• JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
  • JoomlaWorks Simple Image Rotator
 
  Bookmark and Share
 
 
Doctoral Thesis
DOI
10.11606/T.43.1999.tde-09102012-145903
Document
Author
Full name
Marilia Emura
E-mail
Institute/School/College
Knowledge Area
Date of Defense
Published
São Paulo, 1999
Supervisor
Committee
Missell, Frank Patrick (President)
Jardim, Renato de Figueiredo
Knobel, Marcelo
Rechenberg, Hercilio Rodolfo
Rodrigues, Daniel
Title in Portuguese
Propriedades Magnéticas de Ímãs Aglomerados e Nanocristalinos
Keywords in Portuguese
ímãs permanentes
magnéticos nanocristalinos
simulações micromagnéticas
Abstract in Portuguese
Imãs são corpos de materiais magnetizáveis utilizados para gerar um forte campo magnético em sua vizinhança. Essa característica faz com que sejam empregados em diversas aplicações na vida moderna, tais como motores para a indústria eletroeletrônica e automobilística, como elementos de fixação e em acoplamentos magnéticos na indústria mecânica. O mercado de ímãs permanentes movimenta atualmente cerca de US$ 5 bilhões por ano e está em plena expansão, sendo estimado um crescimento de 12% por ano até o final desta década de 90. Tal crescimento é atribuído aos "novos materiais" desenvolvidos a partir da década de 80 (ímãs de terras-raras) e aos novos mercados, que foram gerados pelos próprios "novos materiais" (Hart, 1996). Tratando-se de materiais tão ligados às facilidades da vida moderna, a pesquisa na área de imãs está intimamente ligada ao seu desenvolvimento tecnológico. Procura-se desenvolver imãs com as melhores propriedades magnéticas para as suas aplicações, investigando ao mesmo tempo os fenômenos que regem os mecanismos físicos de magnetização.
Title in English
Magnetic Properties of bonded and nanocrystalline magnets
Keywords in English
magnetic materials
micromagnetic simulation
permanent magnets
Abstract in English
Permanent magnets composed of magnetic powders bonded with a polymer represent the fastest growing sector of the magnetic materials market since they are ideal for the fabrication of small motors. This work presents a magnetic and structural characterization of TIve eommereial bonded magnets, Reversible and irreversible components of the total magnetization as well as magnetic interactions in the five commereial magnets are also studied, the magnets are composed by ferrite and MQP-Q nanoerystelline powders and mixtures of these two powders with 80%, 60% and 40% ferrite. Magnelie interactions were analyzed by Henkel plots, gM plots and switching field distributions. In bonded magnets, since the magnetic particles are separated from each other by a binder, it is expected that interactions are mainly dipolar in Nature. There is a progressive change in the data as the fraction of MQP-Q powder is increased. The sample with 100% ferrite shows strong magnetizing interactions at low fields. Date for hybrid magnets present increasing demagnetizing interactions as the fermion of MQP-Q increases and for the 100% MQP-Q sample, the data indicate demagnetizing effects. Reversible and irreversible magnetization components were obtained by applying two methods commanly used in magnetic materials characterization, the DCD -IRM method and the reversible susceptibility method. For the 100% ferrite magnet, in which the reversible component is small, the methods lead lo similar results. The results for both methods diverge as the reversible component! Increases, which in this case occurs with the increase of the MQP-Q powder fraction. The divergence is attributed to the idealized conditions of non-inleracting particles assumed by the DCD-IRM method. Magnetic interactions and lotai magnetization components were also studied in a melt-spun nanocrystalline Nd9Fe85B5 sample. This composition is similar to that of the MQP-Q powder and the magnetic behavior of both the bonded magnetic and the nanocrystalline precursor could be compared. Micromagnetic simulations allowed the evaluation of exchange, anisotropy and magnetostatic interactions on the magnetization reversal of nanocryslalline romposlle systems. The Monte Carlo method was applied lo a linear array of 300 magnetic moments distributed in three grains, two magnetically hard with a soft grain between them.
 
WARNING - Viewing this document is conditioned on your acceptance of the following terms of use:
This document is only for private use for research and teaching activities. Reproduction for commercial use is forbidden. This rights cover the whole data about this document as well as its contents. Any uses or copies of this document in whole or in part must include the author's name.
45609EmuraMarilia.pdf (5.74 Mbytes)
Publishing Date
2012-10-09
 
WARNING: Learn what derived works are clicking here.
All rights of the thesis/dissertation are from the authors
Centro de Informática de São Carlos
Digital Library of Theses and Dissertations of USP. Copyright © 2001-2022. All rights reserved.