Safer Pyrotechnic Obscurants Based on Phosphorus(V) Nitride

The potential of phosphorus(V) nitride, P₃ N₅  , as a replacement for red phosphorus, P_R , in pyrotechnic obscurants has been theoretically and experimentally investigated. P₃ N₅ can be safely mixed with KNO₃ and even KClO₃ and KClO₄  . The corresponding formulations are surprisingly insensitive to friction and only mildly impact-sensitive. P₃ N₅  /KNO₃ pyrolants with ξ=20-80 wt % P₃ N₅ burn 200 times faster than the corresponding mixtures based on P_R and generate a dense smoke. Hence obscurants based on P₃ N₅  /KNO₃ have a figure of merit that by far exceeds that of current state-of-the-art P_R -based obscurants. Furthermore, unlike P_R , which slowly degrades in moist air to phosphoric acids and phosphine (PH₃ ), P₃ N₅ is stable under these conditions and does not produce any acids or PH₃  . P₃ N₅ is hence a safe, stable, and powerful replacement for P_R for use in insensitive munitions.