Supercritical Seds Prepared Nano Rdx/the Sio < Sub > 2 < / Sub > Aerogel Research

Nano-SiO2aerogel has a special purposeinthefieldofEnergetic Materials considering its excellent anti-heat and heat insulation properties,catalytic properties and good biocompatibility. Combining the excellent properties of Nano-SiO2aerogel with elemental high-energy explosives, its energy release efficiency and rate can be adjusted according to need by improving the microstructure, dispersion, sensitivity and reactivity and so on of energetic materials. Therefore, the preparation of small particle size, narrow distribution and good dispersion of Nano-composite explosives are the pursuit of this topic.The paper researches the mechanism of the solution enhanced dispersion by supercritical fluids (SEDS) preparing nanoparticles on the basis of the classical crystallization theory. The degree of supersaturation and the concentration of the anti-solvent is the driving force for the nucleation and crystallization of solutes and the key of controlling crystal particle properties in the progress of the solution enhanced dispersion by supercritical fluids. The system is in three-phase equilibrium, that is, the system is in a total critical state, conducive to the high degree of supersaturation. Considering nucleation and development of solutes are in the same area, so the particles that morphology and particle size distribution are uniform can be get.Preparing Nano-RDX/SiO2composite energetic materials by SEDS method was first designed on the basis of the above theories. Theconfigured RDX/SiO2sol was entered the nozzlevia a coaxial but different lines before the sol changed to gel. The RDX/SiO2solwas injected in the supercritical fluid before a short time of mix.The sol was scattered into a small gels by the high momentum of supercritical fluid. The solventwas extracted by supercritical fluid at the same time, and theover-saturated crystallization of the solute was separated out.In order to ensure that the particle morphology and particle size distribution wereuniform, the process parameters of the solution enhanced dispersion by supercritical fluids were controlled. Such as the velocity of supercritical CO2(VC), the velocity of sol (VS), the system temperature (T) and the pressure (P); The formula of the sol was also researched to control the particle nucleation and the growth speed of crystal nucleus.Such as the hydrolyzed formula of TEOS and mixed solvent formula of RDX. The above contents were discussed and researched via a series of experiments.The results of optimized experiment show that:the mixed solvent of RDXischoseacetone and DMF, the proportionof the mixed solventis2:3and the concentrationis0.16g/mL; The hydrolyzed formula of ethyl orthosilicateis TEOS:H2O:EtOH:DMF=1:6:8:4(Mole ratio),hydrolyze120min in the temperature of60℃,and the PH value of RDX/SiO2sol is7; The proportion of supercritical CO2velocity (VC) and the solvelocity (Vs) is60:1, and the selected conditions are Vs=5mL/min, T=50℃, P=120bar. Above experimental conditions for the optimal experimental conditions, under the experimental conditions, the overall shape and uniform particle size distribution nanoenergetic material aerogel can be obtained. The performancesof Nano-RDX/SiO2composite powder were characterized by polarized electron microscope, field emission scanning electron microscope, fourier infrared spectrometer,impact sensitivity tester, detonation velocity tester and so on. The results show that:the composite explosive powder which morphology is uniform and particle size distribution is in50～100nm can be prepared by SEDS. The impact sensitivity (H50) is86cm (the weight of drop hammer is5.0kg), and the detonation velocity is8012m/s. The preparation technology is simple, the reaction conditions are mild and CO2is cheap and green environmental protection. In a word, the method is suitable for industrial production.