Crystal structure transformation and step-by-step thermal decomposition behavior of dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate

Abstract

The crystal structure transformation and step-by-step thermal decomposition behavior of dihydroxylammonium 5,50 -bistetrazole-1,1 0 -diolate (TKX-50) under thermal stimulation were studied and the whole process included thermal expansion, primary decomposition and secondary decomposition.The thermal expansion and primary decomposition of TKX-50 were studied using in situ powder X-ray diffraction (in situ XRD) together with Rietveld refinement, by which the crystal structure transformation process can be accurately traced. The results showed that the thermal expansion of TKX-50 was anisotropic. In particular, the a-axis exhibited a negative thermal expansion (NTE) that may be attributed to the distortion of the six-membered ring, which results in H-transfer between the cation and dianion.The crystal structure of the intermediate product after primary decomposition was also obtained. The secondary decomposition process was analysed using thermogravimetric-differential scanning calorimetry (TG-DSC) due to the safety risk of TKX-50 analyzed by in situ XRD. The crystal structure transformation process from TKX-50 to the intermediate product under heat stimulation was deduced.Meanwhile, the morphological change of the whole process was obtained using hot stage microscopy (HSM). Combined with TG-FTIR technology, the gaseous decomposition products at each step were analysed and the thermal decomposition mechanism of TKX-50 was proposed. This study further reveals the thermal decomposition behavior of TKX-50 and is helpful for better understanding the thermal decomposition mechanism.

Study on Thermal Characteristics of TNT Based Melt‐Cast Explosives

“…According to Jia et al. study, the intermediate product diammonium 5,5′‐bistetrazole‐1,1′‐diolate (ABTOX) is formed in the primary decomposition stage, when the temperature continues to rise, ABTOX mainly decomposes into N 2 O, CO 2 , N 2 , etc. in the secondary decomposition stage.…”

“…In the DSC curve of TKX-50, two exothermic peaks are observed at 251°C and 308°C., which correspond to the primary and secondary decomposition stages. According to Jia et al [30] study, the intermediate product diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX) is formed in the primary decomposition stage, when the temperature continues to rise, ABTOX mainly decomposes into N 2 O, CO 2 , N 2 , etc. in the secondary decomposition stage.…”

Stability of Dihydroxylammonium 5,5’‐Bistetrazole‐1,1’‐Diolate (TKX‐50) in Solvents

“…The HS and the corresponding 2D fingerprint plot for ABTOX were shown in ESI Figure S11 and Figure S12. ABTOX is known as the main thermal decomposition intermediate product of TKX-50 [17][18][19]. The reported ABTOX before was obtained by thermal decomposition in the solid phase or directly obtained by synthesis [17][18][19]27].…”

“…However, in another point of view, these positive and negative charges in the structure have a risk of increasing the reactivity between the molecular components. For instance, it has been predicted theoretically and observed in experiments that proton transfer from hydroxylamine to the bistetrazole moiety occurs in the initial thermal decomposition of TKX-50 [16][17][18][19]. Therefore, estimation of the reactivity of TKX-50 in different environments and under different stimuli is sig-nificant for evaluating its security and its applications for weaponry.…”

“…Therefore, estimation of the reactivity of TKX-50 in different environments and under different stimuli is sig-nificant for evaluating its security and its applications for weaponry. Recently, plenty of research has been focused on the thermal stability of TKX-50 in solid state [13][14][15][16][17][18][19][20][21][22][23][24][25]. In particular, the main purpose in the literature [20] is to determine the solubility of TKX-50 in different pure solvents by gravimetric method between 25 and 50°C, and the results show that the solubility in DMF has the strongest dependency on temperature.…”