10-24-07 - 10/24/07 Magnetics IV Ferrofluids Curie...

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10/24/07 Magnetics IV Ferrofluids Curie Temp-makes a material lose its magnetic properties. o Melting iron-twice the temperature as the curie temp/ending Cparticles with surfactants suspentded in medium Ferrofluids o Magnetic material: Spontaneously magnetized. o Fluid: Flow or assume shape of container o Can change its orientation, etc… the bullets are on slides. o R. Rosenwieg, Scientific American Oct. 1982, 136 o Magnetic force can overcome the gravitational force Ferrofluid seal o Liquid O ring for vacuum chamger o Ferrofluid is held in place by permanent magnets and forms a tight seal eliminating the friction of solid seals. Utilized in audio speakers History: o Magnetic clutch-app of magnetic field causes the clutch fluid to congeal Have liquid that flows, when app field, the particles become magnetized, it changes the viscosity of the medium. o NASA-60s-manipulate liquids in space Ferrofluids/backgrounds o Sufficieintly small particles can remain suspended in a liquid even if their density is higher than the liquid Oxide has an order between 2 to 7 g/cubic cm. A metal is even higher.
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Suspend it in hydrocarbon liquid… possible because of size. It bounces around the media particles—due to thermal energy. o Particles kept from settling because of collisions with liquid molecules o Energy per particle is kT -k: Boltzmann’s constant, T: Temperature o Thermal energy greater than gravitational energy needed to raise the particles. o
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This note was uploaded on 10/24/2008 for the course ENGRI 1110 taught by Professor Giannelis during the Fall '07 term at Cornell.

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10-24-07 - 10/24/07 Magnetics IV Ferrofluids Curie...

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