Thermite performance

The effect of the aluminum oxide layer is also known to reduce the propagation of thermite reactions since alumina is an effective absorber of thermal energy. A study by Weismiller et al. of a 49 % active aluminum nanopowder in a thermite with copper oxide supports the idea that too much oxide can actually reduce thermite performance. Table 13.4 shows Weismiller s data which indicates the negative effect of a thick oxide layer on aluminum nanoparticles. 

Aluminium powders are also used for the thermite reaction. This is the reaction traditionally used to weld rail tracks together in situ 2Al(s)+Fe203(s)=2Fe(l) + Al203(s), which produces so much heat that molten iron is produced, but it can also be used to produce other less easily reduced metals, such as Mo, from their oxides. Using nanometer particles dramatically improves performance, and these reactions are used as priming reactions for munitions and in fireworks. 

SDO (Synthetic Drying Oil). A commercial polymer of acetylene (such as SDO-80) which was evaluated as an incendiary mixt component during WWII. A typical mixt contg 1 p of SDO-80 was mixed with 2p of Na nitrate, and the material was exposed to the air with occasional stirring until it had absorbed sufficient oxygen (about 64% of its wt) to form a sticky brown-colored gel. The gel, when ignited, gave a burn time of brief duration and little incendiary value. It was considered to be about 1/10 as effective as a Mg bomb and 1/5 as effective as a gum incendiary mixt of that era. Its performance was comparable to that of thermite Refs 1) L.F. Fieser, OSRD 173 (1941)... 

A very important application of the heats of reaction is the calcn of the reaction temp of propints which determine in part the ballistic performance. Heats of reaction also permit the calcn of the adiabatic reaction temp of pyrot reactions which are of value in judging the luminous yield of flares as well as the heat output of thermite reactions... 

The molten iron is then the heat transfer medium that is used to perform the specific task of the thermite device, usually welding. Other fuels include nickel, and other oxidizers include Fe304 and CU2O. 

A recent concrete development is the dispersion of metals and compounds at high altitude(80—100 km and more). While 1 cubic kilometer of air at atmospheric pressure weighs 1 million tons, the same volume at 150 km altitude weighs no more than 2 kg In such a rarefied medium, a metal vapor such as sodium dispersed from a rocket will create a large brilliant yellow train visible at twilight, useful for the study of ionospheric wind and of temperature. The sodium release has been performed by the heat from 8 kg of thermite evaporating (at a temperature of 900 C) 2 kg of sodium powder mixed with the thermite. Oxidation of the sodium takes place slowly. 

While other methods of reparing machine parts, such as electroslag and submerged-arc welding, have become popular, the thermite process has remained competitive because it requires no capital investment and is easily performed as a one-at-a-time operation. Normally, a certain amount of preheating is desirable, but recently a Self-Preheat process has dispensed with this. ... 

Next to combustion in air, the simplest reactions ace those between an element and an oxide, generally called thermitic reactions after the thermite reactions repeatedly mentioned earlier. Table 22 shows a sizable number of such combinations. This table is merely a handy reference for expected heat output on the basis of grams or (theoretical) cubic centimeters of combined reactants and gives no information on the character of the reaction or even if it takes place at all, though the reactions of smallest heat output can be expected to be incomplete or difficult to perform. 

Prentice D, Pantoya ML, Clapsaddle BJ (2005) Effect of nanocomposite synthesis on the combustion performance of ternary thermite. J Phys Chem B 109 20180-20185. 

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