Preparation Of N₅^–-based Energetic Compounds Based On Self-assembly

As an important class of high energy density materials（HEDMs）,multi-nitrogen energetic materials have huge military application potential,and all-nitrogen energetic compounds have attracted widespread attention due to their environmentally friendly properties.The compound composed of N-N and N=N can release a large amount of energy during decomposition,and the decomposition product is only N₂,which is harmless to the environment.Through the unremitting efforts of scientists for a long time,pentazolate（cyclo-N₅-）and a series of metal salts,non-metal salts and energetic cocrystal compounds based on cyclo-N₅-were finally synthesized.These achievements have laid a foundation for the application and promotion of all-nitrogen clean explosives.Theoretical calculation results show that cyclo-N₅-can be combined with energetic cations through a self-assembly process to obtain new high-energy compounds.Therefore,in this thesis,cyclo-N₅-is taken as the research object.Based on self-assembly,a series of lead-containing pentazolate coordination polymers and a cyclo-N₅--based energetic cocrystal were synthesized.The relationship between the crystal structure and the properties of the compounds was studied,and their related properties were obtained through characterization.Firstly,the low solubility of AgCl was used to obtain[Pb₄（OH）₄]⁴⁺（N₅^–）₄through metathesis reaction,and then the other two high-energy coordination polymers containing[Pb₄（OH）₄]⁴⁺and N₅-were synthesized through self-assembly.The composition and structure of these three compounds are determined by single crystal X-ray diffraction.They all show unique crystal structures（1D～3D）and very high density(3.913～4.537 g·cm^-3).In addition,these compounds were further characterized by infrared spectroscopy,Raman spectroscopy,SEM-EDX,MS and DSC,and the results showed that these compounds have good thermal stability.Through the calculation of the activation energy of the mixture of AP and the three compounds,the effect on the thermal decomposition of AP was studied.The results showed that perchlorate has a significant catalytic effect on AP.At the same time,these compounds all show low mechanical sensitivity（IS:9.5～20J,FS:120～240N）and good detonation performance(D:6.340～6.890km·s^-1,P:34.92～50.56 GPa).Secondly,a high-energy coordination polymer containing Pb²⁺and N₅^–was designed and synthesized by self-assembly using the hydrate of Na N₅as the raw material.The structure of the compound was confirmed by single crystal X-ray diffraction,and it has a relatively high crystal density of 2.852 g·cm^-3and unique crystal structure.The compound was characterized by infrared spectroscopy,Raman spectroscopy,SEM-EDX,MS and DSC.Its initial decomposition temperature was 89°C,and the thermal stability was acceptable.In addition,by calculating,this compound is believed to catalyze the decomposition of AP.Moreover,the detonation velocity and detonation pressure of the compound were 6.155km·s^-1and 22.37 GPa,respectively.Its detonation pressure was higher than that of the traditional explosive TNT.IS and FS which are measured by the standard BAM method are 20J and 240N,respectively.Its mechanical sensitivity is higher than most lead-based high-energy metal organic frameworks,but lower than RDX,HMX and TNT,showing that it is an insensitive energetic coordination polymer.Finally,Acyclo-pentazolateanion-basedenergeticcocrystal（NH₃OH⁺N₅^-）₂·NH₃OH⁺Cl^-·H₂O was designed and synthesized by Ag N₅（or NH₃OH⁺N₅^-）and hydroxylamine hydrochloride（NH₃OH⁺Cl^-）as raw materials.The single crystal of the compound was cultivated by solvent volatilization,and the structure and performance of the compound were characterized by single crystal diffraction,IR,DSC and elemental analysis.The crystal molecules form a stable structure through a strong hydrogen bond network andπ-πinteractions.The peak temperature of the DSC exothermic peak is 96.7°C,showing the compound has good stability.The detonation velocity of the compound is calculated to be8.260 km·s^-1,and the detonation pressure is 23.79 GPa;it has low impact and friction sensitivities（IS>40 J;FS>360 N）,which indicates that it is an insensitive energetic cocrystal compound.