Wikipedia

Thermite: Difference between revisions

Browse history interactively
← Previous editNext edit →
Content deleted Content added
VisualWikitext
added to paragraph 4 of civilian uses
Gamboler (talk | contribs)
398 edits
m →Military uses: fixed typo
(16 intermediate revisions by 13 users not shown)
Line 3:
{{About|the flammable material|the comic book character|Thermite (comics)|the explosive device with the same name|incendiary grenade}}
{{Use dmy dates|date=December 2014}}
[[Image:Thermite mix.jpg|thumb|A thermite mixture using iron (III) oxide]]
 
'''Thermite''' ({{IPAc-en|'|θ|ɜːr|m|aɪ|t}})<ref>{{cite book|title=Longman pronunciation dictionary|last=Wells|first=John C.|publisher=Longman|year=1990|isbn=978-0-582-05383-0|location=Harlow, England|page=715}} entry "thermite"
Line 35:
Red iron(III) oxide (Fe<sub>2</sub>O<sub>3</sub>, commonly known as [[rust]]) is the most common iron oxide used in thermite.<ref>{{cite web |url=https://news.google.com/newspapers?id=QKBQAAAAIBAJ&pg=6875,1422491 |title=Thermite Bombs used to Set Fires |publisher=The Milwaukee Journal |date=1 December 1939 |access-date=13 October 2011 }}{{Dead link|date=October 2022 |bot=InternetArchiveBot |fix-attempted=yes }} (dead link 25 April 2020)</ref><ref>{{cite web|url=https://news.google.com/newspapers?id=lR8sAAAAIBAJ&pg=5630,1866720 |title=what it Means: Thermite Bombing |publisher=the Florence Times |date=31 August 1940 |access-date=12 October 2011}}</ref><ref>{{cite news|url=https://www.nytimes.com/1997/05/06/science/hydrogen-may-not-have-caused-hindenburg-s-fiery-end.html?pagewanted=all |title=Hydrogen May Not Have Caused Hindenburg's Fiery End |work=The New York Times |date=6 May 1997 |access-date=12 October 2011}}</ref> Black iron(II,III) oxide (Fe<sub>3</sub>O<sub>4</sub>, [[magnetite]]) also works.<ref name="amazingrust">{{cite web|url=http://amazingrust.com/experiments/how_to/thermite.html |title=Thermite |publisher=Amazing Rust.com |date=7 February 2001 |access-date=12 October 2011 |url-status=dead |archive-url=https://web.archive.org/web/20110707122232/http://amazingrust.com/experiments/how_to/thermite.html |archive-date=7 July 2011 }}</ref> Other oxides are occasionally used, such as [[manganese(IV) oxide|MnO<sub>2</sub>]] in manganese thermite, [[chromium(III) oxide|Cr<sub>2</sub>O<sub>3</sub>]] in chromium thermite, SiO<sub>2</sub> (quartz) in silicon thermite, or copper(II) oxide in copper thermite, but only for specialized purposes.<ref name="amazingrust"/> All of these examples use aluminium as the reactive metal. [[Fluoropolymer]]s can be used in special formulations, [[Polytetrafluoroethylene|Teflon]] with magnesium or aluminium being a relatively common example. [[Magnesium/Teflon/Viton]] is another [[pyrolant]] of this type.<ref>{{cite journal |doi=10.1002/1521-4087(200211)27:5<262::AID-PREP262>3.0.CO;2-8 |title=Metal-Fluorocarbon-Pyrolants: III. Development and Application of Magnesium/Teflon/Viton (MTV) |journal=Propellants, Explosives, Pyrotechnics |volume=27 |issue=5 |pages=262–266 |year=2002 |last1=Koch |first1=Ernst-Christian}}</ref>
 
Combinations of dry ice (frozen carbon dioxide) and reducing agents such as magnesium, aluminium and boron follow the same chemical reaction as with traditional thermite mixtures, producing metal oxides and carbon. Despite the very low temperature of a dry ice thermite mixture, such a system is capable of being ignited with a flame.<ref>{{cite web |url=https://www.youtube.com/watch?v=_xCbal2YyaE |archive-url=https://ghostarchive.org/varchive/youtube/20211211/_xCbal2YyaE |archive-date=2021-12-11 |url-status=live |title=Burning magnesium in dry ice |publisher=Royal Society of Chemistry |via=YouTube}}{{cbignore}}</ref> When the ingredients are finely divided, confined in a pipe and armed like a traditional explosive, this cryo-thermite is detonatable and a portion of the carbon liberated in the reaction emerges in the form of [[diamond]].<ref>{{Cite web |url=http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/patent/2710026/summary.html |title=Method For Creating Diamonds |last=Swanson |first=Daren |date=2007-12-21 |website=www.EnviroDiamond.com |publisher=Daren Swanson |access-date=17 October 2016 |archive-date=18 October 2016 |archive-url=https://web.archive.org/web/20161018221400/http://brevets-patents.ic.gc.ca/opic-cipo/cpd/eng/patent/2710026/summary.html |url-status=dead }}</ref>
 
In principle, any reactive metal could be used instead of aluminium. This is rarely done, because the properties of aluminium are nearly ideal for this reaction:
Line 50:
The temperature achieved during the reaction determines the outcome. In an ideal case, the reaction produces a well-separated melt of metal and slag. For this, the temperature must be high enough to melt both reaction products, the resulting metal and the fuel oxide. Too low a temperature produces a mixture of sintered metal and slag; too high a temperature (above the boiling point of any reactant or product) leads to rapid production of gas, dispersing the burning reaction mixture, sometimes with effects similar to a low-yield explosion. In compositions intended for production of metal by [[aluminothermic reaction]], these effects can be counteracted. Too low a reaction temperature (e.g., when producing silicon from sand) can be boosted with addition of a suitable oxidizer (e.g., sulfur in aluminium-sulfur-sand compositions); too high a temperature can be reduced by using a suitable coolant and/or slag [[Flux (metallurgy)|flux]]. The flux often used in amateur compositions is [[calcium fluoride]], as it reacts only minimally, has relatively low melting point, low melt viscosity at high temperatures (therefore increasing fluidity of the slag) and forms a eutectic with alumina. Too much flux, however, dilutes the reactants to the point of not being able to sustain combustion. The type of metal oxide also has dramatic influence to the amount of energy produced; the higher the oxide, the higher the amount of energy produced. A good example is the difference between [[manganese(IV) oxide]] and [[manganese(II) oxide]], where the former produces too high temperature and the latter is barely able to sustain combustion; to achieve good results, a mixture with proper ratio of both oxides can be used.<ref>{{cite web |url=http://developing-your-web-presence.blogspot.com/2008/07/manganese-thermite-based-on-manganese.html |title=Manganese thermite based on manganese (II) oxide |publisher=Developing your Web presence |date=10 July 2008 |access-date=7 December 2011}}</ref>
 
The reaction rate can be also tuned with particle sizes; coarser particles burn slower than finer particles. The effect is more pronounced with the particles requiring being heatedheating to higher temperature to start reacting. This effect is pushed to the extreme with [[nano-thermite]]s.
 
The temperature achieved in the reaction in [[adiabatic process|adiabatic conditions]], when no heat is lost to the environment, can be estimated using [[Hess'sHess’s law]] – by calculating the energy produced by the reaction itself (subtracting the [[enthalpy]] of the reactants from the enthalpy of the products) and subtracting the energy consumed by heating the products (from their specific heat, when the materials only change their temperature, and their [[enthalpy of fusion]] and eventually [[enthalpy of vaporization]], when the materials melt or boil). In real conditions, the reaction loses heat to the environment, the achieved temperature is therefore somewhat lower. The heat transfer rate is finite, so the faster the reaction is, the closer to adiabatic condition it runs and the higher is the achieved temperature.<ref>{{cite book|author=Gupta, Chiranjib Kumar |title=Chemical Metallurgy: Principles and Practice|url=https://books.google.com/books?id=Tq6MTFXk3cQC&pg=PA387 |date= 2006|publisher=John Wiley & Sons|isbn=978-3-527-60525-5|pages=387–}}</ref>
 
=== Iron thermite ===
Line 89:
 
== Civilian uses ==
[[Image:Velp-thermitewelding-1.jpg|thumb|Thermite reaction proceeding for a railway welding:. Shortly after thisafterwards, the liquid iron flows into the mould around the rail gap.]]
[[Image:Thermite residues (railway welding).JPG|thumb|Remains of ceramic moulds used for thermite welding like thesethe ones pictured here, left by railway workers near Årstafältet tramway station in Stockholm, Sweden, can sometimes be found along tracks.]]
 
Thermite reactions have many uses. It is not an explosive; instead, it operates by exposing a very small area to extremely high temperatures. Intense heat focused on a small spot can be used to cut through metal or weld metal components together both by melting metal from the components, and by injecting molten metal from the thermite reaction itself. {{citation needed|date=June 2021}}
Line 96:
Thermite may be used for repair by the welding in-place of thick steel sections such as [[locomotive]] [[axle]]-frames where the repair can take place without removing the part from its installed location.<ref>{{cite book|last1=Jeffus|first1=Larry|title=Welding principles and applications|date=2012|publisher=Delmar Cengage Learning|location=Clifton Park, N.Y.|isbn=978-1111039172|pages=744|edition=7th|url=https://books.google.com/books?id=uU0gBN2aYSgC&q=thermite+welding&pg=PA744|language=en}}</ref>
 
Thermite can be used for quickly cutting or welding steel such as [[rail tracks]], without requiring complex or heavy equipment.<ref>{{cite web|url=http://paperspast.natlib.govt.nz/cgi-bin/paperspast?a=d&d=TS19061115.2.43 |title=Papers Past — Star — 15 November 1906 — NEW WELDING PROCESS |publisher=Paperspast.natlib.govt.nz |date=15 November 1906 |access-date=12 October 2011}}</ref><ref>{{cite news|url=https://news.google.com/newspapers?id=wHw1AAAAIBAJ&pg=6875,1950492 |title=How Many Ways to Weld Metal? |newspaper=Eugene Register-Guard |date=8 December 1987 |access-date=12 October 2011}}</ref> However, defects such as slag inclusions and voids (holes) are often present in such welded junctions, so great care is needed to operate the process successfully. The numerical analysis of thermite welding of rails has been approached similar to casting cooling analysis. Both this [[finite element analysis]] and experimental analysis of thermite rail welds has shown that weld gap is the most influential parameter affecting defect formation.<ref>{{cite journal|last1=Chen|first1=Y|last2=Lawrence|first2=F V|last3=Barkan|first3=C P L|last4=Dantzig|first4=J A|title=Heat transfer modelling of rail thermite welding|journal=Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit|date=24 October 2006|volume=220|issue=3|pages=207–217|doi=10.1243/09544097F01505|citeseerx=10.1.1.540.9423|s2cid=17438646}}</ref> Increasing weld gap has been shown to reduce shrinkage cavity formation and cold lap [[welding defect]]s, and increasing preheat and thermite temperature further reduces these defects. However, reducing these defects promotes a second form of defect: microporosity.<ref>{{cite journal|last1=Chen|first1=Y|last2=Lawrence|first2=F V|last3=Barkan|first3=C P L|last4=Dantzig|first4=J A|title=Weld defect formation in rail thermite welds|journal=Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit|date=14 December 2006|volume=220|issue=4|pages=373–384|doi=10.1243/0954409JRRT44|citeseerx=10.1.1.501.2867|s2cid=16624977}}</ref> Care must also be taken to ensure that the rails remain straight, without resulting in dipped joints, which can cause wear on high speed and heavy axle load lines.<ref>{{cite web|url=http://goliath.ecnext.com/coms2/gi_0199-2063863/Strengthening-the-track-structure-for.html |title=Strengthening the track structure for heavy axle loads: strengthening track infrastructure provides another method of dealing with ever-increasing car capacities. (TTCI R&D). |publisher=Goliath Business News|date=1 September 2002 |access-date=12 October 2011}}</ref> Studies to make the hardness of thermite welds to repair tracks have made improvements to the hardness to compare more to the original tracks while keeping its portable nature.<ref name=":02">{{Cite journal |last=Oo |first=Hein Zaw |last2=Muangjunburee |first2=Prapas |date=March 2023-03 |title=Improving microstructure and hardness of softening area at HAZ of thermite welding on rail running surface |url=https://linkinghub.elsevier.com/retrieve/pii/S2352492823001757 |journal=Materials Today Communications |language=en |volume=34 |pages=105485 |doi=10.1016/j.mtcomm.2023.105485}}</ref>
 
As the reaction of thermite is oxidation-reduction and environmentenvironmentally friendly, it has started to be adapted into use for sealing oil wells instead of using concrete. Though thermite is usually in a powder-state, a diluted mixture can reduce damage to surroundingthe surroundings during the process, though too much alumina can risk hurting the integrity of the seal.<ref>{{Cite journal |last=De Souza |first=Kesiany M. |last2=de Lemos |first2=Marcelo J.S. |date=May 2023-05 |title=Advanced one-dimensional modeling of thermite reaction for thermal plug and abandonment of oil wells |url=https://linkinghub.elsevier.com/retrieve/pii/S0017931023000686 |journal=International Journal of Heat and Mass Transfer |language=en |volume=205 |pages=123913 |doi=10.1016/j.ijheatmasstransfer.2023.123913}}</ref><ref>{{Cite journal |last=De Souza |first=Kesiany M. |last2=de Lemos |first2=Marcelo J.S. |last3=Ribeiro |first3=Roberta dos R. |last4=Marin |first4=Ana M.G. |last5=Martins |first5=Paulo G.C. |last6=Gouvêa |first6=Leonardo H. |date=March 2024-03 |title=Experimental investigation of Al-Fe2O3 thermite reactions for thermal plug and abandonment of oil wells |url=https://linkinghub.elsevier.com/retrieve/pii/S2949891023012071 |journal=Geoenergy Science and Engineering |language=en |volume=234 |pages=212620 |doi=10.1016/j.geoen.2023.212620}}</ref> A higher concentration of mixture was needed to melt the plastic of a model tube, making it a favorable mixture.<ref>{{Cite journal |last=Pena |first=Fabrício J.C. |last2=de Souza |first2=Kesiany M. |last3=de Lemos |first3=Marcelo J.S. |date=December 2023-12 |title=Thermal behavior of aluminothermic thermite reaction for application in thermal sealing of oil wells |url=https://linkinghub.elsevier.com/retrieve/pii/S073519332300502X |journal=International Communications in Heat and Mass Transfer |language=en |volume=149 |pages=107113 |doi=10.1016/j.icheatmasstransfer.2023.107113}}</ref> Other experiments have been done to simulate the heat flux of the well sealing to predict the temperature on the surface of the seal over time.<ref>{{Cite journal |last=Dourado da Silva |first=Rodrigo G. |last2=Magalhães |first2=Elisan S. |last3=Pires |first3=Luis Carlos M. |date=November 2023-11 |title=Estimation of thermal input in thermite reaction for innovative wellbore plugging & abandonment techniques |url=https://linkinghub.elsevier.com/retrieve/pii/S0735193323004608 |journal=International Communications in Heat and Mass Transfer |language=en |volume=148 |pages=107071 |doi=10.1016/j.icheatmasstransfer.2023.107071}}</ref>
 
A thermite reaction, when used to purify the [[ore]]s of some metals, is called the {{vanchor|thermite process}}, or aluminothermic reaction. An adaptation of the reaction, used to obtain pure [[uranium]], was developed as part of the [[Manhattan Project]] at [[Ames Laboratory]] under the direction of [[Frank Spedding]]. It is sometimes called the [[Ames process]].<ref>{{cite patent | country = US | number = 2830894 | status = patent | title = Production of Uranium | gdate = 1958 | fdate = 1947 | invent1 = Spedding, Frank H. | invent2 = Wilhelm, Harley A. | invent3 = Keller, Wayne H. | assign1 = [[United States Atomic Energy Commission]]}}</ref>
Line 107:
Thermite [[hand grenade]]s and charges are typically used by armed forces in both an anti-[[materiel]] role and in the partial destruction of equipment, the latter being common when time is not available for safer or more thorough methods.<ref>{{cite web|url=http://www.kmike.com/Grenades/fm-23-30.pdf |title=Grenades and Pyrotechnics Signals. Field Manual No 23-30 |date=27 December 1988 |publisher=Department of the Army |url-status=unfit |archive-url=https://web.archive.org/web/20120119103936/http://www.kmike.com/Grenades/fm-23-30.pdf |archive-date=19 January 2012 }}</ref><ref>{{cite web |title=AN-M14 TH3 incendiary hand grenade |url=https://man.fas.org/dod-101/sys/land/m14-th3.htm |website=Military Analysis Network |publisher=Federation of American Scientists |access-date=2 October 2023}}</ref> For example, thermite can be used for the emergency destruction of [[cryptographic]] equipment when there is a danger that it might be captured by enemy troops. Because standard iron-thermite is difficult to ignite, burns with practically no flame and has a small radius of action, standard thermite is rarely used on its own as an incendiary composition. In general, an increase in the volume of gaseous [[Chemical reaction|reaction products]] of a thermite blend increases the heat transfer rate (and therefore damage) of that particular thermite blend.<ref>{{cite journal|last1=Collins|first1=Eric S.|last2=Pantoya|first2=Michelle L.|last3=Daniels|first3=Michael A.|last4=Prentice|first4=Daniel J.|last5=Steffler|first5=Eric D.|last6=D’Arche|first6=Steven P.|title=Heat Flux Analysis of a Reacting Thermite Spray Impingent on a Substrate|journal=Energy & Fuels|date=15 March 2012|volume=26|issue=3|pages=1621–1628|doi=10.1021/ef201954d}}</ref> It is usually used with other ingredients that increase its incendiary effects. [[thermate|Thermate-TH3]] is a mixture of thermite and pyrotechnic additives that have been found superior to standard thermite for incendiary purposes.<ref name="EugeneSong">{{cite patent | country = US | number = 5698812 | status = patent | title = Thermite destructive device | gdate = 1997 | fdate = 1996 | invent1 = Song, Eugene| assign1 = [[United States Secretary of the Army]]}}</ref> Its composition by weight is generally about 68.7% thermite, 29.0% [[barium nitrate]], 2.0% [[sulfur]], and 0.3% of a [[binder (material)|binder]] (such as [[Polybutadiene acrylonitrile|PBAN]]).<ref name="EugeneSong"/> The addition of barium nitrate to thermite increases its thermal effect, produces a larger flame, and significantly reduces the ignition temperature.<ref name="EugeneSong"/> Although the primary purpose of Thermate-TH3 by the armed forces is as an incendiary anti-materiel weapon, it also has uses in welding together metal components.
 
A classic military use for thermite is disabling [[artillery]] pieces, and it has been used for this purpose since World War II, such as at [[Pointe du Hoc]], [[Normandy]].<ref>{{cite news |url=https://pqasb.pqarchiver.com/newsday/access/101869797.html?dids=101869797:101869797&FMT=ABS |title=THEThe INVASIONInvasion, CHAPTERChapter 9 THEThe GUNSGuns OFof POINTEPointe-DUdu-HOCHoc |publisher=Pqasb.pqarchiver.com |access-date=12 October 2011 |date=29 May 1994 |archive-date=24 July 2012 |archive-url=https://web.archive.org/web/20120724224948/http://pqasb.pqarchiver.com/newsday/access/101869797.html?dids=101869797:101869797&FMT=ABS |url-status=dead }}</ref> ThermiteBecause canit permanently disabledisables artillery pieces without the use of explosive charges, so thermite can be used when silence is necessary to an operation. This can be doneaccomplished by inserting one or more armed thermite grenades into the [[breechloader|breech]], and then quickly closing it; this welds the breech shut and makes loading the weapon impossible.<ref>{{cite news|url=https://news.google.com/newspapers?id=JmkKAAAAIBAJ&pg=6924,4473828 |title=Corporal Tells of Gunning of Yank Prisoners |newspaper=Ellensburg Daily Record |first=Hal |last=Boyle |date=26 July 1950 |access-date=28 July 2021}}</ref>
 
During World War II, both German and Allied [[incendiary bomb]]s used thermite mixtures.<ref>{{cite news |url=https://pqasb.pqarchiver.com/chicagotribune/access/466735872.html?dids=466735872:466735872&FMT=ABS&FMTS=ABS:AI |title=Archives: Chicago Tribune |publisher=Pqasb.pqarchiver.com |date=30 August 1940 |access-date=12 October 2011 |first=E R |last=Noderer |archive-date=24 July 2012 |archive-url=https://web.archive.org/web/20120724225011/http://pqasb.pqarchiver.com/chicagotribune/access/466735872.html?dids=466735872:466735872&FMT=ABS&FMTS=ABS:AI |url-status=dead }}</ref><ref>{{cite news|url=https://news.google.com/newspapers?id=AdA-AAAAIBAJ&pg=2697,5764756 |title=Bitter Fighting in Libya |newspaper=The Indian Express |date=25 November 1941 |access-date=12 October 2011}}</ref> Incendiary bombs usually consisted of dozens of thin, thermite-filled canisters ([[bomblet]]s) ignited by a magnesium fuse. Incendiary bombs created massive damage in manynumerous cities due to the fires started by the thermite. Cities that primarily consisted of wooden buildings were especially susceptible. These incendiary bombs were used primarily during [[Bombing of Tokyo#B-29 raids|nighttime air raids]]. Bombsights could not be used at night, creating the need to usefor munitions that could destroy targets without the need forrequiring precision placement.
 
Drones equipped with thermite munitions were used by the [[Ukrainian Ground Forces|Ukrainian army]] during the [[Russian invasion of Ukraine]] against Russian trenches.<ref>{{Cite web |last=Hambling |first=David |title=Flamethrowing Drone Burns Up Russian Positions (Additional Videos) |url=https://www.forbes.com/sites/davidhambling/2024/09/02/dragonfire-flamethrowing-drone-burns-up-russian-positions/ |access-date=2024-09-05 |website=Forbes |language=en}}</ref>
 
== Hazards ==
Retrieved from "https://en.wikipedia.org/wiki/Thermite"