Self-assembly Of A Typical Insensitive Explosive Nanoparticles

Insensitive explosives(2,6-diamino-3,5-dinitropyrazine-1-oxide, 1,3,5–tri amino-2,4,6-trinitrobenzene), possess many excellent properties, such as high energy, low sensitivity and good thermal stability, widely used in military fields. Insensitive explosive molecules have a large number of amino and nitro, which easily forming hydrogen bond, having poor dissolve in most common solvents, the crystal quality and morphology were control by recrystallization, have defects with solvent required for large, high energy consumption. Crystal morphology has a significant effect on processing and product performance. Hence, developing a new route is important to attract the most attention, which can easily and economically control crystal morphology. Therefore, in this paper, we use the aggregation proprety of nanoparticles, and present the solvent-induced self-assembly process to modify the morphology of insensitivity explosive by using insensitivity nanoparticles as raw material. The main contents are as follows:(1) Preparation of rectangular micro-rods by nano-LLM-105 self-assembly. The 2, 6-diamino-3, 5-dinitropyrazine-1-oxide micro-rods with cross section of rectangular were prepared by solvent-induced self-assembly process using nano-LLM-105 as raw materials. The rectangular micro-rods and LLM-105 twin crystal synthesized directly are compared. The effect of solvent, nano-LLM-105 addition, stirring rate and self-assembly time on the crystal morphology of LLM-105 prepared by self-assembly were studied. The regular rectangular micro-rods were assembled under the optimal conditions of self-assembly with DMSO as solvent, nano-LLM-105 addition of 40 g·L-1, stirring rate of 600 r·min-1, and the possible growth mechanism was proposed. The morphology, structure, thermal property and purity of crystals prepared by s elf-assembly were characterized by scanning electron microscopy, X-ray powder diffraction, different scanning calorimetry-thermogravimetry and high performance liquid chromatography. Comparing to LLM-105 twin crystals synthesized directly, the assembled regular rectangular micro-rods have the same diffraction peaks, but the intensity of peaks has weakened at 11.1o, 22.3o, 24.8o and 33.0o, it indicates that the crystal may be preferred to grow in the direction of the(1 0 0). And its purity was improved 1.8 % to 98.8 %. The regular rectangular rod-like crystals exhibit better thermal stability, its only o ne exothermic peak of is 356.7 ℃, its thermo-gravimetric starting temperature have been improved 34.8 ℃.(2) Preparation of gem-like micro-crystals by nano-TATB self-assembly. The gem-like crystals of TATB were prepared by solvent-induced self-assembly process using nano-TATB as raw materials. And the TATB crystal synthesized directly were compared. The effects of solvent, nano-TATB addition and self-assembly time on the crystal morphology of TATB prepared by self-assembly were studied and the possible growth mechanism of gem-like micro-crystals was proposed. The morphology, structure, thermal property, purity and density of crystals prepared by self-assembly were characterized by scanning electron microscopy, X-ray powder diffraction, different scanning calorimetry-thermogravimetry, high performance liquid chromatography and density gradient method. Results show that the regular gem-like crtstals are assembled under the optimal conditions with dimethylsulfoxide as solvent, nano-TATB addition of 10 g·L-1. Comparing to TATB crystals synthesized directly, the gem-like crystals have the same diffraction peaks, but all the intensities were weaken, which indicates that the crystal may be habit have changed and present different facets. Its puri ty was improved by 0.7 % to 98.9 %, and its density was improved by 0.0124 g·cm-3 to 1.9254 g·cm-3. Gem-like crystals have obtained not only characteristic of nanoparticles, but also property of micron molecules, which thermo-gravimetric starting temperature of 300℃,and the exothermic peak temperature have advanced 4 ℃ to 379.7 ℃.(3) Preparation of nano-FOX-7 by solvent/nonsolvent spray-crystallization method. Hexagonal FOX-7 crystals with particle size distribution at the range of 200-400 nm of were prepared by solvent/nonsolvent spray-crystallization method with dimethylformamid(DMF) as solvent, petroleum ether as nonsolvent. The effect of solvent, nonsolvent and FOX-7 addition on the crystal morphology and particle size were studied. And obtained the optimum conditions of nano FOX-7 with solvent as DMF, nonsolvent as petroleum ether, and FOX-7 addition is 0.05 g·m L-1.The morphology, structure, thermal properties of nano-FOX-7 were characterized by scanning electron microscopy, X-ray powder diffraction and different scanning calorimetry-thermogravimetry. Comparing with the raw FOX-7, nano-FOX-7 has a higher decomposition rate, and more easy to break down.(4) The micron crystals with cross section of octahedral were prepared by solvent-induced self-assembly process using nano-FOX-7 as raw materials and ultra-pure water as a solvent. But we have to further explore the optimum conditions.