Osmium Alloys and UV reflection

In summary: Os–Rh–Os Layer Reflectivity. The Os–Rh–Os layer was deposited by vacuum deposition onto an Ir-coated glass slide. The Os–Rh–Os layer was chosen as the grating reflectivity layer as it had a reasonable measured reflectivity value at the input light’s grating facet angles for greater than 90% of the CHIPS bandpass and its ability to withstand the environmental constraint of atomic O.In summary, the Ir–Os–Ir layer is a good reflectivity layer for the CHIPS grating. The Os–Rh–Os layer was deposited by vacuum deposition and is good for spaceborne spectrometers that use grazing incidence reflection optics.
  • #1
rppearso
204
3
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?
 
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  • #2
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?
 
  • #3
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

ABSTRACT.The deposition of a 30-Å-thick layer of iridium upon a 250-Å-thick osmium reflective layer for use as a diffraction grating in the Cosmic Hot Interstellar Plasma Spectrometer #CHIPS# satellite observatory has provided sufficient protection from an expected maximum orbital atomic-oxygen fluence of 1 # 1016 atoms#cm2. The grating parameters of groove constant and depth, efficiencies of zeroth-order, first and second inside orders, and first inside-order efficiency positional uniformity as well as stray light near the first inside order of the Ir–Os-coated grating were measured within a CHIPS spectral bandpass of 90–260 Å. Stray-light measurements were also made near the first inside spectral order at 304, 584, and 1216 Å. The results make the Ir–Os coat an acceptable grating reflectivity layer for CHIPS and other spaceborne extreme-ultraviolet spectrometers that employ grazing-incidence reflection optics.
© 2003 Optical Society of America
OCIS codes: 050.2770, 290.5820, 310.1620, 310.6860.

2. Ir–Os–Ir Layer Reflectivity.
Before we proceeded with deposition of the grating coating, a sample consisting of an Ir–Os bi-layer on top of an Ir-coated glass slide #Ir–Os–Ir# was designed, fabricated, and characterized to verify the EUV optical properties of the Ir–Os bilayer.

3. Ir–Os–Rh-Coated Grating.
Given the Ir–Os–Ir flat’s reasonable measured reflectivity values at the input light’s grating facet angles for greater than 90% of CHIPS bandpass and its ability to withstand the environmental constraint of atomic O, a CHIPS grating that had been poorly coated with 150 Å of Rh was overcoated with 250 Å of Os and then 25 Å of Ir to permit the grating’s EUV diffraction efficiency and scattering along its dispersion direction to be examined. The original Rh coating of the grating was deemed to be poor owing to its low-EUV first-, second-, and zero-order measured efficiencies compared to five other otherwise identical gratings also coated with Rh.
 

1. What is osmium and why is it used in alloys?

Osmium is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, blue-gray metal that is commonly used in alloys to increase their strength and hardness. Osmium also has a high melting point and is resistant to corrosion, making it a valuable addition to many alloys in various industries.

2. How does the addition of osmium affect the properties of alloys?

The addition of osmium to alloys can significantly increase their strength and hardness. Osmium is also highly resistant to corrosion, so it can improve the durability and longevity of alloys in harsh environments. However, too much osmium can make alloys too brittle, so it is often added in small amounts to achieve the desired properties.

3. Can osmium alloys reflect UV light?

Yes, osmium alloys can reflect UV light. Osmium has a high reflectance for UV light and is often used in the production of mirrors and other reflective surfaces for UV light applications. This makes osmium alloys useful in industries such as aerospace, where UV radiation is a concern.

4. How does the UV reflectivity of osmium alloys compare to other metals?

Osmium alloys have one of the highest reflectivities for UV light among all metals. It has a reflectance of around 95% for UV light, which is significantly higher than other commonly used metals such as aluminum and silver. This makes osmium alloys a preferred choice for UV-reflective applications.

5. Are there any safety concerns when working with osmium alloys?

Osmium is a highly toxic element, and care must be taken when handling and working with osmium alloys. It is important to follow proper safety protocols and use protective equipment, such as gloves and a respirator, to avoid inhaling osmium particles or getting it on the skin. Proper disposal methods should also be followed to prevent environmental contamination.

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