Micro-explosion combustion characteristics of boron/ammonium perchlorate/polyvinylidene fluoride high-energy composite microspheres with different diameters

Owing to their high energy densities, boron-based energetic composite fuels are widely utilized in explosives. In this study, the flame characteristics, emission spectra, and combustion temperatures of boron/ammonium perchlorate/polyvinylidene fluoride (B/AP/PVDF) energetic composite fuel microspheres with five different diameters (400, 450, 500, 600, and 700 μm) were investigated using an ultrasonic suspension laser ignition system, with the surface morphology and internal structure of the microspheres analyzed using scanning electron microscopy (SEM). The combustion of the microspheres proceeded through three distinct stages: developing combustion, steady combustion and declining combustion. Micro-explosions were observed throughout the combustion process. Notably, significant BO₂ emission spectra were detected. However, the specific flame area and specific spectral integral initially increase and then decrease as the microsphere diameter increases, peaking at a diameter of 600 μm, with values of 3.73 mm⁻² and 0.256 μm⁻², respectively, indicating the highest energy release efficiency. The microspheres exhibited a near-spherical morphology, with a uniform distribution of B, AP, and PVDF components. This study investigated the micro-explosion combustion characteristics and reaction mechanisms of microspheres, established a physical combustion model for individual microspheres, and identified the optimal particle diameter with the highest energy release efficiency. The findings provide valuable experimental data and scientific guidance for the preparation and application of boron-based composite fuels.