Study On Excitation Mechanism Of Energetic Materials Under External Stimulation

At present,energetic materials have important applications in military affairs,industry,aerospace and other fields.Energetic materials can react independently and release energy under external energy loading,and energetic materials are susceptible to external energy during producing,keeping,transporting and using,resulting in resolving or exploding,causing serious damage and injury to the country,society and people.Starting with the microstructure of energetic materials under external energy loading,and exploring the mechanism of excitation,which is beneficial to improve the safety performance of energetic materials.Therefore,this paper mainly studies the excitation mechanism of energetic materials under impact,pressure and heat loading,which lays a foundation for further improving the safety properties of energetic materials.This paper mainly includes three parts:the first part study the excitation mechanism of RDX under impact loading,and analyze the radial distribution function RDX perfect supercell and vacancy supercell at impact velocity of 10 km/s and 11 km/s,and explore the influence of impact velocity and molecular vacancy on RDX excitation mechanism.The results show that the radial distribution function peak intensity of the N-NO₂ bond decreases with the increase of the impact velocity,while the radial distribution function peak intensity of the H-O bond increases,indicating that some N-NO₂ bonds break or C-H bonds break,and that hydrogen ions transfer to oxygen in the nitro group to form hydroxyl groups.The possible initial reaction of the RDX is N-NO₂ fracture or C-H bond fracture as the impact velocity increases.However,the calculation shows that the peak intensity of the radial distribution function of molecular vacancy crystal is higher than that of the corresponding perfect crystal,which indicates that the existence of vacancy defect will unload part of the impact pressure,and reduce the impact on the chemical bond,then inhibit the initial reaction.And the second part study the excitation mechanism of benzofurazan under pressure loading,Starting with the vibration characteristics of benzofurazan,the activation vibration modes of benzofurazan under different pressure were obtained according to Raman experimental spectra,and the vibration of bond length,bond angle and dihedral angle were analyzed by first principle method.The results show that the initial decomposition of benzofurazan is an open-loop reaction N?O?-O position,and the optimal reaction channel leading to the initial open-loop reaction is dihedral angle O-C-N?O?-O benzofurazan external vibration(518 cm^-1).Then the transition state structure during the initial reaction is determined by IRC method,and the reaction energy barrier is calculated to be about 18.0 kcal/mol,and the scanning energy barrier obtained by O-C-N?O?-O is about 22.6 kcal/mol which is consistent.And the three part study the excitation mechanism of liquid-phase nitromethane under heat loading,analysing the vibration characteristics of different modes of liquid-phase nitromethane molecules by CARS experimental system,and then probing into the excitation mechanism.The results show that the phase loss time of C-H bond stretching vibration of 3000 cm^-11 is only 0.18 ps,much less than 6.2 ps phase loss time of 917 cm^-1representing the stretching vibration between methyl and nitro groups,and indicate that the stretching vibration of the C-H bond is more likely to be heated by phonon than the stretching vibration of the C-N bond.C-H bonds of nitromethane molecules are expected to be excited first and cause initial chemical reactions under heat loading.