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The European Physical Journal E

, Volume 4, Issue 2, pp 201–208 | Cite as

Nanoparticle chain-like formation in electrical double-layered magnetic fluids evidenced by small-angle X-ray scattering

  • R. Itri
  • J. Depeyrot
  • F.A. Tourinho
  • M.H. Sousa

Abstract:

Small-angle X-ray scattering (SAXS) was performed on a series of Electric Double-Layered Magnetic Fluids (EDL-MF) composed of ferrite type-- CoFe2O4, MnFe2O4, ZnFe2O4, NiFe2O4 and CuFe2O4--nanoparticles of different crystalline sizes ( DXR ranging from 40 to 139Å, as determined by X-ray diffraction). The information concerning the scattering objects was obtained through the analysis of the distance distribution function p(r) and of the size distribution function D(R), both retrieved from SAXS data. The results show that EDL-MF, in the absence of an applied magnetic field, are composed of small magnetic particle aggregates in solution. These agglomerates are elongated in one direction (chain-like) with the longest dimension varying from 240 to 330Å. The cross-section size is of the order of DXR. The data also demonstrate that the maximum dimension of these aggregates is independent of the ferrite type. On the other hand, the number of aggregated magnetic particles is nanoparticle-size-dependent. Accordingly, larger ferrite-type nanoparticles as those with DXR = 139Å form aggregates composed of 2-3 magnetic particles, whereas smaller ones with DXR\(\) 40Å form agglomerates of about 6 magnetic particles in solution. As the nanoparticle size is reduced, it might increase the particle surface defects. Such occurrence would affect the particle surface charge density, which could reduce the electrostatic screening, favoring the agglomeration phenomenon.

PACS. 75.50.Mm Magnetic liquids – 75.50.Tt Fine-particle systems – 61.10.Eq X-ray scattering (including small-angle scattering) 

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Copyright information

© EDP Sciences, Springer-Verlag, Società Italiana di Fisica 2001

Authors and Affiliations

  • R. Itri
    • 1
  • J. Depeyrot
    • 2
  • F.A. Tourinho
    • 3
  • M.H. Sousa
    • 3
  1. 1.Instituto de Fısica da Universidade de S ao Paulo, Caixa Postal 66318, S ao Paulo, SP, 05315-970, BrazilBR
  2. 2.Complex Fluids Group - Instituto de Fısica - Universidade de Brasılia, CP 04455, 70919-970 Brasılia (DF), BrazilBR
  3. 3.Complex Fluids Group - Instituto de Quımica - Universidade de Brasılia, CP 04478, 70919-970 Brasılia (DF), BrazilBR

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