Revealing the Hygroscopic Behavior of Ultrahigh Nitrogen Content Cyclo‐Pentazolate Salts

Abstract Three representative cyclo ‐pentazolate salts including N 2 H 5 + N 5 − , NH 3 OH + N 5 − and NH 4 + N 5 − , are highly favored for their ultrahigh nitrogen content (80–96%). However, their ambiguous nature has severely restricted the application exploration. Herein, the relationships between humidity and moisture content of salt were established by quantitative analysis. Among the three salts, the hygroscopic ability has the following order: NH 3 OH + N 5 − >NH 4 + N 5 − >N 2 H 5 + N 5 − . Especially in the range of 40% RH −60% RH, the NH 3 OH + N 5 − has a high sensitivity to water, and the absorbed moisture content can be as high as 20.8% at 60% RH. When the relative humidity exceeds 60% RH, the hygroscopic rate of NH 3 OH + N 5 − rises sharply, at 80% RH, NH 3 OH + N 5 − will absorb excess moisture and turns into liquid form. After treating NH 3 OH + N 5 − at 40% RH, the very sensitive friction sensitivity (FS) and impact sensitivity (IS) of dried NH 3 OH + N 5 − (FS=20 N, IS=2 J) will change into insensitive salt (FS>360 N, IS>40 J). The higher moisture content in NH 3 OH + N 5 − , the lower the thermal stability, its thermal decomposition temperature (103.22°C) is 3.24°C lower than that of dry salt (106.46°C) at 75% RH (moisture content is 30.2%). The other two salts N 2 H 5 + N 5 − and NH 4 + N 5 − have the similar properties. Molecular dynamics simulation was further applied to explain the strong hygroscopicity of salts.