Preparation, morphologies and thermal behavior of high nitrogen compound 2-amino-4,6-diazido-s-triazine and its derivatives

•The crystal morphologies of azido-triazine derivatives are examined using SEM.•The thermal stability and decomposition processes are compared by TGA and DSC.•The effect of function group on the thermal behavior of title compounds is clarified.

The crystal morphologies, thermal behavior, sensitivity and performance of 2-amino-4,6,-diazido-s-triazine and its derivatives have been investigated using SEM, DSC, TG techniques and related theories. It has been shown that the DANT crystal is in 1–5 μm thickness layered regular hexagon structure with severe agglomeration. DAAT crystal is very hydrophobic and can be dispersed in water, which has layered rectangle structure with thickness less than 0.5 μm. The TAHT materials exist in a form of amorphous irregular particles with diameters of more than 200 μm while its analogue TAAT can be crystallized in needle shape with a length of 30 μm. TNADAzT crystal has a shape of regular polyhedron with average size of about 120 μm. The thermal analysis indicates that there is only one complex step for decomposition of DAAT, while at least three steps are included for the other materials. DAAT started to decompose at around 148.4 °C with a peak temperature of 197.0 °C, while TAHT started to decompose at 167.2 °C with shoulder-peak of 193.4–206.7 °C at the heating rate of 2.0 °C min−1. DANT decomposes with a heat release of 2420–2721 J g−1, which is much higher than that of DAAT indicating that the heat and its release rate are greatly enhanced by transformation of amino to nitroamino group. Different from the analogue TAHT, there is an obvious melting process at about 152 °C before TAAT decomposition covered by an enthalpy of fusion 93–100 J g−1. The thermal stability of TNADAzT is slightly worse than that of DAAT, and it decomposes in liquid state with a melting point of about 171 °C.

Graphical abstractHigh nitrogen compound 2-amino-4,6-diazido-s-triazine (DAAT) can be substituted by different function groups, forming many other new energetic materials. Such materials that have very close molecular structure may be very different in terms of crystal structure, thermal behavior, as well as performances (e.g., TAAT vs. TAHT). Generally, the increase of the molecular weight results in better thermal stability.Figure optionsDownload full-size imageDownload as PowerPoint slide