Aluminothermic reactions are

exothermic In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity ...

chemical reactions using

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

as the

reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth met ...

at high temperature. The process is industrially useful for production of

alloy An alloy is a mixture of chemical elements of which at least one is a metal. Unlike chemical compounds with metallic bases, an alloy will retain all the properties of a metal in the resulting material, such as electrical conductivity, ductili ...

s of

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in ...

. The most prominent example is the thermite reaction between

iron oxides Iron oxides are chemical compounds composed of iron and oxygen. Several iron oxides are recognized. All are black magnetic solids. Often they are non-stoichiometric. Oxyhydroxides are a related class of compounds, perhaps the best known of w ...

and aluminum to produce iron itself: : Fe₂O₃ + 2 Al → 2 Fe + Al₂O₃ This specific reaction is however not relevant to the most important application of aluminothermic reactions, the production of ferroalloys. For the production of iron, a cheaper reducing agent, coke, is used instead via the

carbothermic reaction Carbothermic reactions involve the reduction of substances, often metal oxides (O^2-), using carbon as the reducing agent. These chemical reactions are usually conducted at temperatures of several hundred degrees Celsius. Such processes are applie ...

History

Aluminothermy started from the experiments of

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-ei ...

n scientist

Nikolay Beketov Nikolay Nikolayevich Beketov (russian: Николай Николаевич Бекетов; , Alferovka (now Beketovka), Penza Governorate, Russian Empire – , St. Petersburg, Russian Empire) was a Russian Imperial physical chemist and metallur ...

at the University of Kharkiv in Ukraine, who proved that

restored metals from their

oxide An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...

s under high temperatures. The reaction was first used for the carbon-free reduction of metal oxides. The reaction is highly

, but it has a high

activation energy In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules p ...

since strong interatomic bonds in the solids must be broken first. The oxide was heated with aluminum in a crucible in a furnace. The runaway reaction made it possible to produce only small quantities of material.

Hans Goldschmidt Johannes Wilhelm "Hans" Goldschmidt (18 January 1861 – 21 May 1923) was a German chemist notable as the discoverer of the Thermite reaction. He was also co-owner of the Chemische Fabrik Th. Goldschmidt, as of 1911 Th. Goldschmidt AG (later to be ...

improved the aluminothermic process between 1893 and 1898, by igniting the mixture of fine metal oxide and aluminum powder by a starter reaction without heating the mixture externally. The process was patented in 1898 and used extensively in the later years for

rail track A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleeper ...

welding.

Applications

The aluminothermic reaction is used for the production of several

ferroalloys Ferroalloy refers to various alloys of iron with a high proportion of one or more other elements such as manganese (Mn), aluminium (Al), or silicon (Si). They are used in the production of steels and alloys. The alloys impart distinctive qual ...

, for example ferroniobium from

niobium pentoxide Niobium pentoxide is the inorganic compound with the formula Nb2 O5. A colorless, insoluble, and fairly unreactive solid, it is the most widespread precursor for other compounds and materials containing niobium. It is predominantly used in alloyi ...

and ferrovanadium from iron, vanadium(V) oxide, and aluminum. The process begins with the reduction of the oxide by the aluminum: :3 V₂O₅ + 10 Al → 5 Al₂O₃ + 6 V Other metals can be produced from their oxides in the same way. Aluminothermic reactions have been used for welding rail tracks on-site, useful for complex installations or local repairs that cannot be done using continuously welded rail. Another common use is the welding of copper cables (wire) for use in direct burial (grounding/earthing) applications. It is still the only type of electrical connection recognized by the IEEE (IEEE, Std 80-2001) as continuous un-spliced cable. Velp-thermitewelding-1

References

{{Reflist Inorganic reactions Metallurgy Russian inventions Ukrainian inventions

History

Applications

See also

References