Application of small-angle neutron scattering to the study of forces between magnetically chained monodisperse ferrofluid emulsion droplets

Journal Article · Wed Jan 01 00:00:00 EST 2014 · Journal of Applied Crystallography

DOI:https://doi.org/10.1107/S1600576713030045· OSTI ID:1122657

Jain, Dr Nirmesh ^[1]; Liu, Dr C K ^[2]; Hawkett, Dr B. S. ^[1]; Warr, G. G. ^[1]; Hamilton, William A ^[3]

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1. University of Sydney, Australia
2. Institute of Materials research and Engineering, A-STAR, Singapore
3. ORNL

The optical magnetic chaining technique (MCT) developed by Leal-Calderon, Bibette and co-workers in the 1990 s allows precise measurements of force profiles between droplets in monodisperse ferrofluid emulsions. However, the method lacks an in-situ determination of droplet size and therefore requires the combination of separately acquired measurements of droplet chain periodicity versus an applied magnetic field from optical Bragg scattering and droplet diameter inferred from dynamic light scattering (DLS) to recover surface force-distance profiles between the colloidal particles. Compound refractive lens (CRL) focussed small-angle scattering (SANS) MCT should result in more consistent measurements of droplet size (form factor measurements in the absence of field) and droplet chaining period (from structure factor peaks when the magnetic field is applied); and, with access to shorter length scales, extend force measurements to closer approaches than possible by optical measurements. We report on CRL-SANS measurements of monodisperse ferrofluid emulsion droplets aligned in straight chains by an applied field perpendicular to the incident beam direction. Analysis of the scattering from the closely spaced droplets required algorithms that carefully treated resolution and its effect on mean scattering vector magnitudes in order to determine droplet size and chain periods to sufficient accuracy. At lower applied fields scattering patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1122657
• Journal Information: Journal of Applied Crystallography, Vol. 47, Issue 1; ISSN 1600--5767
• Country of Publication: United States
• Language: English

Related Subjects

SANS (Small Angle Netron Scattering)
Colloid
Superparamagnetic
surface forces