Novel insensitive energetic-cocrystal-based BTO with good comprehensive properties

Series of AzTO-Based Energetic Materials: Effect of Different π-π Stacking Modes on Their Thermal Stability and Sensitivity

π-Stacking is common in materials, but different π-π stacking modes remarkably affect the properties and performances of materials. In particular, weak interactions, π-stacking and hydrogen bonding, often have a great impact on the stability and sensitivity of high-energetic compounds. Therefore, several of energetic materials based on 1,1'-dihydroxyazotetrazole (1) with a nearly flat structure, such as the salts of aminoguanidine (2), 1,3-diaminoguanidine (3), imidazole (4), pyrazole (5) and triaminoguanidine (6), and a cocrystal of 2-methylimidazole (7), were designed and synthesized. Based on single-crystal diffraction data, thermal decomposition behaviors, and the mechanical sensitivity test, the compounds of 4, 5, and 7 with face-to-face π-π stacking display outstanding thermal stability and insensitivity.

Comparative investigation on the thermostability, sensitivity, and mechanical performance of RDX/HMX energetic cocrystal and its mixture

Molecular mechanics (MM) and molecular dynamics (MD) simulation method were applied to explore the impact of temperature (220-380 K) on the thermostability, sensitivity, and mechanical performance of RDX (1,3,5-trinitro-1,3,5-triazacyco-hexane)/HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) energetic cocrystal and mixture models. The mechanical property, the maximum trigger bond length ([Formula: see text]), binding energy, and cohesive energy density (CED) of the pure RDX, β-HMX crystal, the cocrystal, and mixture models were acquired and compared. The results manifest that temperature has an important impact on the binding capacity between the components of the cocrystal and mixture. The binding energies decrease as the temperature rises, and the cocrystal has larger values than those of mixture. For all the models, the [Formula: see text] increases and the CEDs decrease with the rising temperature, implying that the sensitivity of the explosives increases, while the [Formula: see text] values of the cocrystal are smaller than those of HMX and the CED values are between those of RDX and β-HMX, indicating that the sensitivity has been enhanced through co-crystallization. As the temperature increases, the shear modulus (G), bulk modulus (K), and tensile modulus (E) values of all models have an evident downtrend. Simultaneously, G, K, and E values of the cocrystal model are less than those of RDX and β-HMX, while the K/G ratio and Cauchy pressure (C₁₂-C₄₄) are larger, signifying that co-crystallization can weaken the brittleness and enhance the ductility of the pure crystals. Compared with the mixture, the cocrystal has better ductility and stability.

Theoretical calculation into the effect of molar ratio on the structures, stability, mechanical properties and detonation performance of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane/ 1,3,5-trinitro-1,3,5-triazacyco-hexane cocrystal

Molecular dynamics (MD) simulation was conducted to research the effect of molar ratio on the thermal stability, mechanical properties, and detonation performance of HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane)/RDX (1,3,5-trinitro-1,3,5-triazacyco-hexane) cocrystal explosive at ambient condition. The binding energy, mechanical properties, and the detonation parameters of the pure β-HMX, RDX crystal, and the cocrystal models were got and contrasted. The results demonstrate that molar ratio has a great influence on the properties of the cocrystal system. The binding energy of the cocrystals has the maximum values at the 1:1 molar ratio, indicating that the stability of HMX/RDX(1:1) cocrystal is the best and HMX and RDX may prefer to cocrystallizing at 1:1 molar ratio. What's more, the tensile modulus (E) and shear modulus (G) of the HMX/RDX(1:1) cocrystals have the minimum value, while the C₁₂-C₄₄ and K/G have the maximum value, implying that the cocrystal at 1:1 molar ratio has the best mechanical properties. Simultaneously, the E, K, and G of the cocrystals are all smaller than those of β-HMX's and generally larger than those RDX's, while the Cauchy pressure (C₁₂-C₄₄) and K/G ratio were greater, demonstrating that cocrystallizing can improve the brittleness and enhance the ductility. The detonation velocity (D) and detonation pressure (P) decrease with the rising RDX content, while the properties are still superior to the pure RDX crystal; thus, the energy properties of the cocrystal are still excellent. In a word, HMX/RDX cocrystal at 1:1 molar ratio has the best thermal stability, mechanical properties, and the excellent energetic performance.

Novel strategies for synthesizing energetic materials based on BTO with improved performances

The layer-by-layer assembly of molecules is ubiquitous in nature. Highly ordered structures formed in this manner often exhibit fascinating material properties. A layer hydrogen bonding pairing approach allows the development of tunable energetic materials with targeted properties. A series of unusual energetic compounds based on 1H,1'H-5,5'-bistetrazole-1,1'-diolate (1), such as the salts of 3-amino-1,2,4-triazolium (2), aminoguanidinium (3), and hydrazinium (4), and the cocrystals of 4-amino-1H-pyrazole (5), 2-methylimidazole (6), and imidazole (7), were synthesized using this strategy. The structures of the obtained products 2-7 were fully characterized by elemental analysis, IR spectroscopy, ¹H NMR and ¹³C NMR spectroscopy, and single-crystal X-ray analysis. Their thermal decomposition behavior was studied by differential scanning calorimetry and thermogravimetry. Their mechanical sensitivities and detonation performances were also analyzed in detail. Results show that products 2-7 exhibit higher density, better detonation performances, and more excellent sensitivities than those of the same species of cation salts previously reported.

Preparation and characteristics of a novel PETN/TKX-50 co-crystal by a solvent/non-solvent method

In order to decrease the sensitivity and broaden the application of pentaerythritol tetranitrate (PETN), a novel energetic co-crystal composed of PETN and dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) with high energy and low sensitivity was successfully prepared through the solvent/non-solvent method. The morphology and structure of the as-prepared co-crystal were characterized by scanning electron microscopy (SEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectron spectrometry (XPS), fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and high performance liquid chromatography (HPLC). The thermal decomposition properties were also analyzed by simultaneous thermogravimetry and differential scanning calorimetry (TG-DSC). The safety performance was judged by mechanical sensitivity tests. The SEM results revealed that the prepared new material was homogeneous with a mean granularity of 1 μm and the morphology was distinct from raw PETN and TKX-50. The XRD analysis indicated that a new crystalline formation appeared in the co-crystal which was quite different from the raw materials and their mixture. The XPS analysis showed peak shifts of C, N, O elements in the co-crystal. The FTIR spectra and Raman spectra suggested that hydrogen bond interactions existed between PETN and TKX-50 molecules. The molar ratio of PETN and TKX-50 was 1 : 1 determined by HPLC. There were two thermal decomposition peaks (194.1 °C and 261.3 °C) for the co-crystal at 20 °C min-1, while the raw materials and mixture had only one. Besides, the activation energy of the co-crystal increased compared to the raw materials, indicating better thermal stability of the co-crystal. The impact sensitivity and friction sensitivity of the PETN/TKX-50 co-crystal were reduced compared to raw PETN, and were even better than for 1,3,5-trimethylene trinitramine (RDX). The results showed a prospective application of the prepared PETN/TKX-50 co-crystal in the future.

Nonisothermal decomposition and safety parameters of HNIW/TNT cocrystal

To explore the thermal decomposition behavior and evaluate the thermal safety of the cocrystal 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (HNIW)/2,4,6-trinitrotoluene (TNT), its thermal and kinetic behaviors were studied by differential scanning calorimetry (DSC) technique. With the help of onset temperature (T_e) and maximum peak temperature (T_p) from the non-isothermal DSC curves of HNIW/TNT cocrystal at different heating rates (β), the following were calculated: the value of specific heat capacity (C_p) and the standard molar enthalpy of formation , the apparent activation energy (E_K and E_O) and pre-exponential constant (A_K) of thermal decomposition reaction obtained by Kissinger's method and Ozawa's method, density (ρ) and thermal conductivity (λ), the decomposition heat (Q_d, as half-explosion heat), Zhang–Hu–Xie–Li's formula, Smith's equation, Friedman's formula, Bruckman–Guillet's formula, Frank-Kamenetskii's formula and Wang–Du's formulas, the values (T_e0 and T_p0) of T_e and T_p corresponding to β → 0, thermal explosion temperature (T_be and T_bp), adiabatic time-to-explosion (t_tiad), 50% drop height (H₅₀) for impact sensitivity, critical temperature of hot-spot initiation (T_cr), thermal sensitivity probability density function [S(T)] vs. temperature (T) relation curves with radius of 1 m and ambient temperature of 300 K, the peak temperature corresponding to the maximum value of S(T) vs. T relation curve (T_S(T)max), safety degree (SD) and critical ambient temperature (T_acr) of thermal explosion. Results show that the kinetic equation describing the exothermic decomposition reaction of HNIW/TNT cocrystal is The following thermal safety parameters for the HNIW/TNT cocrystal are obtained: T_e0 = 464.45 K; T_p0 = 477.55 K; T_be = 472.82 K; T_bp = 485.89 K; t_tiad = 4.40 s, 4.42 s, and 4.43 s for n = 0, 1, and 2, respectively; T_cr = 531.90 K; H₅₀ = 19.46 cm; and the values of T_acr, T_S(T)max, SD and P_TE are 469.69 K, 470.58 K, 78.57% and 21.43% for sphere; 465.70 K, 470.58 K, 78.17% and 21.83% for infinite cylinder; and 459.39 K, 464.26 K, 77.54% and 22.46% for infinite flat.

To explore the thermal decomposition behavior and evaluate the thermal safety of the cocrystal HNIW/TNT, its thermal and kinetic behaviors were studied by DSC technique.