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110 g thermite

Thermit ( . AltGr θερμός thermos , warm ') is a commercial and trade name for a mixture of iron (III) oxide - ( colloquially' grate ' ) and aluminum - granules which primarily for aluminothermic welding z. B. of rail joints and for other thermite processes or aluminothermics . The two substances are usually granulated with a binder to keep them free flowing and to prevent potential segregation and water absorption .

The thermite reaction was discovered by Hans Goldschmidt in the 1890s and patented in 1895 .

"Thermit" is a protected trademark of the Goldschmidt-Thermit-Group, which separated from Goldschmidt AG in 1999 .

In general, the term Thermite describes free-flowing mixtures of more or less finely divided metals with certain metal oxides, which develop extremely strongly within a short time after the initiation of the reaction by special pyrotechnic ignition means (e.g. a mixture of barium peroxide and magnesium , or barium nitrate and fine-grain aluminum) Heat (approx. 2400 ° C) and convert with the formation of the metal previously contained in the metal oxide. In order to set the strongly exothermic reaction in motion, an ordinary viscose fuse filled with black powder (or even the flame of a normal lighter) is usually not sufficient, which is also the result of the normally coarse-grained aluminum. Aluminum that is too fine would increase the risk of explosive decomposition and also unintentionally increase the reaction rate.

Reaction equation

In the reaction, 1 mole of iron (III) oxide and 2 moles of aluminum react to form 1 mole of aluminum oxide and 2 moles of iron. The reaction is highly exothermic, with temperatures of up to 2400 ° C being possible.

At these temperatures, the iron and aluminum oxide are in liquid form. The liquid iron sinks due to its higher density and is protected by the liquid aluminum oxide against oxidation by the oxygen in the air.


The use of thermite when welding tracks

The thermite reaction is used in track construction to weld rail ends together and create a seamless track structure. Another use was the construction of large ship components and their repair without having to separate them from the hull. Thermit is also suitable for demolishing buildings with a steel structure. Militarily it is used as a component of grenades or incendiary bombs (e.g. stick incendiary bombs ).

Further development

A reduction in the size of the ingredients to nanoparticles led to the development of the nanothermite . This has different properties than conventional thermite, which makes it interesting for military applications beyond incendiary agents .

Individual evidence

  1. Thermit trademark register
  2. H. Goldschmidt, "Process for the production of metals or metalloids or alloys of the same", German Imperial Patent No. 96317 (March 13, 1895).
  3. 4.4.13 Thermit reaction. Retrieved December 14, 2018 .
  4. Patent US5877468 .
  5. W. Ahlert: Application of the THERMIT steel casting process in the repair and construction of heavy ship components . In: Yearbook of the Shipbuilding Society 1953 . Vol. 47. Springer Verlag, Berlin / Göttingen / Heidelberg 1953, pp. 300-315 .
  6. Patent US5698812 .

Web links

Commons : Thermit welding  - collection of pictures, videos and audio files
Wiktionary: Thermit  - explanations of meanings, word origins, synonyms, translations