Design, Preparation And Performance Of Micro/Nano Energetic Cocrystal Materials

HMX and CL-20,which act as high energetic materials,possess high mechanical sensitivity.If they are applied to the weapon ammunition formula,the security of weapons faces significant challenges.The domestic and foreign relevant researches show that both micro/nano and cocrystal technology can effectively reduce sensitivity and improve security for energetic materials.Based on TNT,HMX,CL-20 and TATB,the effects of micro/nano and cocrystal for energetic materials were achieved simultaneously through one-step method and several micro/nano energetic cocrystal materials were prepared in this dissertation.Moreover,the influence of micro/nano cocrystal technology on mechanical sensitivity and energy output properties of energetic materials was investigated.This dissertation plays an active role in promoting the development of high energy and low sensitivity energetic materials.The main contents of this research are as follows.First,the surface electrostatic potential energy of TNT,HMX,CL-20,and TATB was calculated by DMol3 module of molecular dynamics simulation software(Materials Studio),respectively.Based on the calculated surface electrostatic potential energy,Forcite Plus module was used to built HMX/TNT,CL-20/TNT,CL-20/HMX,and HMX/TATB energetic cocrytal models.Their most probable cocrystal crystal structures were selected by Polymorph Predictor module.Results show that the most probable crystal structure of HMX/TNT cocrytal belongs to the monoclinic crystal system with space group P21/c.CL-20/TNT cocrytal crystallizes is in orthorhombic crystal system with space group P212121.CL-20/HMX cocrytal crystallizes is in monoclinic crystal system with space group P21/c.HMX/TATB cocrytal crystallizes is in orthorhombic crystal system with space group Pna21.The main driving force for forming HMX/TNT,CL-20/TNT,and CL-20/HMX cocrytal is van der Waals force and hydrogen bond provides a synergistic effect.The additive effects of van der Waals force and hydrogen bond are the main power to HMX/TATB cocrytal formation.Second,micro/nano HMX/TNT,CL-20/TNT,and CL-20/HMX energetic cocrystal materials were prepared by the spray drying method,respectively.The micro/nano cocrystals were characterized using scanning electron microscopy(SEM),X-ray diffraction(XRD),differential scanning calorimetry(DSC),and Raman spectroscopy.Furthermore,impact sensitivity,friction sensitivity,and steel dent of the cocrystals were tested and analyzed.Results show that HMX/TNT and CL-20/TNT cocrytals prepared by this method are spherical in shape and the particle size of HMX/TNT and CL-20/TNT cocrytals is 50 ~ 200 nm and under 1 ?m,respectively.They all aggregate into many microparticles,which are spherical in shape and 1 ~ 10 ?m in size.CL-20/HMX cocrystals exhibit plate-like structure and the thicknesses of plate-like crystal is about 100 nm.These tiny plate-like cocrystals aggregate into many microparticles,which were spherical in shape and 0.5 ~ 5 ?m in size.Compared with respective energetic monomers,these three micro/nano energetic cocrystal materials possess unique crystal structure and thermal decomposition properties.The peak temperature of exothermic decomposition of micro/nano HMX/TNT cocrystals is 3.67 ? lower than that of raw HMX.The melting point of micro/nano CL-20/TNT cocrystals is 55.78 ? high than that of TNT.The peak temperature of exothermic decomposition of micro/nano CL-20/HMX cocrystals is 3.86 ? lower than that of raw CL-20.The intermolecular hydrogen bond C-H���O exists in these three micro/nano cocrystals.On the basis of preparation of micro/nano energetic cocrystal materials by the spray drying method,the crystallization principle of instantaneous recognition nucleation was advanced.Two energetic solute moleculars automatically identified and assembled to fom the cocrystal nucleus at the moment of precipitation through spray drying.Then they grow into micro/nano particles.Moreover,when micro/nano energetic cocrystal materials form,impact and friction sensitivity of the cocrystals reduce obviously compared with raw HMX or raw CL-20.The formation of micro/nano HMX/TNT,CL-20/TNT,and CL-20/HMX energetic cocrystal materials can improve the energy output properties of their respective mixtures.Finally,based on the principle of mechanochemical effect micro/nano CL-20/HMX and HMX/TATB energetic cocrystal materials were prepared by mechanical ball milling,respectively.These micro/nano cocrystals were characterized using SEM,particle size analyzer,XRD,DSC,and Raman.Furthermore,impact sensitivity,friction sensitivity,and steel dent of the cocrystals were tested and analyzed.The results show that the optimal conditions of micro/nano CL-20/HMX cocrystal explosive are grinding ball size of 0.1 mm,liquid to explosive weight ratio of 10/1,rotating speed of 300 r�min-1,ball to explosive weight ratio of 20/1,and milling time of 120 min.CL-20/HMX and HMX/TATB cocrytals prepared under above optimal conditions are spherical in shape and the particle size of CL-20/HMX and HMX/TATB cocrytals is 80 ~ 250 nm and 82 ~ 435 nm,respectively.Compared with respective energetic monomers,these two micro/nano energetic cocrystal materials exhibit unique crystal structure and thermal decomposition properties.The peak temperature of exothermic decomposition of micro/nano CL-20/HMX cocrystals is about 7 ? lower than that of raw CL-20.The peak temperature of exothermic decomposition of micro/nano HMX/TATB cocrystals is about 3 ? lower than that of raw HMX.After micro/nano cocrystals have been prepared,the thermal stability is slightly reduced.The intermolecular hydrogen bond C-H���O and N-H���O exists in micro/nano CL-20/HMX and HMX/TATB cocrystals,respectively.When micro/nano CL-20/HMX and HMX/TATB energetic cocrystal materials form,impact and friction sensitivity of the micro/nano cocrystals reduce obviously compared with raw HMX.Moreover,the energy output properties of micro/nano CL-20/HMX and HMX/TATB energetic cocrystal materials are equivalent to that of raw CL-20 and raw HMX,respectively.