NMR study on colloidal magnetic fluids of various viscosities

Abstract

NMR experiments on mobile spins in the liquid continuous phase of a magnetic fluid are applied to characterize the particle arrangement and to study self diffusion of the fluid medium. It is observed that the resonance frequencies and line shapes depend on the particle concentration, particle magnetization, particle agglomeration and on the sample geometry. A controlled variation of the self diffusion constant is performed either by addition of macromolecules to or by adjusting the sample temperature. The influence of the solvent viscosity on the NMR line shape is analyzed by numerical simulation of the spectra. The method presents a valuable tool for the observation of changes in dispersion structure or molecular mobility, e.g., during phase transitions.

Keywords:

• Nuclear magnetic resonance (NMR)
• Magnetic fluids
• Self diffusion
• Nanoparticles

Acknowledgments

This work was initially funded by a special grant of the University of Duisburg. Additional financial support was received from the Deutsche Forschungsgemeinschaft (DFG) in connection with the research project SFB 445 titled “Nano-Particles from the Gas Phase”.