Combustion performance modulation of propellant by boron/catalyst/oxidant interface combination

High-energy solid propellant is an important direction for future development of missiles and aerospace technology. At present, metal/non-metal fuels (including boron (B), aluminum (Al), and aluminum trihydride (AlH₃)) and high-energy oxidants are added to improve its energy level. Among them, boron is favored for its high calorific value, but boron has problems of difficult ignition and low combustion efficiency. In order to solve these problems, boron powder needs to be modified. In this paper, B-Fe@AP/PVDF and B-Fe-Bi₂O₃@AP/PVDF composites have been prepared by high-energy ball milling combined with spray drying, and the formula was designed according to the maximum calorific value and combustion efficiency, so the boron/catalyst/oxidant interface combination could be fully utilized. At the same time, the heat of explosion, burning rate, and the condensed combustion products (CCPs) of the propellant containing these boron-based composites were systematically investigated. After well controlling the boron/catalyst/oxidant structure, the heat of explosion for the propellant can be increased by up to 5.0 % (from 6.0 kJ·g^-1 to 6.3 kJ·g^-1), the burning rate of various propellants also increases accordingly. Among them, the propellant with nB-Fe-Bi₂O₃@AP/PVDF (28 %) has the highest burning rate with a sputtering phenomenon. At a pressure of 1 MPa, its burning rate surpasses that of an Al-based propellant by 87.5 % (from 4.7 mm·s^-1 to 8.9 mm·s^-1). Under 15 MPa, this enhancement is even more pronounced, with a 102.3 % increase in burning rate (from 19.0 mm·s^-1 to 38.5 mm·s^-1). The sudden increase in burning rate is due to the integration of fuel-oxidizer, heat conduction, and erosion combustion. Because of the influence in the interface structure, the CCPs of boron-based propellants are more complex, including Al₂O₃, AlB₂, B₄C and Al-B-O-C composites, but boron/catalyst/oxidant interface combination can further reduce the agglomeration of the propellant. Novelty and significance statement: The interface combination of boron/catalyst/oxidant in solid propellants have successfully achieved through high-energy ball milling, spray drying and acoustic resonance, regardings of the ignition and combustion enhancement and agglomeration inhibition. These technologies can increase the contact area of boron, catalyst and oxidant, and improve the reaction efficiency between fuel and oxidant while regulating the interface, thereby improving the ignition delay and combustion efficiency of propellant. This finding provides valuable insights for the development of advanced propulsion applications with improved reaction efficiency and maintained energy density.