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Effects of Two Step Annealing on Complex Permeability of Fe-Cu-Nb-Si-B Nanocrystalline Soft Magnetic Materials

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dc.contributor.advisor Sikder, Prof. Dr. Shibendra Shekher
dc.contributor.author Noor, Saroaut
dc.date.accessioned 2018-08-30T04:41:43Z
dc.date.available 2018-08-30T04:41:43Z
dc.date.copyright 2005
dc.date.issued 2005-03
dc.identifier.other ID 0055506
dc.identifier.uri http://hdl.handle.net/20.500.12228/440
dc.description This thesis is submitted to the Department of Physics, Khulna University of Engineering & Technology in partial fulfillment of the requirements for the degree of Master of Philosophy, March 2005. en_US
dc.description Cataloged from PDF Version of Thesis.
dc.description Includes bibliographical references (pages 110-114).
dc.description.abstract The typical nanocrystalline alloy known as Finemet with the composition Fe73.5Cu jNb3Si135B9 has been studied for the soft magnetic properties. The crystalline phases that evolved after crystallization were studied by X-ray diffraction, crystallization temperature by DTA and magnetic properties by VSM and impedance analyzer. The change of magnetic properties with annealing temperature, Ta in the range 400-700°C and annealing time 1-60 minutes have been investigated. The effect of a two-step annealing on the permeability Fe735Cu)Nb3Si135B9 alloy has been studied. The grain size was determined from the line broadening of the fundamental peak using Scherrers method. Annealed at 555°C, the grain size, the solute silicon content of a-Fe(Si) grains and the improvement in magnetic softness saturate as a function of time. As compared to a nanocrystalline alloy obtained by conventional one-step annealing at around the crystallization temperature, the alloy subjected to preannealing at Ta = 400°C and subsequent high temperature annealing at Ta=555°C shows similar soft magnetic properties. An enhancement of initial permeability with increasing annealing temperature was observed until the annealing temperature TL = 475°C and corresponds to the amorphous relaxed structure. An abrupt deteroriation of permeability takes place at the beginning of crystalization beyond which permeability rises dramatically attaining a maximum value at Ta = 555°C which is attributed to the nanometri grain size effect as a result of averaging out of effective magnetic anisotropy by exchange interaction and decrease of magnetoelastic energy. A sharp decrease of permeability above 580°C is assumed to be connected with iron-boride phase at the beginning of second crystallization stage. The initial permeability for the optimum annealed sample has been found to be 20786 as compared with 284 for its amorphous counterpart. The behavior of very high permeability is explained on the basis of random anisotropy model. From the temperature dependence of magnetization the Curie temperature of the amorphous state and crystallized ferromagnetic phases like Fe(Si) and iron-boride phases and the onset of crystallization temperatures of these phases have been determined. Saturation magnetization measured on the amorphous and annealed samples at different annealing temperature gradually increases with Ta and show a maximum at the medium stage of nanocrysallization at Ta 525°C beyond which magnetization decreases. The results are interpreted on the basis of irreversible structural relaxation as well as enrichment of the nanograins with Si. en_US
dc.description.statementofresponsibility Saroaut Noor
dc.format.extent 114 pages
dc.language.iso en_US en_US
dc.publisher Khulna University of Engineering & Technology (KUET), Khulna, Bangladesh. en_US
dc.rights Khulna University of Engineering & Technology (KUET) thesis/ dissertation/internship reports are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission.
dc.subject Complex Permeability en_US
dc.subject Nanocrystalline Alloy en_US
dc.subject Soft Magnetic Properties en_US
dc.subject Nanocrystalline Amorphous Ribbon en_US
dc.title Effects of Two Step Annealing on Complex Permeability of Fe-Cu-Nb-Si-B Nanocrystalline Soft Magnetic Materials en_US
dc.type Thesis en_US
dc.description.degree Master of Philosophy
dc.contributor.department Department of Physics


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