Synthesis and Properties of [1,2,4]Triazolo[4,3‐b][1,2,4,5]Tetrazine and Their Salts: High‐nitrogen Materials for Solid Propellants

ABSTRACT [1,2,4]triazolo[4,3‐b][1,2,4,5]tetrazine high‐nitrogen materials are a unique class of high‐energy‐density materials. In this work, two [1,2,4]triazolo[4,3‐b][1,2,4,5]tetrazine compounds and their five salts in excellent yields were synthesized, and characterized by multinuclear nuclear magnetic resonance, infrared, high‐resolution mass spectrometry, and EA. The thermal stability and safety of the obtained compounds were tested. These high‐nitrogen materials exhibited a high positive enthalpy of formation (613.0–886.7 kJ·mol −1 ), which was higher than hexanitrohexaazaisowurtzitane (CL‐20). They had an acceptable density (1.54–1.73 g·cm −3 ) and excellent detonation properties ( p = 20.0–27.6 GPa; D = 7819–9000 m·s −1 ). All compounds were insensitive in mechanical sensitivity (impact sensitivity > 50 J, friction sensitivity > 360 N). In addition, these compounds had good thermal stability ( T d = 182–354°C). Among them, 6‐(3‐Amino‐1,2,4‐triazol)‐[1,2,4]triazolo[4,3‐b][1,2,4,5]tetrazine had the highest heat resistance ( T d = 354°C) and was ∼120°C thermally more stable than CL‐20. Moreover, the specific impulse for the novel materials showed an improvement of 2–3 s over CL‐20.