Abstract:Abstract:A new insensitive explosive based on RDX and with Nitrocellulose (NC) as binder has been prepared using a flash vaporization process. Scanning electron microscopy was used to characterize the morphology and particle size of the resulting RDX-NC microspheres. X-ray photoelectron spectroscopy, Differential Scanning Calorimetry, impact sensitivity, vacuum stability and burning rate of raw RDX, RDX-NC and RDX-1 were also used to characterize the explosive. The RDX-NC microspheres were found to have a fibr… Show more
“…The spray-drying [20][21][22][23] method was suitable for the preparation of heat-sensitive substances due to the stable preparation process, the convenient operation, and the products which did not need to be crushed and sieved after drying. The spray-drying method was used to prepare the spherical RDX with a particle size of 0.5 μm to 4 μm by Jingyu et al [21] with the spray speed of 10 ml/min. The measured properties were all higher than those of the raw material RDX.…”
Cyclotrimethylene trinitramine (RDX, C3H6N6O6) with the size of 400 to 600 nm was prepared by low-speed spray-drying method. Meanwhile, the crystal morphology, particle size, crystal structure, thermal decomposition properties, and impact sensitivity properties of the raw materials of RDX and the prepared ultrafine spherical RDX were characterized by scanning electron microscope (SEM), laser particle size analyzer (LPSA), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), and impact sensitivity instrument. The factors affecting experimental results were discussed; the size and morphology of RDX crystals were found to be affected by drying temperature, spray speed, and RDX mass fraction in solution. The optimal preparation conditions for the ultrafine spherical RDX were studied, and the results showed that the RDX particles with the best morphology and particle uniformity were prepared when the drying temperature was 90°C, spray speed was 1 ml/min, and the RDX mass fraction in solution was 4%. As a result, the activation energy (Ea) of the ultrafine spherical RDX was lower than that of raw RDX by 24.52 KJ·mol-1, and the characteristic drop (H50) of the ultrafine spherical RDX was higher by 35.3 cm.
“…The spray-drying [20][21][22][23] method was suitable for the preparation of heat-sensitive substances due to the stable preparation process, the convenient operation, and the products which did not need to be crushed and sieved after drying. The spray-drying method was used to prepare the spherical RDX with a particle size of 0.5 μm to 4 μm by Jingyu et al [21] with the spray speed of 10 ml/min. The measured properties were all higher than those of the raw material RDX.…”
Cyclotrimethylene trinitramine (RDX, C3H6N6O6) with the size of 400 to 600 nm was prepared by low-speed spray-drying method. Meanwhile, the crystal morphology, particle size, crystal structure, thermal decomposition properties, and impact sensitivity properties of the raw materials of RDX and the prepared ultrafine spherical RDX were characterized by scanning electron microscope (SEM), laser particle size analyzer (LPSA), X-ray diffractometer (XRD), differential scanning calorimeter (DSC), and impact sensitivity instrument. The factors affecting experimental results were discussed; the size and morphology of RDX crystals were found to be affected by drying temperature, spray speed, and RDX mass fraction in solution. The optimal preparation conditions for the ultrafine spherical RDX were studied, and the results showed that the RDX particles with the best morphology and particle uniformity were prepared when the drying temperature was 90°C, spray speed was 1 ml/min, and the RDX mass fraction in solution was 4%. As a result, the activation energy (Ea) of the ultrafine spherical RDX was lower than that of raw RDX by 24.52 KJ·mol-1, and the characteristic drop (H50) of the ultrafine spherical RDX was higher by 35.3 cm.
Composite modified double‐base (CMDB) propellant, benefitting from the outstanding performances of high energy and low signature, has attracted increasing focus in the past decade. To improve the integrative performance, such as enhancing the mechanical property and decreasing the sensitivity, CMDB propellant with low solid content containing nano‐sized RDX has been prepared. The microstructure, mechanical properties, sensitivity and combustion performance of the prepared propellant are studied. Results have shown that the interface of the CMDB propellant contained nano‐sized RDX (N‐CMDB) is more compact and the internal defects are less than those of the CMDB propellant with micro‐sized RDX (M‐CMDB). Compared with the maximum tensile strength (σm) and the corresponding elongation at maximum tensile strength (ϵm) of M‐CMDB, the σm values of N‐CMDB are improved by 37.4 % at +50 °C, 27.5 % at +20 °C and 26.7 % at −40 °C, and the ϵm values are increased by 16.1 %, 19.4 % and 39.6 %, separately. Moreover, the friction and impact sensitivities of N‐CMDB propellant are decreased by 51.3 % and 50.4 %, respectively. In the range of 8–18 MPa, the combustion performance of N‐MCDB propellant has been demonstrated more attractive with higher burning rate coefficient (8.692→10.950) and lower pressure exponent (0.384→0.299). All these results lead us to believe that the usage of nano‐sized explosives will contribute to improve the comprehensive performance of CMDB propellants and promote their application in weapon system.
Spray drying is an effective method to reduce shock sensitivity of energetic materials with the advantages of integrating atomization, drying, crystallization, and coating in one step. However, with the complex hydrodynamics and crystal growth process during spray drying, the development of theoretical models is very difficult. Therefore, five types of artificial neural network (ANN) models are proposed to accurately predict the mean particle size of energetic materials prepared by spray drying, such as Cascade-forward back propagation neural network (CFBP), Elman-forward back propagation neural network (EFBP), Feed-forward back propagation neural network (FFBP), Generalized regression neural network (GR) and Radial basis neural network (RB). The model input parameters are the inlet temperature (T), the liquid flow rate (L), the gas flow rate (G), the mass fraction (w), the molecular weight (M), and the surface tension (δ). The output parameter is the mean particle sizes (dp). To further illuminate the superior performance of ANN model, the effects of temperature, liquid flow rate, gas flow rate, mass fraction, and surface tension on the mean particle size are conducted. The ANN model of mean particle size for the energetic materials prepared by spray drying could be much useful for further improving its property.
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