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Organization of Paramagnetic and Nonmagnetic Colloidal Particles in Ferrofluid
(2012)
- In this thesis, I have studied magnetic dipolar interactions between paramagnetic and nonmagnetic colloidal particles immersed in a magnetic fluid under the influence of an external time dependent magnetic field. These interactions play an important role in colloidal self-assembly. As a result, of these interactions different forms of anisotropic superstructures evolve in 2-Dimension and 3-Dimension during the self-assembly process. The time dependent external magnetic field is an important controlling parameter for the self-assembly process. The interactions leads to a specific equilibrium positions of the paramagnetic and nonmagnetic particles with specific orientations of the magnetic moments. Three different colloidal systems immersed in ferrofluid with external time dependent magnetic field have been investigated. In each of them the effect of inter dipolar interactions on the particles is discussed. Three systems are arranged and discussed in three separate chapters. In chapter 3, an attempt has been made to study the diffusion of particles in a colloidal flower system and compare the diffusion of the petals of the flower with other single file diffusion in 1-dimension. Beside the long-range interactions, in chapter 4, we have studied the strength of the systems and order of phase transition taking place due to core size effects of self-assembled flower shaped magnetic colloidal clusters and diamagnetic clusters in a precessing magnetic field. In chapter 5, different anisotropic assemblies and colloidal phases are studies as a function of the composition mixture of paramagnetic and diamagnetic particles in an external time dependent magnetic field.
