Study On The Structure Evolution And Decomposition Mechanism Of LLM-105 Under High Temperature And High Pressure

Energy and safety are the two most important properties of energetic materials for practical applications.Understanding the physicochemical origin of energy and safety is essential to design and synthesize novel high-energy density materials.Since first synthesized about 20 years ago,LLM-105 has been regarded as a representative of the new generation of low sensitive energetic materials.In this work,we carry out a systematic study of the thermo-mechanic response of LLM-105 at high temperature and pressure.The main work of this thesis includes:(1)We study the pressure and thermal effect on the crystal structure of LLM-105.In diamond anvil cell(DAC)experiments combined with Raman spectroscopy and first-principle calculation,we examine the vibrational spectrum and polymorphic behavior of LLM-105.We find that the LLM-105 phase remains stable from ambient conditions to 30GPa.And there is no heat induced phase transition until thermal-induced decomposition,which is in agreement with the previous studies.Our findings indicate that LLM-105 has good structural stability.(2)We study the mechanism of the primary thermal decay steps of condensed state LLM-105.Four pathways are identified to initiate the thermal decay,i.e.,the intramolecular H transfer from a NH2 group to its neighboring acyl O atom,the dissociation of C-NO2 bond,and the partition of acyl O and the partition of O from a NO2 group.The intramolecular H transfer and the C-NO2 partition dominate the initial decay steps at relatively low and high temperatures,respectively,while O partitions each occurs once only at high temperature.Importantly,we find that the intramolecular H transfer is reversible which can partly be responsible for the low sensitivity of LLM-105.In this work,we investigated the response of LLM-105 under the effect of temperature and pressure.Additionally,we examined the thermal decomposition of condensed state LLM-105.The results of this thesis are of great importance to design appropriate usage,transport and storage methods for this high energetic density material.Further,we have put forward the future work of LLM-105.We will concentrate on the pressure effect on the thermal decomposition of LLM-105.In a word,this study may provide significant implications for the understanding and the development of energetic materials.