Energetic metal salts based on 3-cyano-1,5-(5-nitro-1,2,4-triazolyl) formazan: Synthesis, crystal structure, thermal stability, and catalysis on the thermal decomposition of ammonium perchlorate

Ammonium perchlorate (AP) serves as an important component in solid propellants. Adding catalysts to facilitate its thermal decomposition can enhance the combustion performance of solid propellants. Inspiring by the remarkable thermal stability and resistance to mechanical stimuli of the 3-cyano-1,5-(5-nitro-1,2,4-triazolyl) formazan, four energetic metal salts with 3-cyano-1,5-(5-nitro-1,2,4-triazolyl) formazan as energy storage units were synthesized and well characterized. The molecular structures of the compounds 1–2 were confirmed by single-crystal X-ray diffraction. The thermal behaviors and sensitivities of these new four energetic metal salts were determined by the differential scanning calorimetry (DSC) and BAM methods. These new four energetic metal salts possess excellent thermal stability with decomposition peak temperatures over 259 °C and low impact and friction sensitivity (IS > 40 J, FS > 360 N). Additionally, the four energetic metal salts exhibited outstanding performance in accelerating the thermal decomposition of AP, the high-temperature peak decreased by 30 to 120 ℃, and the heat release increased significantly, which was 1.1 to 2.8 times of pure AP. The decomposition activation energy (\({E}_{a}\)) of pure AP and AP with 10 wt% compounds 1–4 were calculated using the Kissinger equations, respectively. The AP decomposition activation energy decreased by 9.41 to 18.45 kJ·mol⁻¹. These experimental results indicate that the four energetic metal salts are expected to be the alternative additives to accelerate the catalytic decomposition of AP in composite solid propellants.