Ignition, initiation and thermal decomposition

Ignition, Initiation and Thermal Decomposition Heat generated or lost... 

Bismuth trioxide may be prepared by the following methods (/) the oxidation of bismuth metal by oxygen at temperatures between 750 and 800°C (2) the thermal decomposition of compounds such as the basic carbonate, the carbonate, or the nitrate (700—800°C) (J) precipitation of hydrated bismuth trioxide upon addition of an alkah metal hydroxide to a solution of a bismuth salt and removal of the water by ignition. The gelatinous precipitate initially formed becomes crystalline on standing it has been represented by the formula Bi(OH)2 and called bismuth hydroxide [10361 -43-0]. However, no definite compound has been isolated. 

The sustained decomposition of a substance without introduction of any other apparent ignition source besides thermal energy and without air or other oxidants present. Autodecomposition is the result of a thermal self-decomposition reaction for given initial conditions (temperature, pressure, volume) at which the rate of heat evolution exceeds the rate of heat loss from the reacting system, thus resulting in an increasing reaction temperature and reaction rate. 

Relationships existing between structure, stability and thermal, photochemical and explosive decomposition (sometimes spontaneous) of the inorganic azides has been extensively investigated and reviewed [1,2]. The ignition characterisitcs of explosive inorganic azides, with or without added impurities under initiation by heat or light have been discussed [3],... 

In a nutshell, it may be concluded that DTA, DSC and TGA have been used mainly to determine the thermal properties of explosives like melting points, thermal stability, kinetics of thermal decomposition and temperatures of initiation and ignition etc. Further, the properties which can be calculated quantitatively from the experimentally obtained values are reaction rates, activation energies and heats of explosion. DTA data of some explosives are given [46] in Table 3.6. 

Ammonium perchlorate has been studied quite often in recent times because it is used for solid rocket fuel(H.Osada and E.Sakamoto Thermal decomposition of ammonium perchlorate, J.Exp.Soc.,JapanNo.5, P 236 (1963) H.Osada and S.Kakinouchi Initiation of the ignition of solid composite propellant, No., p.290(1965)) It is thought that there are two kinds of decomposition the first occurs below 300 0, and the other over 300 0. The reactions seem to be different from each other. They are very complicated and the products are detected as N iO, N i, NO, NO., NHj, HCIO, HNO3, HCl, HNOj, 0. ... 

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