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The calculation of electromechanical forces that are present in a machine due to the magnetic field set up by current-carrying conductors and coils, especially when in the presence of permeable iron, is one of the most important and difficult problems in the vast field of the theory and design of electrical machines. It is a problem, moreover, which is usually dealt with by empirical methods based upon test results or by the use of numerical techniques such as Finite Element Analysis (FEA). In this thesis, analytical formulas are developed to evaluate the electromechanical forces and torques involved in brushless surface-mounted permanent magnet machines directly from, design parameters. In the first model, a slotless stator design is assumed while in the second model, the conductors are considered as being embedded in the stator iron. Both the models thus developed are then tested by means of a numerical method (FEA) and their utility in performing parametric studies is demonstrated in the case of the first model. / Master of Science

Nesse trabalho estudou-se a influência da adição de 0,5 % at. de zircônio (Zr) e gálio (Ga) nos ímãs permanentes à base de praseodímio (Pr) HD sinterizados obtidos por uma mistura de ligas. As ligas utilizadas foram: Pr12,6Fe68,3Co11,6B6Zr0,5Ga1, Pr16Fe75,5B8Zr0,5 e Pr13Fe80,5B6Zr0,5. A investigação foi realizada a partir das medidas das propriedades magnéticas e da microestrutura. Inicialmente, compararam-se as fases das ligas com as fases obtidas nos ímãs sinterizados. Posteriormente, os ímãs foram submetidos a um ciclo de tratamento térmico (de duas horas a 1000º C com resfriamento rápido até 10 horas, em seguida, de cinco horas nas mesmas condições, até 35 horas). Para o entendimento do papel de cada aditivo na fase magneticamente dura (fase Φ), foram analisadas as mudanças na microestrutura e relacionadas com as mudanças nas propriedades magnéticas. O Ga e Zr atuam como refinadores da fase Φ (matriz). O Ga atua no grão da fase Φ possibilitando a estabilidade da sua forma e melhorias das propriedades magnéticas. Para o ímã Pr14,3Fe71,9Co5,8B7Zr0,5Ga0,5 a evolução das propriedades magnéticas, após 15 h de tratamento térmico, foi: remanência de (1,25±0,02) T para (1,30±0,02) T, coercividade intrínseca de (1,11±0,02) T para (0,87±0,02) T, fator de quadratura de (0,68±0,02) para (0,89±0,02) e produto de energia de (285±5) kJ/m3 para (317±5) kJ/m3. O Zr tem uma atuação dual. Inibe o crescimento desordenado do grão e aumenta a anisotropia, mas, ao alojar-se no contorno de grão, gera domínios reversos prejudicando a coercividade intrínseca. Para o ímã Pr14.5Fe78B7Zr0.5 a evolução das propriedades magnéticas, após 15 h de tratamento térmico, foi: remanência (1,19±0,02) T para (1,25±0,02) T, coercividade de (0,74±0,02) T para (0,94±0,02) T, fator de quadratura de (0,88±0,02) para (0,85±0,02) e produto de energia (258±5) kJ/m para (291±5) kJ/m. Para o ímã Pr3316Fe75.5B8Zr0.5 a evolução das propriedades magnéticas, após 20 h de tratamento térmico, foi: remanência (1,17±0,02) T para (1,24±0,02) T, coercividade de (0,90±0,02) T para (1,22±0,02) T, fator de quadratura de (0,93±0,02) para (0,66±0,02) e produto de energia (258±5) kJ/m3 para (272±5) kJ/m3. / In this work was studied the influence of the addition of 0.5 at. % of zirconium and gallium on praseodymium-based HD sintered magnets obtained using a mixture of alloys. The alloys used in this study were: Pr12.6Fe68.3Co11.6B6Zr0.5Ga1, Pr16Fe75.5B8Zr0.5, Pr13Fe80.5B6Zr0.5. The investigation started by measuring the magnetic properties and observing the microstructure of the magnets. After that, the magnets were annealed at 1000ºC for 2 hours followed by rapid cooling, in a total of 10 hours. This heat treatment was followed by 5 hours at the same temperature up to a total of 35 hours. Changes in the microstructure were compared to the change in the magnetic properties aiming at a proper understanding of the role of each added element in relation to the magnetically hard phase (phase Φ). It has been shown that gallium and zirconium act as grain refiners of the matrix phase Φ. Gallium acts in the grain and favoring of the shape stability and improvement of the magnetic properties. For the Pr14.3Fe71.9Co5.8B7Zr0.5Ga0.5 sintered magnet the evolution of the magnetic properties after 15 hours heat treatment was: remanence from (1.25±0.02) T to (1.30±0.02) T, intrinsic coercivity from (1.11±0.02) T to (0.87±0.02) T, squareness factor from (0.68±0.02) to (0.82±0.02) and energy product from (285±5) kJ/m3 to (317±5) kJ/m3. Zirconium has two effects on the sintered magnets. Firstly, avoiding random grain growth and enhancing anisotropy. However, by concentrating on the grain boundaries, yield reverse domains and is detrimental to the intrinsic coercivity. For the sintered Pr14.5Fe78B7Zr0.5 magnet the evolution of the magnetic properties achieved after a heat treatment of 15 hours was: remanence from (1.19±0.02) T to (1.25±0.02) T, coercivity from (0.74±0.02) T to (0.94±0.02) T, squareness factor from (0.88±0.02) to (0,85±0.02) and energy product from (258±5) kJ/m to (291±5) kJ/m. For the Pr3316Fe75.5B8Zr0.5 sintered magnet the evolution of magnetic properties after 20 hours heat treatment was: remanence from (1.17±0,02) T to (1.24±0.02) T, coercivity from (0.90±0,02) T to (1.22±0.02) T, squareness factor from (0,93±0,02) to (0.66±0.02) and energy product from (258±5) kJ/m3 to (291±5) kJ/m3.

Neste estudo, as propriedades magnéticas dos ímãs sinterizados, produzidos a partir de uma mistura de ligas Pr16Fe76B8 e Pr14FebalCo16B6Nb0,1Mx, onde M= Al, Cu, P, Si, Gd, Ga, Dy, Tb e x= 0,1, 0,3, 0,5 % at. em iguais proporções, foram correlacionadas com as características microestruturais através de microscopia eletrônica de varredura (MEV) e de transmissão (MET). Utilizou-se microscopia eletrônica de varredura (MEV) e processamento computacional das micrografias, na investigação das características associadas ao tamanho e formato dos grãos magnéticos (Φ). A correlação utilizada indicou que fatores de quadratura superiores estão associados a grãos mais arredondados e com distribuição de tamanho mais estreita. Considerando que a variação no tamanho de grão e os valores de coercividade não se mostraram conclusivas com MEV, utilizou-se o recurso da microscopia eletrônica de transmissão (MET), microanálise com EDS e padrão de difração eletrônica. A associação da coercividade com a microestrutura foi feita com base nas investigações das fases não magnéticas, ricas em praseodímio dos pontos triplos e nos contornos de grãos. Com o microscópio de transmissão de alta resolução (HRTEM), foi possível observar a presença de uma camada contínua e regular entre os grãos da fase magnética para o ímã com adição de Ga 0,25% at. A modificação da microestrutura no contorno de grão do ímã com adição de Ga pode ser indicada como responsável pelo aumento de 10% na coercividade (1100 mT) comparado com o ímã Pr15FebalCo8B7Nb0,05. / In this study the magnetic properties of sintered magnets, prepared with a mixture of Pr16Fe76B8 and Pr14FebalCo16B6Nb0.1Mx alloys, where M = Al, Cu, P, Si, Gd, Ga, Dy, Tb and x = 0.1, 0.3, 0.5 at.% in the same proportions, were correlated with the microstructural features by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and computer processing of the micrographs were used in order to provide the characteristics associated with the size and shape of the magnetic grains (Φ phase). The correlation used shows that superior squareness factors are associated with rounder and narrower size distribution grains. Considering that the variation in the grain size and coercivity values were not conclusive with SEM, it has been used TEM, micro analysis by EDS and electron diffraction pattern. The coercivity relation with the microstructure was based on investigations of non-magnetic phases, in triple points, and in the grain boundary. With a high resolution transmission microscope (HRTEM), it was possible to observe a regular and continuous layer between the grains of the magnetic phase for the magnet with 0.25 at.% of Ga. The presence of such boundary can be indicated as responsible for higher coercivity values of this magnet. Microstructure was modified in the grain boundary by Ga addition and can be indicated as responsible for coercivity value (1100 mT) 10% higher than Pr15FebalCo8B7Nb0.05 magnet.

Nesse trabalho estudou-se a influência da adição de 0,5 % at. de zircônio (Zr) e gálio (Ga) nos ímãs permanentes à base de praseodímio (Pr) HD sinterizados obtidos por uma mistura de ligas. As ligas utilizadas foram: Pr12,6Fe68,3Co11,6B6Zr0,5Ga1, Pr16Fe75,5B8Zr0,5 e Pr13Fe80,5B6Zr0,5. A investigação foi realizada a partir das medidas das propriedades magnéticas e da microestrutura. Inicialmente, compararam-se as fases das ligas com as fases obtidas nos ímãs sinterizados. Posteriormente, os ímãs foram submetidos a um ciclo de tratamento térmico (de duas horas a 1000º C com resfriamento rápido até 10 horas, em seguida, de cinco horas nas mesmas condições, até 35 horas). Para o entendimento do papel de cada aditivo na fase magneticamente dura (fase Φ), foram analisadas as mudanças na microestrutura e relacionadas com as mudanças nas propriedades magnéticas. O Ga e Zr atuam como refinadores da fase Φ (matriz). O Ga atua no grão da fase Φ possibilitando a estabilidade da sua forma e melhorias das propriedades magnéticas. Para o ímã Pr14,3Fe71,9Co5,8B7Zr0,5Ga0,5 a evolução das propriedades magnéticas, após 15 h de tratamento térmico, foi: remanência de (1,25±0,02) T para (1,30±0,02) T, coercividade intrínseca de (1,11±0,02) T para (0,87±0,02) T, fator de quadratura de (0,68±0,02) para (0,89±0,02) e produto de energia de (285±5) kJ/m3 para (317±5) kJ/m3. O Zr tem uma atuação dual. Inibe o crescimento desordenado do grão e aumenta a anisotropia, mas, ao alojar-se no contorno de grão, gera domínios reversos prejudicando a coercividade intrínseca. Para o ímã Pr14.5Fe78B7Zr0.5 a evolução das propriedades magnéticas, após 15 h de tratamento térmico, foi: remanência (1,19±0,02) T para (1,25±0,02) T, coercividade de (0,74±0,02) T para (0,94±0,02) T, fator de quadratura de (0,88±0,02) para (0,85±0,02) e produto de energia (258±5) kJ/m para (291±5) kJ/m. Para o ímã Pr3316Fe75.5B8Zr0.5 a evolução das propriedades magnéticas, após 20 h de tratamento térmico, foi: remanência (1,17±0,02) T para (1,24±0,02) T, coercividade de (0,90±0,02) T para (1,22±0,02) T, fator de quadratura de (0,93±0,02) para (0,66±0,02) e produto de energia (258±5) kJ/m3 para (272±5) kJ/m3. / In this work was studied the influence of the addition of 0.5 at. % of zirconium and gallium on praseodymium-based HD sintered magnets obtained using a mixture of alloys. The alloys used in this study were: Pr12.6Fe68.3Co11.6B6Zr0.5Ga1, Pr16Fe75.5B8Zr0.5, Pr13Fe80.5B6Zr0.5. The investigation started by measuring the magnetic properties and observing the microstructure of the magnets. After that, the magnets were annealed at 1000ºC for 2 hours followed by rapid cooling, in a total of 10 hours. This heat treatment was followed by 5 hours at the same temperature up to a total of 35 hours. Changes in the microstructure were compared to the change in the magnetic properties aiming at a proper understanding of the role of each added element in relation to the magnetically hard phase (phase Φ). It has been shown that gallium and zirconium act as grain refiners of the matrix phase Φ. Gallium acts in the grain and favoring of the shape stability and improvement of the magnetic properties. For the Pr14.3Fe71.9Co5.8B7Zr0.5Ga0.5 sintered magnet the evolution of the magnetic properties after 15 hours heat treatment was: remanence from (1.25±0.02) T to (1.30±0.02) T, intrinsic coercivity from (1.11±0.02) T to (0.87±0.02) T, squareness factor from (0.68±0.02) to (0.82±0.02) and energy product from (285±5) kJ/m3 to (317±5) kJ/m3. Zirconium has two effects on the sintered magnets. Firstly, avoiding random grain growth and enhancing anisotropy. However, by concentrating on the grain boundaries, yield reverse domains and is detrimental to the intrinsic coercivity. For the sintered Pr14.5Fe78B7Zr0.5 magnet the evolution of the magnetic properties achieved after a heat treatment of 15 hours was: remanence from (1.19±0.02) T to (1.25±0.02) T, coercivity from (0.74±0.02) T to (0.94±0.02) T, squareness factor from (0.88±0.02) to (0,85±0.02) and energy product from (258±5) kJ/m to (291±5) kJ/m. For the Pr3316Fe75.5B8Zr0.5 sintered magnet the evolution of magnetic properties after 20 hours heat treatment was: remanence from (1.17±0,02) T to (1.24±0.02) T, coercivity from (0.90±0,02) T to (1.22±0.02) T, squareness factor from (0,93±0,02) to (0.66±0.02) and energy product from (258±5) kJ/m3 to (291±5) kJ/m3.

Neste estudo, as propriedades magnéticas dos ímãs sinterizados, produzidos a partir de uma mistura de ligas Pr16Fe76B8 e Pr14FebalCo16B6Nb0,1Mx, onde M= Al, Cu, P, Si, Gd, Ga, Dy, Tb e x= 0,1, 0,3, 0,5 % at. em iguais proporções, foram correlacionadas com as características microestruturais através de microscopia eletrônica de varredura (MEV) e de transmissão (MET). Utilizou-se microscopia eletrônica de varredura (MEV) e processamento computacional das micrografias, na investigação das características associadas ao tamanho e formato dos grãos magnéticos (Φ). A correlação utilizada indicou que fatores de quadratura superiores estão associados a grãos mais arredondados e com distribuição de tamanho mais estreita. Considerando que a variação no tamanho de grão e os valores de coercividade não se mostraram conclusivas com MEV, utilizou-se o recurso da microscopia eletrônica de transmissão (MET), microanálise com EDS e padrão de difração eletrônica. A associação da coercividade com a microestrutura foi feita com base nas investigações das fases não magnéticas, ricas em praseodímio dos pontos triplos e nos contornos de grãos. Com o microscópio de transmissão de alta resolução (HRTEM), foi possível observar a presença de uma camada contínua e regular entre os grãos da fase magnética para o ímã com adição de Ga 0,25% at. A modificação da microestrutura no contorno de grão do ímã com adição de Ga pode ser indicada como responsável pelo aumento de 10% na coercividade (1100 mT) comparado com o ímã Pr15FebalCo8B7Nb0,05. / In this study the magnetic properties of sintered magnets, prepared with a mixture of Pr16Fe76B8 and Pr14FebalCo16B6Nb0.1Mx alloys, where M = Al, Cu, P, Si, Gd, Ga, Dy, Tb and x = 0.1, 0.3, 0.5 at.% in the same proportions, were correlated with the microstructural features by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). SEM and computer processing of the micrographs were used in order to provide the characteristics associated with the size and shape of the magnetic grains (Φ phase). The correlation used shows that superior squareness factors are associated with rounder and narrower size distribution grains. Considering that the variation in the grain size and coercivity values were not conclusive with SEM, it has been used TEM, micro analysis by EDS and electron diffraction pattern. The coercivity relation with the microstructure was based on investigations of non-magnetic phases, in triple points, and in the grain boundary. With a high resolution transmission microscope (HRTEM), it was possible to observe a regular and continuous layer between the grains of the magnetic phase for the magnet with 0.25 at.% of Ga. The presence of such boundary can be indicated as responsible for higher coercivity values of this magnet. Microstructure was modified in the grain boundary by Ga addition and can be indicated as responsible for coercivity value (1100 mT) 10% higher than Pr15FebalCo8B7Nb0.05 magnet.

New 1,2,3,5-dithiadiazolyl (DTDA), 1,2,3,5-diselenadiazolyl (DSDA) radicals and their resulting metal complexes were synthesized and characterized. The overarching theme of this thesis is the utility of intermolecular interactions for facilitating previously unseen magnetic behaviours in thiazyl radical-metal complexes. This thesis contains the first examples of thiazyl radical metal complexes acting as molecule based magnets. The 4-benzoxazol-2′-yl-1,2,3,5-dithiadiazolyl (boaDTDA) radical and its selenium analogue 4-benzoxazol-2′-yl-1,2,3,5-diselenadiazolyl (boaDSDA) were coordinated to several paramagnetic metal ions including transition metal ions Mn(II), Co(II) and Ni(II). The Ni(hfac)2(boaDTDA) and Ni(hfac)2(boaDSDA) complexes are isomorphous and both demonstrate step like π-stacking leading to additional ferromagnetic (FM) intermolecular interactions. The Mn(hfac)2(boaDTDA) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato) complex was the first DTDA metal complex to conclusively show that intermolecular S(DTDA)…O(hfac) contacts can lead to intermolecular anti-ferromagnetic (AF) interactions which, in turn, can lead to a large spin ground state. Based on the magnetic properties of the Mn(hfac)2(boaDTDA) complex, a new DTDA biradical ligand, 4,6-bisDTDApyrimidine (bisDTDApym), was developed and coordinated to Mn(hfac)2. The resulting dinuclear Mn(II) complex, [Mn(hfac)2]2(bisDTDApym), is arranged in the solid state by short S(DTDA)…O(hfac) interactions forming two dimensional ferrimagnetic sheets. These ferrimagnetic sheets AF couple to one another, giving rise to AF ordering below 4.5 K. The [Mn(hfac)2]2(bisDTDApym) is the first thiazyl metal complex to magnetically order and is a unique example of a molecular coordination complex which magnetically orders. This thesis also presents the synthesis and characterization of precursor materials of the form Ln(hfac)3(DME) (DME = dimethoxyethane) for coordination reactions to thiazyl radical ligands. The Dy(hfac)3(boaDTDA) and Dy(hfac)3(pyDTDA) (pyDTDA = 4-(2′-pyridyl)-1,2,3,5-DTDA) complexes demonstrate single molecule magnetism with energy barriers of 100 K and 70 K respectively. Ten-coordinate Ln(hfac)3(pyDTDA)2 (Ln = La, Ce, Pr) complexes demonstrate phase transition behaviour between dimerized and undimerized phases and were studied by X-ray crystallography and magnetometry. The aforementioned compounds are some of the over 50 new compounds which have been synthesized and fully characterized in this thesis.

Bakalauro darbą „ Neodimio magnetų eksperimentinis tyrimas“ sudaro įvadas, keturi skyriai, išvados, priedai ir literatūros sąrašas. Šio darbo apimtis 30 puslapių. Darbe yra 26 paveikslėliai ir 1 lentelė.Įvade iškeliama darbo problema, tikslai ir uždaviniai. Pirmajame skyriuje pateikta literatūros analizė. Antrajame skyriuje aprašoma eksperimento metodika. Trečiajame skyriuje pateikti sistemų su neodimio magnetais tyrimo rezultatai. Ketvirtajame skyriuje pateikta eksperimento rezultatų analizė. Darbo pabaigoje pateiktos išvados apibendrinančios atliktą darbą ir pateikti pasiūlymai, kur būtų galima panaudoti neodimio magnetus. / The final bachelor‘s work “Experimental analysis of neodymium magnets” consist of introduction, four chapters, conclusions and references. The work consists of 30 pages. There are 26 images and 1 table.Problem of the research along with objectives and goals are provided in the introduction of this work. The first chapter provides analysis of literature. The second chapter is about methodology of experiment. The third chapter provides the results of systems of neodymium magnets. The fourth chapter provides analysis of the experiment results. At the end of the work there are conclusions and suggestions about neodymium magnets usage.

The mechanisms by which magnetisation changes occur in magnetic materials may be investigated by a variety of hysteresis measurements. During this study both alternating and rotational hysteresis measurements were used to characterise the mechanisms of magnetisation change in a number of permanent magnet materials. Studies of the time dependence of magnetisation, remanent magnetisations and the dependence of the reversible magnetisation on the irreversible magnetisation were undertaken. These studies revealed that in sintered rare-earth iron magnets the magnetisation change is predominately controlled by domain nucleation, with a lesser contribution from domain wall pinning within the boundary regions of the grains. Similar mechanisms control the magnetisation change in the larger grains of melt-quenched rare-earth iron magnets. In the single domain grains of the melt-quenched materials incoherent rotation mechanisms control the changes of magnetisation. Magnetisation change in MnAlC and sintered AlNiCo was found to be controlled by domain wall pinning within the interior of the grains of the materials. Two devices were constructed for the measurement of rotational hysteresis. The first measures the angular acceleration of a sample set spinning in a magnetic field, from which the rotational hysteresis loss may be determined. The second employs rotating search coils to make direct measurements of the component of magnetisation that contributes to rotational hysteresis loss during the rotation of a sample in a field. Both devices were found to produce data consistent with that in the literature and to be useful for the characterisation of rotational hysteresis in permanent magnet materials. A simple model was used to examine the dependence of rotational hysteresis loss on various material parameters. It was found that the value of the rotational hysteresis integral is dependent on interactions and to a lesser extent distributions in anisotropy. This is contrary to assumptions commonly made in the literature but consistent with published experimental data, which has been reinterpreted. Measurements of rotational hysteresis losses in the materials studied were found to be effected by geometric demagnetisation effects. A method by which such data may be corrected for these effects is proposed. Following correction and consideration of the interactions within the materials, the rotational hysteresis data was found to be consistent with the characterisations performed in linearly alternating fields.

No description available.