Desensitizing Effect of Graphene Oxide on Thermolysis Mechanisms of 4,4′-Azo-1,2,4-triazole Studied by Reactive Molecular Dynamics Simulations

Graphene oxide (GO) has obvious desensitizing effect on the thermal decomposition of energetic materials such as HMX, CL-20, etc. 4,4'-Azo-1,2,4-triazole (ATRZ) is known as a new type of energetic material with high N content; the underlying thermal decomposition mechanism of graphene oxide-ATRZ (GO-ATRZ) complex with low sensitivity has not been studied. The present work studies the thermal decomposition mechanisms of GO, ATRZ,and the GO-ATRZ complex (the number of carboxyl groups on GO:ATRZ = 2:1) by the ReaxFF molecular reactive dynamic simulations and kinetics calculations. As a result, it has been found that the main decomposition pathway of GO is the exfoliation of hydroxyl and carboxyl groups on the graphene sheet, whereas ATRZ breaks its five-membered ring as the main decomposition path, and the ring further decomposes into small molecules, such as CHN, N2, HN2, H2N2, etc. The major effect of GO on ATRZ is probably derived from the stable graphene sheet, which has a space effect on ATRZ, and the strong oxidizing hydroxyl groups produced during GO decomposition, which results in the formation of CON and CHON. By calculating the activation energy of N2 generation in the reactions, it can be concluded that the addition of GO can increase the decomposition activation energy of ATRZ (41.1 kJ·mol-1) in comparison with that of its pure substance (25.0 kJ·mol-1). Therefore, GO can be combined with ATRZ as a desensitizer where GO can improve the molecular stability of ATRZ.