CHEMISTRY WITH REFRIGERATOR MAGNETS : FROM MODELING OF NANOSCALE CHARACTERIZATION TO COMPOSITE FABRICATION

Flexible sheet refrigerator magnets (RMs) have interesting magnetic structures that allow them to be used to demonstrate a number of chemical principles. RMs are a composite of strontium ferrite dispersed in the elastomer Hypalon. The magnetic alignment of the ferrite particles gives rise to a striped array of alternating north and south poles on the back side of the RM that may be visualized by a number of techniques and altered with a strong magnet. When the back sides of two RMs are rubbed against each other, the magnets may slide or alternately attract and repel one another ("chatter"), depending on their relative orientation. These effects lend themselves to demonstrations of scanning probe microscopy and models of mechanical properties of metals and salts. Concepts of composite materials and surface chemistry may be illustrated with student laboratory fabrications of refrigerator magnets utilizing strontium ferrite dispersed in polydimethylsiloxane elastomer.