Synthesis And Properties Of C-N Combined And Fused Triazole-based Energetic Salts

Recently, much attention have been focused on the development of modern highenergy density materials (HEDMs) with improved performance and low sensitivity as wellas environmental compatibility in the research of energetic materials. Unfortunately, mostenergetic materials with high performance characteristics concomitantly tend towardgreater sensitivity. Thus, suitable design strategies are necessary to guide energeticmaterials synthesis to harmonize the contradictory nature of high performance and lowsensitivity.One exciting developments in the field of HEDMs are heterocyclic energetic saltswith high nitrogen content. Salt-based energetic materials often possess advantages overnonionic molecules, as these salts tend to exhibit lower vapor pressures and higher thermalstability than their atomically similar nonionic analogues. In addition, their properties arereadily improved and optimized through judicious combination of different anions andcations, as well as a result of independent modification of cationic and anionic components.In this thesis,3-nitro-1-(2H-tetrazol-5-yl)-1H-1,2,4-triazol-5-amine (HANTT) andits eight nitrogen-rich energetic salts were designed and synthesized successfully, which were then fully characterized using1H NMR，13C NMR，IR and EA. HANTT，its guanidinium, aminoguanidinium and1,5-diamino-tetrazolium salts were further confirmed by single-crystal X-ray diffraction. All the salts exhibit excellent thermal stabilities with decomposition temperatures over the range231oC321oC. The measured densities of enegetic salts ranged between1.65-1.81g cm-3. HANTT and its energetic salts are insensitive to impact, friction. All energetic salts are insensitive against electrostatic discharge (ESD>44J) while while the neutral compound HANTT is relatively insensitive (ESD=7.04J). The heats of formation of these energetic salts were calculated to be in the range of1637.22465.2kJ kg1by Gaussian software based on the designed isodesmic reactions. The detonation pressures and velocities of these energetic salts were calculated by EXPLO5to be between22.632.6GPaand77428779m s1, respectively. Among them, ammonium ANTT (vD=8507ms1, P=29.6GPa) has an excellent detonation performance due to its high densityand moderate oxygen balance; hydroxylammonium ANTT possesses the highest density and the best oxygen balance, thus confirming its excellent detonation performan ce (vD=8779m s1, P=32.6GPa). Finally, in view of thermal and mechanical stabilities, both of them possess the best comprehensive properties among the series salts that allow them a promising application.A unique and facile approach to7-nitro-4-oxo-4,8-dihydro-[1,2,4]triazolo[5,1-d][1,2,3,5]tetrazine2-oxide (HBCM) hasbeen developed. This process involved the cleavage of tetrazole ring followed bycyclization of C=N bond with nitro group. In sharp contrast to HBCM, the sodium salt ofHBCM is stable in air and thus transformation into salt-based compounds would be areasonable and simple approach to overcome the hydroscopicity of HBCM. Energetic saltsof HBCM are stable in air and decompose in the range from197℃to269℃. Theiroxygen balance range from48.5%to20.6%. All salts are insensitive toward impact andtend to be insensitive against friction and electrostatic discharge. The densities of allnitrogen-rich salts lie in the range between1.77g cm-3and1.97g cm-3while those of salts3.6and3.83.10fall in the range designated for new HEDMs (1.82.0g cm-3). Mostenergetic salts show highly endothermic heat of formation in the range from151.8kJ mol-1(3.7) to475.6kJ mol-1(3.9). Their detonation velocities and detonation pressures werecalculated to be7856m s1to9069m s1and25.2GPa to39.5GPa, respectively. Amongthem, hydroxylammonium salt (3.6) shows high density (d=1.97g cm-3), acceptabledecomposition temperatures (Td=197℃), low sensitivities (IS>40J, FS=324N,negative ESD), excellent detonation velocity (9069m s1), and pressure (39.5GPa).Especilly the combination of the high performance superior to RDX and low sensitivity tomechanical stimuli highlights hydroxylammonium salt (3.6) as potential HEDMs.A novel energetic compounds N-(5-(1H-tetrazol-5-yl)-2H-1,2,3-triazol-4-yl)-4-nitro-1,2,5-oxadiazol-3-amine (HTANFT), in which there are four energetic fragments (nitrogroup, the tetrazole ring,1,2,3-2H-triazole and the furoxan ring) emerging together for thefirst time, and its ten energetic salts were design and synthesized. The crystal structures ofneutral HTANFT was determined by single-crystal X-ray diffraction. The decompositiontemperature of these energetic salts were measured in the range of193-241oC. Themeasured densities of enegetic salts ranged between1.601.83g cm-3. The IS and FS ofenergetic salts4.24.11are higher than those of HTANFT (IS=25J, FS=128N, ESD= 5.39J), whereas their ESD are better than that of HTANFT. The IS of energetic saltsranged between2740J; the FS ranged between160324N; the ESD ranged between0.694.64J. The heats of formation were calculated between857.5-1308.7kJ mol1. Thedetonation pressure and velocity of the new energetic salts were calculated using EXPLO5to be24.632.9GPa and79568757m s-1. The vDof salt4.3(vD=8703m s1) iscomparable to that of RDX (vD=8748m s1). Salt4.5possesses the highest density and thesecond highest△Hfamong the salts, thus confirming its excellent detonation performancegiven a P of32.1GPa and a vDof8741m s1. Among this family of salts, salt4.6has thebest detonation performance (P=32.9GPa, vD=8757m s1) because of its ideal OB andhigh density. Therefore, salts4.3,4.5and4.6are potential alternatives to RDX in explosiveapplications based on their good thermal stabilities, detonation properties, high nitrogencontents and low IS values.