Silicon nanowire-based energetic materials with significantly improved hygroscopicity

The large energy release potential and highly adjustable combustion characteristics of nanostructured silicon compounded with sodium perchlorate (NaClO4) make it one of the most attractive inorganic energetic materials. Compared with nanoporous silicon, the silicon nanowires prepared by metal-assisted chemical etching are easily loaded with NaClO4 to obtain energetic materials, due to their one-dimensional array structure and tight contact with the silicon substrate. However, the high hygroscopicity of NaClO4 greatly degrades the long-term storage property of the material, and must be addressed. In this study, sulfur, as a known stable and non-hygroscopic oxidant that reacts with nanostructured silicon, was impregnated on the silicon nanowires/NaClO4 energetic material to insulate NaClO4 from H2O in the ambient air. After sulfur impregnation, the mass of the sample increased by 8.7 ​mg after being exposed to 98% relative humidity at 25 ​°C for 12 ​h, while the sample without sulfur increased by 50 ​mg, indicating significant improvement in the hygrophobicity of the sulfur-containing energetic material. Laser ignition experiments showed that the combustion performance was only slightly affected after sulfur treatment. This work provides a new strategy for improving the hygrophobicity of silicon-based energetic materials, which can improve their applicability in micro-electromechanical systems.