Surface Encapsulation of Micron-Aluminum with Both Cobalt and Iron Metallic Nanoparticles and Its Enhanced Combustion...

The energy release efficiency of aluminum fuel in composite solid propellants is limited by diffusion-controlled kinetics arising from the native Al₂O₃ passivation layer, which elevates ignition thresholds and suppresses combustion efficiency. Herein, this limitation is addressed through interfacial engineering by constructing a cobalt/iron bimetallic nanoscale interface on micron-sized aluminum (μAl) particles. Using an in situ replacement strategy, a [nCo+nFe]/μAl core-shell composite is developed, in which the inert Al₂O₃ layer is transformed into an active Co/Fe bimetallic shell. The synergistic coupling between this interfacial redox cycle and the intrinsic catalytic activity of Co/Fe modifies the thermolytic behavior of ammonium nitrate (AN) and the DAP-4. The decomposition peak of DAP-4 decreases by 81.3 °C, accompanied by a ∼30% reduction in apparent activation energy, while the reaction pathway evolves from a complex multistep process into a more concentrated oxidation-dominated process. When incorporated into AN/DAP-4-based energetic microunits, the [nCo+nFe]/μAl composite exhibits enhanced combustion performance, including increased peak pressure (∼10-fold), elevated flame temperature (∼1000 °C), and improved luminous efficiency (∼22-fold). By integrating a self-driven energy cycle with interfacial catalytic coupling, this strategy provides an effective pathway to overcome the intrinsic limitations of aluminum-based fuels and offers potential for next-generation high-performance solid propellants.