Wooram Kim

Structural Effect of Potassium Sulfamate on Synthesis of Ammonium Dinitramide

Abstract Potassium sulfamate (PS) is an efficient starting material for the nitration reaction used in the synthesis of ammonium dinitramide (ADN), which is an environmentally friendly high-energy oxidizer for propellants that does not release chlorine-based compounds. PS is a core structure to form dinitramide, -N(NO2)2, by taking NO2− from nitric acid. In this work, five test batches of PS were prepared using a few solvents including ethanol, methanol, acetone, isopropanol, and their mixtures. The lab-made PSs matched well with the commercial PS in terms of the chemical structure. The use of acetone led to a high recovery of PS up to 97 w/w% and ultimately contributed to the formation of high-purity and (99.2%) and a high yield (57.3%) that are greater than those for commercial PS (87.3% purity and 31.3% yield). Therefore, we proved that the crystallinity and homogeneity of PS influenced the properties of ADN and the synthesis efficiency.

Comparative evaluation of purity of green energetic material (ammonium dinitramide) depending on refining method

Although the solid propellant, ammonium dinitramide (ADN, NH4N(NO2)2) is safe and thermally stable, it requires high purity for practical commercial applications. Even a small amount of impurities in ADN can create negative effects, including catalyst poisoning and thruster nozzle cloggings when it is used as a liquid propellant. Thus, we explored several purification processes for the precipitated ADN particles, such as repetition extraction, adsorption by activated carbons, and low-temperature extraction. These purifying methods help to improve the chemical purity as evaluated by FTIR, UV-vis, DSC, and IC analyses. Among the purification processes, adsorption was found to be the best method, showing a final purity of 99.768% based on relative quantification by ion chromatography.

Ordered Mesoporous Cu–Mn Metal Oxides for the Catalytic Decomposition of an Energetic Ionic Liquid

Ordered mesoporous Cu-Mn binary metal oxide (meso-CuMnOx) catalysts were successfully synthesized by a hard-templating method from a mesoporous silica template with a cubic Ia3d mesostructure (KIT-6) or hydrophobic KIT-6, exhibiting a well-developed crystalline framework, a regular pore size distribution and a high surface area. The copper and manganese elements in the mesoporous Cu-Mn binary metal oxides (meso-CuMnOx-N and meso-CuMnOx-HP), obtained from the KIT-6 and hydrophobic KIT-6, respectively, were homogeneously dispersed in the whole particles. The activities of meso-CuMnOx catalysts for the decomposition of a liquid monopropellant containing an energetic ionic liquid, ammonium dinitramide, were much higher than that over a CuMnOx catalyst prepared by a conventional precipitation method. This is attributed to the well-developed mesoporosity of the meso-CuMnOx catalysts. Among the mesoporous CuMnOx catalysts, the decomposition onset temperature over meso-CuMnOx-HP (87.9 °C) was found to be lower than that over meso-CuMnOx-N (100.4 °C), probably due to its higher mesoporosity and surface area.

Preparation of Mesoporous CuCe-Based Ternary Metal Oxide by Nano-Replication and Its Application to Decomposition of Liquid Monopropellant

Mesoporous CuCe-based ternary metal oxides were synthesized using KIT-6 as a hard template through a nano-casting method. The mesoporous CuCe-based metal oxides were applied to the catalytic decomposition of the ammonium dinitramide-based liquid monopropellant. The decomposition onset temperature over the meso-CuCe ternary metal oxides was much lower than that over the CuCeOx catalyst prepared by conventional precipitation method. Higher activity of the meso-CuCe ternary metal oxides is attributed to higher surface area and larger pore size of the meso-CuCe ternary metal oxides than those of the conventional CuCe oxide. The highest activity of meso-CuCeZr catalyst among the meso-CuCe ternary metal oxide catalysts is likely due to the highest mesoporosity.

Field Application of a Double Filtration Process to Control Fine Dust in a Metro Subway Station

This study attempted to find an alternative method for fine dust control in the pre-exiting facilities of metro-subway stations. A new double-layer design was proposed for the MVAC (mechanical ventilation and air control) system. Several filter lay-outs were combined a pre-filter with electret filter (EF), electret bundle filter (EBF), or electret pleated filter (EPF), and were then examined focusing on the collection efficiency of particulate matters and pressure drop across the filter layers. The experimental results from the lab and field tests showed the best collection efficiency with EPF, which achieved 85% for and 55% for . It was also found from the long term field test that the new filter lay-out could provide quite consistent dust level particularly in underground platform regardless of external condition.