Kinetics of thermal decomposition of ε-hexanitrohexaazaisowurtzitane by TG-DSC-MS-FTIR

Pyrolysis Kinetics and Combustion Behaviors of a High-Nitrogen Compound, 4,4′-Azobis(1,2,4-triazole)

To study the thermal decomposition behavior of 4,4′-azobis(1,2,4-triazole) (ATRZ), the non-isothermal thermal decomposition kinetics of ATRZ were studied using the thermogravimetric–differential scanning calorimetry (TG–DSC) method. The TG–DSC of ATRZ was analyzed at heating rates of 5, 10, 15, and 20 K·min⁻¹ in an argon atmosphere. The thermal decomposition kinetic parameters at peak temperature (T_p), such as apparent activation energy (E_a) and pre-exponential factor (lgA) of ATRZ, were calculated using the Kissinger, Ozawa, and Satava–Sestak methods. E_a and lgA calculated using the Kissinger, Ozawa, and Satava–Sestak methods are very close, at 780.2 kJ·mol⁻¹/70.5 s⁻¹, 751.1 kJ·mol⁻¹/71.8 s⁻¹, and 762.1 kJ·mol⁻¹/71.8 s⁻¹, respectively. Using a combination of three methods, the reaction mechanism function g(α) of ATRZ was obtained. The results show that the decomposition temperature of ATRZ is about 310 °C, and the decomposition is rapidly exothermic. The pyrolysis path of ATRZ was investigated through a pyrolysis-gas chromatography mass spectrometry (PY-GC/MS) experiment. ATRZ has three different decomposition paths and finally generates N₂, HC-N-CH, N≡C-N, and HC=N-C≡N. The laser ignition combustion duration of ATRZ was 0.5033 s and the peak temperature was 1913 °C. The laser ignition combustion duration of ATRZ+CL-20 was 1.0277 s and the peak temperature was 2105 °C. The rapid energy release rate of ATRZ promotes the combustion energy release of CL-20.

Preparation of CNTs Coated with Polydopamine-Ni Complexes and Their Catalytic Effects on the Decomposition of CL-20

To improve the condensed-phase reaction rate of ε-CL-20, polydopamine (PDA)-nickel complex-coated multiwalled carbon nanotubes (CNTs) have been prepared and used as combustion catalysts. The PDA-Ni complex has been prepared and in situ coprecipitated with ε-CL-20 by an antisolvent crystallization process in its dimethyl sulfoxide (DMSO) solution. It has been shown that crystalline CL-20 composites included with PDA-Ni complexes are polygon-shaped with a smooth surface and an average diameter of 10-15 μm, whereas it is 140 μm for raw ε-CL-20 crystals. The catalytic reactivity of the complex on thermolysis of CL-20 has been investigated using the differential scanning calorimetry (DSC) and thermogravimetry (TG)-coupled Fourier transform infrared (FT-IR) spectroscopy technique. It has been found that CNT@PDA-Ni complexes have catalytic effects on the decomposition of ε-CL-20 by decreasing/shifting of the exothermic peak from T _p = 240.1 to 238.7 °C. The FT-IR spectra of CL-20 decomposition products under the effect of the catalyst predominantly show peaks at 1274, 1644 and 1596, 1912, 2265, and 1956-1800 cm^-1, indicating the presence of fragments with N₂O, NO₂, NO, HNCO, and NO/CO, respectively. The change in the ε-CL-20 decomposition mechanism should be attributed to the catalytic action of CNT, decreasing the formation of NO₂. Also, under the effect of the carbon-based catalyst, the HNCO formation was detected at another temperature in comparison with raw CL-20, with peak absorption at 224.1 vs 232.3 °C and the evolution was completed at 250.8 vs 246.2 °C, respectively.

Nitrated Graphene Oxide Derived from Graphite Oxide: A Promising Energetic Two-Dimensional Material

In order to synthesize a novel two-dimensional energetic material, nitrated graphene oxide (NGO) was prepared by the nitrification of graphite oxide to make a functional modification. Based on the morphological characterization, the NGO has a greater degree of curl and more wrinkles on the surface. The structure characterization and density functional theory calculation prove that epoxy and hydroxyl groups on the edge of graphite oxide have reacted with nitronium cation (NO2+) to produce nitro and nitrate groups. Hydrophobicity of NGO implied higher stability in storage than graphene oxide. Synchronous simultaneous analysis was used to explore the decomposition mechanism of NGO preliminarily. The decomposition enthalpy of NGO is 662.0 J·g-1 and the activation energy is 166.5 kJ·mol-1. The thermal stability is similar to that of general nitrate energetic materials. The hygroscopicity, thermal stability and flammability of NGO prove that it is a novel two-dimensional material with potential applications as energetic additives in the catalyst, electrode materials and energetic devices.

Laser-Ignited Relay-Domino-Like Reactions in Graphene Oxide/CL-20 Films for High-Temperature Pulse Preparation of Bi-Layered Photothermal Membranes

Light-ignited combustions have been proposed for a variety of industrial and scientific applications. They suffer, however, from ultrahigh light ignition thresholds and poor self-propagating combustion of typical high-energy density materials, e.g., 2,4,6,8,10,12-(hexanitrohexaaza)cyclododecane (CL-20). Here, reported is that both light ignition and combustion performance of CL-20 are greatly enhanced by embedding ε-CL-20 particles in a graphene oxide (GO) matrix. The GO matrix yields a drastic temperature rise that is sufficient to trigger the combustion of GO/CL-20 under low laser irradiation (35.6 mJ) with only 6 wt% of GO. The domino-like reduction-combustion of the GO matrix can serve as a relay and deliver the decomposition-combustion of CL-20 to its neighbor sites, forming a relay-domino-like reaction. In particular, a synergistic reaction between GO and CL-20 occurrs, facilitating more energy release of the GO/CL-20 composite. The novel relay-domino-like reaction coupled with the synergistic reaction of CL-20 and GO results in a deflagration of the material, which generates a high-temperature pulse (HTP) that can be guided to produce advanced functional materials. As a proof of concept, a bi-layered photothermal membrane is prepared by HTP treatment in an extremely simple and fast way, which can serve as a model architecture for efficient interfacial water evaporation.