Precision-engineered burn rate modulation of solid propellants via multifunctional C₃N₄ catalytic implantation

The combustion characteristics and energy output properties of solid propellants play a decisive role in rocket engine and propulsion system performance. Particularly for HTPB propellant systems incorporating CL-20 as the high-energy oxidizer, achieving wide-range burn rate regulation and maintaining low pressure exponents constitute fundamental requirements for practical implementation. Through advanced interfacial control methodology, this study successfully constructed two types of aluminum/oxidizer integrated composites (Al@AP and Al@CL-20), while employing precise catalysis to accurately distribute C₃N₄ burn rate modifiers within the target oxidizer. This innovative approach has demonstrated significant enhancement in aluminum combustion efficiency within the composite propellant system. The strategic incorporation of C₃N₄, coupled with the optimized interfacial architecture between fuel and oxidizer components, establishes a new paradigm for performance modulation in solid propellant formulations. Thermal analysis (DSC/TGA) results reveal that both Al@AP/CN and Al@CL-20/CN composites exhibit concentrated exothermic characteristics, yet demonstrate fundamentally distinct heat release profiles. By strategically exploiting these differential energy release features, propellant formulations with tailored interfacial compositions and precisely engineered catalytic sites were developed. The modified propellants displayed markedly different combustion behaviors: the Al@CL-20/CN-based formulation achieved a 33 % reduction in pressure exponent (n=0.18) with significantly enhanced low-pressure burning rates, while the Al@AP/CN-modified system maintained ultra-low burning rates (<5 mm·s^-1) but with high combustion efficiency across broad pressure ranges with an exceptionally low pressure exponent of 0.23. Complementary analysis of condensed combustion products (CCPs) confirmed substantial improvements in combustion completeness, showing a 78 % reduction in micron-sized aluminum agglomerates and significantly refined CCPs particle size distribution. These findings collectively demonstrate that the synergistic combination of interfacial modification and precision catalysis effectively optimizes aluminum combustion efficiency and tunability of burn rate of high-energy HTPB propellants.