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Hydrogen-induced defects in titanium
Knapp, Jan ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Titanium is a very important industrial material with quite a versatile use. This thesis examines the influence of hydrogen absorbed in metal lattice of titanium on defects inside the lattice. In this work titanium samples were loaded with hydrogen using two different methods: electrochemical charging, where titanium sample was immersed in solution of H3PO4 and glycerin as a cathode. The anode was be made of platinum and constant electrical current in order of miliampers was run throw the solution. The H+ cations went to the cathode and were neutralized to a hydrogen atom there. The hydrogen atoms subsequently penetrated into the titanium lattice by diffusion. Gas loading was used as the second method of hydrogen doping. Titanium samples were put into hydrogen atmosphere with defined pressure and kept at constant temperature. Hydrogen loaded samples were examined by positron lifetime spectroscopy which represents a non-destructive technique for studying defects in materials. Analysis of phase composition was performed by X- ray diffraction. Developments of mechanical properties of hydrogen loaded samples were monitored by Vickers micro-hardness testing. Differential Scanning calorimetry was employed for investigation of thermal stability of absorbed hydrogen.
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Investigation of vacancies in Fe-Al alloys
Lukáč, František ; Čížek, Jakub (advisor) ; Král, Robert (referee) ; Schneeweiss, Oldřich (referee)
Title: Investigation of vacancies in Fe-Al alloys Author: RNDr. František Lukáč Department: Department of Low Temperature Physics Supervisor: doc. Mgr. Jakub Čížek, Ph.D., Department of Low Temperature Physics, Faculty of Mathematics and Physics Abstract: Fe-Al alloys exhibit relatively high vacancy concentrations, which significantly influence the mechanical properties of these alloys. Positron annihi- lation spectroscopy was employed for investigations of vacancies in this work and the vacancy concentrations in Fe-Al alloys were determined by positron lifetime spectroscopy and measurements of positron diffusion length of implanted mono- genergetic positrons. The correlation of hardness with the vacancy concentration was characterized by determination of the vacancy hardening coefficient in Fe- Al alloys. The thermal evolutions of hardness and the vacancy concentration were compared during the annealing of the Fe-Al alloys with various composi- tions. Coincidence Doppler broadening of annihilation peak was employed for determination of the chemical composition of quenched-in vacancies in Fe-Al al- loys. Increased concentration of Al atoms in surrounding vacancies in Fe-Al alloys was related to the attractive interaction between the Al atoms and the vacancy. Quantum mechanical ab initio calculations were...
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Hydrogen-induced defects in titanium
Knapp, Jan ; Čížek, Jakub (advisor) ; Vlach, Martin (referee)
Titanium is a very important industrial material with quite a versatile use. This thesis examines the influence of hydrogen absorbed in metal lattice of titanium on defects inside the lattice. In this work titanium samples were loaded with hydrogen using two different methods: electrochemical charging, where titanium sample was immersed in solution of H3PO4 and glycerin as a cathode. The anode was be made of platinum and constant electrical current in order of miliampers was run throw the solution. The H+ cations went to the cathode and were neutralized to a hydrogen atom there. The hydrogen atoms subsequently penetrated into the titanium lattice by diffusion. Gas loading was used as the second method of hydrogen doping. Titanium samples were put into hydrogen atmosphere with defined pressure and kept at constant temperature. Hydrogen loaded samples were examined by positron lifetime spectroscopy which represents a non-destructive technique for studying defects in materials. Analysis of phase composition was performed by X- ray diffraction. Developments of mechanical properties of hydrogen loaded samples were monitored by Vickers micro-hardness testing. Differential Scanning calorimetry was employed for investigation of thermal stability of absorbed hydrogen.
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