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

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 scatteringmore » patterns indicate structural correlations transverse to the magnetic field direction due to the formation of intermediate structures in early chain growth.« less
 [1] ;  [2] ;  [1] ;  [1] ;  [3]
  1. University of Sydney, Australia
  2. Institute of Materials research and Engineering, A-STAR, Singapore
  3. ORNL
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Crystallography; Journal Volume: 47; Journal Issue: 1
Research Org:
Oak Ridge National Laboratory (ORNL)
Sponsoring Org:
SC USDOE - Office of Science (SC)
Country of Publication:
United States
SANS (Small Angle Netron Scattering); Colloid; Superparamagnetic; surface forces