Construction Of CL-20/H₂O₂ Host-guest Energetic Material And Its Mechanism

With the rapid development of energetic materials,the pursuit of new energetic materials with high energy density have been attracting widely attention in recent decades.It is difficult to design and synthesize new explosives in a short period of time,and the performance of cocrystal is often between two components,which reduces the performance of high-energy explosives.Formulated explosives tend to reduce energetic components,that is,the energy of high-energy explosives is diluted.Based on these situations,we need to find new ways to design and improve the performance of explosives.Modification on the basis of high-energy explosive CL-20 is a convenient way to obtain explosives with good comprehensive explosive performance.The structure of the host-guest explosives have drawn our attention.In 2010,Saint MS et al.first obtained CL-20/CO2 host-guest explosive by high-pressure utilization of critical state CO2 and ε-CL-20 In 2016,Matzger et al.successfully prepared CL-2O/H₂0₂ host-guest explosive,the excellent performance of it was better than ε-CL-20.However,their preparation method has great safety hazards.Besides,the preparation mechanism has not been studied.Herein,this study provides two mild preparation methods of CL-2O/H₂0₂ and their preparation mechanism was studied.Method 1:Three-dimensional porous orthorhombic CL-2O/H₂0₂ was successfully prepared by volatilizing the co-solvent of H₂0₂ and CL-20 in low temperature and low pressure drying environment with urea peroxide available in the market as the source of hydrogen peroxide.Its space group was Pbca,and the molar ratio of CL-20 to H₂0₂ was about 2:1.The sensitivity of CL-2O/H₂0₂ host-guest explosive was tested.It was found that its impact sensitivity was 13.8 cm similar to that of ε-CL-20（14 cm）,but its friction sensitivity unchanged.The thermal phase transition temperature was studied by in situ high temperature XRD.It was found that the thermal phase transition temperature is 140℃,which is higher and more stable than the thermal phase transition temperature of ε-CL-20（130℃）.The thermal phase transition rate of CL-2O/H₂0₂ host-guest explosives is faster than that of ε-CL-20,while the continuous heating will lead to the rapid transformation of CL-2O/H₂0₂ into y-CL-20（the transformation efficiency is higher than that of ε-CL-20）.Mechanisms:By tracing the crystallization process of CL-2O/H₂0₂,it is found that it undergoes a metastable CL-2O/CH3CN as the intermediate state,and the hydrogen peroxide gas molecules interact with it to form CL-2O/H₂0₂ by solid phase transformation.Method 2:Using dry metastable phase CL-20/CH3CN as raw material,directly adding into the solution of H₂0₂ and crystallizing in the volatile solution under low temperature and low pressure drying environment,the orthorhombic Pbca CL-2O/H₂0₂ with a molar ratio of 2:1 was successfully obtained,and its optical morphology showed microcrystaline clusters.Mechanisms:Follow-up experiments and showed that it via α-CL-20 as an intermediate.It was verified by experiments that the appearance of β-CL-20 was due to the extraction of CH3CN from metastable solvent compound CL-20/CH3CN,which resulted in the rearrangement and transformation of CL-20 molecule.Moreover,CL-20/H₂0₂ can be successfully prepared by using β-CL-20 as the reaction substrate.The process from β-CL-20 to CL-20/H₂0₂ is a solution-mediated transformation induced by H₂0₂ solution.