Study On Granularity And Morphology Controlling Of 3,3'-Diamino-4,4'-azoxyfurazan(DAOAF)

3,3'-diamino-4,4'-azofurazan(DAOAF)is a high energy and low sensitivity energetic material with high standard enthalpy of formation and good heat resistance.The detonation critical diameter of DAOAF is small while the threshold of high-voltage short-pulse response is low,due to which it is expected to be applied in impact-plate detonators.However,DAOAF synthesized directly in the experiment is usually flaky,angular and low purity,which can't be directly used for charge of impact plate detonator.Therefore,the DAOAF synthesized needs to be modified.High quality and high purity DAOAF can be obtained by recrystallization technology.The optimum technological conditions for refining DAOAF were determined by solvent-nonsolvent method: DAOAF solution(0.03 g/m L)was solwlydropwise added into the water(400m L,8?).The crystalline size of yellow cube-like DAOAF was 0.3-0.5?m On the basis of ultrafine recrystallization,the explosive self-assembly technology was introduced to control the shape of DAOAF secondary particles accurately through in-situ self-assembly.DAOAF particles with high purity,different shapes and structures can be obtained by this technique.Combined with analog compulation and based on evaporation method,the self-assembly process of DAOAF in different polar solvents was tested.Finally the optimum solvent was DMSO to prepare porous polycrystalline sphere DAOAF,the self-assembly mechanism of porous DAOAF crystals was as follows: with the slow evaporation of DMSO,the solution was supersaturated,leading to primary nucleation and DAOAF crystal growth.In order to reduce the surface energy of particles,small particles will aggregate into large particles.During the subsequent crystallization process,some grains grow out of the aggregated particles.Subsequently,the nuclei in the solution accumulate on the surface of the grown crystal by directional driving force.With the increase of crystallization time,DAOAF particles continued to grow and finally assembled into porous polycrystalline sphere DAOAF.In order to solve the problem of low energy of DAOAF,confined self-assembled spherical shell DAOAF was prepared by using the idea of DAOAF coated high-energy explosives to improve the energy of the system.The effects of different surfactants and stirring speed on the morphology of DAOAF were studied.Finally,the confined self-assembled spherical shell DAOAF was obtained.The optimum process conditions were determined as follows: adding PVP in non-solvent,controlling stirring speed to 280 r/min,and the confined self-assembled mechanism was proposed as follows: PVP formed spherical micelles in water at appropriate stirring speed,hydrophilic groups formed hydrogen bonds with DAOAF,and finally formed confined self-assembled spherical shell DAOAF.The morphology,particle size,crystal structure and thermal stability of DAOAF with different morphologies were characterized and analyzed by scanning electron microscopy(SEM),X-ray powder diffraction(XRD)and differential scanning calorimetry(DSC).The XRD results showed that the crystal morphology of the self-assembled DAOAF crystal was not changed,and the crystal orientation has changed during the self-assembly process.DSC results show that the apparent activation energy of thermal decomposition of porous polycrystalline sphere DAOAF was 10.76 k J/mol lower than that of DAOAF synthesized,and the critical temperature of thermal explosion than DAOAF synthesized reduced by 2.66 ?.The apparent activation energy of thermal decomposition of the confined self-assembled spherical shell DAOAF and refining DAOAF than DAOAF synthesized were increased by 18.50 k J/mol and 14.61 k J/mol,and the critical temperature of thermal explosion than DAOAF synthesized increased by 5.01 ? and 4.69 ?,respectively.The results show that spherical shell shaped DAOAF activity is the largest.In this study,the ultra-fine and high-purity of DAOAF explosive crystals were firstly realized by using ultrafine particle preparation technology,and then porous polycrystalline sphere DAOAF and confined self-assembled spherical shell DAOAF were obtained by self-assembly technology.The shape/structure control of DAOAF was realized.The samples obtained in this study are expected to maintain the activity of ultrafine DAOAF particles for a long time.The research results can lay a technical foundation for the application of DAOAF in impact plate detonators.