| The detonation processes of energetic materials will undergo extreme conditions such as high pressure and high temperature(HP-HT).The exploration of microstructural evolution and reaction kinetics of energetic materials under high temperature and high pressure contributes to the understanding of their microscopic physicochemical origins,which can provide critical experimental data for the design and synthesis of novel energetic materials.Furthermore,the knowledge of the thermo-mechanic response and reaction behavior of energetic materials is critical for addressing the safety issues such as the sensitivity mechanisms.This thesis investigates the layered-packed aromatic heterocycle energeric materials LLM-105 and DAAF.The structural evolution and the chemical reaction mechanisms of LLM-105 and DAAF under high pressure and high temperature conditions are explored by HP-HT experiments and molecular dynamics simulations.The interaction of these two types of energetic materials with water under HP-HT is also thoroughly discussed.Understanding the response of energetic materials at extreme conditions not only provide theoretical guidance for the design and synthesis of novel energetic materials,but also be important when energetic materials are in manufacture,transportation and military applications,as well as the green disposal of expired explosives.The following are the key contents and outcomes:In the first chapter,the high pressure science and technology and its application fields,the review of energetic materials at extreme conditions are introduced in brief.The objective and significance of the thesis are also demonstrated.In the second chapter,the thermal decomposition of LLM-105 under high pressure are examined and the pressure effects are discussed in detail.Thermal decomposition pressure-temperature boundaries have been constructed as well.The experimeantal methods such as Raman measurements were performed to obtain the pressuretemperature phase diagram at 0-4.6 GPa and the decomposition products were determined.The experimets reveal that increasing pressure decelerates the thermal decay processes,i.e.when the pressure is from atmospheric to 4.6 GPa,the decay temperature increases from 352℃ to 560℃.To further study the pressure effects and the underlying mechanisms for the initial decomposition of LLM-105,the molecular dynamics calculations were conducted.The initial chemical reaction steps,the evolutions of major chemical species including the reactant,the major intermediates and the products,as well as potential energy evolution were discussed to confirm the coupling effects of pressure and temperature.The initial steps under HP-HT includes the intramolecular H transfer,te NO2 partition and the intermolecular hydrogen transfter.Molecular dynamics confirms the decomposition products found in the experiments.In particular,we discussed the intermolecular hydrogen transfer under HP-HT conditions in detail.This work significantly contributes to understanding the thermal decomposition of LLM-105 as a function of pressure using experimental and computational methods.In the third chapter,the interaction between LLM-105 and water under HP-HT are investigated.The pressure-temperature water dissolution boundary and the temperature-pressure decomposition boundary of the water environment were established,and the green treatment path of explosives was discovered.The dissolution behavior of LLM-105 in high pressure and high temperature water is related with the initial pressure,i.e.,when the initial pressure is less than 1 GPa,LLM-105 dissolve in the high temperature water;when the initial pressure is above 1 GPa,LLM-105 only decomposes in the high temperature water.The high pressure and high temperature water can not only act as a solvent when dissolving the samples,but also can be a catalyst.When the water account for a large percentage of the whole volume,it can dissolve the sample;while the water is only a small portion of total volume,it conducts as a catalyst.The presence of water significantly lowered the LLM-105 crystal decomposition temperature.When the HP-HT water exist,the decompostion temperature of the crystal reduces from 470℃ to 320℃ at 0.7 GPa.After LLM-105 has been dissolved,the sample can be recrystallized under appropriate conditions.The recrystallization is associated with the initial pressure and the percentage of the sample.Through Raman spectroscopy and a single crystal XRD analysis,the recystal sample was identified as NH4HCO3.This research supports environmentally friendly approaches to treating energetic materials.In the fourth chapter,the thermal decompositions of DAAF under high temperature and high temperature-high pressure conditions are studied.The interaction between DAAF and water under HP-HT is also investigated.Under high temperature and ambient pressure,the decomposition sequence of DAAF begins with the unimolecular homolysis of C-Nazoxy and N-H in NH2 group simultaneously and further followed by the rupture of furazan ring.When neon is used as the pressure transfer medium,the initial decomposition of DAAF is the breakdown of N-H bond under HPHT,which facilitates the bimolecular hydrogen transfer from NH2 group to Oazoxy-N and finally induces the dissociation of the O from azoxy group,resulting in the conversion of DAAF to DAAzF.DAAF crystals can be dissolved in HP-HT water when the pressure transfer medium is water.Moreover,big and fine rod-like DAAzF crystals are formed above 493 K at 0.8 GPa when employing water as pressure transmitting medium.The presence of ultra-high temperature water leads to the bimolecular hydrogen transfer and dissociation of Oazoxy from DAAF more easily for the interaction of Oazoxy...H and more DAAF crystals transformation into DAAzF.In the fifth chapter,the research content and the results of this paper are summarized,and an outlook on the future is given. |
