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Ferrofluids

Ferrofluids. Ferrofluids: Magnetic Liquids. Liquid That Responds to a Magnetic Field = Colloidal Suspension of Superparamagnetic Magnetic Material. How Does A Magnetic Liquid Work?. 2FeCl 3 + FeCl 2 + 8NH 3 + 4H 2 O → Fe 3 O 4 + 8NH 4 Cl . Tetramethylammonium Cation

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Ferrofluids

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  1. Ferrofluids

  2. Ferrofluids: Magnetic Liquids Liquid That Responds to a Magnetic Field = Colloidal Suspension of Superparamagnetic Magnetic Material

  3. How Does A Magnetic Liquid Work? 2FeCl3 + FeCl2 + 8NH3 + 4H2O → Fe3O4 + 8NH4Cl Tetramethylammonium Cation (NH4+) Electrostatic Repulsion Hydroxide Anion (OH-) ~ 10nm Berger, P.; Adelman, N. B.; Beckman, K. J.; Campbell, D. J.; Ellis, A. B.; Lisensky, G. C. Journal of Chemical Education1999, 76, 943-8.

  4. Synthesis of Magnetite Nanocrystals FeCl3 + 3NH4OH → FeO(OH) + 3NH4Cl + H2O FeCl2 + 2NH4OH → Fe(OH)2 + 2NH4Cl 2FeO(OH) +Fe(OH)2→ Fe3O4 + 2H2O Processes: 1) Nucleation 2) Growth 3) Termination + + + + + → → + + + + + • Fe(III) coordinates to 6 water molecules and • Fe(II) coordinates to 4 water molecules (not • shown) until the solid forms • The water molecules on the periphery of the • magnetite are ultimately replaced by • tetramethylammonium hydroxide + + + + + + + + +

  5. Unique Properties • Stick to Magnets • Take on 3-Dimensional Shape of a • Magnetic Field • Change Density in Proportion to • Magnetic Field Strength

  6. Applications • Inks • money • Biomedical • attach drugs to magnetic particles, • proposed artificial heart • Damping • speakers, graphic plotters, instrument • gauges • Seals • gas lasers, motors, blowers, hard drives Berger, P.; Adelman, N. B.; Beckman, K. J.; Campbell, D. J.; Ellis, A. B.; Lisensky, G. C. Journal of Chemical Education1999, 76, 943-8.

  7. Damping: Speakers Rosensweig, R. E. Scientific American1982, 247, 136-45. See how a speaker works at: http://electronics.howstuffworks.com/speaker6.htm

  8. Damping: Rotating Shafts Cross-sectional view of a ferrofluid viscous inertia damper Energy band gap apparatus Ray, K.; Moskowitz, B.; Casciari, R. Journal of Magnetism and Magnetic Materials1995, 149, 174-180.

  9. Seals Atmosphere Vacuum Rotating Shaft Ferrofluid Magnetically Permeable Material Permanent Magnet Rosensweig, R. E. Scientific American1982, 247, 136-45.

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