Question

What effect does increasing the particle size of an oxidizer have on the energy release rate of an improvised energetic mixture?

Accepted Answer

Increasing the particle size of an oxidizer decreases the energy release rate of an energetic mixture. The energy release rate is determined by the speed at which chemical reactions occur, a process known as reaction kinetics. An oxidizer is a substance that provides oxygen to fuel the combustion reaction. Energetic mixtures rely on the physical contact between the fuel particles and the oxidizer particles to react. When the particle size of the oxidizer is increased, the total surface area of the oxidizer available for contact with the fuel is reduced. Because the chemical reaction only takes place at the interface where the fuel and oxidizer touch, a smaller total surface area results in fewer active sites for the reaction to occur simultaneously. This reduction in the surface-to-volume ratio forces the reaction front to travel through a larger volume of material for each particle, slowing the propagation of the reaction through the mixture. Consequently, larger particles lead to a slower energy release, while smaller particles allow for a faster, more intense release of energy.

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What effect does increasing the particle size of an oxidizer have on the energy release rate of an improvised energetic mixture?