High-efficiency combustion of boron composites via DAAF-driven B₂O₃ removal and agglomeration suppression

The development of high-energy-density fuels is critical for efficient energy conversion and next-generation energetic systems. Boron (B) is attractive due to its outstanding gravimetric and volumetric energy densities, but its practical use is hindered by the native oxide layer and pronounced agglomeration during combustion. To address these limitations, 3,3′-diamino-4,4′-azoxyfurazan (DAAF), a low-temperature exothermic and gas-generating compound, was incorporated into B to form B/DAAF composite microspheres. DAAF addition tailored the pore structure and particle-size distribution of the microspheres, thereby lowering the main oxidation peak temperature from 765 to 720 °C. As the DAAF content increased, the combustion performance of B was markedly enhanced; an optimal formulation (B/DAAF₂₅) exhibited a specific calorific value of 39.14 MJ·kg⁻¹ and a combustion efficiency of 87.01 %. Upon DAAF incorporation, laser-ignition tests showed an 88 % reduction in ignition delay and a 3.7-fold increase in combustion duration relative to B/DAAF₀. At higher DAAF loadings, micro-explosive fragmentation was induced, yielding finely dispersed residues. Additionally, the combustion residues evolved from dense agglomerates to finely dispersed structures, and B₆O was detected only in intermediate DAAF formulations, indicating higher combustion temperatures. These results indicate that DAAF enhances B combustion through a synergistic mechanism of low-temperature heat release, continuous disruption of the oxide layer, and improved dispersion. This study highlights the potential of nitrogen-rich compounds such as DAAF for enabling efficient B-based energetic systems.