Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Microscale Precise Position Measurement and Monitoring of Sliding Valves(Izmir Institute of Technology, 2019) Özdemir, Serhan; Özdemir, Serhan; Özdemir, Serhan; 03.10. Department of Mechanical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyIn present study, a sensor, Accuciser, is presented to know the position of sliding valves which have ferromagnetic or diamagnetic guide. The main objective is to develop a sensor, which has low cost and high resolution, that measures the displacement of engine valves or SCR injectors which are used in especially in the automotive industry. For now, the position of the valves, which are using in propulsion systems, or SCR injector cannot be known with a signal from an analog sensor. Instead of analog sensor, the mapping is used from experimental data. However, this mapping gives inaccurate results due to driving style or usage of the system. After seeing the gap in these systems, the sensor was developed, and it fulfils this gap. The sensor is developed based on Faraday’s Law of Induction which was discovered by Michael Faraday in 1830. The sensor consists of two coils and one coil located on top of the other. The most important property of the proposed sensor is working with a direct current. In fact, if the valve is actuated by an electromagnetic force, there is no power consumption on the sensor. The experimental results, for the latter property, are corroborated by theoretical calculations. The output of the sensor is directly proportional to the displacement of the core and it has high signal-to-noise ratio because of the nature of magnetism. The results show that using Accuciser, the proposed sensor, to monitor valve displacement gives more reliable results than current technology.Master Thesis The Growth and Characterization of Fe/Tao Multilayers for Spintronics Applications(Izmir Institute of Technology, 2008) Tokuç, Hüseyin; Tarı, Süleyman; Tarı, Süleyman; 04.05. Department of Pyhsics; 04. Faculty of Science; 01. Izmir Institute of TechnologyIn this thesis, the effect of Ta buffer layer and the thickness of the Ta2O5 barrier layer on the structural and magnetic properties of Fe/Ta2O5/Co multilayers have been studied. XRD and AFM techniques were used for structural investigations and VSM was used for investigation of magnetic properties. Refractive index of the barrier layer was determined by ellipsometry technique. In this study, magnetic tunnel junctions have also been fabricated by using photolithography technique and then electrical and magnetoresistance measurements were done.The structural investigations showed that Ta under layer increases the crystalline quality of Fe layer and causes a change on magnetic parameters of Fe films. The AFM results showed that the range of the roughness for all layers is between 1.7 A and 6.3 A. When the thickness of the oxide layer was 4 nm, magnetic decoupling appears. Clear differences between the coercive fields of the ferromagnetic layers were observed in further increase of the barrier layer thickness. The effect of annealing on the Fe/TaOx/Co multilayer was studied and it was found that only the coercivity of Fe film increases with increasing temperature up to the 250C. Then, annealing at 400C showed a sharp decrease in the coercivity of Fe film indicating an intermixing at the interface of Fe/TaOx. Co minor loops showed that the magnetostatic coupling is large for thin barriers and decreases with increasing the barrier thickness. Electrical measurements showed that conduction occurs via tunneling electrons. However, no TMR ratio has been observed after magnetoresistance measurements.