Deepti Joshi, Naveen Bhagat, Sumit Pant
2017 International Journal of Advanced Research  
Magnetic fluids are basically classified into two categories; first one is ferromagnetic fluids (or ferrofluids) and another one is magnetorheological fluids. Ferromagnetic fluids are colloidal suspensions of very fine magnetic particles (~10 nm), whereas magnetorheological fluids are suspensions of larger magnetic particles, which are usually non-stable. In this review article we mainly focused on ferromagnetic fluids. We review the general classification of ferromagnetic fluids, properties of
more » ... uids, properties of ferromagnetic fluids and applications of ferromagnetic fluids. A large portion of this review included the results of maximum work which has been done in stability of ferromagnetic fluids till the present. Copy Right, IJAR, 2017,. All rights reserved. ...................................................................................................................... Introduction:- Ferromagnetic fluid (also called ferrofluid) is electrically non-conducting colloidal suspensions of solid ferromagnetic particles in a non-electrically conducting carrier fluid like water, kerosene, hydrocarbon or organic solvent etc. These colloidal particles are coated with a stabilizing dispersing agent (surfactants) who prevents particle agglomeration even when a strong magnetic field gradient is applied to the ferromagnetic fluid. These suspensions are stable and maintain their properties at extreme temperatures and over a long period of time. Ferromagnetic fluids behave as a homogeneous continuum and indicate a variety of interesting phenomena. The two main features that distinguish ferromagnetic fluid from ordinary fluid are the body couple and the polarization force. Ferromagnetic fluids are not found in nature, these fluids are artificially synthesized. Ferromagnetic fluid becomes strongly magnetized in the presence of a magnetic field. Stene Papell invented ferromagnetic fluid for NASA in 1963. The difference between ferromagnetic fluids and magnetorheological fluids is the size of the particles. The particles in a ferromagnetic fluid primarily consist of nano-particles (diameter usually 10 nano meters or less) suspended by Brownian motion and generally will not settle under normal conditions. A typical ferromagnetic fluid contains 10 23 particles per cubic meter. Magnetorheological fluids formed by micron sized particles dispersed in oil, used for dampers, brakes and clutches. For strong magnetic fields, magnetorheological fluids behave like a solid. On the other hand, a ferromagnetic fluids keeps its fluidity even strong magnetic field is applied. Ferromagnetic fluids are optically isotropic, but in the presence of an external magnetic field, they exhibit induced birefringence. Soon after the method of formation of ferromagnetic fluids, during mid sixties of the twentieth century, the importance of ferrohydrodynamics (FHD) was realized. Ferromagnetic fluids has wide ranges of applications in instrumentation, lubrication, printing, vacuum technology, vibration damping, metals recovery, acoustics and medicine. Ferromagnetic fluids are widely used in sealing of the hard disk drives, the novel zero leakage rotating
doi:10.21474/ijar01/4395 fatcat:j2yefqlvwfhorcvrqju365iquy