TABLE OF CONTENTS The heat of explosion Q can be increased by adding to the explosive composition another fuel which has a high heat of combustion ? H c. Such fuels can be found with the lighter elements of the periodic table as shown in Table 5.17.
| Element | Relative atomic mass | ? H c /kJ mol ?1 | ? H c /kJ g ?1 |
|---|---|---|---|
| Beryllium | 9.0 | ?602.1 | ?66.9 |
| Boron | 10.8 | ?635.0 | ?58.8 |
| Lithium | 6.9 | ?293.9 | ?42.6 |
| Aluminium | 27.0 | ?834.3 | ?30.9 |
| Magnesium | 24.3 | ?602.6 | ?24.8 |
| Sulfur | 32.1 | ?295.3 | ?9.2 |
| Zinc | 65.4 | ?353.2 | ?5.4 |
Beryllium has the highest heat of combustion of the solid elements, followed by boron and aluminium. Aluminium is a relatively cheap and useful element, and is used to increase the performance of explosive compositions, such as aluminized ammonium nitrate and aluminized TNT. Aluminium is also used in some commercial blasting explosives, particularly in water-based slurry explosives, which contain a high percentage of ammonium nitrate.
The oxidation of aluminium is highly exothermic producing ?1590 kJ, as shown in Reaction 5.13.
In an explosive composition the aluminium reacts with the gaseous products particularly in oxygen-deficient compositions where no free oxygen exists as shown in Reaction 5.14.
The volume of gas does not change in the first two reactions, i.e. 3 moles ? 3 moles. Consequently, the increase...
