Design And Manipulation Of Microstructure Of HMX Based On Supramolecular Assembly-Disassembly Method

In order to improve the performance of explosives,the physical and chemical properties and performance of explosives have been enhanced,and the microstructure and crystal morphology of explosive has been efficiently adjusted to obtain explosive with specific micro-nano structure,which is also an important field in research of insensitive high explosive(IHE).Cyclotetramethylene-tetranitramine(HMX,C4H8N8O8),the single-compound explosive with best combination property,has been widely used in military and civil areas.For the sake of the safety performance of HMX and improve its sensibility to the specific stimulation,many attempts in recent years have been focused on adjustment of microstructures of HMX to increase the output of energy or other performance.Especially,micro-nano HMX with significantly large specific surface area and large amount of active atoms and groups at the surface possesses better performance for detonation and boost.In this work,the strategy of supramolecular assembly-disassembly has been proposed to design and control the microstructure of HMX In the process of supramolecular assembly,different guest molecules were introduced and the crystal of supramolecular compound with modulate structures were prepared by controlling conditions of crystallization process.After that,the guest molecules were removed in process of fast disassembly by using physical and chemical methods in controlled conditions to eliminate the interactions between host and guest molecules.The morphology of HMX crystal was affected by temperature and atmosphere of disassembly process,and the rearrangement and growth of host molecules,the disassemblied HMX,were confined.Thus,the morphology of HMX can be designed and controlled.Firstly,the selection of guest molecule is important for supramolecular assembly-disassembly.The supramolecular moleclue formed from the guest molecules and host molecules.And this supramolecular compounds,should be stable under ambient conditions and be able to be got rid of guest molecules under specific conditions.Thus,the solvate of HMX becomes the best choice.In this work,several solvates of HMX were studied as the module of supramolecular assembly.The effects of assembly methods,e.g.recrystallization with procedural cooling,complexation by soaking in solvent,and assembly in vapour with vacuum,The morphology of supramolecular crystal have been researched.The results indicate that the morphology of HMX solvates obtained from different methods are different,which could be used as templates with different morphology for disassembly process.After that,micro-crystal clusters of HMX with different morphology were obtained by disassembly process,e.g.vacuum drying,freeze drying,and anti-solvent extraction,based on the different HMX solvates obtained before.The effects of guest molecules and temperature on microstructure of HMX were investigated.The feasibility of multiple supramolecular assembly-disassembly process for micro-nano hierarchical structure has been explored.The results indicate that the micro-nano hierarchical structures of HMX can be obtained by multiple assembly-disassembly process.The sensibility to the specific stimulations of HMX with this novel microstructure remarkably changed.Moreover,this strategy has been used for other explosives,e.g.hexanitrohexaazaisowurtzitane(HNIW,C6H6N12O12),hexanitrostibene(HNS,C14H6N6O12),and hexogen(RDX,C3H6N6O6),which confirms that this strategy is efficient to obtain explosives with micro-nano hierarchical structures.Furthermore,the microstructure evolution process in supramolecular disassembly,e.g.decomposition,rearrangement,nucleation and growth of crystals,and phase transformation,has been investigated by in situ powder X-ray diffraction(XRD)and in situ infrared spectroscopy(FT-IR).According to the results,the microstructure formation mechanism of HMX in the process of supramolecular assembly-disassembly was discussed.This work provides novel strategy to not only design and control of explosive microstructure,but also decrease mechanic sensitivity and improve the response sensibility to the specific stimulations or other performance,which promotes the improvement of explosive microstructure,understanding of relationship between microstructure and performance of explosives,and development of new technology,new microstructure and new theory of explosive for weapons.