No description available.

Several new families of organic acceptors that are candidates as building blocks of molecule-based ferrimagnets were synthesized and characterized. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The magnetic networks were synthesized by reacting each acceptor with V(CO)6. The magnets synthesized in this study were characterized using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Although some combinations failed to yield magnetically ordered materials, others exhibited ordering temperatures in the range of 95 K – 260 K. The ordering temperatures and saturation magnetizations were compared among families of acceptors and correlated with individual properties of the acceptors such as reduction potential and structure. / Doctor of Philosophy / Several new families of organic molecules have been created and examined for use as building blocks of molecule-based magnets. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The 3-D magnetic scaffoldings were created by combining an individual organic molecule in one of the families listed above with vanadium. The magnets created in this study were examined using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Some of the combinations of the organic molecules with vanadium failed to result in a 3-D magnetic scaffolding and showed no magnetic properties. Others showed magnetic properties in the below certain temperatures in the range of 95 K – 260 K. The magnetic properties were compared among families of molecules and correlated with individual properties of each molecule such as electronic effects and structure.

Elektronen- und Positronenstrahlen mit niedrigsten Emittanzen und hohen Strömen werden in zukünftigen Linearbeschleunigern, wie zum Beispiel dem Compact Linear Collider (CLIC), benötigt, um die geforderte Leuchtkraft für physikalische Experimente bereit zu stellen. Diese Strahlen können in Dämpfungsringen, ausgestattet mit starken, supraleitenden Dämpfungswigglermagneten, erzeugt werden. In dieser Arbeit sind Designkonzepte verschiedener supraleitender Dämpfungswigglermagnete entwickelt worden. Testspulen sowie Modelle sind gebaut und getestet, elektrische Verbindungstechniken entwickelt worden. Eine Wärmelastrechnung für den Betrieb in Dämpfungsringen und ein Designkonzept für den kryogenen Betrieb bei 4.2 K ist erstellt worden. Es konnte theoretisch und experimentell gezeigt werden, dass supraleitende Dämpfungswigglermagnete mit Nb-Ti und Nb3Sn Niedertemperatursupraleitern die magnetischen, mechanischen, elektrischen und thermischen Anforderungen erfüllen und in Dämpfungsringen betrieben werden können.

Made available in DSpace on 2014-10-09T12:26:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:28Z (GMT). No. of bitstreams: 1 14042.pdf: 6705801 bytes, checksum: 3dbb089e18c9947629283f47af921286 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:05/04711-2

Made available in DSpace on 2014-10-09T12:26:42Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:28Z (GMT). No. of bitstreams: 1 14042.pdf: 6705801 bytes, checksum: 3dbb089e18c9947629283f47af921286 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho, avaliou-se inicialmente a preparação de ímãs sinterizados de Pr16Fe76B8 (% at.) por meio de moagem de alta energia em moinho tipo planetário, averiguando-se os efeitos do tempo de moagem bem como da velocidade rotacional do moinho. Encontraram-se as melhores propriedades magnéticas para um magneto preparado com a matéria-prima cominuída durante 75 minutos e velocidade rotacional de 200rpm [JR = (1,02 ± 0,02) T, 0JHc = (1,42 ± 0,03) T e (BH)max = (200 ± 4) kJm-3]. De forma a melhorar a remanência, reduziu-se o tempo de exposição da liga ao hidrogênio, de 60 minutos para 2 minutos, obtendo-se um ímã com JR = (1,14 ± 0,02) T, 0JHc = (1,44 ± 0,03) T e (BH)max = (250 ± 5) kJm-3, constatando-se que a causa para a reduzida remanência no primeiro caso decorria do baixo grau de orientação cristalográfica. Durante esta investigação, desenvolveu-se e validou-se uma nova metodologia para quantificação do parâmetro . Posteriormente, propôs-se uma correlação quantitativa inédita entre a microestrutura e o fator de quadratura em magnetos anisotrópicos de TR16Fe76B8 (TR = Nd ou Pr) sinterizados. A expressão apresentada utiliza o tamanho, a elongação e a circularidade médios dos grãos e seus respectivos desvios padrões. Melhora-se o fator de quadratura quando a microestrutura apresenta grãos arredondados e com estreita distribuição de tamanho. A homogeneidade de tamanho dos grãos apresenta uma influência maior sobre o fator de quadratura quando comparada à homogeneidade de forma dos grãos. Ademais, verificou-se que o tratamento térmico após a sinterização melhora a ix homogeneidade de forma ao passo que a moagem melhora a homogeneidade de tamanho dos grãos. Avaliou-se, adicionalmente, o efeito da temperatura sobre o fator de quadratura em magnetos sinterizados anisotrópicos, verificando-se que o mesmo é controlado principalmente por sua microestrutura e confirmando a expressão previamente proposta. Além disso, propôs-se uma correlação quantitativa entre o produto de energia máximo e o fator de quadratura. Compararam-se valores experimentais e calculados, utilizando a expressão apresentada, e a discrepância encontrada foi de 5%. Por fim, avaliou-se qual seria o valor mínimo do fator de quadratura em ímãs sinterizados, constatando-se que magnetos isotrópicos devem apresentar o menor valor para tal parâmetro em virtude do reduzido grau de alinhamento cristalográfico. Ademais, verificou-se que para este tipo de amostra, em geral, 0,20 FQ 0,30. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP / FAPESP:05/04711-2

When a permanent magnet is considered for an application, the quantity that quantifies the usability of that material is the magnetic energy product (BH)max. In today’s world, rare earth transition metal permanent magnets like Nd-Fe-B, Sm-Co possesses the maximum magnetic energy product. But still for the industrial application, the ferrite permanent magnets are the primary choice over these rare transition metal magnets. Thus, in the present context, the magnetic energy product of the low cost ferrite system makes it unsuitable for the high magnetic energy application. In this regard, exchange spring magnets which combine the magnetization of the soft phase and coercivity of the hard magnetic phases become important in enhancing the magnetic energy product of the system. In this thesis, the exchange spring behaviour is reported for the first time in hard/soft oxide nanocomposites by microstructural tailoring of hard Barium Ferrite and soft Nickel Zinc Ferrite particles. We have analyzed the magnetization reversal and its correlation with the coercivity mechanism in the Ni0.8Zn0.2Fe2O4/BaFe12O19 exchange spring systems. Using this exchange spring concept, we could enhance the magnetic energy product in Iron Oxide/ Barium Calcium Ferrite nanocomposites compared to the bare hard ferrite by ~13%. The presence of the exchange interaction in this nanocomposite is confirmed by the Henkel plot. Moreover, a detailed Reitveld study, magnetization loop and corresponding variation of the magnetic energy product, Henkel plot analysis and First Order Reversal Curve analysis are performed on nanocomposites of hard Strontium Ferrite and soft Cobalt Ferrite. We have proved the exchange spring behaviour in this composite. In addition, we could successfully tailor the magnetization behaviour of the soft Cobalt Ferrite- hard Strontium Ferrite nanocomposite from non exchange spring behaviour to exchange spring behaviour, by tuning the size of the soft Cobalt Ferrite in the Cobalt Ferrite/Strontium Ferrite nanocomposite. The relative strength of the interaction governing the magnetization process in the composites has been studied using Henkel plot and First Order Reversal Curve method. The FORC method has been utilized to understand the magnetization reversal behaviour as well as the extent of the irreversible magnetization present in both the nanocomposites, having smaller and larger particle size of the Cobalt Ferrite. It has been found that for the all the studied composites, the pinning is the dominant process for magnetization reversal. The detailed structural analysis using thin film XRD, angle dependent magnetic hysteresis and remanent coercivity measurement, coercivity mechanism by micromagnetic analysis and First Order Reversal Curve analysis are performed for thin films of Strontium Ferrite which are grown on c-plane alumina using Pulsed Laser Deposition (PLD) at two different oxygen partial pressures. The magnetic easy directions of both the films lie in the out of plane direction where as the in plane direction corresponds to the magnetic hard direction. Depending on the oxygen partial pressure during deposition, the magnetization reversal changes from S-W type reversal to Kondorsky kind of reversal. Thus, the growth parameter for the Strontium Ferrite single layer which will be used further as a hard layer for realizing oxide exchange spring in oxide multilayer, is optimized. The details of the magnetic and structural properties are analyzed for Nickel Zinc Ferrite thin film grown on (100) MgAl2O4. We have obtained an epitaxial growth of Nickel Zinc Ferrite by tuning the growth parameters of PLD deposition. The ferromagnetic resonance and the angle dependent hysteresis loop suggest that, the magnetic easy direction for the soft Nickel Zinc Ferrite lie in the film plane whereas the out of plane direction is the magnetic hard direction. Using the growth condition of respective Nickel Zinc Ferrite and Strontium Ferrite, we have realized the exchange spring behaviour for the first time in the trilayer structure of SrFe12O19 (20 nm)/Ni0.8Zn0.2Fe2O4(20 nm)/ SrFe12O19 (20 nm) grown on c-plane alumina (Al2O3) using PLD. The FORC distribution for this trilayer structure shows the single switching behaviour, corresponding to the exchange spring behaviour. The reversible ridge measurement shows that the reversible and the irreversible part of the magnetizations are not coupled with each other.

No description available.

The diplomatic thesis will describe the principle functions of synchronous motors with permanent magnets, for therein analysis of PMSM and BLDC motors. We will make calculation of the required parameters from the power unit for glider Discus 2. We will create a design of BLDC and PMSM motor from specified parameters. Features of the proposed engines will be verified with the help of the programs FEMM, RMxprt, Maxwell. At the end of the work will make conclusion about the diplamatic project and diffrences between PMSM and BLDC motor.

Elektronen- und Positronenstrahlen mit niedrigsten Emittanzen und hohen Strömen werden in zukünftigen Linearbeschleunigern, wie zum Beispiel dem Compact Linear Collider (CLIC), benötigt, um die geforderte Leuchtkraft für physikalische Experimente bereit zu stellen. Diese Strahlen können in Dämpfungsringen, ausgestattet mit starken, supraleitenden Dämpfungswigglermagneten, erzeugt werden. In dieser Arbeit sind Designkonzepte verschiedener supraleitender Dämpfungswigglermagnete entwickelt worden. Testspulen sowie Modelle sind gebaut und getestet, elektrische Verbindungstechniken entwickelt worden. Eine Wärmelastrechnung für den Betrieb in Dämpfungsringen und ein Designkonzept für den kryogenen Betrieb bei 4.2 K ist erstellt worden. Es konnte theoretisch und experimentell gezeigt werden, dass supraleitende Dämpfungswigglermagnete mit Nb-Ti und Nb3Sn Niedertemperatursupraleitern die magnetischen, mechanischen, elektrischen und thermischen Anforderungen erfüllen und in Dämpfungsringen betrieben werden können.

The thesis at hand addresses design, characterization and experimental testing of pulsed high-field magnets for utilization in the field of laser-plasma physics. The central task was to establish a technology platform that allows to manipulate laser-driven ion sources in a way that the accelerated ions can be used in complex application studies, e.g. radiobiological cell or tumor irradiation. Laser-driven ion acceleration in the regime of target normal sheath acceleration (TNSA) offers the unique opportunity to accelerate particles to kinetic energies of few 10MeV on the micrometer scale. The generated bunches are short, intense, show broad exponentially decaying energy spectra and high divergence. In order to efficiently use the generated particles, it is crucial to gain control over their divergence directly after their production. For most applications it additionally is favorable to reduce the energy spread of the beam. This work shows that the developed pulsed high-field magnets, so-called solenoids (cylindrical magnets), can efficiently capture, transport and focus laser-accelerated protons. The chromaticity of the magnetic lens thereby provides for energy selection. Three prototype solenoids, adapted to fit different application scenarios, and associated current pulse drivers have been developed. The magnets generate fields of several 10 T. Pulse durations are of the order of one millisecond and thus the fields can be considered as quasi-static for laser-plasma interaction processes taking place on the ps- to ns-scale. Their high field strength in combination with abandoning magnetic cores make the solenoids compact and light-weight. The presented experiments focus on a solenoid magnet designed for the capture of divergent laser-driven ion beams. They have been carried out at the 6MV tandetron accelerator and the laser acceleration source Draco of Helmholtz-Zentrum Dresden – Rossendorf as well as at the PHELIX laser of GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt.