A nanoenergetic gas-generating composite based on aluminum (Al), bismuth trioxide (Bi 2 O 3 ), and sodium azide (NaN 3 ) was developed to achieve rapid energy release and efficient gas evolution within a single integrated formulation. The composite was synthesized via aerosol spray-drying, producing microscale spherical aggregates (∼4–12 μm) with uniform elemental distribution, ensuring intimate interfacial contact among the components. Thermal analysis revealed a sequential reaction pathway in which NaN 3 decomposition (∼350–380 °C) initiated nitrogen evolution, followed by a highly exothermic Al/Bi 2 O 3 thermite reaction (∼500–600 °C). The early-stage decomposition of NaN 3 is suggested to promote interfacial activation, lowering the effective reaction threshold and facilitating thermite initiation under non-melting conditions. Combustion and ignition analyses demonstrated ultrafast reaction kinetics, with ignition delay and combustion duration both within approximately 1 s. Closed pressure cell experiments showed rapid pressure buildup (2500–3000 kPa from a 15 mg charge), while gas-collection measurements confirmed a nitrogen yield of ∼700 mL g −1 . Post-combustion phase analysis verified the formation of metallic Bi and Al 2 O 3 and the disappearance of crystalline NaN 3 . These results reveal a kinetically coupled thermite–azide reaction mechanism in which initial azide decomposition promotes interfacial activation, while the heat released from the thermite reaction accelerates subsequent gas generation. This heat–gas coupling enables simultaneous gas evolution and pressure amplification within sub-second timescales, providing a mechanistic framework for designing compact nanoenergetic systems with rapid dynamic response.
Kim et al. (2026) studied this question.