| The brisant nitramine explosives (RDX, HMX and CL-20) have relatively high detonation heats, detonation velocities and detonation pressures. They can be extensively used in composite explosives and solid propellants so that the weapons will be benefitted. However, the industrial micron-sized nitramine explosives are sensitive during development, procuction, storage, transportation and application, which seriously threatens the safety of the ammunitions and the lives. Thus, the reduction in sensitivity had become a research focus in order to insure the safety. In this thesis, nanometer RDX, HMX and CL-20 were prepared in control using the HLGB-10 pulverizer, which was designed by National Special Superfine Powder Engineering Research Center located in Nanjing University of Science and Technology of China, to reduce sensitivities of industrial micron-sized raw nitramine explosives. The properties of the prepared nanometer explosives, the mechanism for decreasing the sensitivity after nanocrystallization, the applications of nanometer RDX/HMX in plastic bonded explosives(PBX) and the the applications of nanometer RDX in composite modified double-based propellants(CMDB) were studied. Those main works were as follows.Firstly, basing on the principle of ’tiny force being exactly given to materials’, the nanometer nitramine explosives(RDX, HMX and CL-20) were prepared using the HLGB-10 pulverizer through controlling the technological parameters of grinding process. The prepared nanometer particles were semi-spherical at the size about 60nm, having narrow size distributions. The principle of ’expansion and separation’ was proposed for anti-agglomeration, the effects of dispersing liquid and drying method on the nanometer nitramine explosive particles were researched and the appropriate drying conditions and parameters were gotten. The chemical purities, crystal structures, molecular structures, thermal decomposition characteristics, thermal stabilities and sensitivities of these prepared nanometer explosives were researched. Results had shown that the chemical purities were very high without any impurities from the pulverization system and the crystal structures and molecular structures maintained the same with the industial micron-sized raw nitramine explosives. Compared with the industrial micron-sized raw nitramine explosives, the thermal decomposition apparent activation energies of nanometer nitramine explosives were a bit lower. The thermal stabilities of nanometer nitramine explosives were consistent with the industrial micron-sized nitramine raw explosives when at 100℃. The friction, impact and shock sensitivities were respectively decreased more than 20%,40% and 50%, which meaned great improvement of safety.Secondly, the mechanism for decreasing the sensitivity after nanocrystallization of nitramine explosives was researched and analyzed. Basing on hot-spot theory, the changing trends of particle sizes, morphologies and crystal perfections during pulverization were researched, and the changes in the relationship between the sensitivities to friction, impact or shock and these factors were studied. The mechanism was discussed from the two aspects of theory and decomposition energy. In the matter of theory, the changing rule of hot-spot temperature with the particle sizes, morphologies and plastic yield strengths of nitramine explosives were analyzed, which had shown that the hot-spot temperature would be decreased with the decrement of particle sized, the increment of specific surface areas and the increment of plastic yield strenghs. Because of the smaller sizes, the larger surface areas, the faster cooling rate and the higher yield strengths of nanometer nitramine explosives, the hot-spot temperature was decreased, and then the sensitivities to friction, impact or shock were reduced. In terms of decomposition energy, we initially proposed the concept of’critical electron excitation energy’ which had been tested and calculated for various sizes of nitramine explosive particles. The simulated changing curves between the critical electron excitation energies and the particle sizes had shown that the calculated excitation energies decreased firstly and then increased with the reduction of particle size at the critical size of about 10μm. Because of the higher critical electron excitation energy, the nanometer nitramine explosives were more stable, the hot-spot temperature would be decreased, and then the sensitivities to friction, impact or shock of nanometer nitramine explosives were reduced. In general, the mechanism for decreasing the sensitivity after nanocrystallization of nitramine explosives lay in small size effect, crystal perfection effect, surface effect, and their synergistic effects.Thirdly, the application of nano RDX in PBX was researched. The mould powder of nano RDX based JH explosive was acquired and the mass ratio of the prepared mould powder ranging in 0.3-2mm was above 99.5% mainly distributing in 0.3-0.6mm. The component contents, thermal decomposition characteristic, thermal stability, microstructure, sensitivities and detonation performance of nano RDX based JH explosive were studied. Results had shown that the component contents of the prepared nano RDX based JH explosive were separately consistent with the given amout of each component, which meaned nano RDX hadn’t lost during the moulding process of JH explosive. Compared with industrial micron-sized RDX based explosive, the thermal decomposition peak temperature of nano RDX based JH explosives was a bit lower, and the apparent activation energy was approximately decreased by 1.9% to be 127.1kJ·mol-1. The thermal stability of nano RDX based JH explosive was consistent with the industrial micron-sized RDX based JH explosive when at 100℃. The nano RDX based explosive had dense surface, when on equal density of 1.68g·cm-3 at 20℃, the compressive strength and the compression ratio were enhanced 91.8% and 39.7% respectively. The friction, impact and shock sensitivities were respectively decreased 21.1%,55.4% and 13.6%, which meaned great improvement of safety. Furthermore, the initiation reliability of nano RDX based JH explosive was better, and the detonation performance was equal.Fourthly, the application of nano HMX in PBX was researched. The mould powder of nano HMX based JO explosive was acquired and the mass ratio of the prepared mould powder ranging in 0.3-2mm was above 99.5% mainly distributing in 0.3-0.6mm. The component contents, thermal decomposition characteristic, thermal stability, microstructure, sensitivities and detonation performance of nano HMX based JO explosive were studied. Results had shown that the component contents of the prepared nano HMX based JO explosive were separately consistent with the given amout of each component, which meaned nano HMX hadn’t lost during the moulding process of JO explosive. Compared with industrial micron-sized HMX based explosive, the thermal decomposition peak temperature of nano HMX based JO explosives was a bit lower, and the apparent activation energy was approximately decreased by 3.6% to be 358.1kJ·mol-1. The thermal stability of nano HMX based JO explosive was consistent with the industrial micron-sized HMX based JO explosive when at 100℃. The nano HMX based explosive had dense surface, when on equal density of 1.71g·cm-3 at 20℃, the compressive strength and the compression ratio were enhanced 272.6% and 32.6% respectively. The friction, impact and shock sensitivities were respectively decreased 30.0%,48.0% and 24.4%, which meaned great improvement of safety. Furthermore, the initiation reliability of nano HMX based JO explosive was better, and the detonation performance was equal.Fifthly, the application of nano RDX in CMDB with low solid content(the solid content was under 30%, and the researched CMDB propellant containing 18% RDX was named GHD propellant in this thesis) was researched. The GHD propellant contained 10% nano RDX was prepared through the screw moulding technology, and the RDX content, thermal decomposition characteristic, thermal stability, microstructure, sensitivities and combustion performance were studied. Results had shown that the nano RDX content was consistent with its given amout, which meaned that nano RDX hadn’t lost during the moulding process of GHD propellant. Compared with the GHD propellant without nano RDX, the thermal decomposition peak temperature of GHD propellant contained 10% nano RDX was a bit lower, and the apparent activation energy was approximately decreased by 4.8% to be 164.2kJ·mol-1. The thermal stability of GHD propellant contained 10% nano RDX was consistent with the GHD propellant without nano RDX when at 120℃. The GHD propellant contained 10% nano RDX had dense surface, when on equal density of 1.66g·cm-3, the tensile strength and elongation were enhanced 37.4% and 16.1% at 50℃, enhanced 27.5% and 19.4% at 20℃, and enhanced 26.7% and 39.6% at -40℃, respectively. The friction and impact sensitivities were respectively decreased 51.3% and 50.4%, which meaned great improvement of safety. With limits of 8-18MPa at 20℃, the burning rate coefficient was enhanced 26.0% from 8.692 to 10.950, and pressure exponent was decreased 22.1% from 0.384 to 0.299, which meaned great improvement of combustion performance.Lastly, the application of nano RDX in CMDB with high solid content(the solid content was above 30%, and the researched CMDB propellant containing 48.5% RDX was named GHG propellant in this thesis) was researched. The GHG propellant contained 20% nano RDX was prepared through the screw moulding technology, and the RDX content, thermal decomposition characteristic, thermal stability, microstructure, sensitivities and combustion performance were studied. Results had shown that the nano RDX content was consistent with its given amout, which meaned that nano RDX hadn’t lost during the moulding process of GHG propellant. Compared with the GHG propellant without nano RDX, the thermal decomposition peak temperature of GHG propellant contained 20% nano RDX was a bit lower, and the apparent activation energy was approximately decreased by 6.0% to be 144.3kJ·mol-1. The thermal stability of GHG propellant contained 20% nano RDX was consistent with the GHG propellant without nano RDX when at 120℃. The GHG propellant contained 20% nano RDX had dense surface, when on equal density of 1.75g·cm-3, the tensile strength and elongation were enhanced 32.6% and 25.2% at 50℃, enhanced 25.4% and 46.9% at 20℃, and enhanced 17.5% and 23.7% at -40℃, respectively. The friction and impact sensitivities were respectively decreased 50.0% and 27.3%, which meaned great improvement of safety. With limits of 6-16MPa at 20℃, the burning rate coefficient was enhanced 36.9% from 6.139 to 8.405, and pressure exponent was decreased 21.6% from 0.463 to 0.363, which meaned great improvement of combustion performance.Basing on the principle of ’tiny force being exactly given to materials’,the nanometer nitramine explosives(RDX, HMX and CL-20) were prepared in control by mechanical milling and shown in this thesis. The principle of ’expansion and separation’ was proposed for anti-agglomeration, and nanometer nitramine explosive particles were effectively prevented to agglomerate and grow up. The’critical electron excitation energy’was proposed as an initial concept, and the mechanism for decreasing the sensitivity after nanocrystallization of nitramine explosives was stated. The prepared nanometer nitramine explosives were successfully applied in PBXs and CMDB propellants. The sensitivities of PBXs and propellants were significantly reduced, their mechanical properties were obviously enhanced, and the combustion performance of CMDB propellant was clearly improved. |
PDF Full Text Request