Título: | MICROANALYTICAL STUDY OF MAGNETIC MICRO AND NANOPARTICLES PRECIPITATED IN DILUTE CU-CO ALLOYS | ||||||||||||||||||||||||||||||||||||||||
Autor: |
ANA LUIZA DE ANDRADE ROCHA |
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Colaborador(es): |
IVAN GUILLERMO SOLORZANO NARANJO - Orientador |
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Catalogação: | 06/DEZ/2007 | Língua(s): | PORTUGUESE - BRAZIL |
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Tipo: | TEXT | Subtipo: | THESIS | ||||||||||||||||||||||||||||||||||||||
Notas: |
[pt] Todos os dados constantes dos documentos são de inteira responsabilidade de seus autores. Os dados utilizados nas descrições dos documentos estão em conformidade com os sistemas da administração da PUC-Rio. [en] All data contained in the documents are the sole responsibility of the authors. The data used in the descriptions of the documents are in conformity with the systems of the administration of PUC-Rio. |
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Referência(s): |
[pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=10984&idi=1 [en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=10984&idi=2 |
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DOI: | https://doi.org/10.17771/PUCRio.acad.10984 | ||||||||||||||||||||||||||||||||||||||||
Resumo: | |||||||||||||||||||||||||||||||||||||||||
The isothermal decomposition processes of dilute Cu-Co
bulk alloys have been
investigated by means of analytical transmission electron
microscopy. The precipitation of
ferromagnetic Co particles in non-magnetic Cu matrix after
aging treatments was revealed
by a variety of electron-microscopy techniques: TEM
diffraction contrast, high resolution
electron microscopy, annular dark field STEM, energy
filtered imaging and electron
holography. Homogeneous spherical particles ranging from
10 to 40 nm in diameter were
consistently observed from the early stages of
precipitation. Precipitates grow monotonic
upon aging, the lattice misfit energy between Co particles
and Cu matrix increases
significantly, which can further result in coherency loss
of the precipitate/matrix. The
precipitation of homogeneous incoherent particles was a
result of double aging treatment,
forming well developed and faceted crystals. In the
heterogeneous decomposition mode,
the kinetics of discontinuous precipitation colonies
consisting of regularly-spaced rod-like
particles aligned perpendicular to the grain boundary
reaction front was studied. Upon
further growth, these rods break down into chains of
aligned particles. Intergranular
diffusion models of lamellar discontinuous precipitation
were found to be inadequate to
apply in this alloy system. However, calculated grain
boundary diffusivity indicated values
two orders of magnitude higher than lattice diffusivity in
this system. Magnetic
measurements indicate a phase transformation from super
paramagnetic to ferromagnetic,
and the temperature of this transformation increases with
the alloy Co composition.
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