skip to main content

Title: Direct observation of electric field induced pattern formation and particle aggregation in ferrofluids

Ferrofluids typically respond to magnetic fields and can be manipulated by external magnetic fields. Here, we report on formation of visually observable patterns in a diluted low-polarity ferrofluid exposed to external electric fields. This presents a specific type of ferrofluid structure driven by a combined effect of electrohydrodynamics and electrical body forces. The free charge and permittivity variation are considered to play a key role in the observed phenomenon. The corresponding changes in the ferrofluid structure have been found at nanoscale as well. By small-angle neutron scattering (SANS), we show that the magnetic nanoparticles aggregate in direct current (dc) electric field with a strong dependence on the field intensity. The anisotropic aggregates preferably orient in the direction of the applied electric field. Conducting SANS experiments with alternating current (ac) electric fields of various frequencies, we found a critical frequency triggering the aggregation process. Our experimental study could open future applications of ferrofluids based on insulating liquids.
Authors:
; ;  [1] ;  [2] ;  [3] ;  [2] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [6]
  1. Institute of Experimental Physics SAS, Watsonova 47, 04001 Košice (Slovakia)
  2. Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Moscow Region (Russian Federation)
  3. (Ukraine)
  4. (Russian Federation)
  5. Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching (Germany)
  6. Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice (Slovakia)
Publication Date:
OSTI Identifier:
22489126
Resource Type:
Journal Article
Resource Relation:
Journal Name: Applied Physics Letters; Journal Volume: 107; Journal Issue: 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; AGGLOMERATION; ALTERNATING CURRENT; ANISOTROPY; CRITICAL FREQUENCY; DIRECT CURRENT; ELECTRIC FIELDS; ELECTROHYDRODYNAMICS; LIQUIDS; MAGNETIC FIELDS; MAGNETIC MATERIALS; NANOPARTICLES; NANOSTRUCTURES; NEUTRON DIFFRACTION; PERMITTIVITY; SMALL ANGLE SCATTERING