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 (e ...

chemical reactions using

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

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 common reducing agents include hydrogen, carbon ...

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

alloy An alloy is a mixture of chemical elements of which in most cases at least one is a metal, metallic element, although it is also sometimes used for mixtures of elements; herein only metallic alloys are described. Metallic alloys often have prop ...

s of

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

. The most prominent example is the

thermite Thermite () is a pyrotechnic composition of powder metallurgy, metal powder and metal oxide. When ignited by heat or chemical reaction, thermite undergoes an exothermic redox, reduction-oxidation (redox) reaction. Most varieties are not explos ...

reaction between

iron oxides An iron oxide is a chemical compound composed of iron and oxygen. Several iron oxides are recognized. Often they are nonstoichiometric, non-stoichiometric. Ferric oxyhydroxides are a related class of compounds, perhaps the best known of which is ...

and aluminium to produce

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 (O2-), using carbon (C) as the reducing agent. The reduction is usually conducted in the electric arc furnace or reverberatory furnace, depending on the metal ore. The ...

History

Aluminothermy started from the experiments of

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

n scientist

Nikolay Beketov Nikolay Nikolayevich Beketov (; , Alferovka (now Beketovka), Penza Governorate, Russian Empire – , St. Petersburg, Russian Empire) was a Russian Imperial physical chemist and metallurgist. He was the father of a well-known Russian architect ...

at the

University of Kharkiv The V. N. Karazin Kharkiv National University (), also known as Kharkiv National University or Karazin University, is a public university in Kharkiv, Ukraine. It was founded in 1804 through the efforts of Vasily Karazin, becoming the second old ...

in Ukraine, who proved that

restored metals from their

oxide An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation st ...

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 the Arrhenius model of reaction rates, activation energy is the minimum amount of energy that must be available to reactants for a chemical reaction to occur. The activation energy (''E''a) of a reaction is measured in kilojoules per mole (k ...

since strong interatomic bonds in the solids must be broken first. The oxide was heated with aluminium 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 aluminium 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 Railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers (railroad ties in American E ...

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 qualitie ...

, for example

ferroniobium Ferroniobium is an important iron-niobium alloy, with a niobium content of 60-70%. It is the main source for niobium alloying of HSLA steel and covers more than 80% of the worldwide niobium production. The niobium is mined from pyrochlore deposits ...

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 Ferrovanadium (FeV) is an alloy formed by combining iron and vanadium with a vanadium content range of 35–85%. The production of this alloy results in a grayish silver crystalline solid that can be crushed into a powder called "ferrovanadium ...

from iron, vanadium(V) oxide, and aluminium. The process begins with the reduction of the oxide by the aluminium: :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 Railway track ( and UIC terminology) or railroad track (), also known as permanent way () or "P way" ( and Indian English), is the structure on a railway or railroad consisting of the rails, fasteners, sleepers ( railroad ties in American ...

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

{{Authority control Inorganic reactions Metallurgy Russian inventions Ukrainian inventions

History

Applications

See also

References