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Título: MICROSTRUCTURAL/ANALYTICAL STUDY OF THE PRODUCTION OF CUNI-AL2O3 NANOCOMPOSITES: FROM NANOPARTICLES SYNTHESIS TO THERMOMECHANICAL PROCESSING INTO RIBBONS
Autor: MARIA ISABEL RAMOS NAVARRO
Colaborador(es): IVAN GUILLERMO SOLORZANO NARANJO - Orientador
EDUARDO DE ALBUQUERQUE BROCCHI - Coorientador
Catalogação: 07/MAR/2019 Língua(s): PORTUGUESE - BRAZIL
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.
Referência(s): [pt] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=37260&idi=1
[en] https://www.maxwell.vrac.puc-rio.br/projetosEspeciais/ETDs/consultas/conteudo.php?strSecao=resultado&nrSeq=37260&idi=2
DOI: https://doi.org/10.17771/PUCRio.acad.37260
Resumo:
In this work it is evaluated the microstructural evolution of two types of metal/ceramic nanocomposites, Cu-10(percent)wt(percent)Ni-1(percent)Al2O3 (Cu-rich) and Ni-10Cu-1(percent)Al2O3 (Ni-rich), consolidated in ribbons. Initially, the precursor nanoparticles were obtained by a chemical route synthesis based on the thermal decomposition of Cu and Ni metal nitrates solution, as it generates co-formed oxides (CuO-NiOAl2O3). This material was selectively reduced by hydrogen in order to produce the nanocomposites. The CuNi matrix with particle size of about 20-100 nm containing a dispersion of even finer Al2O3 was uniaxially cold pressed into pellets and then aggregated by heating for 30 minutes. The treated pellets were cold rolled aiming a thickness reduction of 40, 60 and 80 (percent). The produced ribbons were then annealed at 600 degrees Celsius for Cu-rich samples and at 900 degrees Celsius for Nirich samples for periods of 5, 30 and 300 minutes. This step has produced different microstructural states due to phenomena of recovery, recrystallization and grain growth. The microstructural analysis was performed by Scanning Electron Microscopy (MEV), Focused Ion Beam (FIB), and Transmission Electron Microscopy (MET). All of the studies included the conventional and scanning (STEM) modes and high resolution (HRTEM). Particularly, the SEM and TEM / STEM compositional analyzes were conducted by x-ray energy dispersive spectroscopy (EDXS). The preparation of the samples for MEV was performed by conventional metallography, if required, the samples were subject to ion beam polishing in the MEV / FIB instrument. Electron transparent samples were prepared by conventional double jet electropolishing of thin foils, ion milling in precision instrument (PIPS) as well as selected lamellae prepared by Focus Ion Beam (FIB).These studies indicate that the ceramic particles are not homogeneously disperse in the polycrystalline metal matrix, but they selfsegregate in fine agglomerates following the direction of the cold rolled, and serve as preferential sites for the heterogeneous nucleation of new grains, due to recrystallization phenomenon, during annealing. It has also been observed that in the regions with the presence of Al2O3 the grain size of the nanoparticles is smaller. Actually, in the samples with high grain of deformation, recrystallization and grain growth occurred, generating highly heterogeneous size for the microstructures (range about 50nm to 10um). Microhardness measurements have showed that Al2O3 is a good reinforcement, as it increased the hardness of the material by up to 100 percent when compared with the same material without Al2O3.
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