Hiroki Matsunaga

Thermal behavior of new oxidizer ammonium dinitramide

Ammonium dinitramide (ADN) is a promising new oxidizer for solid propellants because of its high oxygen balance and high energy content, and halogen-free combustion products. One of the characteristics needed for solid propellants is stability. Heat, light, and moisture are factors affecting stability during storage, manufacture, and use. For practical use of ADN as a solid propellant, clarification of the mechanism of decomposition by these factors is needed to be able to predict lifetime. This study focused on thermal decomposition of ADN. Exothermal behavior of ADN decomposition was measured by isothermal tests using high-sensitive calorimetry (TAM) and non-isothermal tests using differential scanning calorimetry (DSC). Based on these results, analysis of the decomposition kinetics was conducted. The activation energy determined by TAM tests was lower than that from DSC tests. Thus, the decomposition path in TAM tests was different from that in DSC tests. The amount of ADN decomposition predicted from TAM tests was closer to that found under real storage conditions than the amount of decomposition predicted from DSC tests. Non-isothermal tests may not be able to precisely predict the lifetime of materials with a decomposition mechanism that changes with temperature, such as ADN. The lifetime predicted from DSC results was much longer than that from TAM tests especially at low temperature. It is necessary to use isothermal tests to predict the long-term stability at low temperature.

Influences of aging on thermal decomposition mechanism of high performance oxidizer ammonium dinitramide

Ammonium dinitramide (ADN) is one of the several promising new solid propellant oxidizers. ADN is of interest because its oxygen balance and energy content are high, and it also halogen-free. One of the most important characteristics of a propellant oxidizer, however, is stability and ADN is known to degrade to ammonium nitrate (AN) during storage, which will affect its performance. This study focused on the effects of aging on the thermal decomposition mechanism of ADN. The thermal behaviors of ADN and ADN/AN mixtures were studied, as were the gases evolved during their decomposition, using differential scanning calorimetry (DSC), thermogravimetry–differential thermal analysis-infrared spectrometry (TG–DTA-IR), and thermogravimetry–differential thermal analysis-mass spectrometry (TG–DTA-MS). The results of these analyses demonstrated that the decomposition of ADN occurs via a series of distinct stages in the condensed phase. The gases evolved from ADN decomposition were N2O, NO2, N2, and H2O. In contrast, ADN mixed with AN (to simulate aging) did not exhibit the same initial reaction. We conclude that aging inhibits early stage, low temperature decomposition reactions of ADN. Two possible reasons were proposed, these being either a decrease in the acidity of the material due to the presence of AN, or inhibition of the acidic dissociation of dinitramic acid by NO3−.

Effects of amino acids on solid-state phase transition of ammonium nitrate

Abstract The purpose of this study was to obtain a better understanding of the effects of amino acids on the solid-state phase transitions of ammonium nitrate (AN). To this end, AN was combined with various amino acids in equimolar ratios and the phase transitions of the resulting mixtures were studied using differential scanning calorimetry (DSC) and in situ Raman spectroscopy. Compositional analysis was also conducted using X-ray powder diffraction (XRD), and the predicted stabilities of various molecular structures were assessed via quantum calculations. DSC and Raman results indicated that l-glycine and l-alanine inhibited the solid-state phase transitions of AN. Both XRD and calculation results suggested that AN reacts with these amino acids to form nitrate salts and that clusters are also generated by interactions between these compounds.

Thermal analysis of ammonium nitrate and basic copper(II) nitrate mixtures

AbstractBasic copper nitrate [Cu(NO3)2·3Cu(OH)2, BCN] is a widely used oxidizer for gas-generating compounds. The oxidizers that replace some BCN with ammonium nitrate (NH4NO3, AN) have been investigated to increase the performance of the gas-generating agents. The purpose of this study was to understand the thermal behavior and stability of AN/BCN mixtures. To this end, mixtures prepared by two kinds of methods, with and without heat treatment, were analyzed by X-ray powder diffraction to investigate composition of samples, and differential scanning calorimetry and thermogravimetry–differential thermal analysis with mass spectrometry (TG–DTA–MS) to investigate the thermal behavior and evolved gases. It was found that [Cu(NH3)2](NO3)2 was formed in the sample with thermal treatment. The samples with and without heating exhibited different decomposition processes. It is considered that the residual AN and the amount of [Cu(NH3)2](NO3)2 in the mixture affected the decomposition behavior.

Thermal decomposition characteristics of mixtures of ammonium dinitramide and copper(II) oxide

Ammonium dinitramide (ADN) is one of the most promising new solid oxidizers for rocket propellants, since its oxygen balance and energy content are relatively high, and it does not contain halogens. To gain a better understanding of the thermal decomposition mechanism of ADN, the thermal decomposition of ADN and copper(II) oxide (CuO) mixtures was investigated. The thermal behavior and activation energy associated with the decomposition of ADN/CuO mixtures were analyzed using sealed cell differential scanning calorimetry (SC-DSC). SC-DSC results showed that CuO affects the thermal characteristics of ADN and promotes its decomposition. Thermogravimetry–differential thermal analysis–evolved gas analysis was also performed, and in addition, the decomposition behavior was observed using hot stage microscopy. From the results, a thermal decomposition mechanism was proposed for ADN/CuO. In this mechanism, copper dinitramide Cu[N(NO2)2]2 is generated at the surface of the CuO almost simultaneously with the melting of the ADN. Next, a significant exothermic reaction occurs, associated with the decomposition of Cu[N(NO2)2]2, followed by decomposition of CuO via [Cu(NH3)2](NO3)2 and Cu(NO3)2.