Synthesis And Properties Of Energetic Compounds Based On 1,2,4-oxadiazole And 1,2,3-triazole Skeletons

In the past few decades,many high energy density materials（HEDMs）have been synthesized.Based on the considerations of actual production,transportation and application,requirements on safety,stability and environmentally friendly have been put forward for these energetic materials.After continuous exploration,heterocycles with high nitrogen and oxygen contents have attracted great attentions from energetic materials researchers and a large number of energetic compounds featuring the combination of energetic groups and heterocycles have been documented and show very impressive properties.In this thesis,five-membered heterocycles 1,2,4-oxadiazole and 1,2,3-triazole,with high energy and stability were selected as the skeleton for constructing two types of energetic compounds.At the same time,their energetic salts were synthesized successfully.All the obtained energetic compounds were fully characterized,and their energetic properties and safety were also studied.5,5’-Dinitramino-3,3’-bi（1,2,4-oxadiazole）,a new heterocyclic energetic compound,was synthesized by the simple nitration of 5,5’-diamino-3,3’-bi（1,2,4-oxadiazole）with 95%fuming nitric acid.By treating 5,5’-diamino-3,3’-bi（1,2,4-oxadiazole）with two equivalents of energetic bases or their salts,a serial of energetic salts based on nitrogen-rich cations were readily obtained.All synthesized energetic salts exhibit excellent thermal stability and high energy.Among them,the hydroxylammonium salt shows the best comprehensive properties(ρ=1.88 g·cm^-3;T_d=190℃;P=36.2 GPa;v _D=8916 m·s^-1).Additionally,the guanidinium salt possesses excellent thermal stability with an onset decomposition temperature of 317℃,which is the most thermally stable energetic salt in this work.A methylene bridged 1,2,4-oxadiazole skeleton energetic compound was constructed through a simple,safe and efficient route.Then the products from the ring-forming reaction reacted with an excess amount of ammonia in methanol to give3,3’-methylenebis（1,2,4-oxadiazol-5-amine）.Further nitration of 3,3’-methylenebis（1,2,4-oxadiazol-5-amine）gave N,N’-（methylenebis（1,2,4-oxadiazole-3,5-diyl））dinitramide.A serial of N,N’-（methylenebis（1,2,4-oxadiazole-3,5-diyl））dinitramide based energetic salts pairing with nitrogen-rich cations were readily obtained by treating with two equivalents of free bases.The physicochemical and energetic properties of these energetic compounds,including density,thermal stability,and sensitivity,were investigated and calculated.Among them,the hydrazinium salt shows the best detonation performances(P=27.1 GPa;v _D=7962 m·s^-1).3-（5-Amino-1H-1,2,3-triazol-4-yl）-1,2,4-oxadiazol-5-amine was successfully synthesized through four steps from 5-amino-1H-1,2,3-triazole-4-carbonitrile,and then different nitrification approaches were applied to achieve its single-nitrated and full-nitrated products,namelyN-（4-（5-amino-1,2,4-oxadiazol-3-yl）-1H-1,2,3-triazol-5-yl）nitramideand N-（3-（5-（nitroamino）-1H-1,2,3-triazol-4-yl）-1,2,4-oxadiazol-5-yl）nitramide.By treating above intermediates with excess free bases,a serial of energetic salts were readily obtained.Among these salts,hydroxylammonium and hydrazinium salts of N-（3-（5-（nitroamino）-1H-1,2,3-triazol-4-yl）-1,2,4-oxadiazol-5-yl）nitramide possess the best detonation performances(P=30.5 GPa,v _D=8493 m·s^-1 and P=33.6 GPa,v _D=8682 m·s^-1).The heat of detonation data（Q）of these salts are distributed from 3077 to 5787 J g^-1.Among them,hydroxylammonium salt of N-（3-（5-（nitroamino）-1H-1,2,3-triazol-4-yl）-1,2,4-oxadiazol-5-yl）nitramide has the most outstanding heat of detonation reaching 5787 J g^-1.The novel nitration of NH on 1,2,3-triazole ring was achieved and several nitrogen-rich energetic compounds were further synthesized based on the key intermediate4-azido-5-（chlorodinitromethyl）-2-nitro-2H-1,2,3-triazole.Starting from 4-amino-1H-1,2,3-triazole-5-carbonitrile,4-azido-5-（chlorodinitromethyl）-2-nitro-2H-1,2,3-triazole was successfully constructed through four steps,which is a promising energetic oxidizer（OB=2.7）with good detonation performances(v _D=8520 m·s^-1,P=33.26 GPa).Subsequently,the dechlorination of 4-azido-5-（chlorodinitromethyl）-2-nitro-2H-1,2,3-triazole was carried out by reacting with KI to yield a lead-free primary explosive potassium4-azido-5-（dinitromethyl）-2H-1,2,3-triazole.Additionally,diammonium and dihydrazinium salts were also successfully synthesized and characterized.A new reaction was found in the process to get suitable crystals of dihydrazinium salt for X-ray diffraction measurement and6H-[1,2,3]triazolo[4,5-d][1,2,3]triazine-6,7-diamine,which is a promising erosion-reduced gun propellant ingredient or gas generator due to its high nitrogen content of 73.66%was finally obtained.Also,the compound shows good thermal stability（T_d=203℃）and is insensitive to mechanical stimuli,while the detonation velocity and detonation pressure reach8421 m·s^-1 and 26.0 GPa,respectively.