• Bulletin of the Korean Chemical Society
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• v.35 no.4
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• pp.989-993
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• 2014

The molecular structures of 2,6-diaza-1,3,5,7-tetraoxaspiro[3,3]heptane (1) and its dinitro derivative, 2,6-dinitro-2,6-diaza-1,3,5,7-tetraoxaspiro[3,3]heptane (2), were fully optimized without symmetry constraints at $HF/6-31G^*$ level of theory. A bisected conformation with respect to the ring is preferred with a $C_2$ symmetric structure. The density of each molecule in the crystalline state was estimated to 1.12 and 2.36 $g/cm^3$ using PM3/VSTO-3G calculations from the molecular volume. The heat of formation was calculated for two compounds at the CBS-4M level of theory. The detonation parameters were computed using the EXPLO5 software: D = 6282 m/s, $P_{C-J}$ = 127 kbar for compound 1, D = 7871 m/s, $P_{C-J}$ = 307 kbar for compound 2, and D = 6975 m/s, $P_{C-J}$ = 170 kbar for 60% compound 2 with 40% TNT. Specific impulse of compound 1 in aluminized formulation when used as monopropellants was very similar to that of the conventional ammonium perchlorate in the same formulation of aluminum.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.05a
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• pp.390-393
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• 2010

The thermal decomposition rate of ammonium perchlorate with 3% of yellow iron oxide, FeOOH was found to be much faster than with red iron oxide, $Fe_2O_3$. By applying yellow and red iron oxide as a burning rate modifier to HTPB/AP propellant, burning rate of the HTPB/AP propellant with yellow iron oxide was shown to be 10 ~ 25% faster than with red iron oxide. There was no special difference in viscosity and hardness buildup of yellow and red oxide added HTPB/AP formulations.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.40-45
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• 2005

In the present work, the effect of formulation on friability of HTPB/AP propellants including Betacene and $Cr_2O_3$ has been studied. The mechanical properties and burning rate of the propellants were measured using Inston tensile tester and strand burner, respectively. Friability was calculated from shot-gun and closed bomb test data. The result showed that friability was higher, as the content of Butacene or AP $6{\mu}m$ in the propellant formulations was increased.

• Journal of the Korean Society of Propulsion Engineers
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• v.9 no.2
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• pp.46-53
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• 2005

We have analyzed the temperature and humidity aging test results of a composite solid propellant. The temperature aging test was performed to evaluate the storage life of a propellant, while the humidity aging test could provide the hygroscopicity of Ammonium Perchlorate(AP) exposed to .elative humidity (RH) 10, 30, $50\%$ environment. A specimen was used in the temperature test, and a block of propellant from the actual motor was used in the humidity test. We report that the 4-month storing at 60 degree is equivalent to the 10-year 60 degree condition. The composite solid propellant with HTPB binder showed signs of hardening with time lapse but the effect of humidity up to RH $50\%$ was not noticeable.

• Bulletin of the Korean Chemical Society
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• v.17 no.2
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• pp.173-179
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• 1996

A series of tetradentate Schiff base ligands; [1,2-bis(naphthylideneimino)ethane, 1,3-bis(naphthylideneimino)propane, 1,4-bis(naphthylideneimino)butane, and 1,5-bis(naphthylideneimino)pentane] and their Ni(Ⅱ) complexes have been synthesized. The properties of these ligands and their Ni(Ⅱ) complexes have been characterized by elemental analysis, IR, NMR, UV-vis spectra, molar conductance, and thermogravimetric analysis. The mole ratio of Schiff base to Ni(Ⅱ) metal was found to be 1:1. The electrochemical redox process of the ligands and their Ni(Ⅱ) complexes in DMF and DMSO solution containing 0.1 M tetraethyl ammonium perchlorate (TEAP) as a supporting electrolyte have been investigated by cyclic voltammetry, chronoamperometry, differential pulse voltammetry, and controlled potential coulometry at glassy carbon electrode. The redox process of the ligands was highly irreversible, whereas redox process of Ni(Ⅱ) complexes were observed as one electron transfer process in quasi-reversible and diffusion-controlled reaction. The electrochemical redox potentials of the Ni(Ⅱ) complexes were affected by the chelate ring size of ligands. The diffusion coefficients of Ni(Ⅱ) complexes containing 0.1 M TEAP in DMSO solution were determined to be 5.7-6.9 × 10-6 cm2/sec. Also the exchange rate constants were determined to be 1.8-9.5 × 10-2 cm2/sec. These values were affected by the chelate ring size of ligands.

• Advances in materials Research
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• v.13 no.2
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• pp.129-140
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• 2024

This study evaluates the ratio of Toluene di-isocyanate (TDI) functional group isocyanate (NCO) to the binder functional hydroxyl group (OH) in HTPB/AP/Al-based propellants on their mechanical properties, flow rate, and viscosity to determine the limitations of NCO/OH in the composition of solid propellants. The propellants consisted of hydroxyl-terminated polybutadiene (HTPB) polyurethane (PU), aluminum (Al) and tri-modal ammonium perchlorate (AP). The tri-modal AP consisted of 30% of coarse AP, 30% of medium AP, and 8% of fine AP. The ratio of NCO/OH varies from 0.73 to 0.85, with two binder percentages of 10.5% and 12%. An increase in NCO/OH ratio with 10.5% binder provided 20%, 95%, and 8 to 9% increments in UTS, modulus, and hardness, respectively. However, the propellant elongation, density, and flow rate decreased by 170%, 0.2%, and 11-12%, respectively. Viscosity increased 20% based on initial hour reading. The 12% binder provides 27%, 47%, and 5~6% an increment of UTS, modulus and hardness respectively. However, the propellant elongation, density, and flow rate decreased by 47%, 0.17% and 27%, respectively. The viscosity increased 30% based on initial hour reading. This study suggests the NCO/OH value of 0.77 and 10.5~11% binder content in propellant based on the mechanical properties, flow rate, and viscosity for better processing and pot life.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.4
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• pp.363-368
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• 2010

In the solid rocket propellant combustion, the dynamic phase change from solid to liquid to vapor occurs across the melt layer. During the surface burning, liquid and gas phases are mixed in the intermediate zone between the propellant and the flame to form micro scale bubbles. The known thickness of the melt layer is approximately 1 micron at $10^5$ Pa. In this paper, we present a model of the melt layer structure and the dynamic motion of the melt front derived from the classical phase field theory. The model results show that the melt layer grows and propagates uniformly according to exp(-1/$T_s$) with $T_s$ being the propellant surface temperature.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.7
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• pp.576-584
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• 2016

In this study, AP added propellant has been proposed as a method of enhancing the low specific impulse performance found for staged hybrid rocket engine. Experimental tests were carried out to analyze and evaluate the effect of AP added propellant on specific impulse performance as well as fuel-rich combustion characteristics in a staged hybrid rocket engine. Upper limit of AP content in propellant was set to be 15 wt% to maintain the hybrid rocket engine advantages. As a result, 15 wt% AP added propellant showed 3% higher specific impulse performance compared to 0 wt% AP added propellant. Moreover, AP addition proved to offer less injected oxidizer mass flow, less O/F variation, and less combustion pressure while producing fuel-rich gas of the same combustion temperature. Future studies will carry out more combustion tests with metal additives to further enhance specific impulse.

• Bulletin of the Korean Chemical Society
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• v.14 no.2
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• pp.195-200
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• 1993

The neutral, reduced, and oxidized 2,2-trans isomers of $Rh_2(ap)_4$ (ap=2-anilinopyridinate) were investigated with respect to dioxygen binding in $CH_2Cl_2$ containing 0.1 M tetrabutyl-ammonium perchlorate. $Rh_2(ap)_4$ binds dioxygen in nonaqueous media and forms a $Rh^{II}Rh^{III}$ superoxide complex, $Rh_2(ap)_4(O_2)$. This neutral species was isolated and is characterized by UV-visible and IR spectroscopy, mass spectrometry and cyclic voltammetry. It can be reduced by one electron at $E_{1/2}$ = -0.45 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^-$ as demonstrated by the ESR spectrum of a frozen solution taken after controlled potential reduction. The superoxide ion in ${[Rh_2(ap)_4(O_2)]}^-$ is axially bound to one of the two rhodium ions, both of which are in a +2 oxidation state. $Rh_2(ap)_4(O_2)$ can also be stepwise oxidized in two one-electron transfer steps at $E_{1/2}$ = 0.21 V and 0.85 V vs. SCE in $CH_2Cl_2$ and gives ${[Rh_2(ap)_4(O_2)]}^+$ followed by ${[Rh_2(ap)_4(O_2)]}^{2+}$. ESR spectra demonstrate that the singly oxidized complex is best described as ${[Rh^{II}Rh^{III}(ap)_4(O_2)]}^+$ where the odd electron is delocalized on both of the two rhodium ions and the axial ligand is molecular oxygen.

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.214-220
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• 2017

The spherical Al/RDX/AP composites with an average size of $550{\mu}m$ were successfully prepared by drowning-out/agglomeration (D/A) process. The surface morphology and dispersion of Al particles of those composites were investigated using SEM and EDS (energy dispersive spectrometry). As a result of thermal analysis, the onset temperature of thermal decomposition of the Al/RDX/AP composites by the D/A process was found to decrease about $50^{\circ}C$ and their thermal stability was shown to be relatively enhanced due to the increase of activation energy compared to those of using the physical mixing method. In the first decomposition region of AP, Prout-Tompkins model was shown to describe well the thermal decomposition of both composites by the physical mixing and D/A process. On the other hand, in the second decomposition region of AP, the decomposition mechanisms of composites by the physical mixing and D/A process were explained by the zero-order and contracting volume model, respectively.