Study On Phase Transition Characteristics And Structure Stabilization Mechanism Of CL-20-based Host-guest Explosives

Designing and preparing energetic materials with high energy passivity is one of the hot topics in the field of energetic materials.At present,the energy density and stability of CL-20-based host-guest explosives constructed based on the idea of host-guest are greatly improved.However,the mechanism of how guest molecules exist stably in anhydrousα-CL-20 cells,how embedded guest molecules can increase the CL-20 phase transition temperature,and the effect of additives on the phase transition behavior of host-guest explosives and the mechanism of action are not clear at present.Therefore,this paper studies the phase transition characteristics of CL-20-based host-guest explosives and the influence of additives on the phase transition behavior of CL-20-based host-guest explosives,so as to have a deeper understanding of the structure stabilization mechanism of CL-20-based host-guest explosives.The main results obtained are as follows:（1）In order to reveal the structure stabilization mechanism of CL-20-based host-guest explosives.It has been shown by Target-MD that guest molecules are more likely to escape from the（002）crystal face than other crystal faces of the host-guest explosives.The escape behavior of guest molecules was studied by molecular dynamics simulation（MD）.The results show that the phase stability sequence of four CL-20-based host-guest explosives is as follows:CL-20/CO₂>CL-20/N₂O>CL-20/H₂O₂>CL-20/H₂O,which is consistent with the results of in-situ XRD and DSC-TG characterization of host-guest explosives.Meanwhile,by studying the escape path of the guest molecule,it is concluded that the escape way of the guest molecule from the CL-20 cell is"jump"diffusion.By studying the MSD of the host molecule CL-20 and the radial distribution function（RDF）between the host molecules and the guest molecules in the host-guest crystals,It is revealed that the main reason for the structural stability of host-guest explosives is the stability of main structure frame and the interaction between host-guest molecules of CL-20.（2）The effect of different additives on the phase transformation behavior ofε-CL-20 and CL-20-based host-guest explosives was studied by in-situ XRD,and explained from the perspective of kinetics by non-isothermal kinetics.The mechanism of interaction between additives andε-CL-20,CL-20-based host-guest explosives was described by infrared characterization and molecular dynamics simulation,when the absolute value of the interaction energy is less than 28.00 kcal?（mol?nm²）^-1,additives onε-CL-20 and CL-20-based host-guest explosives phase transition has a promoting effect,When the absolute value of the interaction energy is greater than about 31.50 kcal?（mol?nm²）^-1,additives onε-CL-20 and CL-20-based host-guest explosives phase change has inhibitory effect,when the absolute value of the interaction energy of 28.00-31.50kcal?（mol?nm²）^-1,The additive neither promotes nor inhibits the phase transition ofε-CL-20 and CL-20-based host-guest explosives.（3）In order to further inhibit the phase transition of CL-20-based host-guest explosives,PEI is selected as the coating agent to coat CL-20/N₂O.The research shows that PEI has obvious inhibition effect on the phase transition of CL-20/N₂O.The simulation results show that,The inhibition effect of PEI coating on CL-20/N₂O phase transition may be attributed in part to the strong interfacial interaction between PEI and CL-20/N₂O.The results are helpful to the application of CL-20-based host-guest explosives in energetic materials engineering.