Magnetic fluids
Abstract
An overview of studies done on ferrofluids is presented, and recently discovered technological uses for such a fluid are examined. By interacting magnetization and pressure, a ferrofluid plug, held in place by a focused magnetic field imposed from the outside, serves as an airtight seal in rotating machinery. A 160 stage rotary seal has withstood a pressure differential of 66 atmospheres. The fluid has also proved useful in the design of loudspeakers, as it does not drip out of the gap in the cylindrical permanent magnet which allows the voice coil to move, thus serving as a coolant for the system. Finally, the fluid can be used to separate materials according to density, as the magnetic-levitation forces that can be established in the fluid are strong enough to float materials of any density. Other applications are being explored, such as an induced convection that can be much more vigorous than simple gravity convection when a gradient magnetic field is applied to a heated ferrofluid.
- Publication:
-
Scientific American
- Pub Date:
- October 1982
- DOI:
- 10.1038/scientificamerican1082-136
- Bibcode:
- 1982SciAm.247d.136R
- Keywords:
-
- Ferrofluids;
- Hydrodynamics;
- Magnetic Effects;
- Rotating Liquids;
- Technology Utilization;
- Dynamic Response;
- Magnetic Fields;
- Seals (Stoppers);
- Physics (General)