Ferrofluids. Ferrofluids: Magnetic Liquids Liquid That Responds to a Magnetic Field = Colloidal...
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Transcript of Ferrofluids. Ferrofluids: Magnetic Liquids Liquid That Responds to a Magnetic Field = Colloidal...
FerrofluidsFerrofluids
Ferrofluids: Magnetic LiquidsFerrofluids: Magnetic Liquids
Liquid That Responds to a Magnetic Field
=
Colloidal Suspension of Superparamagnetic Magnetic Material
Berger, P.; Adelman, N. B.; Beckman, K. J.; Campbell, D. J.; Ellis, A. B.; Lisensky, G. C. Journal of Chemical Education 1999, 76, 943-8.
How Does A Magnetic Liquid How Does A Magnetic Liquid Work?Work?
ElectrostaticRepulsion
2FeCl3 + FeCl2 + 8NH3 + 4H2O → Fe3O4 + 8NH4Cl
Tetramethylammonium Cation (NH4
+)
Hydroxide Anion (OH-)
~ 10nm
Synthesis of Magnetite NanocrystalsSynthesis of Magnetite NanocrystalsFeCl3 + 3NH4OH → FeO(OH) + 3NH4Cl + H2O
2FeO(OH) + Fe(OH)2 → Fe3O4 + 2H2O
Processes:1) Nucleation 2) Growth 3) Termination
→ →
+
++
+ +
+
++
+ +
+
+
+
+
+
++
+
+
FeCl2 + 2NH4OH → Fe(OH)2 + 2NH4Cl
• 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
Unique PropertiesUnique Properties
• Stick to Magnets• Take on 3-Dimensional Shape of a Magnetic Field• Change Density in Proportion to Magnetic Field Strength
ApplicationsApplications• 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 Education 1999, 76, 943-8.
Damping: SpeakersDamping: Speakers
See how a speaker works at:http://electronics.howstuffworks.com/speaker6.htm
Rosensweig, R. E. Scientific American 1982, 247, 136-45.
Damping: Rotating Shafts Damping: Rotating Shafts
Ray, K.; Moskowitz, B.; Casciari, R. Journal of Magnetism and Magnetic Materials 1995, 149, 174-180.
Cross-sectional view of a ferrofluid viscous inertia damper
Energy band gap apparatus
SealsSeals
Rosensweig, R. E. Scientific American 1982, 247, 136-45.
VacuumAtmosphere
Permanent Magnet
Ferrofluid
Rotating Shaft
MagneticallyPermeable Material