Combustion performance of several nanosilicon-based nanoenergetics

Silicon-based nanoenergetics have great potential due to silicon's good thermochemical properties, high active content, and surface modification potential. The combustion characteristics of several silicon-based nanoenergetics were studied by performing equilibrium calculations, initial screening tests, and instrumented burn tube experiments. Results of constant pressure equilibrium calculations predicting adiabatic combustion temperatures and volumetric gas production are shown and the mechanisms that produce these results are discussed. For 14 of the 19 Si/oxidizer systems studied, such as Si/perchlorate systems, the predicted maximum adiabatic combustion temperatures are about 3000 K. For the materials considered the highest predicted combustion temperature is for the Si/polytetrafluoroethylene system at 3531 K, whereas the Si/metal oxide systems are predicted to have adiabatic combustion temperatures ranging from 2282 to 2978 K. The dissociation of SiO₂ to SiO was observed to limit predicted adiabatic combustion temperatures. Theoretical maximum gas production of the reactive Si composites ranged from 350 to 6500 cm³/g, with Si/NH₄ClO₄ producing the most gas and Si/Fe₂O₃ producing the least. Based on initial screening tests, the nanopowder systems Si/NaClO₄ · H ₂O, Si/KMnO₄, Si/NH₄ClO₄, and Si/sulfur were chosen for loose powder burn tube experiments using Si nanopowder. Of the reactive composites studied, Si/NH₄ClO₄ yielded the fastest loose powder tube burning rate, which was about 530 m/s.