Investigação da ordem local de nanocolóides magnéticos por espalhamento em baixo ângulo

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

In this work, we investigate using small angle scattering measurements the colloidal stability and the local order (typically between 10 nm and 100 nm) of magnetic nanocoloides, made of solution of magnetic ferrite nanospheres and mixed systems of magnetic nanospheres and laponite nanoplatelets. The balance of interparticles interactions has been quantitatively characterized and related to the colloidal state. In diluted ferrofluids, the interparticles attractions are dominating and induce a behavior typical of adhesive spheres. An external magnetic field applied to solutions initially monophasic induces a liquid-gas phase transition and an anisotropic 2D scattering pattern. In more concentrated solutions, the dispersions are fluid for the lower concentration and present a vitreous transition fluid-solid when the concentration increases. The interactions balance is completely governed by the long range electrostatic repulsion and the dispersions behave as a hard-spheres system. The solid phase is always a colloidal glass with a glassy transition occurring always below 20 % due to the high size polidispersity. In mixed systems, the behavior presents effective attractive interactions between magnetic nanoparticles on a longer scale, induced by the presence of Laponite platelets, which lead to a segregation phenomenon and a progressive spatial exclusion of the two kinds of nanostructures.

ASSUNTO(S)

ferrofluidos saxs sans estabilidade coloidal nanocolóides fisica

ACESSO AO ARTIGO

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