Outgassing

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Outgassing (sometimes called offgassing, particularly when in reference to

seepage from cracks or internal volumes, and gaseous products of slow chemical reactions. Boiling is generally thought of as a separate phenomenon from outgassing because it consists of a phase transition of a liquid into a vapor
of the same substance.

In a vacuum

Outgassing is a challenge to creating and maintaining clean high-

thermal radiators, or solar cells and obscure them. Materials not normally considered absorbent can release enough lightweight molecules to interfere with industrial or scientific vacuum processes. Moisture, sealants, lubricants, and adhesives are the most common sources, but even metals and glasses can release gases from cracks or impurities. The rate of outgassing increases at higher temperatures because the vapor pressure and rate of chemical reaction increases. For most solid materials, the method of manufacture and preparation can reduce the level of outgassing significantly. Cleaning of surfaces, or heating of individual components or the entire assembly (a process called "bake-out") can drive off volatiles
.

NASA's

space probe suffered reduced image quality due to an unknown contaminant that had condensed on the CCD sensor of the navigation camera. A similar problem affected the Cassini space probe's Narrow Angle Camera, but was corrected by repeatedly heating the system to 4 °C. A comprehensive characterisation of outgassing effects using mass spectrometers could be obtained for ESA's Rosetta spacecraft.[2]

Natural outgassing is commonplace in comets.[3]

From rock

Outgassing is a possible source of many tenuous

lunar surface have completely outgassed and been blown away by solar winds long ago, but volatile materials may remain at depth. The lunar atmosphere
probably originates from outgassing of warm material below the surface.

Once released, gases almost always are less

primordial radionuclides
(and their decay products) produces the vast majority of the helium that continues to gas out of rocks on terrestrial planets.

In a closed environment

Outgassing can be significant if it collects in a closed environment where air is stagnant or recirculated. For example, new car smell consists of outgassed chemicals released by heat in a closed automobile. Even a nearly odorless material such as wood may build up a strong smell if kept in a closed box for months. There is some concern that plasticizers and solvents released from many industrial products, especially plastics, may be harmful to human health.[5] Long-term exposure to solvent vapors can cause chronic solvent-induced encephalopathy (CSE). Outgassing toxic gases are of great concern in the design of submarines and space stations, which must have self-contained recirculated atmospheres.

In construction

The outgassing of small pockets of air near the surface of setting concrete can lead to permanent holes in the structure (called bugholes) that may compromise its structural integrity.[6][7]

See also

References

  1. ^ Strong, John (1938). Procedures in Experimental Physics. Bradley, IL: Lindsay Publications., Chapter 3
  2. doi:10.1029/2010JA015734
    .
  3. S2CID 118376416
    .
  4. ISBN 9780792367949
    .
  5. ^ "Health Concerns [archived on archive.today]". United States Environmental Protection Agency. Archived from the original on 2014-12-03. Retrieved 2020-04-17.
  6. ^ Thin-Patch Repair of Concrete in Wastewater Environments Using Commercially Available Cementitious Resurfacers (PDF), Concrete Repair Bulletin, January 2008, archived from the original (PDF) on 2020-04-17, retrieved 2014-10-21
  7. ^ Preventing Air-Induced Coating Failures on Concrete (PDF), JPCL, January 2007, archived from the original (PDF) on 2014-10-22, retrieved 2014-10-21

External links

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