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Ferrofluids

Ferrofluids. Overview. Definitions Engineering Applications. Definition.

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Ferrofluids

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  1. Ferrofluids

  2. Overview • Definitions • Engineering • Applications

  3. Definition • A ferrofluid is a specific type of liquid which responds to a magnetic field. Ferrofluids are composed of nanoscale magnetic particles suspended in a carrier fluid. The solid particles are generally stabilized with an attached surfactant layer. Ferrofluids are extremely stable meaning that they will not cluster together even in extremely strong magnetic fields

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

  5. Physics • Ferromagnetismisamagneticdipolethatisfromthealignmentofunpairedelectronspinsinelementssuchasiron,cobalt,andnickel.Inthisexperimentwewillsynthesizemagneticnanoparticlesfromironchloridesandthendisperseintoatetramethylammoniumhydroxidesurfactanttoformacolloidalsuspension

  6. 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.

  7. Chemistry • The formation of ferrofluid involves various types of forces that hold the components together. For example, magnetite is held together by ionic interactions. Ionic attractions between hydroxide anions and tetramethylammonium cations allow colloidal suspension of the magnetite in the solution. Without the tetramethyl ammonium hydroxide as a surfactant, the magnetite nanoparticles tend to cluster together. Therefore it is necessary to have the appropriate surfactant to stabilize an aqueous ferrofluid

  8. 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 + + + + + + + + +

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

  10. 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.

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

  12. 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.

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

  14. Ferrofluid Preparation • Step 1 • Step 2 • Step 3 • Step 4 • Step 5 • Step 6

  15. Ferrofluids Step 1 Dissolve 67.58g FeCl3.6H2O in 250ml of 2M HCl. Dissolve 39.76g FeCl2.4H2O in 100ml of 2M HCl. Modified from Berger et al, Journal of Chemical Education, 1999, 26, 7, 943-948

  16. Ferrofluids Step 2 1M FeCl3 should be used within one week of preparation. 2M FeCl2 should be used within one week of preparation.

  17. Ferrofluids Step 3 Combine 3ml of FeCl2 solution and 12ml of FeCl3 solution and fill a burette with 150ml of 0.7M ammonium hydroxide solution. Add ammonia very slowly whilst stirring. A black precipitate of magnetite will form.

  18. Ferrofluids Step 4 After addition is complete, stop stirring and use a strong magnet (Nd2Fe12B) to settle the black precipitate to the bottom of the flask. Decant off the water and add fresh water. Rinse the precipitate and again decant off the water. Repeat three times to remove excess ammonia.

  19. Ferrofluids Step 5 Transfer the viscous liquid to a weighing boat using a little extra water if necessary. Use a magnet on the base of the weighing boat to remove excess water. Add 24ml of tetramethylammonium hydroxide (25% solution) and stir with a glass rod

  20. Ferrofluids Step 6 Hold a magnet on the base of the weighing boat and let the solid settle to the bottom. Decant off any excess liquid to leave a very viscous black liquid. The viscous liquid should form spikes if a magnet is held underneath the weighing boat. You may need to adjust the amount of water.

  21. Mechanical Applications • Ferrofluids are used in many ways mechanically. They are used in applications such as gaslasers, motors, and blowers. In some of these applications the ferrofluid is held in place by a strong magnet and separate by two different pressured chambers.They are also used as substances for vibrational dampening in electronic applications

  22. Summary

  23. References • voh.chem.ucla.edu/classes/Magnetic_fluids/pdf/Ferrofluids.ppt • www.chemlabs.bris.ac.uk/outreach/resources/Ferrofluids.ppt • http://www.slideworld.com/slideshows.aspx/Ferrofluids-ppt-426340 • http://www.slideshare.net/vponsamuel/aqueous-ferrofluid (method)

  24. Acknowledgements Aqueous Ferrofluid 10.19.2006 By:Victor Samuel 8th Grader at Creekside Middle School Carmel, IN 460322006 (Fall session):Gifted Education Resource Institute Super Saturday Program on Nanotechnology

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