Fabrication Of NC-based Energetic Microspheres By Electrospray Method

Energetic material’s particle size and shape affect its sensitivity and energy output to a large extent.Mechanical sensitivity reduces,diffusing performance gets better and charge density becomes larger after material spherized.Energy release quantity and energy release rate will increase after micro/nanosizing.In this paper,energetic materials were spherized and micro/nanosized by electrospray-drying method.Preparation of composite spherized energetic materials by this method has become a hotspot in recent years.What’s more,it has turned into a research field with good prospect and huge challenge.Firstly,the atomization and drying theory in the process of electrospray were summarized in this paper.Then the mechanism of droplets charged,droplets breakage and droplets atomized were analyzed and studied.The influence of solvent evaporation rate and phase separation rate in the drying process on morphology and particle size of microspheres were discussed.NC（Nitrocellulose）microspheres were prepared by electrospray based on this theory.The preparation process parameter of NC microspheres was obtained.Microspheres with good sphericity,smooth surface and uniform particle size distribution can be prepared when the solvent was acetone/ethanol,NC concentration was 2.5%,the voltage was 20²5 kV,receive distance was 10¹5 cm and sampling rate was 3 ml/h.Secondly,NC/CL-20 composite microspheres were prepared by electrospray.Microspheres with diameter 1³μm can be obtained by controlling experimental condition.The influence of the content of CL-20 on the microspheres particle size was explored.The microspheres were tested by infrared spectrometer,X-ray diffractometer（XRD）and differential scanning calotimeter.Results showed that CL-20 and NC just combined physically in the composite microspheres.Raw-CL-20 was epsilon crystal type,but CL-20in the composite microspheres was beta crystal type.Several kinds of composite microspheres’exothermic peak temperature were lower than that of raw-CL-20.Compared to raw-CL-20,the activation energy of NC/CL-20 microsphere decreased 28.47 kJ/mol.Finally,Al/CuO/NC and Al/KIO₄/NC microspheres were prepared by electrospray.The influence of the content of NC on the Al/CuO/NC microspheres’morphology and particle size was explored.To detect the uniformity of each element dispersion,X-ray spectrometer（EDS）was carried out on the Al/CuO/NC microsphere to element scanning analysis.Thermal analysis and closed bomb experiments were carried out on the two kinds of microspheres respectively.The maximum value of pressure peak by electrospray wasabout twice more than physical ultrasonic mixing method.The combustion residues of microspheres were test by XRD.The residues of Al/CuO/NC microsphere wereCu,Cu₂O,Al₂O₃ and CuO;The residues of Al/KIO₄/NC microsphere were KI,KIO₃,Al₂O₃and KIO₄.