Osmium Alloys and UV reflection

  1. So I was reading that Osmium will break down into a poison oxide gas if it is heated in the presence of air. If Osmium is blended into an alloy will that eliminate its ability to oxidize in such a manner.

    I have been looking at Osmium as a UV reflective material but poison gas break down is an extremely negative side effect.

    Are there any other materials that have a VERY high reflection of very short wave length UV radiation, far from the visible spectrum?
  2. jcsd
  3. Baluncore

    Baluncore 3,305
    Science Advisor

    There may always be a problem with osmium in the presence of UV generated ozone.
    If you vacuum deposit onto a surface, then toxicity problems may occur when the vacuum chamber is opened.

    Does osmium oxide form on a UV radiated surface?
    Does osmium evaporate from a UV radiated surface?
    Osmium metal is very hard, what is the bond energy?

    Alloys usually have a lower temperature eutectic than either of the alloy components. So I doubt if it will be any advantage to alloy osmium compared to the pure metal in the presence of short UV and ozone.

    Osmium is usually found alloyed with iridium, as the mineral “osmiridium” or “iridosmium”.
    They were once used predominantly to electroplate the nibs of fountain pens to give a very hard polished finish.

    If you are coating a non-conductive material, it should be possible to first vacuum deposit a film of say copper or platinum, then follow that by electroplating with osmium. The selection of the base metal may influence the osmium evaporation or oxidation rate.

    Is it possible to eliminate oxygen from the mirror by flooding the chamber with a heavy inert gas?
  4. Baluncore

    Baluncore 3,305
    Science Advisor

    Extracts from;

    Osmium atomic-oxygen protection by an iridium overcoat for increased extreme-ultraviolet grating efficiency.
    Richelieu Hemphill, Mark Hurwitz, and Maria G. Pelizzo
    1 September 2003 Vol. 42, No. 25 APPLIED OPTICS 5149

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