Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 101-107). Also available on the World Wide Web.

Th. 3e cycle--Électronique--Grenoble--I.N.P., 1982. N°: D3 175.

Made available in DSpace on 2014-06-11T19:32:11Z (GMT). No. of bitstreams: 0 Previous issue date: 1997Bitstream added on 2014-06-13T20:27:17Z : No. of bitstreams: 1 janasi_sr_dr_araiq.pdf: 2566763 bytes, checksum: e10173459cbf62287b0478669d7c6ed0 (MD5) / A substituição parcial de íons Fe3+ por pares de íons (Co2+-Ti4+ ou Co2+-Sn4+) na ferrita de bário hexagonal (BaFe12O19) leva a uma substancial diminuição no campo coercitivo (Hc) com uma pequena mudança na magnetização de saturação (Ms), permitindo seu uso em gravação magnética e magneto-óptica de alta densidade. Os diferentes métodos de preparação de ferritas de bário resultam em produtos com propriedades distintas. Neste trabalho, preparou-se BaFe12-2xCoxTixO19 e BaFe12-2xCoxSnxO19 (0,25 £ x £ 1) por coprecipitação, utilizando cloretos dos metais precursores e solução de KOH/K2CO3 como precipitante. Após a secagem, o produto obtido foi calcinado a 950oC por 3h, lavado e seco. Os difratogramas de raios X indicaram a formação da ferrita de bário. As micrografias eletrônicas de varredura mostraram que os pós obtidos apresentam-se na forma de plaquetas hexagonais de 1 a 2mm. As curvas de magnetização das ferritas de bário dopadas mostraram que o campo coercitivo e a remanência diminuem em função do aumento da razão de substituição x. A curva de magnetização da amostra dopada com Co-Ti, com x = 1 é característica de uma ferrita mole, com Hc = 13,5 kA.m-1 (0,17 kOe), Ms = 46,1 emu.g-1 e Mr = 11,0 emu.g-1. Para a amostra dopada com Co-Sn a diminuição de Mr não é significante. Estes resultados mostraram que as propriedades magnéticas das ferritas de bário dopadas obtidas por coprecipitação foram melhoradas, em relação aos dados da literatura para ferrita de bário pura ou dopada. / The partial substitution of Fe3+ ions with pairs of ions (Co2+-Ti4+ or Co2+-Sn4+) in hexagonal barium ferrite (BaFe12O19) leads to a substantial reduction on coercivity (Hc) with only a low change in saturation magnetization (Ms), allowing its use in high density magnetic and magneto-optical recording. Different preparative methods result in barium ferrites with distinguished properties. In this work, BaFe12-2xCoxTixO19 and BaFe12-2xCoxSnxO19 (0.25 £ x £ 1) were prepared by the coprecipitation method using chloride salt precursors and KOH/K2CO3 solution. After drying, the powder was calcinated at 950oC by 3 h, washed and dried. The X ray diffraction patterns indicated the barium ferrite phase formation. The scanning electron micrographs showed that the particles are hexagonal platelike with diameter size ranging from 1 to 2 mm. The magnetization curves of substituted barium ferrites showed that the values of Hc and Mr decrease with the increase of the substitution ratio x. The magnetization curve profile for Co-Ti substituted sample with x =1 is characteristic of a soft ferrite with Hc = 13.5kA.m-1 (0.17 kOe), Ms = 46.1 emu.g-1 and Mr = 11.0 emu.g-1. These results indicated that the magnetic properties of substituted barium ferrites obtained by coprecipitation were improved when compared with the literature data for pure and substituted barium ferrite.

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TRIUMF, Canada’s nuclear and particle physics research laboratory is currently in development of an Advanced Rare Isotope Facility (ARIEL) that will contain a newly designed electron target station. The target at this station is susceptible to destruction from instantaneous spot heating of the beam. To mitigate this, a raster system consisting of two AC electromagnets was proposed. The two magnets will work in tandem, vertical and horizontal, bending to produce raster patterns at 10 kHz. Since complex patterns consist of harmonics higher than the fundamental frequency, a design frequency of 100 kHz was chosen. AC current causes eddy currents which lead to the skin effect, causing high frequency current to concentrate on the outside of the conductor. To address this, a conductor diameter smaller than the skin depth at the given frequency must be chosen. This led to the choice of litz wire consisting of 400 insulated strands for the conductor. The radiation resistance insulation ethylene tetrafluoroethylene (ETFE) was chosen for these conductors and a 3D printed polyethylene sulfide (PPS) will be used for the coil bobbins. The effects of eddy currents were eliminated from the core material by choosing ferrite, an amorphous material consisting of iron-oxide crystals. Simulations were completed to ensure a homogenous magnetic field in the region of the beam, and the subsequent pole profile was determined. Lastly, a metalized ceramic beampipe is used to integrate with the existing beamline and allow for discharge of any static buildup on the inner surface of the beampipe due to the electron beam. / Graduate

<p> The subject of this thesis is the design, fabrication and comparative testing of two prototype L-band ferrite digital latching phase shifters. One phaser is a variation of a design published by G.T. Roome and H.A. Hair, "Thin Ferrite Devices for Microwave Integrated Circuits", IEEE Trans. Microwave Theory Tech, vol. MTT-16 pp. 411-420, July 1968. The second design is original and is experimentally and theoretical compared to the first phaser. A comparative study was made because of technological difficulties in making these devices. Insertion losses of 2dB and an order of magnitude less than possible phase shift occurred because of inadequate production facilities. Thus, the comparative study gave a common mode error to the published device and the new device.</p> <p> Also, the theory of ferrite microwave phasers and a discussion of a particular system application which prompted this study are included in this thesis.</p> / Thesis / Master of Engineering (MEngr)

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Over the years, industrial partners experienced issues related to inconsistent free ferrite in gray cast iron. In the course of a hot summer and a cold winter, machinability balance varies up to 350%. During warm months it is better and cold months worse. The inconsistent machinability increases the scrap rates by up to 400% and reduces tool life by up to 70%. The ultimate objective of this research is to collaborate with an automotive industrial partner to investigate the periodic machinability variability of gray cast iron engine sleeves, with a goal to reduce the cost and scrap rate of tool inserts. In this study, a significant amount of work was conducted concerning sample preparation for a metallography check. Samples from different months with varying amount of “free ferrite” were collected to study the seasonal effect on their machinability and high-speed machining under similar industrial conditions. Furthermore, a room temperature age strengthening of gray cast iron was conducted to demonstrate how the hardness increase from aging could improve the machinability of gray cast iron. A CBN insert is the second hardest cutting tool after the diamond insert, and is widely used in industry for machining cast iron. It has a high cutting speed is commonly used due to its high hardness and impressive wear resistance. It is known that gray cast iron can naturally age at room temperature or artificially age under a controlled temperature. Under different aging temperatures and times, gray cast iron exhibits a greater hardness after age strengthening, which affects the CBN tool life. The latter is usually limited by flank wear length, however the content of free ferrite in gray cast iron can generate ferrous built-up on the CBN cutting edge and significantly shorten the tool life of the CBN cutting tool. / Thesis / Master of Applied Science (MASc)

Controlled decarburization experiments were carried out on ternary and quaternary iron alloys. The planar ferrite interfaces formed during decarburization were subsequently investigated using atom probe tomography (APT) to measure interfacial segregation. The segregation results for the Fe-Si-C, Fe-Mn-C, and Fe-Mo-C were used to improve the three-jump-model developed Zurob et al. These three systems were accurately modelled using interfacial binding energy values in agreement with the atom probe tomography results. Qualitative explanations for the modelling results of Sun et al. on the Fe-Mn-Mo-C system and Qiu et al. on the Fe-Mn-Si-C system have also been provided using the results from the atom probe tomography investigation. / Thesis / Master of Applied Science (MASc) / Controlled decarburization experiments were carried out on ternary and quaternary iron alloys. The planar ferrite interfaces formed during decarburization were subsequently investigated using atom probe tomography (APT) to measure interfacial segregation. The segregation results for the Fe-Si-C, Fe-Mn-C, and Fe-Mo-C were used to improve the three-jump-model developed Zurob et al. These three systems were accurately modelled using interfacial binding energy values in agreement with the atom probe tomography results. Qualitative explanations for the modelling results of Sun et al. on the Fe-Mn-Mo-C system and Qiu et al. on the Fe-Mn-Si-C system have also been provided using the results from the atom probe tomography investigation.

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