No abstract

Ultrafine hexanitrohexaazaisowurtzitane (CL‐20) samples were prepared by a ultrasound‐ and spray‐assisted precipitation method. Raw CL‐20 and ultrafine CL‐20 samples were characterized by SEM, FT‐IR spectroscopy, XRD, and particle size analysis. The impact sensitivity and thermal stability of two CL‐20 samples were also tested and compared. The results indicate that by this recrystallization process, the mean particle size of CL‐20 is 470 nm, and the particle size distribution was in the range from 400–700 nm. The particle morphology is nearly spheric with a smooth surface. Compared with raw CL‐20, the impact sensitivity of the ultrafine sample is significantely reduced and the drop height (H50) is increased from 12.8 to 37.9 cm. The critical explosion temperature of ultrafine CL‐20 decreased from 235.6 to 229.0 °C, which suggests that the thermal stability of ultrafine CL‐20 is lower than that of raw CL‐20.

A new insensitive booster explosive based on 2,6‐diamino‐3,5‐dinitropyrazing‐1‐oxide (LLM‐105) was prepared by a solvent‐slurry process with ethylene propylene diene monomer (EPDM) as binder. SEM (scanning electron microscopy) was employed to characterize the morphology and particle size of LLM‐105 and molding powder. The mechanical sensitivity, thermal sensitivity, shock wave sensitivity, and detonation velocity of the LLM‐105/EPDM booster were also measured and analyzed. The results show that both mechanical sensitivity and thermal sensitivity of LLM‐105/EPDM are much lower than that of conventional boosters, such as PBXN‐5 and A5. Its shock wave sensitivity is also lower than that of PBXN‐5 and PBXN‐7. When the density of charge is 95 % TMD, its theoretical and measured detonation velocities are 7858 m s−1 and 7640 m s−1, respectively. These combined properties suggested that LLM‐105/EPDM can be used as an insensitive booster.

To improve the safety of HMX without sacrificing energy properties, the composites of TNT and an energetic material (HP-1) were used to coat HMX particles by a method of integrating solvent -nonsolvent with aqueous suspension-melting. SEM (scanning electron microscopy) and XPS (X-ray photoelectron spectrometry) were employed to characterize the samples. The effect of the processing parameters, such as mass ratio of HP-1 to TNT (MRHT), stirring speed, and cooling rate, on the quality of coated samples were investigated and discussed. The mechanical sensitivity, thermal sensitivity, thermal decomposition characteristic, and heat of detonation of raw and coated HMX samples were also measured and contrasted. Results show that when MRHT, stirring speed in the second stage and cooling rate are 1 : 5, 1000 r · min À1 and 5 8C · min À1 respectively, the optimal coating effect is achieved. Compared with that of raw HMX, both impact and friction sensitivity of HMX coated with 2.5 wt.-% TNT and 0.5 wt.-% HP-1 decrease obviously, whereas there is a slight change in their thermal sensitivity and thermal decomposition characteristics. Meanwhile, such surface coating does not result in the decrease of its energy properties.

1IntroductionIn the field of research and application of explosives, it is generallya ccepted that improving the power and reducing the sensitivity of explosives are often two opposingc haracteristics. Only an explosive with high energya nd low sensitivity can meet the application requirements adequately [1,2].I no rder to improve the performance of materials, cocrystalt echnology had been widely applied in the pharmaceutical field [3,4].N evertheless,s ince Levinthal patented the HMX/AP cocrystal explosivei n1 978 [5],t he cocrystal technology had not attracted extensive attention in the explosives arena. Nowadays, the technology of cocrystal explosives has been preliminarily researched. By cooling crystallization, Zhou obtaineda nu rea nitrate and RDX cocrystal explosive, whose explosionp erformance was superior to that of am ixtureo fu rea nitrate and RDX [6].T he HMX/ TATB cocrystal explosive wasd esigned based on crystale ngineeringa nd its crystals tructure was predicted using the polymorph predictorm ethodi namoleculard ynamics simulation by Wei [7].B ased on the research of Wei,S hen prepared the HMX/TATBc ocrystal explosive by as olvent/nonsolvent process [8].T he cocrystals tructures of HMX/NTO and HMX/NMPw ere designed using Monte Carlo simulations and first principle method by Lin [9,10].ACL-20/HMX cocrystale xplosive wasp repared by Andersonu sing the resonant acoustic mixing technology [ 11]. CL-20 and BTF cocrystale xplosive, which was prepared by Yang, was about 600 mminsize and its detonation power was predicted to be superior to that of BTF [12].B oth CL-20 and TNT were used to prepare the CL-20/TNT cocrystal explosiveb y Bolton and Yang, respectively [13,14].So far,t he cocrystal methods of explosivem ainly included solvent evaporation, cooling crystallization, solvent/nonsolvent crystallization, and resonant acoustic mixing crystal-lization. However,t he cocrystals size rangedf rom tens to hundreds of micrometers, which limited its application. It is generally accepted that ultrafine explosives possess better performance both in energy and sensitivityt han those in large size [15][16][17][18][19].I nt he aspect of highb urning rate, detonation rate and low criticald iameter,n ano or submicron explosivep articles are generally favored over the large particles [20][21][22][23].O nly little research is done on nano or submicrometer cocrystal explosives.The spray drying method had been used to prepare nano explosive using the high supersaturation in the rapid evaporation process and it had been used to prepare pharmaceutical cocrystals as well [24][25][26][27][28].B ased on this property of spray drying, nanoH MX/TNT cocrystals with high energy and low sensitivity were preparedi nt his paper.F urthermore, the structural characterization,t he formation reasons of cocrystals, impact sensitivity,a nd thermolysis of HMX/TNT cocrystals were investigated in detail.Abstract:C ocrystals of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane( HMX) and 2,4,6-trinitrotoluene (TNT) with high energy and low sensiti...