Thermite: Difference between revisions

{{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}}

 

'''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"

Red iron(III) oxide (Fe₂O₃, 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 (Fe₃O₄, [[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|MnO₂]] in manganese thermite, [[chromium(III) oxide|Cr₂O₃]] in chromium thermite, SiO₂ (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>

 

 

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:

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 heating to higher temperature to start reacting. This effect is pushed to the extreme with [[nano-thermite]]s.

 

 

=== Iron thermite ===

 

== Civilian uses ==

 

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}}

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.

 

 

 

== Hazards ==