Magnetic Fluids :: GCSE Chemistry

1.1 PRELUDEThe phenomenon of ferromagnetism is associated only with the solid state of matter like iron, nickel, conscientious objector and some r are earth metals and their alloys. Thus, up to now, there is no inhering homogeneous fluid having ferromagnetic properties although, theories admit the possibility of ferromagnetism in the semi perspicuous state, and suggest that there is no inherent reason why they should not exist 1-3,5. Ferromagnetism occurs when paramagnetic ions in a solid lock unitedly in such a way that their spins all point (on the average) in the same direction . At a certain temperature this locking breaks level and ferromagnetic materials become paramagnetic. This transition temperature is called the Curie point (TC), which is invariably nearly below the melting point of the corresponding material 1,8,12.1.2 MAGNETIC FLUIDS magnetic fluids ( MF ) are stable colloidal suspensions of ultrafine ferro- or ferri- magnetic particles ( D100Ao ), coat with a surf actant like oleic acid, in a suitable liquid carrier waves such as Isopar-M, kerosene, decalin, etc., 1,2. The idea of MF was put forward independently and almost simultaneously by several investigators. The first prepared MF was developed by Stephen Papell of the National Aeronautics and Space Administration (NASA) in the early 1960s. After that, Ronald E. Rosensweig and his colleagues succeeded in formulating MFs that were 10 times as rugged magnetically as Papells original MF 1.The special feature article of magnetic fluids is given by the fact, that they combine normal liquid behavior with superparamagnetic properties, as will be discussed later. The possibility of magnetic fluid pick up gave rise to the development of many technical applications in our everyday sprightliness 1-3.Mixtures are classified into lead kinds colloidal suspensions, suspensions, and solutions, and one of the principal features that narrow one kind of mixture from another is the size of the partic les 6. Colloidal suspensions (also called colloids) are mixtures that are intermediate between solutions and suspensions. Typically the radius of the particle is of the rig 100Ao. Since this is much smaller than the size of a single magnetic terra firma in bulk solids, which is about , the magnetization of the individual particle is saturated, scarcely the direction of the magnetic moment is subject to thermal agitation 1,2,5. The particles employ are commonly Fe3O4, Fe, Co and Ni.MF is a two-phase system with three components, which combines magnetic properties, carried by the solid magnetic fine particles, with fluidity of the carrier liquid.