The Atomic Show #007 (MP3 – 14.5MB – 42min)

4 Comments

1. I was a bit surprised to hear that different isotopes of Silicon actually had tangibly different physical properties in the way the show described. That was quite interesting, and I’d be fascinated to know more details of why this works this way. One of the reasons isotopes took so long to be discovered and why enrichment is so tough (or extracting deuterium or tritium from regular water) is because isotopes have virtually identical physical and chemical properties. Of course, they have a few subtly different properties, as easily seen with U235 vs U238, but I didn’t really expect something more mundane like heat handling properties.

2. PowerPointSamurai,

   It’s not so much that the physical properties of the different Si isotopes

   differ; they all vary subtly in mass, just like the more newsworthy U. The

   effect is more subtle in that the different masses of the isotopes cause

   inclusions and flaws in the crystalline structure of cooled and purified Si,

   in effect increasing the “thermal resistance” of the end product. This

   effect is as dominant as impurities in the final product, but is potentially

   much simpler to do something about; hence the interest.

   For more information on the phenomenon, you can Google on the terms

   . The most informative of the results I’ve seen:

   http://www.isonics.com/isopure_main.htm

3. That’s what I get for trying to be clever with delimiters; the terms are “isotopic silicon thermal”.

4. This is an area of continuing education for me. Fascinating reference there, Shane.

   This is a key paragraph in the document after learning about the mechanisms that provide isotopically pure SI with higher thermal conductivity and greater value in tightly packed microprocessors:

   Idled nuclear weapons facilities in the former Soviet Union manufacture the isotopically pure raw material, silicon tetra fluoride using gas centrifuge technology. This raw material is imported into the U.S. where it is chemically purified and transformed into more commercially useful materials such as silane, trichlorosilane, polysilicon, and ultimately silicon wafers. Isonics continues to explore improved isotope separation methods and is funding research in chemical exchange technology at the Institure of Stable Isotopes in Tblisi, Georgia.

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