Lab1-S08-Ferrofluid - Lab 1: Synthesis of Ferrofluids...

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20 Lab 1: Synthesis of Ferrofluids Laboratory Goals In this lab, you will: Learn how a ferrofluid is prepared Learn some properties and uses of ferrofluids Important Notes Do not get the ferrofluid liquid on your skin or clothing, as it will stain (possibly permanently). Although the NH 3 solution is diluted, it is still a strong potent and should be handled carefully. Introduction What is a “ferrofluid?” A ferrofluid is a colloid of magnetic particles within a liquid. They are unusual in that they act like a liquid that reacts to a magnetic field. A true ferrofluid is stable enough that even in the presence of an extremely strong magnetic field, the particles will not separate. When a ferrofluid is exposed to a magnetic force, the particles form chains and create spikes. If the ferrofluid is in a confined, essentially 2- dimensional space (such as between two sheets of glass) it will still form unique patterns. These shapes are the result of the repulsion between the like magnetic poles of the particles being counteracted by the confining force of the suspending liquid. The difficulty in creating a ferrofluid is the tendency of particles in a liquid to aggregate, form clumps, and to separate. This is especially true of magnetic particles, which are naturally attracted to each other. The most common method of preventing this problem (and creating a true ferrofluid rather than just a magnetic suspension) is to use a surfactant. These are substances whose molecules have contrasting properties, such as a cation-anion pair. The surfactant forms a sort of “shell” around each particle in suspension, preventing them from aggregating and separating from the liquid. The shell is formed when the anions are attracted to the slightly positive surface of the particles. This anion layer will then attract a cation layer. Since each particle will have an outer shell of positive cations, and like charges repel, the particles will avoid getting near enough to each other to bond. One way that ferrofluid technology is used today is as a liquid sealant. The
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This note was uploaded on 04/15/2009 for the course LB 171L taught by Professor All during the Spring '08 term at Michigan State University.

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Lab1-S08-Ferrofluid - Lab 1: Synthesis of Ferrofluids...

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