Silicon powder reacts with water, liberating hydrogen gas, which poses an explosion
risk. Adding metal ions with a high reduction potential suppresses hydrogen generation.
Copper (II) ions are particularly effective in this regard. In their presence the
reaction features three distinct stages. In the initial phase copper is deposited on the
silicon surface concomitant with a rapid drop in the solution pH. Most of the hydrogen
evolves during a second active stage with the pH showing a slight upward drift.
Finally, in the third stage, the silicon surface passivates and hydrogen evolution
comes to a halt. A comparison of this method and two other methods previously
reported, i.e., controlled air oxidation of the silicon powder before slurrying and adding
organic corrosion inhibitors, shows that silane surface modification of silicon is
the most effective method in terms of decreasing the greatest amount of hydrogen
released and increasing silicon reactivity in a typical pyrotechnic composition.