Intrinsic thermal hazard analysis of tetrazole energetic compounds: A macroscopic-microscopic investigation perspective

Background

Tetrazole energetic compounds present considerable thermal hazard, limiting their engineering applications.

Methods

The thermal decomposition behavior of 1H-Tetrazole and its derivative was comprehensively investigated by using DSC and RSD, with the ‘pure’ exothermic behavior precisely quantified through the AKTS decoupling technique. Additionally, the decomposition kinetic model was established by experiments with hypothetical model fitting method. Finally, DFT simulations, along with TG-IR and GC/MS analyses, studied the thermal decomposition mechanism.

Significant Findings

The endothermic-exothermic coupling effect of 1H-Tetrazole was resolved, with ∆H and q_gas recorded at 3276.0 J·g^-1 and 32.9 mol·kg^-1, respectively, with P_max reaching 107.1 bar. The ∆H and q_gas of Diisopropyl Ammonium Tetrazolide were 1388.7 J·g^-1 and 13.9 mol·kg^-1, respectively. The 'N-order + autocatalytic' two-step decomposition kinetic models were established. A two-step decomposition mechanism involving 'isomerization-ring opening' and 'autocatalysis' of 1H-Tetrazole was proposed. The highly reactive intermediate nitrene is the fundamental substance driving the autocatalytic chain reaction, whereas the metastable intermediates HN₃ and NH₂CN constitute the primary sources of risk. This study clarifies the strong exothermic mechanism and overpressure causes contributing to the multi-path synergy of 1H-Tetrazole from a multi-dimensional viewpoint, proposing thermal safety recommendations from the dual views of intrinsic safety and passive prevention and control.