Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Synthesis and Characterization of Mgb2 Superconducting Wires(Izmir Institute of Technology, 2008) Horzum Polat, Nesrin; Özgen, TamerkanIn this study, the superconducting properties of laboratory synthesized MgB2 was investigated. In the first part, MgB2 synthesis using commercial magnesium and boron (95-97% purity), and its microstructural and electrical characterization was investigated.Effects of sheath material and annealing temperatures were also examined. The microstructural studies showed that when Cu tubes were used as sheath material, MgCu2 forms instead of MgB2 even at 700oC, while on Fe clad cores, the major phase was MgB2 with minor MgO constituent. The transition temperatures of Fe clad wires were measured between 39K and 40K, whereas no transition temperature was observed for Cu clad wires. The Ic value of the Fe clad MgB2 wire was about 25 A at 4K, while the copper clad wire could not carry current and formed resistance. In Fe clad wires, better results were obtained at annealing temperature of 800°C for 30 minutes. In the second part, MgB2 synthesis using commercial magnesium and boron (90% purity) was tried. 0-5-10-15 wt% of Mg doping and, additionally annealing temperatures were examined. Powder-In-Tube method was used for wire production. 10 wt% Mg addition was seen to be beneficial as compared to the stoichiometric MgB2. 750°C was found to be the most suitable temperature for the formation of MgB2 phase. The Ic value of the wire was measured as 13 A at 4K and it showed a broader transition with non-zero resistivity, transition temperature of 24K.In the third part, 200 m long four filament MgB2/Cu wire was successfully produced in laboratory conditions.Master Thesis Synthesis of Magnesium Hydride and Sodium Borohydride at Low Temperatures(Izmir Institute of Technology, 2006) Akyol, Emel; Özgen, TamerkanIn this study, experimental conditions for production of magnesium hydride and sodium borohydride by low temperature grinding are investigated. In the first set of experiments, it was attempted to confirm the information presented in the literature that magnesium hydride could be produced by heating at 350oC for 24 hours under 10 atmospheres of pressure. The results obtained in this study indicated that even a higher temperature heating at 400oC under 10 bar hydrogen pressure was insufficient for magnesium hydride formation. Heating and grinding time were selected as the most effective parameters by which a full-factorial experimental design methodology was implemented. Statistical analysis results indicated that a combination of grinding and a 50oC heating was most effective. Hence, grinding was identified as the most significant factor effect on the production of magnesium hydride. Two different mills were used, in this study, and it was found that disc mill was more effective than ball mill. Different combinations of dehydrated borax, sodium carbonate, magnesium, hydrogen gas, sodium hydride and sodium metaborate were tested without success to produce sodium borohydride. In the final set of experiments, sodium borohydride could be successfully produced by using trimethyl borate and sodium hydride in a disc mill at 50oC under 10 bars hydrogen pressure.