Levitation, magnetic

Turbomolecular (turbo) pumps are very clean (especially magnetically levitated version) mechanical pumps, with pumping speed up to more than 70001/s. 

Light gases with higher thermal velocity are pumped less than heavier ones. This is why turbo pumps produce an (almost) oil-free vacuum. The lubrication of turbo pumps is made with a special vacuum grease. Pumps with magnetically levitated rotor are available, but they are more expensive. 

Advances in microminiaturization of pumps, battery technology, and transcutaneous energy transmission may make these concepts a reality in the near future. It is now possible to make a pump that is as small as a pencil eraser deliver 5 1/min of blood flow and both axial and centrifugal pumps are being developed with magnetically levitated... 

Fig. 1.5. Apparatus for demonstrating vacuum tunneling. The tunneling unit consists of a W tip and a Pt plate. Vibration isolation is achieved by magnetic levitation on a superconducting bowl. (Reproduced from Binnig et al., 1982a, with permission.)...

Permanent magnet levitates above superconducting disk cooled in a pool of liquid nitrogen. Redox titrations are crucial in measuring the chemical composition of a superconductor. [Photo courtesy D. Cornelius, Michelson Laboratory, with materials from 1 Vanderah.J... 

FIGURE 3.43 High-temperature superconductors may make magnetically levitated vehicles a reality. This picture shows an experimental train in Japan. 

The discovery of high-temperature superconductors is surely one of the most exciting scientific developments in the last 20 years. It has stimulated an enormous amount of research in chemistry, physics, and materials science that could some day lead to a world of superfast computers, magnetically levitated trains, and power lines that carry electric current without loss of energy. 

FIGURE 21.15 An experimental magnetically levitated train (Maglev) in Japan is suspended above superconducting magnets that are cooled with liquid helium. This five-car train has attained a speed of 552 km/h in a manned vehicle run. 

What new developments the future holds nobody knows for certain. In electronics people will try to miniaturise electric equipment even further. Non-functional, ceramic packaging will be converted into functional components. For this new ceramic materials are necessary, as are ways to process them. High-temperature superconductors will lead to magnetic levitation craft, cheap electricity and improved MRI (magnetic resonance imaging). 

Only the two first methods allow measurement of the temperature coefficient of the surface energy. The maximum bubble pressure technique is well-adapted for metals with low and intermediate melting points and specially for oxidizable metals, while the sessile drop technique has been applied with success to measure ctlv values up to 1500°C. The drop weight method is particularly useful for very high melting-point metals because it avoids liquid contact with container materials. This is also true for the recently developed levitation drop technique that analyses the oscillation spectrum of a magnetically levitated droplet. 

FIGURE 18.15 Test setup for CMP slurry handling and filter characterization. Experiments can be performed emplo5hng an air operated diaphragm (AOD) pump or a magnetically levitated centrifugal (MLC) pump. 

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