Sürdürülebilir Yeşil Kampüs Koleksiyonu / Sustainable Green Campus Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7755
Browse
3 results
Search Results
Master Thesis Development of Nanofiltration Membranes Through Surface Modification of Polysulfone Based Ultrafiltration Membranes(Izmir Institute of Technology, 2017) Bar, Canbike; Alsoy Altınkaya, Sacide; Alsoy Altınkaya, Sacide; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyStimuli responsive membranes have been used for suppressing fouling and regulating selectivity in different applications. These types of membranes are usually manufactured in thin film composite structure by either polymerizing stimuli-responsive monomer or coating stimuli-responsive polymer on a support. Responsiveness is due to their characteristic features which rely on reversible changes in mass transfer and interfacial properties as a result of changes in external environment such as pH, temperature and ionic strength. In this study, a pentablock copolymer (PBC) which consists of temperature responsive Pluronic F127 (PEO-b-PPO-b-PEO) in the middle block and pH responsive poly(N,N-(diethylamino)ethyl methacrylate) (PDEAEM) in the end blocks was used for designing a new type of thin film composite (TFC) nanofiltration membrane. The support of the composite membrane was prepared from a blend of polysulfone/sulfonated polyethersulfone using nonsolvent induced phase separation and the PBC was attached to the support via electrostatic interaction. The conformation of grafted PBC chains was determined by adsorption studies. The effects of PDEAEM block length, concentration of the copolymer and adsorption time on the adsorbed amount were investigated. Among three copolymer samples investigated (15, 20 and 25 kDa), the 25 kDa PBC displayed the highest responsiveness, thus, rejection properties were determined for the membranes prepared only from this sample. The influences of operation pH and temperature on the structure integrity of the membrane were investigated with pure water permeability measurements and the change in pore size was assessed by determining rejection of neutral solutes by the membranes. The membranes were further characterized with SEM, AFM, contact angle, XPS and zeta potential measurements. It was demonstrated that a new pH and temperature responsive, high flux TFC NF membrane was manufactured.Master Thesis Temperature Dependence of Resistivity and Hall Coefficient in Cu2znsns4 Absorbers for Thin Film Solar Cells(Izmir Institute of Technology, 2017) Akça, Fatime Gülşah; Aygün, Gülnur; Özyüzer, Lütfi; Aygün Özyüzer, Gülnur; Özyüzer, Lütfi; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of Technologyenergy is the most powerful clean energy source to act on the current energy needing all over the world. The utilization of green energy systems should be promoted since these energy systems benefit consumers, industry and the environment effectively for the developing countries. This advancement can be solely achieved if renewable energy sources become more accessible. It means that not only cheaper but also handy clean energy systems are needed. In spite of relatively high efficiency obtained by using c-Si, Si solar modules require high budget for manufacturing. The high production cost of c-Si, PV industry is lead to search for cheaper candidate materials like Cu2ZnSnS4 (CZTS) as absorber layer in solar cells. The aim of the thesis is to investigate electrical properties of CZTS p-type intrinsic semiconductor compound on soda lime glass substrates, including the temperature dependent electrical conductivity, carrier concentrations and mobility extracted from Hall Effect measurements. Firstly, the metal precursor films were fabricated in multi-target sputtering system, then they were sulfurized inside the tubular furnace in order to obtain the CZTS compound. X-ray diffraction and Raman spectroscopy measurements revealed the formation of kesterite structure. A good crystallinity and grain compactness of the films were determined by scanning electron microscopy (SEM). Electrical properties were measured by van der Pauw techniques. Hall effect measurements showed the p-type semiconductor behavior for all samples at room temperature. Also, optical properties including absorption coefficient, spectral transmission, and optical band gap were determined to characterize CZTS thin films.Master Thesis Growth and Characterization of Aluminum Doped Transparent and Conductive Zinc Oxidethin Flims(Izmir Institute of Technology, 2010) Ataç, Derya; Selamet, Yusuf; Selamet, Yusuf; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyThis thesis focuses on fabrication, characterization and understanding physical properties of transparent and conductive Al doped zinc oxide (ZnO) thin films. Films were deposited by magnetron sputtering technique, using separate ZnO and Al targets. SiO2 and glass (microscope slides) were used as substrates. Growths were performed at room temperature in Ar environment at a constant pressure of 3 mTorr. Films were characterized by atomic force microscope, x-ray diffractometer, scanning electron microscope, UV-vis spectroscophotometer and four point probe electrical measurements. Using transmission data, band gaps of the films and using four point probe measurements, resistivities of films were calculated. Firstly properties of pure ZnO films were studied. They were found to be highly transparent; however their resistivity was very high that we could not measure with our instrument. Therefore, ZnO films were uniformly doped with Al. It was seen that decreasing Al content was improving electrical and optical properties. Al concentration of the films was decreased firstly by decreasing deposition power of Al. After that, content was further decreased by depositing stacks of doped and undoped layers (modulation doping). Following that, modulation doped films were deposited with applying RF bias power to substrates. All films were annealed at 300oC for 1 hour in vacuum. The lowest resistivity obtained in this study was 1.68x10-3 .cm. Transmittance and band gap of the corresponding film were 80% and 4.1 eV respectively. The film was fabricated by modulation doping accompanied with substrate bias of 10 W, followed by annealing at 300oC in vacuum.