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

Journal Article · Mon Aug 17 00:00:00 EDT 2015 · Applied Physics Letters

DOI:https://doi.org/10.1063/1.4929342· OSTI ID:22489126

Rajnak, Michal; Kopcansky, Peter; Timko, Milan ^[1]; Petrenko, Viktor I. ^[2]; Avdeev, Mikhail V. ^[2]; Ivankov, Olexandr I. ^[2]; Feoktystov, Artem ^[3]; Dolnik, Bystrik; Kurimsky, Juraj ^[4]

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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. Jülich Centre for Neutron Science (JCNS) at Heinz Maier-Leibnitz Zentrum (MLZ), Forschungszentrum Jülich GmbH, Lichtenbergstr. 1, 85747 Garching (Germany)
4. Faculty of Electrical Engineering and Informatics, Technical University of Košice, Letná 9, 04200 Košice (Slovakia)

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.

• OSTI ID: 22489126
• Journal Information: Applied Physics Letters, Vol. 107, Issue 7; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
• Country of Publication: United States
• Language: English

Related Subjects

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