File:Zone refining 1961.jpg
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Summary
| Description |
English: Zone refining of a bar of rare earth metal at University of Michigan in 1961. Zone refining, invented in 1953 by William Pfann at Bell Laboratories, is a technique for removing impurities from crystals, widely used in the semiconductor industry. In the picture a narrow bar of metal runs down the center of the glass tube. The coil of copper wire around the tube is attached to an electronic oscillator generating a radio frequency alternating current through the wire. This heats the bar by induction heating, melting a short length of the bar. The coil is moved slowly down the tube by the lead screw (right), so the molten zone moves down the bar. The impurities in the bar stay in the molten section and are moved to the end of the bar, which is cut off. |
| Date | |
| Source | Retrieved May 17, 2015 from Bryan Whipple, "Unusual Metals" in The Michigan Technic magazine, Univ. of Michigan, Ann Arbor, Michigan, Vol. 79, No. 6, March 1961, p. 14 on Google Books |
| Author | Bryan Whipple |
| Permission (Reusing this file) |
This 1961 issue of The Michigan Technic magazine would have the copyright renewed in 1989. Online page scans of the Catalog of Copyright Entries, published by the US Copyright Office can be found here. Search of the Renewals for Periodicals for 1978 and later show no renewal entries for The Michigan Technic. Therefore the copyright was not renewed and it is in the public domain. |
Licensing
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This work is in the public domain because it was published in the United States between 1929 and 1963, and although there may or may not have been a copyright notice, the copyright was not renewed. For further explanation, see Commons:Hirtle chart and the copyright renewal logs. Note that it may still be copyrighted in jurisdictions that do not apply the rule of the shorter term for US works (depending on the date of the author's death), such as Canada (70 years p.m.a.), Mainland China (50 years p.m.a., not Hong Kong or Macao), Germany (70 years p.m.a.), Mexico (100 years p.m.a.), Switzerland (70 years p.m.a.), and other countries with individual treaties.
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| Date/Time | Thumbnail | Dimensions | User | Comment | |
|---|---|---|---|---|---|
| current | 13:47, 18 May 2015 | | 1,452 × 1,788 (190 KB) | Chetvorno | User created page with UploadWizard |
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