Research on the preparation, characterization and performance of three manganese oxide thermites

As classic energetic materials, transition-metal thermites face persistent challenges in balancing energy release efficiency and combustion stability. This study evaluates three manganese oxide-based thermites (MnO2, Mn2O3, and Mn3O4 with μAl) prepared via conventional physical mixing (PM) and electrostatic spray (ES) methods using a PVDF binder. We highlight a fundamental thermodynamic boundary: the multi-step reduction of manganese oxides intrinsically terminates at the Mn2+ state, fundamentally restricting the total heat release per unit mass. Microstructural characterization reveals that the ES process successfully assembles 20-micrometer microspheres featuring a very thin but highly compact core-shell encapsulation. By employing these ES architectures, we effectively overcome the kinetic mass-transfer limitations and physical diffusion barriers inherent in PM mixtures. Consequently, the ES samples achieve stable, splash-free combustion, contrasting sharply with the violent micro-explosions and severe product sintering observed in PM samples. Furthermore, thermal analysis indicates that the PVDF binder presents a critical dual role: it physically stabilizes the reaction front by buffering direct contact, while its endothermic pyrolysis and competitive fluorination act chemically as an energy sink. These findings provide a structural design paradigm for optimizing highly reactive multi-step energetic composites.