outgassing

Ref : wiki

Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality) is the slow release of a gas that was trapped, frozen, absorbed or adsorbed in some material.[1]
It can include sublimation and evaporation which are phase transitions of a substance into a gas, as well as desorption, 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 occurs much more rapidly.

Outgassing in a vacuum
Outgassing is a challenge to creating and maintaining clean high-vacuum environments. NASA maintains a list of low-outgassing materials to be used for spacecraft, as outgassing products can condense onto optical elements, thermal radiators, or solar cells and obscure them. Materials not normally considered absorbent can release enough light-weight molecules to interfere with industrial or scientific vacuum processes. Even metals and glasses can release gases from cracks or impurities, but moisture, sealants, lubricants, and adhesives are the most common sources. The rate of outgassing increases at higher temperatures because the vapour 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 surfaces or baking individual components or the entire assembly before use can drive off volatiles.
NASA's Stardust spaceprobe 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-Huygens spaceprobe's Narrow Angle Camera, but was corrected by repeatedly heating the system to 4 degrees Celsius.


Ref : www.vacuum.or.kr
Outgassing
진공 중에서 재료로부터 기체가 튀어나오는 현상
진공 기술의 한계로 작용진공공정의 질과 생산성에 직결

Outgassing, the evolution of gas from the material in a vacuumenvironment, is not only a source of micro contamination in thesemiconductor and the flat panel producing process, but also alimitation factor in a ultra clean process for nano-technology.
Outgassing from the materials for satellites & spacecraft mustbe controlled for their safety and functions, because space isalso a vacuum environment.