Preparation and Properties of an Aqueous Ferrofluid
Patricia Berger Department of Chemistry, Southern Oregon University, Ashland, OR 97520
Nicholas B. Adelman, Katie J. Beckman, Dean J. Campbell, and Arthur B. Ellis Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706
George C. Lisensky Department of Chemistry, Beloit College, Beloit, WI 53511
Ferrofluids are colloidal suspensions of surfactant-coated magnetic particles in a liquid medium. This paper describes a simple synthesis of an aqueous-based ferrofluid that may be used in an introductory science or engineering laboratory. Magnetite (Fe3O4) particles are precipitated by combining FeCl3 and FeCl2 in a 2:1 stoichiometric ratio in aqueous ammonia solution. The resulting particles, ~10-20 nm in diameter based on powder X-ray diffraction, are then treated with aqueous tetramethylammonium hydroxide, which acts as a surfactant. When the resulting ferrofluid is placed near a magnet, it forms conical spikes. This paper also describes a method for repelling both oil- and water-based ferrofluid from solid surfaces that would otherwise be stained by the fluid. Finally, a demonstration of the interaction between ferrofluid and magnetic fields, in which ferrofluid is induced to leap upward by a stack of magnets, is described.
A detailed version of the laboratory experiment is available as supplement material and can be accessed as a pdf file with Acrobat Reader. The experiment is also supplied as one Microsoft Word file and two eps files, which can be opened with Photoshop. These word and graphics files have been compressed into zip (for Windows) and sit (for Macintosh) files.
There are also two videos of the formation of spikes in aqueous ferrofluid in response to a magnetic field. The height of the spikes depends on the distance between the ferrofluid and the magnet. You will need QuickTime 3 in order to view this dramatic sequence and can download a free copy from http://www.apple.com.
Enzel, Patricia; Adelman, Nicholas B.; Beckman, Katie J.; Campbell, Dean J.; Ellis, Arthur B.; Lisensky, George C. J. Chem. Educ.1999 76 943.
Keywords
Inorganic Chemistry; Introductory / High School Chemistry; Laboratory Instruction; Magnetic Properties; Materials Science; Nanotechnology; Stoichiometry
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Contents
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