Formation of Hotspots

The formation of hotspots depends upon the energy input and the physical properties of the explosive composition. The diameter of the hotspots is in the region of 0.1-10 fim and their duration is about HTMO-3 s with temperatures greater than 900 °C. There have been various theories put forward to describe the mechanisms for the formation of hotspots, some of which are described below. 

The energy from the stimulus is converted into heat by adiabatic compression of small, entrapped bubbles of gas. The heat generated forms 

Explosive substance Temperature of ignition via hotspots/ °C Temperature of thermal ignition/ °C 

The energy from the stimulus is converted into heat by adiabatic compression of small, entrapped bubbles of gas. The heat generated forms hotspots. For an ideal gas, the temperature inside the gas bubbles T2 depends on the compression ratio as shown in Equation 4.1, 

Another source of hotspots is the presence of grit particles, such as crystals. When the particles are small and sharp only a small amount of frictional or impact energy is needed to produce a hotspot. This is because localized energy is generated at the stress points soft particles are unable to generate enough energy to 

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Other microwave-assisted parallel processes, for example those involving solid-phase organic synthesis, are discussed in Section 7.1. In the majority of the cases described so far, domestic multimode microwave ovens were used as heating devices, without utilizing specialized reactor equipment. Since reactions in household multimode ovens are notoriously difficult to reproduce due to the lack of temperature and pressure control, pulsed irradiation, uneven electromagnetic field distribution, and the unpredictable formation of hotspots (Section 3.2), in most contemporary published methods dedicated commercially available multimode reactor systems for parallel processing are used. These multivessel rotor systems are described in detail in Section 3.4. 

Usually it is assumed, that on impact most primary explosives are initiated by hotspots from inter-crystalline friction. For secondary explosives, as a general rule, initiation by impact results in the formation of hotspots, which originate (adiabatic compression) from gas bubbles between the crystals. Such hotspots only exist for approximately 10 6 s. 

The formation of hotspots depends upon the energy input and the physical properties of the explosive composition. The diameter of... 

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