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Volumetric behaviour under pressure and thermal conductivity of ethylene glycol based FexOy ferrofluids


L. Lugo1, M. Pastoriza-Gallego2, J. Legido3 and M. Pineiro4

1Departamento de Fisica Aplicada, Facultad de Ciencias del Mar, Universidad de Vigo, Spain

Keywords: volumetric behavior, ferrofluid
property: density, thermal conductivity
material: hematite, magnetite, ethylene glycol

Following previous studies on thermophysical properties of metallic oxide nanofluids [1-3], in this work homogeneous and stable magnetic nanofluids containing iron oxide nanoparticles, alpha-Fe2O3(hematite) and Fe3O4 (magnetite) in ethylene glycol (EG), were prepared at concentrations up to 5 % in mass fraction. Commercial Hexagonal Scalenohedral-shaped alpha-Fe2O3 nanoparticles were selected while Fe3O4 nanoparticles were synthesized using a co-precipitation method. The products were characterized by transmission and scanning electron microscopy and X-ray diffraction. The density of these ferrofluids was measured as a function of volume fraction, from atmospheric conditions to 45 MPa, and from 283.15 to 323.15 K. Density data were obtained using an Anton Paar DMA 512P/60 vibrating tube densimeter temperature and pressure. Enhancements of the density up to 3% and 4% were found for Fe3O4/EG and Fe2O3/EG nanofluids, respectively. The volumetric behaviour of ferrofluids containing hematite is closer to ideality than those including magnetite. Then, the thermal conductivity at atmospheric pressure was determined from 283.15 to 323.15 K using an apparatus based on the hot-wire technique, and the enhancement of this magnitude was finally compared with several models of nanocolloid thermal conductivity.

References
  1. M.J. Pastoriza-Gallego, C. Casanova, R. Paramo, B. Barbes, J.L. Legido, M.M. Pineiro, Journal of Applied Physics, 106, 43011-43018, (2009).

  2. M.J. Pastoriza-Gallego, C. Casanova, J.L. Legido, M.M. Pineiro, Fluid Phase Equilibria, 300, 188-196 (2011)

  3. M.J. Pastoriza-Gallego, L. Lugo, J.L. Legido, M.M. Pineiro, Nanoscale Research Letters, (2011), accepted for publication.

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