Research on sulfur-free black powder with low smoke signature

K_0.333(NH₄)_0.667NO₃ was prepared using a recrystalization method. The micro-morphology and crystal structure of K_0.333(NH₄)_0.667NO₃ were characterized by scanning electron microscopy (SEM), X-ray diffraction energy spectrum (XRD) and differential scanning calorimetry (DSC). Taking the equilibrium solid-phase products, combustion temperature and combustion heat as target functions, the combustion thermodynamic parameters of K_0.333(NH₄)_0.667NO₃/ C₁₂H₄O₂ were calculated using the least free-energy principle, and the low-smoke igniting charge formulas were designed, the flame sensitivity and combustion heat effects of optimized formulas were tested and compared. The results show that the intermolecular mixing between KNO₃ and NH₄NO₃ is achieved, the crystal structure of double salt is well-ordered, and the thermal decomposition temperature decreases. Compared with KNO₃/C₁₂H₄O₂ igniting charge, the flame sensitivity and heat effect of K_0.333(NH₄)_0.667NO₃/ C₁₂H₄O₂ decrease less than 10%, its combustion solid phase products and smoke signature also decrease, and the attenuation rate of 1.06 μm laser decreases about 73.9%.