Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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 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 Rheological Behavior of Carbon Black Inks(01. Izmir Institute of Technology, 2022) Ekerler, Deniz; Çiftçioğlu, Muhsin; Çiftçioğlu, MuhsinThe printing ink industry is increasingly facing challenges in terms of high manufacturing costs and quality requirements. Rheological properties of the inks must be better understood for the development of production and application processes. Effects of pigment and dispersant content, varnish/solvent ratio, grinding medium, grinding time and storage period on rheological and printed optical properties were investigated for carbon black inks in this thesis work. The viscosity of the dispersant free ink was higher than inks with dispersant. The viscosity of the dispersant-free ink increased after three months storage whereas the viscosity of the dispersant-containing ink remained almost constant. Pigment content or V/S ratio increase resulted in higher viscosities. Grinding with 0.5 mm beads provided a finer size distribution and lower viscosities than ink ground with 0.8 mm beads. Longer grinding time increased the ink viscosities at pigment contents over 20 wt%. Thixotropy of dispersant free ink was determined to be about 12 times higher than 0.5 wt% dispersant containing ink. The thixotropy area of the 30 wt% pigment containing ink was determined to be five times higher than that of 25 wt% pigment containing ink. The thixotropy of the 25 wt% pigmented ink increased when the grinding time was changed from 30 to 60 minutes. Inks with coarser particle size distribution had higher thixotropy. Loss tangent (G''/G') at 10 Hz was used to create a correlation with color strength. Color strength of 14 out of 16 inks was determined higher with lower loss tangent values. Inks containing dispersant, higher pigment contents, varnish/solvent ratios close to one, increasing grinding time at higher pigment content increased the color strengths in printings.Master Thesis Ceramic Microfiltration Membrane Design Towards Oil Removal in Metal Industry Wastewater Streams(01. Izmir Institute of Technology, 2020) Eren, Muhammet Şakir Abdullah; Çiftçioğlu, MuhsinIncreasing water scarcity is an important threat to the whole world. The use of too much water during the production processes and the insufficient level of reuse of this water and the increasing quantities of oil containing waste generated in many industrial activities cause dangerous consequences for the environment. Highly concentrated oil-inwater emulsions are very harmful for aquatic life, soil, atmosphere and human health. Traditional treatment methods are not effective in the removal of emulsified oil droplets which have less than 20 µm of droplet size. Ceramic micro/ultrafiltration membranes have been explored and developed in recent years due to their superior advantages in oil containing water treatment/purification. The aim of this MSc study was to produce tubular ceramic supports and microfiltration membranes for the removal of oil from stable oil in water emulsions used as metal cutting fluids. The prepared metal cutting fluids were fed to the crossflow filtration system and the effects of experimental parameters such as transmembrane pressure (TMP), crossflow velocity (CFV) and oil content on membrane performance/permeate flux were investigated. The single/double layered coatings on the support surfaces were formed in the preparation of the microfiltration membranes by using stable 0.4 µm α-alumina suspensions. The 1 layer and 2 layers containing microfiltration membranes were heavily fouled and very low permeate fluxes were obtained in an hour of treatment. This was attributed to the formation of a thin oil layer on the microfiltration membrane surfaces. The reduction of the total suspended solids (TSS) and turbidity were determined as ~100 %. A stable permeate flux with a lower extent of membrane fouling and concentration polarization was obtained with 1% oil content and the support membrane and TMP=2 bars.Master Thesis Determination of the Electrocalorinc Properties of the Ferroelectric (1-x)batio3-bi(li1/3ti2 (0?x?0.2) System(Izmir Institute of Technology, 2018) Demirtay, Tuğçe; Adem, Umut; Çiftçioğlu, MuhsinThe aim of this study is to develop electrocaloric (EC) materials for alternative eco-friendly cooling technologies. Considering the dielectric and piezoelectric properties of the (1-x)BaTiO3- xBi(Li1/3Ti2/3)O3 (0≤x≤0.2), this system was selected to study electrocaloric properties due to the presence of morphotropic phase boundary (MBP). The crystal structure of the samples that were synthesized by convential solid state reaction technique were determined by the X-Ray Diffraction experiments. The electrical properties of the ceramics were characterized by temperature-dependent dielectric measurements and the phase transition temperatures of the samples were identified. Temperature-dependent electrical polarization curves were measured for all compositions and electrocaloric temperature change values were calculated with the help of Maxwell equations. Using the dielectric measurements, a phase diagram was obtained. Strain-electric field measurements were done to complement dielectric and polarization measurements. A new antiferroelectric phase was discovered at high temperatures in the samples. As Bi(Li1/3Ti2/3)O3 content is increased, phase transition from the ferroelectric to antiferroelectric phase decreases. Since in the antiferroelectric phase the net polarization is very small, a large polarization change therefore large electrocaloric temperature change is obtained. Highest electrocaloric temperature change (ΔT=0.66 K under 22 kV/cm) is obtained for x=0.03 sample.Master Thesis The Investigation of the Water Splitting Activities of Coprecipitated Doped Nanotitania Powders(Izmir Institute of Technology, 2018) Gözel, Gözde; Çiftçioğlu, MuhsinThe increase in the extent of greenhouse gases in earth’s atmosphere lies behind the global warming and climate change. The extensive use of unsustainable fossil fuels have intensified the greenhouse effect, causing global warming. Hydrogen is considered as an ideal fuel for the future. Hydrogen fuel can be produced from renewable energy sources and its life cycle is clean. Artificial photosynthesis has been considered as a promising prospect for the synthesis of renewable and sustainable fuels. Photocatalysis is expected to make a great contribution to environmental problems and renewable energy generation in the very near future. Titania based photocatalytic materials are one of the widely used materials in artificial photosynthesis research due to their unique chemical and optical properties. Photocatalytic water-splitting by using TiO2 based photocatalysts for hydrogen production offers a promising alternative for clean, low-cost and environmentally friendly production of hydrogen. ZrO2 doped TiO2 photocatalyst powders were prepared by coprecipitation and characterized in this work. The photocatalytic water splitting activities of these ZrO2 doped TiO2 photocatalyst powders in hydrogen production was investigated under UVVis light. The phase structures of the powders were significantly affected by the level of dopants and the primary particle sizes increased from about 130 nm to about 500 nm during heat treatments in the 550-700°C range. Maximum hydrogen yield of about 5000 μmol/hr gcat. was obtained with the 550°C heat treated powder doped at 0.1-0.1 mol% ZrO2-Nd2O3 level. ZrO2 doping above 10 mol% decreased the hydrogen yields of the catalysts to lower than 1000 μmol/hr gcat.Master Thesis Investigation of the Performances of Ceramic Micro/Ultrafiltration Membranes in Stable Oil in Water Emulsion Purification(Izmir Institute of Technology, 2018) Çetin, Pınar; Çiftçioğlu, MuhsinIncreasing water scarcity is an important threat to the whole world. The use of too much water during the production processes and the insufficient level of reuse of this water and the increasing quantities of oil containing waste generated in many industrial activities cause dangerous consequences for the environment. Highly concentrated oil-in-water emulsions are very harmful for aquatic life, soil, atmosphere and human health. Traditional treatment methods are not effective in the removal of emulsified oil droplets which have less than 20 μm of droplet size. Ceramic micro/ultrafiltration membranes have been explored and developed in recent years due to their superior advantages in oil containing water treatment/purification. The aim of this MSc study was to produce tubular ceramic micro/ultrafiltration membranes for the removal of oil from stable oil in water emulsions. The prepared emulsions with about 5-6 μm of droplet sizes were fed to the crossflow filtration system and the effects of experimental parameters such as transmembrane pressure (TMP), crossflow velocity (CFV) and temperature on membrane performance/permeate flux was investigated. Titania, zirconia and neodymium doped polymeric sols were prepared and coated on the MF layer in order to investigate coating/surface modification on probable permeate flux enhancement and separation ability of the membrane. The reduction of the total suspended solid (TSS) and turbidity were determined as 100 %. A stable permeate flux with a lower extent of membrane fouling and concentration polarization was obtained with 1 m/s of CFV and 2 bar of TMP.Master Thesis Preparation and Application of Subnano Ceramic Filtration Membranes for Organic Species Removal From Aqueous Streams(Izmir Institute of Technology, 2017) Yaltrık, Kaan; Çiftçioğlu, Muhsin; Çiftçioğlu, MuhsinThe purpose of this MSc work was to investigate the effects of neodymium/zirconium doping on the phase structure evolution of the selective titania nanofiltration (NF) membrane layers for the rejection of subnano sized organic compounds. A dilatometric study was carried out on unsupported membranes prepared from polymeric sols with different neodymium and zirconium levels. The development of functional abilities towards the design of the pore structure in the subnano range by controlling the nanostructural evolution of the selective NF layers was the fundamental purpose of this work. The neodymium doping level was varied in the 0.3-5.0% range and the zirconium mixing level was varied in the 0-100% range based on stable metal oxide molar compositions. Dilatometric characterization results have shown that dopant level effects the nanophase evolution and the densification behavior considerably. The dynamic light scattering results have shown that the polymeric species in the sol were predominantly 2-4 nm in size and had a very narrow size distribution. XRD analysis results indicated titania anatase crystallite sizes were reduced significantly with neodymium doping or zirconia mixing and the phase transformations were retarded by about 200°C. HR-TEM images of selected zirconia mixed or neodymium doped unsupported membrane powders also added new information to the XRD/dilatometry derived nanophase evolution results. The determination of the molecular weight cut-off values and pure water fluxes of the NF membranes which would be prepared by using these polymeric sols in the near future may generate valuable knowledge on the subnano separation abilities of these NF membranes.Master Thesis Preparation of Asymmetric Ti̇o2 Based Nano/Ultrafiltration Membranes for Wastewater Treatment(Izmir Institute of Technology, 2017) Odabaşı, İklima; Çiftçioğlu, MuhsinFresh water scarcity have been the most fundamental problem in the world and is already affecting mankind and human activities. This problem forced an increasing effort in the reuse of wastewater originating from municipal, agricultural, and industrial activities. The textile industry demands large amounts of water and produces large quantities of wastewater. Adsorption, filtration, ozonation and photocatalysis techniques are currently used for wastewater treatment and safe discharge to the environment. Although membrane filtration necessitates a high initial setup cost, it has a high potential and may cause significant cost savings through the reuse of water and salts. The membrane based technologies are widely accepted to be the best method when compared with the currently available technologies for wastewater treatment. Extruded tubular alumina supports were coated by stable colloidal sols and polymeric sols prepared by using sol-gel based techniques for the formation of selective micro/ultra/nanofiltration layers in this work. Textile wastewater treatment (with and without pre-treatment) and membrane fouling analysis was conducted. The performances of the membranes were determined through the characterization of permeates by spectrophotometer. The reduction of colors (Pt-Co, m-1), turbidity and suspended solids content were about 99%, 100% and 100%, respectively. The incorporation of a coagulation stage by using Al2(SO4)3 followed by a successive filtration reduced the membrane/irreversible fouling levels in the MF/UF membranes significantly. The Pt-Co 455 values of permeates were determined to be in the 15-260 range which are below the discharge criteria bringing the possibility of the reuse of some of these permeates.Master Thesis Application of Tubular Ceramic Nanofiltration Membranes for Textile Waste Water Desalination(Izmir Institute of Technology, 2017) Yaldız, Safiye; Çiftçioğlu, MuhsinTextile industry generates coloured wastewater containing a significant level of dye/inorganic salts. Environmental concerns and efficient energy use make the recovery of reusable water and salts from textile wastewater vital globally. Ceramic nanofiltration (NF) membranes are becoming increasingly important for the recovery and purification of dyes and salts (e.g., NaCl) in high salinity waste streams. They have superior chemical/mechanical/thermal properties compared to their polymeric counterparts. Desalination performances of the ceramic NF membranes depend on the concentration and chemical structure of the target ions, pH of feed and the wastewater stream along with the chemical/surface/nanostructural properties of the selective NF layer. Metal oxides are generally used as NF layer materials due to their amphoteric behaviour. Repulsive/attractive forces between the ionic species in the solution and the NF layer may make the separation of ionic species possible. In this work, zirconia doped titania based NF layers were designed. Desalination experiments were conducted with 10-3 M Na2SO4 and MgSO4 salts at different pH values. Salt retention capacities of 5 different membranes were determined. Percent retention was calculated using ion concentrations in permeate and retentate streams. The Mg2+ and SO4 -2 ion concentrations were determined by titration with 0.01 M EDTA and by spectrophotometer at 420 nm, respectively. A clear pH dependency of the salt retention was found in filtration tests. The highest SO4 -2 and Mg+2 ion retentions were obtained with using MF+disperel (boehmite)+P2 (600 0C)+TTIP hydrosol+Ti/Zr polymeric (double layer) membrane as 95% and 91%, respectively.