Abstract: When an external magnetic field was applied on the suspension composed of ferromagnetic Ni and nonmagnetic ZrO₂ particles, the viscosity of the suspension increased drastically. The relation of viscosity and inner structure of suspension was investigated by using magnetic coils, rotational viscometer and optical microscope. The results show that the viscosity increases with the magnetic field strength and Ni content increasing because of the formation of chain-like clusters in the suspension. As the magnetic field increases, Ni clusters become larger, which hinders the free move of particles, so the viscosity increases. Similarly, Ni clusters in the suspension increase with Ni content increasing, and hence the viscosity increases.

Key words: viscosity, magnetic particle, chain-like cluster, magnetic field, FGM