; Akdoğan, Yaşar; Adem, Umut
    Serum albumin-based nanoparticles (NPs) are commonly used for drug delivery due to their stability, biodegradability, ease of particle size control and no toxicity. In this study, bovine serum albumin (BSA) was functionalized with catechol-containing dopamine (D) to synthesize D-BSA NPs using pH responsive catechol-metal coordination bonds. Instead of using glutaraldehyde, V(III) ion was used as a cross-linker for synthesizing NPs. Catechol-V(III) coordination bonds provided pH responsive NPs due to their different stoichiometry of catechol-metal complexes (e.g. mono-, bis- or tris-) at different pH values. For the synthesis of D-BSA NPs, desolvation method was used with acetone as desolvating agent. Uniformly sized NPs were synthesized with an average of 294 nm with a PDI value of 0.15. Doxorubicin is loaded to NPs with a 15:1 DOX:D-BSA molar ratio. DOX encapsulation efficiency and drug loading capacity of D-BSA NPs were found to be 98% and 10%, respectively. Conversion to bis- and/or mono- catechol-V(III) complexes in acidic medium resulted in degradation of NPs and rapid release of the loaded doxorubicin (DOX). DOX releases reached to 51, 76 and 95% at pH values 7.4, 5.5 and 4.2, respectively at the end of 80 hours. Furthermore, the cytotoxic effects of prepared D-BSA NPs, in comparison to free DOX were studied with MCF-7 cells. Increasing D-BSA concentrations up to 0.2 mg/mL did not affect the cell viability, significantly. But, upon cell (MCF-7) uptake in vitro, DOX-loaded D-BSA NPs and free DOX reduced cell viability by 75% and 20% in 24 hours, respectively.
  • Master Thesis
    Effect of Arc Deposition and High Power Impulse Magnetron Sputter Coatings on the Performance of Tools for Machining Various Ferrous Materials and Ti6al4v Alloys
    (Izmir Institute of Technology, 2023) Nohuz, Mine; Davut, Kemal; Davut, Kemal
    In this thesis, the performance of different coating techniques in machining various steels and Ti6Al4V is investigated. Currently, most of the carbide tools with the coating because of the tool life. In order to increase the productivity of the manufacturing processes and to use new materials, the research on the coating of cutting tools has been increased. Recently, the interest in physical vapor deposition has increased because the tool life is increased for many difficult-to-machine materials and difficult machining conditions. Two types of PVD coating were used in this work. The surfaces of the coated tools were examined under scanning electron microscope. The effects of cathodic arc deposition and high pulse magnetron sputtering on tool performance were investigated on various workpieces such as 4140 and CK45 steels, D2 tool steel (60HRC), GG25 cast iron and also on Ti6Al4V alloy. In the performance tests, the cutting forces were measured over a period of time and the wear patterns were recorded. The results indicate that HIPIMS coated tools perform better in operations where normal load is low and torsion forces are high. Those tools also work better in materials harder than 250 BHN. The better performance of HIPIMS coated tools were attributed to their less smooth and droplet free surfaces.
  • Master Thesis
    Sintering and Densification Behavior of Nanoparticle-Infiltrated Alumina Scaffolds
    (Izmir Institute of Technology, 2023) Özbekler, Meti̇n; Akkurt, Sedat
    This 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, Sedat
    Packaging 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, Sedat
    Magnesium 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
    Piezocatalytic and Piezoelectric Properties of P(vdf) and Its Copolymer/Terpolymer Films
    (01. Izmir Institute of Technology, 2023) Tengizdeniz, Ceren; Adem, Umut; Genç, Aziz
    Nowadays, the release of colored organic pollutants such as Rhodamin B dye, resulting from industrial activities endanger the people, animals, and plants. Many methods have developed to destroy these harmful pollutants. Piezocatalysis, a newly used environmentally friendly method, takes advantage of the piezoelectric effect, and uses mechanical vibration to produce active species on opposite surfaces of matter for degradation of dye. In this study, piezocatalytic and piezoelectric properties of P(VDF) based homopolymer, copolymer and terpolymers were investigated. With the addition of 2nd and 3rd monomer to the homopolymer, observation of change in piezoelectric and piezocatalytic properties and removal efficiency of pollution in water, were aimed. P(VDF) homopolymer, P(VDF-TrFE) copolymers with composition of 55/45 and 50/50 mol%, and P(VDF-TrFE-CTFE) terpolymer with 62/31/7 mol% were synthesized by solution casting method. It was observed that the 2nd and 3rd monomer added to the homopolymer enhanced the piezoelectric properties and strain characteristics of the polymers. Maximum polarization and strain of terpolymer was observed as 11 µC/cm2 and 5.6 %, respectively. Due to the increase in piezoelectricity, a noticeable increase in piezocatalytic properties was observed. Terpolymer exhibited the highest and most efficient piezoelectric and piezocatalytic performance. P(VDF) homopolymer was reached 27% dye degradation efficiency. While copolymers with mol% 55/45 and 50/50, dye degradation efficiencies were 40% and 47%, respectively, terpolymer efficiency was 54%. From the dielectric measurements, within the transition region (49 mol% ≤ CVDF ≤ 55 mol%) of P(VDF-TrFE), both normal-ferroelectric and relaxor characteristics were observed. Terpolymer showed relaxor properties as expected.