Study On Preparation And Properties Of CL-20-based Composite Energetic Microspheres

At present,with the continuous development of weapon systems and high-technology and increasingly harsh battlefield conditions,the development of high-energy,low-sensitivity and highly reliable energetic materials is an developing trend of weapons and ammunition.Hexanitrohexaazaisowurtzitane?CL-20?is currently the most attractive high-energy density compound?HEDC?,and it is favored by all countries in the world for its remarkable properties of high energy.While its high mechanical sensitivity and bad safety were obstructing its further application.In order to satisfy the requirements of high-energy insensitivity ammunition for weapon systems,raw CL-20 as major research object,TATB as desensitizer,The CL-20/TATB composite energetic materials were successfully prepared by traditional water slurry coating method and the one-step spray drying method.The main contents of this paper are as follows.?1?Submicron CL-20 was prepared by ultrasonic jetting refining device firstly.Ethyl acetate was used as the solvent of CL-20,N-heptane as nonsolvent.The prepared refined CL-20 and the raw CL-20 were characterized by a scanning electron microscope?SEM?,differential scanning calorimeter?DSC?,X-ray diffractometer?XRD?,and the impact sensitivity instrument.The results showed that the size of refined CL-20 was 1?m-2?m,the surface of the crystal was smooth and regular shape,the crystal form is stable epsilon phase and had wider diffraction peak compared with raw CL-20.Thermal analysis results show that the activation energy of refined CL-20 is 203.67 KJ/mol,and the temperature of thermal explosion is 231.04�C.The impact sensitivity results show that the ultra-fine CL-20 has a characteristic drop height value H₅₀ of 31.69cm.Compared with the raw material,the H₅₀value was increased 111.26%,and the impact sensitivity of refined CL-20 was significantly reduced.?2?ultrafine CL-20 was prepared by spray drying method.Using acetone as the solvent,ultrafine CL-20 particles were prepared at different inlet temperatures?50?,60?,70?and 80??.The results show that when the inlet temperature is set to 60?,the CL-20-2sample has the best morphology and performance.The test results show that the prepared CL-20-2 crystal has a good spherical shape effect,smooth surface,uniform particle size distribution,about 500 nm-1?m,good fluidity and no agglomeration.Compared with the raw material CL-20,the crystal form of ultrafine CL-20 particles is still?type,and the inlet temperature has little effect on its crystal form.The DSC test results show that the temperature of thermal explosion and the peak temperature Tp₀ of CL-20-2 sample are increased by 1.28?and 1.59?,respectively.The thermal stability is better than the raw material CL-20.The impact sensitivity test shows that the CL-20-2 characteristic drop height value is 32.08cm,compared with raw material,the H₅₀ value was increased 113.86%,and the impact sensitivity was significantly reduced.?3?CL-20/TATB-based high polymer bonded explosive was prepared by solution-water slurry method.Using water suspension device,and Estane5703 as the binder,TATB was successfully coated on the surface of CL-20.The CL-20/TATB-based PBXs was analyzed by SEM,XRD,DSC and impact sensitivity.The test results show that CL-20/TATB-based PBXs has better thermal stability and lower mechanical impact sensitivity.The composite particles show a spherical structure with uniform particle size,but there are still edges and defects on the surface.?4?In the article,a one-step method which involves forming CL-20/TATB composite microspheres by using spray-drying is presented.Under ultrasonic high temperature environment,the suspension CL-20/TATB/VitonA spray precursor was prepared with ethyl acetate as the solvent,and the CL-20/TATB composite energetic microspheres were prepared by spray drying technology.The microspheres were characterized by scanning electron microscopy?SEM?,X-ray diffraction?XRD?,differential scanning calorimetry?DSC?,and impact and friction sensitivity tests.Compared with PBXs using water slurry method,the results showed that the microspheres were spherical nanocomposites with better dispersion,smooth surface and good spheroidization effect.The mean particle size was 500-1000 nm and it could be seen that the characteristic diffraction peaks of the composite particles can correspond to the raw CL-20 one to one,and the typical TATB diffraction peaks could be observed on the diffraction curves.The H₅₀ values of CL-20/TATB composite microsphere samples prepared by suspension spray drying were increased to 39.90 cm,50.2 cm,69.6 cm and 83.6cm,respectively.Friction sensitivity is also significantly reduced,and mechanical safety performance was significantly improved.