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[LUFER]

Regarding long-term stability, I was not able to specifically understand stability. Refers to the stability of the material did not undergo a reaction before the moment of the explosion or something like that?

 

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The long-term stability of the explosive device requires a stability of the PSi surface against aging. The
surface can be long-time stabilized via thermal annealing the PSi in an oxygen ambient resulting in a
passivating oxidized surface layer. At annealing temperatures below 250 °C the oxygen is mainly back
bonded to surface Si atoms and the PSi surface remains organophilic. This process can be called artificial
aging because after one year of natural oxidation in air the amount of surface-bound oxygen is roughly
the same. At higher temperatures the oxygen will also be bonded directly to the surface, making it more
hydrophilic. While annealing at lower temperatures where oxygen is mainly back bonded to the surface
does not noticeably influence the layers reactivity, tempering at high temperatures (up to 700 °C) decreases the efficiency of the reaction. Furthermore, naturally aged samples which were exposed
~10 years to the air react as freshly prepared ones.

 

Source: Materiais compostos à base de nanossilício altamente explosivos

[Pilesar]

Long term stability means that the chemical does not change much over time. Explosive materials can change characteristics when exposed to other chemicals such as oxygen or water vapor. Regardless of whether it becomes more or less impact sensitive or thermally sensitive with exposure over time, it is not stable if it changes over time. An unstable explosive is less predictable. Your quoted paragraph describes changes that take place on the outer layer of the chemical substance that would protect the bulk of the chemical from further changes.