Master Degree / Yüksek Lisans Tezleri
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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 Synthesis of Natural Adsorbents From Lignocellulosic Biomass for the Recovery of Boron From Water Resources(01. Izmir Institute of Technology, 2023) Altınbaş, Bekir Fırat; Yüksel Özşen, AslıThis work investigated the valorization of olive tree pruning waste as a biosorbent for the removal of environmentally hazardous boron from aqueous solution using batch adsorption. For this purpose, a novel, waste-based, boron-selective biosorbent from pristine cellulose and olive tree pruning waste (N-OPW) was synthesized. After confirming the proposed synthesis route with pristine cellulose, an alkali pretreatment, followed by glycidyl-methacrylate (GMA) grafting and providing boron selectivity with n-methyl-d-glucamine (NMDG) steps were applied to the biomass, respectively. N-OPW was characterized using SEM, TGA and FT-IR analyses. N-OPW showed excellent boron biosorption capacity (21.80 mg/g) in an operation pH range between 2-12. The equilibrium was attained in two hours and the Freundlich isotherm (R2=0.997) and pseudo-second-order kinetics (R2=0.99) provided the strongest match to experimental data. According to thermodynamic studies, boron adsorption was exothermic (ΔH°= - 34.14 kJ/mol). The reusability tests with real geothermal water showed that adsorbent had no significant decrease in boron removal capacity while desorbing >99% of the boron adsorbed for three cycles of adsorption/desorption. Results indicated that a promising, reusable, and boron-selective biosorbent was successfully synthesized while utilizing olive pruning waste.Master Thesis Preparation and Rheological Characterization of Calcium Silicate/Aluminate Based Cementitious Inks(01. Izmir Institute of Technology, 2022) Keleş, Pelin; Çiftçioğlu, Muhsin; Şahin, ErdemIncreasing number of bone tissue transplant operations conducted every year has increased the use of bone grafts and bone replacement materials. The commonly employed treatment methods however have several disadvantages. Bone tissue engineering scientists has been conducting intensive research on 3D scaffolds to overcome these disadvantages. Although different materials such as hydrogels, polymers, and metals are heavily used for scaffolds the most suitable material is agreed to have a ceramic/inorganic structure since they have a similar composition to the natural bone. The perfect material for 3D scaffolds formation however has not been found due to the rheological limits of inks/suspensions used in this versatile consolidation technique. Tricalcium aluminate (C3A) and tricalcium silicate (C3S) cement powders were produced with three different marble dust sources and two different silica sources in this work. The produced powders were combined with additives such as magnesium sulfate (MgSO4), hydroxyethyl cellulose (HEC), gluconic acid (GA), polyethylene glycol (PEG), trisodium sulfate (TSC) and sodium dodecyl sulfate (SDS) for the optimization of 3D printing cementitious inks/suspensions through the investigation of their rheological properties. The optimum firing temperature for C3A powder was determined to be 1300oC with 2 hours hold period while it was found to be 1400oC for 4 hours for C3S powder preparation with rapid cooling to room temperature. The use of C3A suspensions in 3D printers necessitate the presence of 1M MgSO4 which acts as a retarder; 2% HEC and 1% PEG for increasing stability; and finally, 10% marble dust and silica. C3S suspensions should contain 1M gluconic acid, 2.5% HEC, 1% PEG, 0.1M trisodium citrate and 0.1M sodium dodecyl sulfate. Capillary rheometer results are compatible with oscillating rheometer results and have been the subject of a preliminary study for 3D printers in this thesis work.Master Thesis Development of Peg-Peptide Conjugate Based Curcumin Delivery Systems(01. Izmir Institute of Technology, 2022) Aydoğan, Gamze; Top, AybenIn this study, a drug delivery system based on Pluronic F127 and a peptide conjugate was proposed. The F127-peptide conjugate was prepared by the reaction between succinimidyl functionalized F127 (SC-F127) and peptide. SC-F127 was synthesized using disuccinimidyl carbonate and DMAP. Folic acid-functionalized F127 (FA-F127) was also prepared to obtain active targeting copolymers. Four peptides containing pH-responsive multiple histidines and endosome disruptive GFWFG domain were synthesized using the Fmoc procedure. H-Gly-2-ClTrt resin and Rink amide MBHA resin were used to synthesize side-chain-protected and deprotected peptides, respectively. 2-chlorotrityl resin failed in synthesizing the high-purity peptides with adjacent histidines in their sequences. Peptide-4 having a sequence of GGH6GFWFG, was prepared with acceptable purity using rink amide MBHA resin and was conjugated to SC-F127. Curcumin was loaded to F127 and F127-peptide using the thin film method with DCM solvent. Almost all curcumin was encapsulated into F127 micelles. However, the entrapment efficiency % of the F127-peptide micelles was ~86% due to the lower solubility of F127-peptide conjugate in DCM. Dynamic light scattering experiments were used to determine the stability and size distribution of the micelles. Number-based size distributions of both micelles indicated that a single peak between 10 and 30 nm was independent of pH. The peak position did not change upon incubating the micelles at 37oC up to a few days. Initially, intensity-based results of both samples indicate bidisperse populations at pH 5.0 and 7.4. Curcumin-loaded F127 micelles aggregated in the three days, as revealed by the formation of the third peak above 1000 nm independent of pH. Curcumin-loaded F127-peptide micelles, on the other hand, retain their stability for up to five days at neutral pH. For this sample, the third peak was observed only at pH 5.0 on days 2 and 5.Master Thesis Photocatalytic Degradation of Rhodamine B Using Ag/Agcl@go(01. Izmir Institute of Technology, 2023) Köse, Taylan Can; Yüksel Özşen, AslıWater is an essential source for earth. According to the United Nation’s report, every day 1800 children dies because of contaminated water. Dyes are one of the most common water pollutants. They are using in many areas like cosmetic, textile, pharmaceutical etc. Every year nearly 140,000 tons of dye releasing to the environment. Therefore, removal of dyes from water is an essential topic. There are many ways to remove dyes from water. However, studies showed that traditional methods are ineffective to removing pollutants from water. On the other hand, photocatalysis is a promising technology. In this study, Ag/AgCl and Ag/AgCl@GO photocatalysts were synthesized and their removal performances on Rhodamine B dye were investigated. In addition, the parameters affecting the removal performance were also studied. Characterization tests such as synthesized photocatalysts, XRD, BET, UV-Vis Analysis, TGA, SEM, TEM was carried out. According to the XRD results, the peak regions of the synthesized photocatalysts were similar to other studies in the literature. The synthesized photocatalysts were first studied under 3 different pH values (pH:3, pH:8, pH:11) using 10 ppm rhodamine b dye and 30 mg catalyst under UV light. According to the results, for both photocatalysts, their natural pH, namely pH:8, showed the best performance. Afterwards, experiments were carried out with different photocatalyst weights and it was observed that the removal performance did not change after 40 mg. Finally, different dye amounts were studied and it was observed that as the dye amount increased, its removal decreased. It has been observed that the addition of graphene oxide significantly improves the performance of the catalyst.Master Thesis Adsorbent Synthesis for the Recovery of Lithium Water Resources(01. Izmir Institute of Technology, 2022) Kahvecioğlu, Anıl; Yüksel Özşen, Aslı; Yüksel Özşen, AslıLithium is a crucial mineral for the 21st century due to its utilization in a wide range of industries. Lithium demand will increase because of car battery developments and the necessity for power storage. Investigating alternative strategies for resource recovery is the only way to fulfill this unexpected rise properly and sustainably in demand. Adsorption has been discovered to have some technological advantages over other methods. It is considerably less expensive, lacks the chemical resistance present in membranes, lacks the significant electrical demand of electrochemical approaches, as well as the restricted selectivity and challenges in integration into commercial processes. Lithium manganese oxides, also known as lithium ion-sieves, are adsorbents for lithium extraction that have remarkably high selectivity, high adsorption capacity, minimal toxicity, good chemical stability and cheap cost. They are one of the most promising inorganic adsorbents. This research emphasized on the recovery of lithium from water resources through the use of lithium manganese oxide, which were synthesized in laboratory. They were transformed into spherical beads by adding chitosan, followed by crosslinking these beads with epichlorohydrin to increase their adsorption yield, stability, and reusability. Characterization techniques such as SEM, XRD and BET were applied on the adsorbents. Results shows that the adsorbents distributed uniformly, the adsorbent powder was mesoporous, and from the adsorption studies it was found that the adsorbent worked much better in alkaline conditions such as pH 12, optimum adsorbent dosage estimated as 4 g/L and the equilibrium time measured as 10 hours. From the desorption study approximately 95% of Li desorbed for the first cycle, after the second cycle the adsorbent efficiency started to decrease.Master Thesis Processing and Characterization of Novel Graphene Containing Inks(01. Izmir Institute of Technology, 2022) Yüksel, Seda Sultan; Çiftçioğlu, Muhsin; Çiftçioğlu, MuhsinScientific and industrial community currently has an increased interest in printed electronics due to its many advantages. Metallic nanoparticles and conductive polymers are mostly used in the processing of commercial conductive inks. There is extensive research and development efforts on alternative materials as conductive fillers due to high cost, chemical instability in air and liquid media of widely used fillers. Graphene materials comprised of a single layer or multiple layers of graphene flakes have recently attracted great interest and used in applications as an excellent conductive filler due to its optical transparency, high conductivity, and flexibility. The aim of this MSc work was to prepare graphite and carbon black based conductive inks. Effects of graphite (G) to carbon black (CB) ratio and the use of exfoliation liquid on conductivity, rheology and particle size distribution were investigated for graphite containing conductive inks. Inks with the lowest resistance of 0.02 kΩ was obtained by using ball milling in N-metil-2-pirrolidon (NMP) as exfoliation liquid with the lowest particle size with an average of 18.0 µm. Inks prepared in this work showed shear thinning behavior independent of the exfoliation liquid used in their preparation. The highest thixotropy was measured in water exfoliated ink with 1801 Pa.s-1 and this dispersion had the lowest conductivity. A series of inks with different graphite to carbon black ratios were prepared under similar conditions. The lowest resistance 0.045 kΩ was determined at a graphite to carbon black ratio of 1 by using ethylene glycol as an exfoliation liquid. The use of ethylene glycol in commercial ink preparation may be advantageous due to its lower cost and environmentally friendly chemical properties. The highest degree of thixotropy and viscosity was measured in ink prepared at G/CB ratio of 0.5. This ink also had the highest resistance due to low amount of graphite compared to carbon black which indicated the critical importance of G/CB ratio.Master Thesis Esterification of Free Fatty Acid Obtained From Waste Cooking Oil Over Solid Catalyst(Izmir Institute of Technology, 2022) Karacasulu, Cem; Şeker, Erol; Şeker, ErolThe objective of this study was to investigate effect of reaction temperature, catalyst weight percentage and composition of Al2O3/SiO2 on conversion of FFA obtained from waste cooking oil (WCO) to take place esterification reaction by using Box-Behnken design. Statistical analysis demonstrates that catalyst weight percentage and temperature were insignificant statistically. Alumina composition was found as significant parameter at certain conditions by considering statistical analysis. It was seen that conversion of Free Fatty Acid (FFA) increases as composition of Al2O3 in Alumina/Silica catalyst increases. %80 Al2O3/20% SiO2 catalyst was found as promising catalyst since conversion of FFA with the catalyst was 32% at 80°C and 15:1 alcohol to FFA ratio. Besides, it was found that alcohol to FFA ratio affected the conversion reversely. When alcohol to FFA ratio was reduced to 2:1, conversion of FFA increased to 41%. The prepared catalysts were characterized by XRD and TPD analysis. Activity of catalysts were attributed to acidic strength and Bronsted acid sites on the aluminum sulfate in the catalysts. After screening effects of catalysts and reaction conditions, optimum levels of parameters were used to investigate the esterification reaction of model WCO. This reveals that conversion of FFA was found as 11% at 80°C and 15:1 alcohol to FFA ratio. Finally, the proposed catalyst does not have catalytic activity of hydrolysis reaction of oil at applied conditions.Master Thesis Anaerobic Digester Modelling for Production of Biogas From Waste Hazelnut Husk(Izmir Institute of Technology, 2022) Demir, Ozan; Şeker, ErolAnaerobic digestion is a degradation process of complex organic matters into methane and carbon dioxide in an oxygen-free environment maintained by microorganisms. An advantage, besides energy production, is it is a waste management technique. Hazelnut husk is a valuable raw material for the anaerobic digestion process with more than 55 % cellulose and hemicellulose content. Anaerobic Digestion Model No. 1 (ADM1) developed by IWA Group was used in this study. This master thesis modeled biogas production by co-digestion of cattle manure and hazelnut husk process in MATLAB. The goal was to evaluate the methane amount of a household bioreactor. Tanks-in-series model with 3 CSTRs was chosen after residence time distribution (RTD) analysis. Ten different cases were investigated to show the effects of carbon source/manure ratio, temperature, carbon source type, total solid (TS) amount, reactor type, and RTD analysis. The carbon source/manure ratio improves the methane yield as it increases. When the ratio is 1, methane yield is 0.229 L/kgVS whilst yield is 0.224 L/kgVS if the ratio is 0.1. The temperature effect on the process is significant. In the thermophilic case, the methane production is 0.432 L/d which is the highest amount compared to mesophilic and psychrophilic cases. When food waste is used as a carbon source with a ratio of food waste/manure of 0.1, the methane production is 0.410 L/d while it is 0.403 L/d in hazelnut husk digester. When the TS amount is doubled, the methane yield goes down from 0.224 to 0.149 L/kgVS because the residence time is not long enough to digest it as well as in case with lower total organic carbon level. In unmixed, mixed, and Chinese Dome Digester types of reactors, methane productions are 0.403, 0.646, and 0.552 L/d, respectively. In the ideal case, the methane production is 1.525 L/d which indicates the necessity of RTD analysis.Master Thesis Modification of Corn Starch by Oxidation and Acetylation(Izmir Institute of Technology, 2022) Çelik, Tilbe; Yılmaz, SelahattinMore sustainable and eco-efficiency industries intend to use bio-based raw materials instead of petroleum-based raw materials. Starch is one of the most useful, easily accessible, and cheap bio-based raw materials in the industry. This study aimed to produce modified starch that had proper solution viscosity for coating and low gelling enthalpy to reduce production energy for the adhesive industry. Corn starch was modified by oxidation with sodium hypochlorite (NaOCl), acetylation with acetic anhydride (AA), and a combination of the two (dual modification). The effect of different amounts of oxidants (6.0, 12.0, and 24.0 g Cl/ kg starch) and acetylation agents 7.50, 15.0, 30.0 g AA) on the properties of corn starch was examined at room temperature. The structural characteristics of starch granules were assessed using FTIR, 1H-NMR, DSC, solution viscosity, light transmittance, and SEM microphotographs. The effectiveness values that were identified as carbonyl and carboxyl percentage and degree of substitution (DS) in modified starches were determined. The results showed that increasing oxidant concentration increased the carbonyl and carboxyl percentage to 0.0061 % and 1.33 % but acetyl groups were independent from increasing acetic anhydride concentration. Oxidation had a superior reduction effect on starch solution viscosity with 42% reduction when compared to 22% reduction with acetylation. Both processes reduced the gelling enthalpy, but double modification was more effective. Acetylation had a greater effect on light transmittance. Surface morphology of starch was only affected by active chlorine content at 24.0 g Cl/ kg starch, but all acetic anhydride amounts caused the changes.