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Thermite is a mixture of a reactive metal and a metal oxide, typically aluminum and iron oxide, that produces an intense exothermic reaction when ignited. It is used for extracting metals and in welding and metal cutting.
Thermite is a chemical compound consisting of a reactive metal and a metal oxide, usually both in a powdered state, mixed together. The type of metals used can vary, although the most common combination is aluminum as a reactive metal and iron oxide, also known as rust. These two metals are ground into powder or chips and then mixed together, at which point they are still relatively safe to handle as long as the mixture isn’t exposed to high temperatures. Thermite produces an intense exothermic reaction, not an inherently explosive reaction, once a suitable ignition source is applied.
While different metals can be used to create thermite, the typical combination used is aluminum and iron oxide. Aluminum is used because it is a reactive metal with a very high boiling point and low melting point. The high boiling point of aluminum is important because the maximum temperature reached during a thermite reaction – the composition combustion process – is typically limited by the boiling point of the reactive metal used, while the low melting point allows the reaction occurs once the aluminum is in the liquid phase. Since aluminum is also quite cheap, it is ideal for commercial and industrial purposes. Iron oxide is also a convenient metal oxide to use, although other metals such as chromium and copper can also be used.
A basic thermite reaction is that the two metals, for example aluminum and iron oxide, are combined and then an ignition source of very high heat is introduced. Standard ignition caps and fuses typically fail, and magnesium strips are often used to obtain the heat needed to initiate the reaction. Once the aluminum reaches a high temperature, the iron oxide and aluminum combine to create free elemental iron, aluminum oxide, and tremendous heat.
Thermite ignition is an exothermic reaction, meaning that more energy is produced in the reaction than is needed to create it, and this energy is released as intense heat up to 4,500° F (about 2,500° C). This thermite reaction is used in a number of commercial and manufacturing applications. Because the resulting composition creates pure metal, this process can be used to extract metals for use in construction.
The intense heat created in this reaction can also be used to melt metals and is used in welding and metal cutting. However, care should be taken when used in welding as there is a tendency for air pockets and potential weak spots to form due to the use of molten metal. Thermite can also be used in limited ways underwater, as the reaction actually creates its own supply of oxygen to keep fueling the reaction.
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