Modified Aerosol Routes to Core-Shell Nano-Energetic Materials Synthesis
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Modified Aerosol Routes to Core-Shell Nano-Energetic Materials Synthesis Jingyu Feng1, Snehaunshu Chowdhury2, Guoqiang Jian1, and Michael R. Zachariah1,2,* 1 Department of Chemistry and Biochemistry and 2Department of Mechanical Engineering, University of Maryland, College Park, MD 20742-3035, U.S.A. *Corresponding author: [email protected] ABSTRACT Following the generic strategy of creating core-shell structured nanoparticles reported by our group previously [1] and exploring its applications, an aerosol route combined with iron carbonyl decomposition was developed to encapsulate strong oxidizer within mild oxidizer particles. This modified method enables the application of hygroscopic nano-energetic materials by stabilizing them within a water-insoluble shell. Fe2O3/I2O5 composite oxidizers have been created. Some of the results obtained from combustion tests show that the composite system significantly outperforms the single metal oxide (Fe2O3) system in both pressurization rate and peak pressure. The time-resolved mass spectrometry shows that a significant amount of O2 and I2 are released from the composite oxidizers. These preliminary results suggest a supplement to the previous strategy of obtaining the core-shell structured composite oxidizers and the method still needs to be further optimized. INTRODUCTION Nano-energetic materials can rapidly generate heat and pressure, which can be applied in the fields of propellants and explosives [2]. They are usually the mixture of two kinds of nanoparticles, one works as the fuel while the other works as the oxidizer. The intimate mixing of the fuel and oxidizer enables larger contact area and smaller diffusion length for both heat and mass that will bring the whole system the higher burning rate, faster energy release rate and possibly higher energy output. Iodine pentoxide is a very strong oxidizer with highly hygroscopic [3] and biocidal properties [4]. It will be fascinating to combine the I2O5’s oxidizer and biocidal feature with the long term stability offered by mild metal oxides. In the present study, the modified approach based on our previous generic method of creating core-shell materials [1] was employed to incorporate the I2O5 inside the metal oxide shell. In order to determine their structures, the samples were imaged by TEM and EDS line scan. In addition, the pressure cell and Time-Resolved Mass-Spectrometry measurement were used to characterize the combustion performances of obtained samples. EXPERIMENT DETAILS Materials: Iodic acid (HIO3, 99.5%), iron (0) pentacarbonyl (Fe(CO)5, > 99.99%), and reference Fe2O3 (< 50 nm) were all purchased from Sigma-Aldrich. The aluminum (50 nm ALEX) used in the pressure cell test was obtained from the Argonide Corporation. The aluminum nanopowders were found to be 70 wt% active as measured by thermogravimetric analysis (TGA).
Aerosol route [1]: Aerosol droplets containing the dissolved precursor solution (HIO3) were generated by a home-made pressure atomizer. Droplets passed through a silica-gel diffusion dryer to remove m
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