|
The '''Explodingexploding Wirewire Methodmethod''' (also known asor '''EWM)''' is a highway energyto densitygenerate process[[Plasma by(physics)|plasma]] whichthat consists of sending a risingstrong currentenough ispulse appliedof to[[electric current]] through a thin [[wire]] of some [[electric conductivity|electrically conductive]] wirematerial. The heat[[Joule heating|resistive heating]] vaporizes the wire, and an [[electric arc]] overthrough that vapor creates a shockwave and explosion. Exploding Wire Method is best known to be used as aan [[Exploding-bridgewire detonatorexplosion|detonator in nuclear munitionsexplosive]], high intensity light source, and production method for metal [[nanoparticlesshockwave]].
Exploding wires are used as [[detonator]]s for [[explosives]], as momentary high intensity light sources, and in the production of metal [[nanoparticle]]s.
Exploding Wire Method has a surprisingly long history for a process only recently appropriated. Progress on the comprehension of the mechanism was intermittent, and even at present day there are many aspects that remain not fully understood.
One of the first documented cases of using electricity to melt a metal occurred in the late 1700s <ref>{{cite book|last1=Dibner|first1=[by] Herbert W. Meyer. Foreword by Bern|title=A history of electricity and magnetism|date=1972|publisher=Burndy Library|___location=Norwalk, Conn.|isbn=026213070X|page=32|url=httphttps://wwwarchive.krizma-ebooks.comorg/booksdetails/A%20History%20of%20electricity%20and%20magnetism.pdfAHistoryof_00_Meye|url-access=registration}}</ref> and is credited to [[Martin van Marum]] who melted 70 feet of metal wire with 64 [[Leyden Jars]] as a capacitor. Van Marum's generator was built in 1784, and is now located in the [[Teylers Museum]] in the Netherlands. Years later, [[Benjamin Franklin]] vaporized thin gold leaf to burn images onto paper.<ref name=Precon>{{cite journal|last1=Holcombe|first1=J.A.|last2=Sacks|first2=R.D.|title=Exploding wire excitation for trace analysis of Hg, Cd, Pb and Ni using electrodeposition for preconcentration|journal=Spectrochimica Acta|date=March 16, 1973|volume=22B|issue=12|pages=451–467|doi=10.1016/0584-8547(73)80051-5|bibcode=1973AcSpB..28..451H|hdl=2027.42/33764|url=http://deepblue.lib.umich.edu/bitstream/handle/2027.42/33764/0000016.pdf?sequence=1|accessdateaccess-date=2 November 2014|hdl-access=free}}</ref><ref name="wireresearch">{{cite journal|last1=McGrath|first1=J.R.|title=Exploding Wire Research 1774 - 19631774–1963|journal=NRL Memorandum Report|date=May 1966|pages=17|url=http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0633623|accessdatearchive-url=https://web.archive.org/web/20141129061758/http://www.dtic.mil/cgi-bin/GetTRDoc?AD=AD0633623|url-status=dead|archive-date=November 29, 2014|access-date=24 October 2014}}</ref> While neither Marum nor Franklin actually incited the exploding wire phenomenon, they were both important steps towards its discovery.
[[Edward Nairne]] was the first to note the existence of the exploding wire method in 1774 with silver and copper wire. Subsequently, [[Michael Faraday]] used EWM to deposit thin gold films through the solidification of vaporized metal on adjacent surfaces. Then, vapor deposits of metal gas as a result of EWM were studied by [[August Toepler]] during the 1800s. [[Spectrography]] investigation of the process, led by J.A. Anderson, became widespread in the 1900s. The spectrography experiments enabled a better understanding and subsequently the first glimpses of practical application. The mid 20th century saw experiments with EWM as a light source and for the production of nanoparticles in aluminum, uranium and plutonium wires. Congruently, [[Luis Walter Alvarez|Luis Álvarez]] and [[Lawrence H. Johnston]] of the [[Manhattan Project]] found use for EWM in the development of nuclear detonators.<ref name="wireresearch"/><ref>{{cite book|last1=Hansen|first1=Stephen|title=Exploding Wires Principles, Apparatus and Experiments|date=2011|publisher=Bell Jar|url=http://www.belljar.net/Exploding_Wires.pdf|accessdateaccess-date=24 October 2014}}</ref>
Current day research focuses on utilizing EWM to produce nanoparticles as well as better understanding specifics of the mechanism such as the effects of the system environment on the process.
== Mechanism ==
The basic components needed for the exploding wire method are a thin conductive wire and a capacitor. The wire is typically gold, aluminum, iron or platinum, and is usually less than 0.5mm5 mm in diameter. The capacitor has an energy consumption of about 25 kWh/kg and discharges a pulse of charge[[current density]] 10<sup>4</sup> - 10<sup>6</sup> A/mm<sup>2</sup>,<ref name=prepnano>{{cite journal |last1=Kotov |first1=Yu |title=Electric explosion of wires as a method for preparation of nanopowders |journal=Journal of Nanoparticle Research |date=2003 |volume=5 |issue=5/6 |pages=539–550 |doi=10.1023/B:NANO.0000006069.45073.0b |bibcode=2003JNR.....5..539K |s2cid=135540834 |url=http://cms.springerprofessional.de/journals/JOU=11051/VOL=2003.5/ISU=5-6/ART=5140986/BodyRef/PDF/11051_2004_Article_5140986.pdf |deadurlurl-status=yesdead |archiveurlarchive-url=https://web.archive.org/web/20141215001933/http://cms.springerprofessional.de/journals/JOU%3D11051/VOL%3D2003.5/ISU%3D5-6/ART%3D5140986/BodyRef/PDF/11051_2004_Article_5140986.pdf |archivedatearchive-date=2014-12-15 |df= }}</ref> leading to temperatures up to 100,000 [[Kelvin|K]]. The phenomenon occurs over a time period of only 10<sup>−5−8</sup> - 10<sup>−8−5</sup> seconds.<ref name=naz>{{cite journal|last1=Nazatenko |first1=O |title=Nanopowders produced by electrical explosion of wires |journal=Dept. ofOf Exology Tomsk Polytechnic University |date=16 September 2007 |url=http://ecce6.kt.dtu.dk/cm/upload/769.pdf |accessdateaccess-date=6 November 2014 |deadurlurl-status=yesdead |archiveurlarchive-url=https://web.archive.org/web/20141129053237/http://ecce6.kt.dtu.dk/cm/upload/769.pdf |archivedatearchive-date=29 November 2014 |df= }}</ref>
The process is as follows:
# A rising current, supplied by the capacitor, is carried across the wire.
# The current heats up the wire through [[ohmic heating]] until the metal begins to melt. The metal melts to form a broken series of imperfect spheres called [[unduloid]]s. The current rises so fast that the liquid metal has no time to move out of the way.
# The unduloids vaporize. The metal vapor creates a lower resistance path, allowing an even fasterhigher current increaseto flow.
# An electric arc is formed, which turns the vapor into plasma. A bright flash of light is also produced.
# The plasma is allowed to expand freely, creating a [[shock wave]].
=== Light Source ===
EWM is an effective mechanism by which to get a short duration high intensity light source. The peak intensity for copper wire, for example, is 9.6*·10<sup>8</sup> candle power/cm<sup>2</sup>.<ref>{{cite journal|last1=Conn|first1=William|title=The Use of "Exploding Wires" as a Light Source of Very High Intensity and Short Duration|journal=Journal of the Optical Society of America|date=October 28, 1949|volume=41|issue=7|pages=445–9|url=http://www.opticsinfobase.org/view_article.cfm?gotourl=http%3A%2F%2Fwww%2Eopticsinfobase%2Eorg%2FDirectPDFAccess%2FC2AAEF95-F7D9-36C6-8FD97DC46DA8F1A9_50214%2Fjosa-41-7-445%2Epdf%3Fda%3D1%26id%3D50214%26seq%3D0%26mobile%3Dno&org=University%20of%20California%20Santa%20Barbara%20%28CDL%29|accessdateaccess-date=30 October 2014|doi=10.1364/josa.41.000445|pmid=14851124|url-access=subscription}}</ref> J.A. Anderson wrote in his initial spectrography studies that the light was comparable to a black body at 20,000K000 K.<ref name=anderson>{{cite journal|last1=Anderson|first1=J.A.|title=The Spectral Energy Distribution And Opacity Of Wire Explosion Vapors|journal=Mount WilsonProceedings Observatory,of the CarnegieNational InstitutionAcademy of WashingtonSciences|date=May 22, 1922|volume=8|pageissue=17|urlpages=http://www231–232|doi=10.1073/pnas.org/content/8/.7/.231|pmid=16586882|pmc=1085099|bibcode=1922PNAS.full.pdf..8..231A|accessdatedoi-access=2 November 2014free}}</ref> The advantage of a flash produced in this way is that it is easily reproducible with little variation in intensity. The linear nature of the wire allows for specifically shaped and angled light flashes and different types of wires can be used to produce different colors of light.<ref>{{cite journal|last1=Oster|first1=Gisela K.|last2=Marcus|first2=R. A.|title=Exploding Wire as a Light Source in Flash Photolysis|journal=The Journal of Chemical Physics|date=1957|volume=27|issue=1|pages=189|doi=10.1063/1.1743665|urlbibcode =http://scitation 1957JChPh.aip.org/content/aip/journal/jcp/27/1/10.1063/1.1743665|accessdate=2189O November 2014|bibcode url= 1957JChPhhttps://authors.library.27caltech.edu/11419/1/OSTjcp57a.189O pdf}}</ref> The light source can be used in [[interferometry]], [[flash photolysis]], quantitative [[spectroscopy]], and [[high-speed photography]].
=== Production of Nanoparticles ===
Nanoparticles are created by EWM when the ambient gas of the system cools the recently produced vaporous metal.<ref>{{cite journal|last1=Mathur|first1=Sanjay|last2=Sing|first2=Mrityunjay|title=Nanostructured Materials and Nanotechology III|journal=Ceramic Engineering and Science Proceedings|date=2010|volume=30|issue=7|page=92|isbn=9780470584361|url=https://books.google.com/books?id=9-OEIi0QIUEC&pg=PA90&lpg=PA90&dq=exploding+wire+method&source=bl&ots=2lshMYkPON&sig=9Rwl4qc0yHl4cT4H8iukV-XYvjE&hl=en&sa=X&ei=TI5WVKHgMNW5oQTkrIDgAQ&ved=0CDkQ6AEwBDgU#v=onepage&q=exploding%20wire%20method&f=false|accessdate=2 November 2014}}</ref> EWM can be used to cheaply and efficiently produce nanoparticles at a rate of 50- – 300 grams per hour and at a purity of above 99%.<ref name=naz/><ref name="prepnano"/> The process requires a relatively low energy consumption as little energy is lost in an electric to thermal energy conversion. Environmental effects are minimal due to the process taking place in a closed system. The Particles can be as small as 10 nm but are most commonly below 100 nm in diameter. Physical attributes of the nanopowder can be altered depending on the parameters of the explosion. For example, as the voltage of the capacitor is raised, the particle diameter decreases. Also, the pressure of the gas environment can change the dispersiveness of the nanoparticles.<ref name="naz"/> Through such manipulations the functionality of the nanopowder may be altered.
When EWM is performed in a standard atmosphere containing oxygen, metal oxides are formed. Pure metal nanoparticles can also be produced with EWM in an inert environment, usually argon gas or distilled water.<ref name=flur>{{cite journalarXiv|eprint=cond-mat/0609369|last1=Alqudami|first1=Abdullah|last2=Annapoorni|first2=S.|title=Fluorescence from metallic silver and iron nanoparticles prepared by exploding wire technique|journalyear=Dpt. of Physics and Astrohpysics New Delhi|pages=15|arxiv=cond-mat/0609369|url=https://arxiv.org/ftp/cond-mat/papers/0609/0609369.pdf|accessdate=2 November 2014|bibcode = 2006cond.mat..9369A 2006}}</ref> Pure metal nanopowders must be kept in their inert environment because they ignite when exposed to oxygen in air.<ref name="prepnano"/> Often, the metal vapor is contained by operating the mechanism within a steel box or similar container.
Nanoparticles are a relatively new material used in medicine, manufacturing, environmental cleanup and circuitry. Metal oxide and pure metal nanoparticles are used in [[Catalysis]], sensors, oxygen antioxident, self repairing metal, ceramics, [[UV rays|UV ray]] protection, odor proofing, improved batteries, printable circuits, [[Optoelectronics|optoelectronic materials]], and [[Environmental remediation]].<ref name=Nanouses>{{cite web|last1=Boysen|first1=Earl|title=Nanoparticles Applications and Uses|url=http://www.understandingnano.com/nanoparticles.html|website=understandingnano|accessdateaccess-date=2 November 2014}}</ref><ref>{{cite journal|last1=Oskam|first1=Gerko|title=Metal oxide nanoparticles: synthesis, characterization and application|journal=Journal of Sol-Gel Science and Technology|date=24 February 2006|volume=37|issue=3|pages=161–164|doi=10.1007/s10971-005-6621-2|urls2cid=http://download.springer.com/static/pdf/613/art%253A10.1007%252Fs10971-005-6621-2.pdf?auth66=1414142128_b35a086ef820646c9afaca28d4f41f64&ext=.pdf98446250}}</ref> The demand for metal nanoparticles, and therefore production methods, has increased as interest in nanotechnology continues to rise. Despite its overwhelming simplicity and efficiency, it is difficult to modify the experimental apparatus to be used on an industrial scale. As such, EWM has not seen widespread utilization in material production industry due to issues in manufacturing quantity. Still, for some time, [[Argonide]] offered metal nanopowders made by the exploding wire method that were manufactured in Russia.<ref>{{cite web |last=Ginley |first=D. S. |date=October 1999 |title=Nanoparticle Derived Contacts for Photovoltaic Cells |url=https://www.nrel.gov/docs/fy99osti/26685.pdf |access-date=July 10, 2023 |website=NREL}}</ref>
== References ==
<!--- Categories --->
[[Category:Articles created via the Article Wizard]]
[[Category:Detonators]]
[[Category:Nuclear weapon design]]
| 