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Brownian Dynamics Simulations to Determine Anisotropy in Diffusion Constants of Nonmagnetic Particle in Magnetic Fluids

Saurabh Tejwani, Kenneth A. Smith, and T. Alan Hatton. Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139

Magnetic field gradients can be exploited to perform a size based separation of nonmagnetic particles. We are developing computation and simulation tools to assist in the in-depth understanding of the thermodynamic and transport properties of such nonmagnetic nanoparticles immersed in magnetic fluids under varying magnetic field conditions. A fundamental understanding of these properties, such as chemical potential, diffusion constants, etc. is important in the development of magnetic separation systems

In the presented work we have performed Brownian dynamic simulations to evaluate the diffusion constants of nonmagnetic particles in magnetic fluids. We have observed a strong anisotropy for these diffusion constants with reference to the applied magnetic field. The diffusion constants of these particles have a lower value in the direction perpendicular to the external magnetic field as compared to the direction parallel to the applied magnetic field. This anisotropy was studied as a function of magnetic particle size, magnetic particle concentration and nonmagnetic particle size.