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The time dependence of the changes of ultrasonic wave velocity in ferrofluid under parallel magnetic field

2003; Elsevier BV; Volume: 256; Issue: 1-3 Linguagem: Inglês

10.1016/s0304-8853(02)00572-3

1873-4766

Arkadiusz Józefczak,

Characterization and Applications of Magnetic Nanoparticles

Under the effect of an external magnetic field, Fe3O4 particles in a ferrofluid undergo aggregation and chain clusters appear arranged along the lines of the field. These phenomena change the propagation velocity and absorption coefficient of the ultrasound wave. Thus, by measuring changes in the ultrasound wave velocity Δc, it is possible to get information on the structural changes of the ferrofluid. The changes Δc have been found to depend on the magnetic field intensity and on its sweep rate. It has been shown that the ferrofluid does not reach a new equilibrium state immediately after the field takes the final value, but the equilibrium is reached after a certain time depending on the field seep rate.