High-energy salts of 5,5'-azotetrazolate. I. Thermochemistry and thermal expansion

Thermal decomposition of disubstituted salts of high-energy 5,5'-azotetrazolate (sodium, ammonium, hydrazine, guanidinium, aminoguanidinium, and triaminoguanidinium salts) under isothermal and nonisothermal conditions in solid and liquid phases is studied. The relationship between the avidity and the thermal stability of the 5,5'-azotetrazolate salt is demonstrated. The boundary of possible existence of 5,5'-azotetrazolate salts in terms of the avidity index p$K_a$ is determined. Gaseous and condensed products of decomposition are analyzed, and a mechanism of thermal decomposition of 5,5'-azotetrazolate is proposed. The enthalpies of formation of some 5,5'-azotetrazolate salts are determined, and the most reliable values are chosen on the basis of the analysis of the data obtained in the present study and those available in publications.