Sketch of the ionic layering around the nanoparticles responsible for the colloidal stability of the dispersion
T. Fiuza, M. Sarkar, J. C. Riedl, A. Cebers, F. Cousin, G. Demouchy, J. Depeyrot, E. Dubois, F. Gelebart, G. Meriguet, R. Perzynski and V. Peyre
Ferrofluids based on maghemite nanoparticles (NPs), typically 10 nm in diameter, are dispersed in an ionic liquid (1-ethyl 3-methylimidazolium bistriflimide – EMIM-TFSI). The average interparticle interaction is found to be repulsive by small angle scattering of X-rays and of neutrons, with a second virial coefficient A2 = 7.3. A moderately concentrated sample at F = 5.95 vol% is probed by forced Rayleigh scattering under an applied magnetic field (up to H = 100 kA m1 ) from room temperature up to T = 460 K. Irrespective of the values of H and T, the NPs in this study are always found to migrate towards the cold region. The in-field anisotropy of the mass diffusion coefficient Dm and that of the (always positive) Soret coefficient ST are well described by the presented model in the whole range of H and T. The main origin of anisotropy is the spatial inhomogeneities of concentration in the ferrofluid along the direction of the applied field. Since this effect originates from the magnetic dipolar interparticle interaction, the anisotropy of thermodiffusion progressively vanishes when temperature and thermal motion increase.
• Physics, chemistry, nanoscience and materials around large instruments › Physique de la matière condensée, étude par l’interaction rayonnement matière Synthèse et caractérisation des nano-objets / Synthesis and characterization of nano-objects › Nanostructured materials and nanocomposites Physique, chimie, nanosciences et matériaux autour des grands instruments
• Laboratoire Léon Brillouin (LLB) • Leon Brillouin Laboratory (LLB)
• Groupe "Matière molle et biophysique" - MMB
• Diffraction de rayons X • Diffusion des Rayons X aux petits angles / Small Angle X-Rays Scattering (SAXS) • Neutrons • Activités instrumentales nationales et internationales du LLB - National and internatonial instrumental activities at the LLB • Neutrons • Small Angle Neutron Scattering (PA)