Applications
Regarding pyrotechnics and welding, what does a thermite reaction create?
Chemical reaction
Exothermic welding Thermite Chemical reaction Thermite Nano-thermite
Exothermic_welding-Abstract Thermite-Copper_thermite Chemical_reaction-Applications Thermite-History Nano-thermite-Abstract
Exothermic welding, also known as exothermic bonding, thermite welding (TW), and thermit welding, is a welding process for joining materials that employs molten metal to permanently join the conductors. The process employs an exothermic reaction of a thermite composition to heat the metal, and requires no external source of heat or current. The chemical reaction that produces the heat is an aluminothermic reaction between aluminium powder and a metal oxide. 
Copper thermite can be prepared using either copper(I) oxide (Cu2O, red) or copper(II) oxide (CuO, black). The burn rate tends to be very fast and the melting point of copper is relatively low so the reaction produces a significant amount of molten copper in a very short time. Copper(II) thermite reactions can be so fast that copper thermite can be considered a type of flash powder. An explosion can occur and send a spray of copper drops to considerable distance. Copper(I) thermite has industrial uses in e.g. welding of thick copper conductors ("cadwelding"). This kind of welding is being evaluated also for cable splicing on the US Navy fleet, for use in high-current systems, e.g. electric propulsion. 
Chemical reactions are central to chemical engineering where they are used for the synthesis of new compounds from natural raw materials such as petroleum and mineral ores. It is essential to make the reaction as efficient as possible, maximizing the yield and minimizing the amount of reagents, energy inputs and waste. Catalysts are especially helpful for reducing the energy required for the reaction and increasing its reaction rate. Some specific reactions have their niche applications. For example, the thermite reaction is used to generate light and heat in pyrotechnics and welding. Although it is less controllable than the more conventional oxy-fuel welding, arc welding and flash welding, it requires much less equipment and is still used to mend rails, especially in remote areas.
The thermite ("thermit") reaction was discovered in 1893 and patented in 1895 by German chemist Hans Goldschmidt. Consequently, the reaction is sometimes called the "Goldschmidt reaction" or "Goldschmidt process". Goldschmidt was originally interested in producing very pure metals by avoiding the use of carbon in smelting, but he soon discovered the value of thermite in welding. The first commercial application of thermite was the welding of tram tracks in Essen, Germany, in 1899. 
A Nano-thermite or "super-thermite" is a metastable intermolecular composite (MICs) characterized by a particle size of its main constituents, a metal and a metal oxide, under 100 Nanometers. This allows for high and customizable reaction rates. Nano-thermites contain an oxidizer and a reducing agent, which are intimately mixed on the nanometer scale. MICs, including nano-thermitic materials, are a type of reactive materials investigated for military use, as well as for general applications involving propellants, explosives, and pyrotechnics. What distinguishes MICs from traditional thermites is that the oxidizer and a reducing agent, normally iron oxide and aluminium, are in the form of extremely fine powders (nanoparticles). This dramatically increases the reactivity relative to micrometre-sized powder thermite. As the mass transport mechanisms that slow down the burning rates of traditional thermites are not so important at these scales, the reactions become kinetically controlled and proceed much more quickly. 