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PROPERTIES OF NANOCRYSTALLINE FE-NI PARTICLES PREPARED BY THERMAL REDUCTION OF OXALATE PRECURSORS
Švábenská, Eva ; Roupcová, Pavla ; Havlíček, Lubomír ; Schneeweiss, Oldřich
Recent technological advancements require development of cost-effective and high-performance magnets \nwhich ideally do not contain rare earth metals or noble metals. The promising candidates are Fe-Ni-based \nalloys, in particular, the Fe50Ni50 L10 phase (tetrataenite), which has a great perspective for producing hard \nmagnetic materials. Our study explores a promising method for preparing nanoparticles of Fe-Ni alloy from an \niron-nickel oxalate precursor. The coprecipitation method was employed to prepare oxalate precursors, \nfollowed by controlled thermal decomposition in a reducing hydrogen atmosphere. The morphology and \nproperties of the resulting particles were analysed using scanning electron microscopy (SEM) coupled with \nenergy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Mössbauer spectroscopy (MS), and \nmagnetic measurements.\nThe SEM analysis revealed that the particles have approximately cube-shaped unit cell morphology with a\nsize in a range of 1 - 2 μm. Upon annealing, the samples contain multiple phases with varying Fe-Ni content.\nMagnetic measurements confirmed the formation of magnetically suitable Fe-Ni phases in the samples after \nannealing. Mössbauer spectroscopy emerged as a highly effective method for characterizing individual phases \nof the Fe-Ni system.
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Electromagnetic pulse accelerator of projectiles
Žamberský, Jan ; Jirák, Josef (oponent) ; Frk, Martin (vedoucí práce)
This work focuses on using magnetic field to accelerate projectile in a device called coilgun. It consists of two parts, first is theoretical discussing magnetism and its use, the other part is about coilgun itself, its benefits and drawbacks. Followed by series of measurements on two experimentally built coilguns and trying optimize it to achieve best results. First part discusses multiple topics. In the beginning, there is a small section defining magnetic field and other constants and phenomenons connected with it. Next two chapters are focused on different types of material, mainly ferromagnetics, how they react to magnetic field and what parameters we can follow, followed by a list of several applications of magnetic field in different areas of human society. The second part describes main principle of coilgun and how the prototypes were made. Measurements on a first prototype consist of trying different materials for projectile, various dimensions of it and benefits of using external shell for accelerating coil. There is also a chapter discussing velocity measurement of a projectile. Second prototype is trying to avoid all the flaws, which were found on the first prototype and find a benefits of using multiple acceleration stages.
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Magnetic properties of 42CrMo4 steel
Bulín, T. ; Švábenská, Eva ; Hapla, Miroslav ; Roupcová, Pavla ; Ondrušek, C. ; Schneeweiss, Oldřich
Low alloyed high-grade chrome-molybdenum ferritic steel was investigated from the point of views of magnetic properties in dependence on heat and mechanical treatment. This steel can be used as components of magnetic circuits or some parts in electrical equipment. The basic information on structure and phase composition was obtained by optical and scanning electron microscopy, X-ray Powder Diffraction and Mössbauer Spectroscopy. The temperature stability of the material was proved by measurements of temperature dependences of magnetic moment. The magnetic parameters were obtained by measuring of magnetic hysteresis loops in dependence on saturation field and their frequencies. The results are discussed from the point of view of possible applications as a magnetic material in the very extremely environment, where high mechanical stresses and elevated temperatures can occur.
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Electromagnetic pulse accelerator of projectiles
Žamberský, Jan ; Jirák, Josef (oponent) ; Frk, Martin (vedoucí práce)
This work focuses on using magnetic field to accelerate projectile in a device called coilgun. It consists of two parts, first is theoretical discussing magnetism and its use, the other part is about coilgun itself, its benefits and drawbacks. Followed by series of measurements on two experimentally built coilguns and trying optimize it to achieve best results. First part discusses multiple topics. In the beginning, there is a small section defining magnetic field and other constants and phenomenons connected with it. Next two chapters are focused on different types of material, mainly ferromagnetics, how they react to magnetic field and what parameters we can follow, followed by a list of several applications of magnetic field in different areas of human society. The second part describes main principle of coilgun and how the prototypes were made. Measurements on a first prototype consist of trying different materials for projectile, various dimensions of it and benefits of using external shell for accelerating coil. There is also a chapter discussing velocity measurement of a projectile. Second prototype is trying to avoid all the flaws, which were found on the first prototype and find a benefits of using multiple acceleration stages.
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