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The evolution of field-induced structure in ferrofluid emulsions is studied during the "gas-solid" phase transition. The chain formation and coarsening are measured by monitoring the average separation between aggregates d using static light scattering and optical microscopy. A powerlaw relation, d -tr, is obtained for all measured cell thicknesses ranging 10 c L c 700 jim along the field direction. The rate of chain coarsening strongly depends on the chain length, weakly depends on the particle volume fraction and is independent of the field strength at a finite cell thickness. A theoretical model based on thermal fluctuation induced coupling and nucleation theory has been developed to explain the data at large L successfully.

We report a real-time study of the evolution of the structure of confined ferrofluid emulsions during the "liquid–solid" phase transition. A monodisperse oil-in-water ferrofluid emulsion is used. The structure evolution of the emulsion after rapidly applying a magnetic field is probed by the static light scattering. The scattering pattern exhibits pronounced rings reflecting the formation of chains and their coalescence to columns or even "worm" structures. The scattering ring is found to decrease in size and brighten in intensity with time. To monitor the structure evolution in time, both the ring peak position in scattering wavevector, q max , and the peak intensity, I max , are measured as a function of time. Both q max and I max saturate in less than 0.5 seconds after applying a magnetic field. At a constant cell thickness of 25 µm, the evolution of structure is essentially independent of volume fraction ranging from 0.015 to 0.13. In addition, a very good scaling is found in the scattered light intensity as a function of the scattering wavevector.

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