Structural Regulation And Performance Of High-energy Insensitive DAAF-based Composite Microspheres

High-tech weapons need to have the characteristics of high damage,energy release efficiency and low sensitivity,in order to better adapt to the harsh battlefield environment.High performance composite explosives can fuse the dual characteristics of composite components,which can not only ensure energy output,but also reduce the sensitivity of explosives.Therefore,the research on the structure regulation and performance of high energy insensitive composite microspheres is an important technical means to improve the energy of explosives and ensure the safety of explosives.3,3’-Diamino-4,4’-azofurazan（DAAF）is a new type of insensitive explosive with environmental friendliness and excellent safety performance.The thesis by doping1,3,5-trinitro-1,3,5-triazacyclohexane（RDX）and 1,1’-diamino-2,2’-dinitroethylene（FOX-7）,respectively),DAAF/RDX and DAAF/FOX-7-based composite high-energy insensitive explosives were successfully prepared.The specific research contents are as follows:（1）In order to study the intermolecular binding energy,mechanical properties and cohesive energy density of composite high-energy insensitive explosives,molecular dynamics simulations were used to evaluate and determine the DAAF/RDX-based and DAAF/FOX-7-based composites with different composite ratios.The results show that when the content of daaf in the composite system decreases gradually,the cohesive energy density,van der Waals force and electrostatic force of the system will gradually increase,but will gradually decrease when they increase to a certain extent,indicating that the energy absorbed by the composite system and the system sensitivity will first increase and then decrease,and the safety will first increase and then decrease.When the ratios of DAAF:RDX:F₂₆₀₂ in the composite system are 70:25:5,60:35:5 and 50:45:5,respectively,the equilibrium system of DAAF/RDX has higher mechanical properties and cohesive energy density.Using the Urizar and Explo5 methods,the calculated detonation velocities are 8101,8182 and 8264 m·s^-1,and the detonation pressures are 29.98,30.68 and 31.28 GPa,respectively,which are comparable to the performance of the booster PBXN-7.Therefore,the ratios of DAAF,RDX and F₂₆₀₂ in the DAAF/RDX-based composite energetic system were determined to be 70:25:5,60:35:5and 50:45:5,respectively.Similarly,the proportions of DAAF,FOX-7 and F₂₆₀₂ in the DAAF/FOX-7-based composite energetic system were determined to be 70:25:5、60:35:5 and50:45:5,respectively.（2）DAAF/RDX and DAAF/FOX-7 composite energetic particles with different stacking morphologies and different composite ratios were prepared by three different processes:self-assembly technology,mechanical ball milling and microfluidic technology.The morphology and crystal structure characteristics of the samples were characterized by scanning infrared spectroscopy（FT-IR）,X-ray diffractometer（XRD）and scanning electron microscopy（SEM）.The properties such as mechanical sensitivity and bulk density were tested and analyzed.The results show that DAAF/RDX and DAAF/FOX-7 composite energetic particles prepared by different processes have great differences in morphology,and all composite particles prepared by self-assembly technology show more regular morphological characteristics.The particles have high sphericity with uniform particle size about 2μm;the particle sizes of all composite energetic particles prepared by mechanical ball milling and microfluidic technology are about 300 nm and 20μm,respectively;FT-IR and XRD of all composite energetic particles test show that the crystal form and crystal structure of the components r unchanged;the bulk density of the composite energetic particles prepared by self-assembly technology is increased by 17%and 11%,respectively,and the thermal stability has been improved and the mechanical safety is higher..（3）DAAF/RDX-based composite energetic microspheres with different mass ratios（70:25:5,60:35:5 and 50:45:5）were prepared based on self-assembly technology.SEM and EDS test results show that the energetic microspheres have a size of 400-600μm with a narrow particle size distribution,the surface element of F is evenly distributed with a content of about 5%;DSC test results show that the energetic microspheres perform better,the thermal stability gradually decreased with the increase content of RDX.The mechanical sensitivity test show that the coating of fluororubber can improves the mechanical safety of the energetic microspheres.（4）DAAF/FOX-7-based composite energetic microspheres with different mass ratios（70:25:5,60:35:5 and 50:45:5）were prepared by microemulsion technology.Firstly,the influence of surfactant type,content,stirring time and other factors on the morphology of energetic microspheres was studied,the optimal preparation process was obtained:polyvinylpyrrolidone（PVP）as surfactant,content of PVP is 0.15%,stirring speed is 400r/min.Secondly,compared with the conventional water suspension process,the energetic microspheres have better formability,higher particle surface smoothness,smaller angle of repose（26.3°）,and better sphericity,the particle size of particle was about 600μm.Finally,the impact sensitivity and friction sensitivity of the energetic microspheres are very insensitive,and the reaction grade of the cook-off test is burning,indicating that DAAF/FOX-7-based composite energetic microsphere is more security.