Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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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.Master Thesis Rheological Characterization and Extrusion of Alumina Based Pastes for the Preparation of Tubular Ceramic Membrane Supports(Izmir Institute of Technology, 2016) Yılmaz, Kenan; Çiftçioğlu, MuhsinMembrane applications in the industry currentlyis dominated by polymeric membranes, however, in recent years the development of ceramic membranes gained significant attention because of their superior chemical/thermal stability and corrosion resistance. The separation capacities of ceramic membranes basically depend on the nature of the selective oxide layers formed on the inner surfaces of tubular ceramic supports. Ceramic tubular membrane supports were prepared from alumina pastes, with solid loadings as high as 55 vol. % and water was used as the major liquid phase. Boehmite along with hydroxypropyl cellulose ethers with different molecular weightswere used as binder materials. Glycerol was used as a lubricant in the paste formulations. Extrusion of alumina paste was conductedwith a ram extruder using capillary dies with a series of L/D ratios at different extrusion velocities and the data was analyzed by using Benbow and Bridgwater model. The rheological properties of various pastes were determined according to the 4 and 6-parameter models.The six parameter model was concluded to better represent the experimental data. The viscosities of the paste batches were also determined by using the model parameters o, 1, and exponent n. The pastes were determined to have a shear thinning behaviour Piston extruder was used for shaping of tubular ceramic supports and the pressure varied in the 20-90 bar range with paste composition and rheology. The tubular extruded supports were dried, debinded to burn out organic binders and sintered at 1525ºC for the formation of about 40% porous mechanically strong membrane supports.Master Thesis Preparation and Characterzation of Ceramic Micro/Ultra Membranes for Separation Processes and Wastewater Treatment(Izmir Institute of Technology, 2016) Kırkbaş, Öncel; Çiftçioğlu, MuhsinThe availability of fresh water is vital for life, sustainable growth and healthy ecosystems on earth. Increasing world population, a changing climate, intensive agricultural practices, economic growth and urbanization will undoubtedly continue to make the issue of water scarcity a global priority for years to come. The gap between the need and the supply of water globally is increasing steadily which necessitates significant measures to be taken towards conservation, and reuse of industrially, domestically and agriculturally used water. Textile industry is one of the leading industries in the use of fresh water and the generation of wastewaters. Technologies currently in use towards industrial and domestic water treatment like sedimentation, chemical coagulation, biological treatment etc. cannot produce reusable water but also generate significant amounts of solid waste. Membranes are now widely accepted to have the potential of supplying cost-effective solutions for water treatment and a growing range of purification and separation problems. The number and the pore structure design of the multiple selective layers on the inner surfaces of tubular α-alumina supports vary with the nature of the intended separation application. Although the nature of MF membranes is relatively well developed, current research is concentrated on the design of nanoporous phase structure in NF and UF selective layers. Selective micro/ultra/nanofiltration layers were formed on extruded tubular alumina supports by colloidal/sol-gel techniques. The performance of these selective layers were investigated by the experiments performed with textile wastewater. Permeates from ceramic tubular membranes were characterized by spectrophotometer. The suspended solids and color (Pt-Co) were reduced by 90% and 80%. respectively.Master Thesis Electrochemical Properties of Titania Based Powders(Izmir Institute of Technology, 2015) Türkay, Cem; Demir, Mustafa Muammer; Çiftçioğlu, MuhsinGlobal warming arising from the greenhouse effect is globally accepted as the main problem which may threaten the life on the earth. Excess emission of carbon dioxide which leads to the more absorption of solar radiation in the atmosphere is the main reason for global warming. Carbon dioxide present in the atmosphere is balanced by natural photosynthesis; however this balance was disturbed by the increasing amount of carbon dioxide emissions after industrial revolution. Intense efforts was made by many scientists to find solutions to decrease the carbon dioxide level in the atmosphere and the pioneering studies were conducted in the early 1970s which founded the basic theory of artificial photosynthesis. The conceptual idea on conducting photosynthesis by technologically feasible processes was accepted by many scientists and the research on artificial photosynthesis accelerated in the last 10 years. The enhancement of the efficieny of artificial photosynthesis, by which alternative fuels such as methane, methanol may be produced, can be realized by doping titanium dioxide which is the most widely used photocatalyst in the literature. The determination of new electrochemical properties obtained by doping titanium dioxide is crucial since the oxidation/reduction reactions are controlled by the electrochemical structure of this material. Bandgap and band position energy levels which are important properties in photocatalysis can be determined and the efficiency of photoreduction under UV or visible light corresponding to these energy levels can be improved. Cyclic voltammetry (CV) can be used to determine the electrochemical properties of titanium dioxide and these properties can be improved by using the information obtained with this method. The effects of rare earth element doping on the electrochemical properties of titanium dioxide were investigated through out this Msc study. It was found that doping of titanium dioxide is significantly increased the electrochemical activity with rare earth elements. The increase in the doping amount of elements showed that articial photosynthesis activity of titanium dioxide may be enhanced by rare earth element doping.Master Thesis An Investigation of Electrochemical Stability of Zinc Electrodes for Battery Applications(Izmir Institute of Technology, 2014) Payer, Gizem; Ebil, Özgenç; Çiftçioğlu, MuhsinEnergy is the most important and inevitable requirement for humankind. The increasing energy demand has been connected with technological advances and the population growth. One of the most serious problems of the world is to provide sustainable energy. New alternative energy sources and renewable energy technologies have become notable research subjects due to wide availability of renewable energy sources in the world. However, most renewable energy sources do not provide uninterrupted energy to consumers. An economic, efficient and reliable energy storage technology is desperately needed. Therefore, academic research has focused on improving the capacity of electrochemical energy storage technologies. The main goal of this study is the preparation and characterization of zinc electrodes for battery applications using different zinc oxide powders with various morphologies and additives. Zinc oxide powders were synthesized with chemical precipitation method under different conditions (precursors, temperatures and aging times) in order to investigate their effects on ZnO morphology and on the performance of nickel-zinc battery. It was found out that the initial morphology of ZnO powder was not crucial for the electrochemical performance. Nickel-Zinc batteries with zinc electrodes prepared from commercial ZnO powder had discharge capacities around 247 mAhg-1 and showed slightly better performance compared to nickel-zinc batteries with zinc electrodes prepared from ZnO powders synthesized via chemical precipitation method. It was also determined that zinc electrode morphology was greatly affected by battery additives (PVA and PEG) and charging current density. The effects of some selected electrode additives (Ca(OH)2, PbO and PEG) on battery performance were also investigated. Zinc electrode with all additives showed improved electrochemical properties, such as higher discharge capacity (322 mAhg-1) and utilization ratio (48.86 %.)
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