Editing Ultraviolet (section)

===Material science uses===

====Fire detection====
{{see also|Flame detector}}
In general, ultraviolet detectors use either a solid-state device, such as one based on [[silicon carbide]] or [[aluminium nitride]], or a gas-filled tube as the sensing element. UV detectors that are sensitive to UV in any part of the spectrum respond to irradiation by [[sunlight]] and [[artificial light]]. A burning hydrogen flame, for instance, radiates strongly in the 185- to 260-nanometer range and only very weakly in the [[Infrared|IR]] region, whereas a coal fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus, a fire detector that operates using both UV and IR detectors is more reliable than one with a UV detector alone. Virtually all fires emit some [[thermal radiation|radiation]] in the UVC band, whereas the [[Sun]]'s radiation at this band is absorbed by the [[Earth's atmosphere]]. The result is that the UV detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors.

UV detectors are sensitive to most fires, including [[hydrocarbon]]s, metals, [[sulfur]], [[hydrogen]], [[hydrazine]], and [[ammonia]]. [[Arc welding]], electrical arcs, [[lightning]], [[X-ray]]s used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate a UV detection system. The presence of UV-absorbing gases and vapors will attenuate the UV radiation from a fire, adversely affecting the ability of the detector to detect flames. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect.

==== Photolithography ====
Ultraviolet radiation is used for very fine resolution [[photolithography]], a procedure wherein a chemical called a photoresist is exposed to UV radiation that has passed through a mask. The exposure causes chemical reactions to occur in the photoresist. After removal of unwanted photoresist, a pattern determined by the mask remains on the sample. Steps may then be taken to "etch" away, deposit on or otherwise modify areas of the sample where no photoresist remains.

Photolithography is used in the manufacture of [[semiconductor]]s, [[integrated circuit]] components,<ref>{{cite web | title = Deep UV Photoresists | date = 23 February 2001 | url = http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/ | archive-url = https://web.archive.org/web/20060312012823/http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/ | archive-date = 2006-03-12}}</ref> and [[printed circuit board]]s. Photolithography processes used to fabricate electronic integrated circuits presently use 193&nbsp;nm UV and are experimentally using 13.5&nbsp;nm UV for [[extreme ultraviolet lithography]].

====Polymers====
Electronic components that require clear transparency for light to exit or enter (photovoltaic panels and sensors) can be potted using acrylic resins that are cured using UV energy. The advantages are low VOC emissions and rapid curing.

[[File:UV effect on finished wood.jpg|thumb|Effects of UV on finished surfaces in 0, 20 and 43 hours]]
Certain inks, coatings, and [[adhesive]]s are formulated with [[photoinitiator]]s and resins. When exposed to UV light, [[polymerization]] occurs, and so the adhesives harden or cure, usually within a few seconds. Applications include glass and plastic bonding, [[optical fiber]] coatings, the coating of flooring, [[UV coating]] and paper finishes in offset [[printing]], dental fillings, and decorative fingernail "gels".

UV sources for UV curing applications include [[UV lamps]], UV [[LED]]s, and [[excimer]] flash lamps. Fast processes such as flexo or offset printing require high-intensity light focused via reflectors onto a moving substrate and medium so high-pressure [[Mercury (element)|Hg]] (mercury) or [[Iron|Fe]] (iron, doped)-based bulbs are used, energized with electric arcs or microwaves. Lower-power fluorescent lamps and LEDs can be used for static applications. Small high-pressure lamps can have light focused and transmitted to the work area via liquid-filled or fiber-optic light guides.

The impact of UV on polymers is used for modification of the ([[surface roughness|roughness]] and [[hydrophobicity]]) of polymer surfaces. For example, a [[poly(methyl methacrylate)]] surface can be smoothed by vacuum ultraviolet.<ref>{{cite journal|author1=R. V. Lapshin|author2=A. P. Alekhin|author3=A. G. Kirilenko|author4=S. L. Odintsov|author5=V. A. Krotkov|year=2010|title=Vacuum ultraviolet smoothing of nanometer-scale asperities of poly(methyl methacrylate) surface|journal=Journal of Surface Investigation. X-ray, Synchrotron and Neutron Techniques|volume=4|issue=1|pages=1–11|issn=1027-4510|doi=10.1134/S1027451010010015|bibcode=2010JSIXS...4....1L |s2cid=97385151|url=http://www.lapshin.fast-page.org/publications.htm#vacuum2010|url-status=live|archive-url=https://web.archive.org/web/20130909230837/http://www.lapshin.fast-page.org/publications.htm#vacuum2010|archive-date=9 September 2013|url-access=subscription}}</ref>

UV radiation is useful in preparing low-surface-energy [[polymer]]s for adhesives. Polymers exposed to UV will oxidize, thus raising the [[surface energy]] of the polymer. Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer is stronger.