Synthesis,Structure and Properties of Tri/Tetrazole Energetic Compounds

Author:Zhang Yin Li

Supervisor:chen san ping

Database:Doctor

Degree Year:2018

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Pages:153

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In the energetic materials field,the contradiction between energy and sensitivity of energetic materials becomes more acute,and so insensitive high-energy-density materials(HEDMs)are central to research in the area.The tri/tetrazole compounds have high nitrogen content,high density,good stability,various coordination modes,and easy to form hydrogen bonds,so that are good choice for new types HEDMs.In this dissertation,14 energetic compounds were prepared by using tri/tetrazole compounds as energy sources.The structures,thermal decomposition mechanisms,detonation parameters and sensitivities of the energetic compounds were studied,that will provid practical and theoretical basis for screening new generation HEDMs.The main research contents and conclusions are as follows:(1)2,3-bis(5-1H-tetrazolyl)pyrazine(H2DTZPZ),3,3′-diamino-5,5′-bis(1H-1,2,4-triazole)(DABT),5-tetrazolyl-3-triazole(H2tztr)and 5-pyrazinyltetrazole(pzta)are used as energetic ligands,and 11 energetic complexes have been prepared:[Co(pzta)2(H2O)2](1),[Ag(pzta)]n(2),[Cu(pzta)2(H2O)2]·H2O(3),{[Cu(pzta)2]·H2O}n(4),[Ag2(DTZPZ)]n(5),[Cu(H2O)(C2O4)(DABT)]·H2O(6),[Cu(H2O)(DABT)2](NO3)2·H2O(7),[Cu(tztr)]n(8),[Pb(Htztr)2H2O]n(9),[Li2(Htztr)2(H2O)4](10)amd[K(Htztr)(H2O)]n(11).1,3,6 and 7 are mononuclear complexes,and the structural analysises show that pzta and DABT both use a bidentate chelation coordination mode.In 2,each pzta bonds with three Ag(Ⅰ)atoms in a tetradentate chelation/bridging coordination pattern,and a two-dimensional layered structure is established.In 4,the one-dimensional chain structure is formed by pzta bonding with two Cu(Ⅱ)atoms in a tridentate chelation/bridging coordination mode.In 5,a three-dimensional framework structure is formed by DTZPZ bonding with Ag(Ⅰ)atoms in an octadentate bridging coordination mode.In 8,each H2tztr bonds with four copper(Ⅱ)atoms in a pentadentate coordination mode to form a three-dimensional framework structure.In 9,every H2tztr bonds to two Pb(Ⅱ)atoms in a bidentate bridging mode,and the complex shows a two-dimensional lamellar structure.10 a and 10 b are binuclear complexes and H2tztr display monodentate coordination,10 a is converted to polymorphic10 b in nitric acid solution.11 is a two-dimensional layered coordination polymer,and each H2tztr exhibits tetradentate chelate/bridging coordination mode with K(Ⅰ)atoms.The ranges of nitrogen content and density for 11 energetic complexes are:31.75%-54.75%,1.5553 g·cm-3(11a)-1.7629 g·cm-3(3)-2.812 g·cm-3(11a).(2)Three energetic supramolecular compounds,MATA·2(HNO3)(12),DABT·2(NO3)(13)and DNBT·Atrz(14),were synthesized with 3,3′-Dinitro-5,5′-bis(1H-1,2,4-triazole)(DNBT),4,4′-azo-(1,2,4-Triazoles(Atrz),3,3′-Diamino-5,5′-bis(1H-1,2,4-triazole)(DABT)and 2-Methyl-5-amino-1,2,4-triazole(MATA).The structural analysis shows that:12 and 14 are energetic cocrystal compounds,and two-dimensional supramolecular structures are formed through hydrogen bond andπ-πstack between molecules.13 is an energetic salt,DABT2+and NO3-through hydrogen bonding andπ-πstacking interactions form a three-dimensional supramolecular structure.The ranges of nitrogen content and density are:37.50%(12)-68.27%(14),1.596g·cm-3(14)-1.820g·cm-3(12).(3)The thermodynamic properties of energetic compounds were studied.The constant-capacity heats of combustion of the energetic compounds(4,5,and 8-14)were measured,and the standard molar enthalpies of formation for 4,5,and 8-14 were calculated:2911.86 kJ·mol-1(4)-3433.59 k J·mol-1(11),-409.54 kJ·mol-1(12)-1502.89 k J·mol-1(14).The standard molar enthalpies of formation(4,5,8-11,and 14)are all positive values and indicate that they are all thermodynamically unstable.The decomposition process should release a lot of heat.Based on the DSC technique,the activation enthalpies,activation entropies and activation free energies of the complexes(2-7 and 9)were calculated.In the process of initial exothermic decomposition,the activation entropies of complexes(2,3,4,5,7 and 9)are positive,and they are all driven by entropy.Once the main frame structures are destroyed,the exothermic decomposition processes occur again,the activation entropies are less than zero(such as complexes 5,6and 7),the activation enthalpies decreases,and the entropy changes are no longer the driving force of the reaction.(4)The thermodynamic properties of energetic compounds were studied.Based on the TG-DSC techniques,the thermal stabilities and thermal decomposition mechanisms of the complexes were studied.The results show that the coordination polymers(2,5,8 and 11)were rapidly decomposed in one step and the decomposition temperatures as high as290°C(2)-390°C(5).Based on the DSC curves,the apparent activation energies of the seven complexes in the initial exothermic decomposition stage were obtained using the Kissinger’s and Flynn-Wall-Ozawa’s methods,the apparent activation energies(>200kJ·mol-1)of complexes(2,3,4,5,7 and 9)indicate that that have high thermodynamic stability.Based on the TG/DTG analysis of complexes,three kinetic factors and kinetic equations of the three energetic complexes were obtained by combining non-isothermal multiple scanning rates and non-isothermal one-scanning rate.(5)The energy characteristics of energetic compounds were studied.The explosion heats of the complexes were calculated by using density functional theory.The Kamlet-Jacobs equations were used to estimate the detonation velocities and the detonation pressures.The results show that the solvent-free coordination polymers(2,5 and 8)and the coordination polymer 11(N%50%)have excellent detonation properties:detonation heat 3.397kcal·g-1,detonation velocities 9000 m·s-1,and detonation pressures>42 GPa.The detonation parameters of energetic cocrystal compounds and energetic salt were estimated using the nitrogen equivalent formulas and the K-J equations.The detonation pressures of12,13 and 14 were higher than that of TNT.(6)The sensitivities and safetis of energetic compounds were studied.The results show that thermal explosion critical temperatures of complexes(2,4,5,6 and 9)are higher than300°C and explain high safety performance.Complexes are all insensitive.12,13,14 have lower impact sensitivity and friction sensitivity than TNT.