Thermite

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Rather than being a specific formula, as is often misunderstood, thermite is a term for a group of chemical mixtures that, when ignited by a sufficiently hot source, react to give extremely high temperatures. Thermites and variants on them have a variety of civilian and military applications, from specialized welding, to incendiary formulations, to destruction charges used to make equipment useless if captured.

The basic mixture in a thermite is a powdered metal, most often aluminum powder, and a metal oxide, most often ferric oxide. With a pure thermite, the heat is generated not by combustion, but by an reduction-oxidation reaction. There is no flame or flame propagation. The reaction, using iron oxide and aluminum, was patented by Goldschmidt in 1895, and is characterized by:

• Minimal gaseous products
• High temperature, typically 2000 to 3000 degrees Celsius; specialized thermites can be prepared for a specific desired reaction temperature
• Production of a slug of molten metal, which can transfer heat efficiently for burning, cutting or welding

If metal oxides of high specific gravity, such as the oxides of tungsten, molybdenum or lead are used, the thermite reaction is especially active, although the mixture can be especially expensive. Nevertheless, these characteristics can be especially important in specialized applications, such as flares used as decoys in electronic warfare.

While the igniter is not part of the mixture, it is critical to thermite applications. The igniter needs to provide a high temperature; magnesium metal ribbon, which can be lit with a match, is a common igniter for ad hoc thermite work.

Theamats add pyrotechnic materials, such as nitrates (most often barium nitrate). They are easier to ignite. Combustion reactions do take place with these substances, and gases are produced. The gases project the liquid metal slug and give increased penetration, desired in incendiary and other specific applications. U.S. Army "thermite" grenades actually contain a thermate, which, in the TH3 grenade, is a mixture of thermite 68.7%, barium nitrate 29.0%, sulfur 2.0% and binder 0.3%.

Date: 2023-04-10     hits: 520    Return