Wednesday, March 19, 2008
Thermite
Thermite is a pyrotechnic composition of aluminium powder and a metal oxide which produces an aluminothermic reaction known as a thermite reaction. It is not an explosive, but can create short bursts of extremely high temperatures focused on a very small target for a short period of time.
Metals are capable of burning under the right conditions similar to the combustion process of wood or gasoline. In fact, rust is the oxidation of steel or iron at very slow rates. Thermite is a process in which the correct mixture of metallic fuels are combined and ignited. Ignition itself requires extremely high temperatures.
The aluminium is oxidized by the oxide of another metal, most commonly iron oxide (rust). The products are aluminium oxide, free elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation.
The reaction is used for thermite welding, often used to join rail tracks. Other metal oxides can be used, such as chromium oxide, to generate elementary metal. Copper thermite, using copper oxide, is used for creating electric joints in a process called cadwelding. Some thermite-like mixtures are used as pyrotechnic initiators such as fireworks. [source]
Thermite burning reaction:
2Al + Fe2O3 = Al2O3 + 2Fe
produces so much energy that even liquid nitrogen won't stop it. Can't believe? Watch it by yourself:
