Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Synthesis of Needle-Like and Rod-Like Nano Baco3 Particles(Izmir Institute of Technology, 2016) Kahyaoğlu, Tuğçe Nefise; Özdemir, EkremBarium carbonate (BaCO3) has been widely used in soft and heavy industries such as ferrite magnets, solid oxide fuel cells, optical glass manufacturing, coatings, and polymeric composite materials as well as ceramic and brick industries. Using BaCO3 in nano sizes will improve some of the physical properties of materials such as tensile strength, opacity, and thermal resistance. Production of BaCO3 by chemical method requires extensive crystallization times and higher temperatures. Production of BaCO3 by carbonation method usually yields particles with some agglomeration. In a study, conducted by our group funded by The Scientific and Technological Research Council (TUBITAK), a method was developed to synthesize hollow nano Calcium Carbonate (CaCO3) particles. It was aimed to apply the developed method, which is unique in its kind, to produce nano BaCO3 particles in different morphologies. Parameters such as effect of barium hydroxide (Ba(OH)2) concentration, CO2 flow rate, length in reaction chamber, and stirring rate were studied. Conductivity and pH values of the solution were monitored during crystallization. Surface morphology and crystal structure of the produced BaCO3 particles were characterized by Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. It was shown that rod-like BaCO3 particles produced in nano sizes with almost homogeneous size distributions. The rod-like BaCO3 particles had a diameter from 100 to 400 nm and an aspect ratio of about from 3 to 10. The produced rod-like nano BaCO3 were all in orthorhombic phase of BaCO3 called as Witherite.Master Thesis Characterization of Gaas (211) Surface for Epitaxial Buffer Growth(Izmir Institute of Technology, 2014) Polat, Mustafa; Selamet, YusufGaAs (211)B wafer can be used for the growth of CdTe buffer layer by MBE after thermal desorption of oxide presents on its surface. Then, CdTe buffered GaAs (211)B called as composite substrate can be used as a template for the growth of HgCdTe. Thermal desorption can be detrimental to surface in some cases if the structure and constituents of this oxide are not fully understood. In this thesis, HF:H2O and H2SO4:H2O2:H2O chemical treatments were applied to epiready GaAs (211)B samples for the determination of suitability of their usage for CdTe buffer layer growth. Effects of these wet chemical etching processes on the surface of samples are characterized and determined by various kinds of characterization techniques including XRD, XPS, SEM, EDX, AFM, and optical microscope. We also analyzed samples cut from 3" epiready GaAs (211)B wafers to determine their oxide structures, surface roughnesses, crystal qualities, and surface morphologies. Crystal quality of as-received samples measured by RC were about 18-21 arcsec. Amounts of arsenic and gallium oxides were decreased after HF treatment according to XPS results. Gallium rich surface was obtained for samples treated with piranha solution. Surface roughnesses of samples increased after piranha treatment. However, it was determined that others treated with HF had smaller surface roughnesses than asreceived samples.