Yu Ichiro Izato

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.

Direct Self-Sustained Fragmentation Cascade of Reactive Droplets

A traditional hand-held firework generates light streaks similar to branched pine needles, with ever smaller ramifications. These streaks are the trajectories of incandescent reactive liquid droplets bursting from a melted powder. We have uncovered the detailed sequence of events, which involve a chemical reaction with the oxygen of air, thermal decomposition of metastable compounds in the melt, gas bubble nucleation and bursting, liquid ligaments and droplets formation, all occurring in a sequential fashion. We have also evidenced a rare instance in nature of a spontaneous fragmentation process involving a direct cascade from big to smaller droplets. Here, the self-sustained direct cascade is shown to proceed over up to eight generations, with well-defined time and length scales, thus answering a century old question, and enriching, with a new example, the phenomenology of comminution.

The decomposition pathways of ammonium dinitramide on the basis of ab initio calculations

ABSTRACT Quantum chemistry calculations incorporating solvent effects were used to investigate the decomposition pathways in molten Ammonium dinitramide (ADN). Optimized structures for reactants and products were obtained at the CBS-QB3//ωB97XD/6–311++G(d,p)/SCRF = (solvent = water) level of theory, considering the isomers ADNI (NH4–N(NO2)2) and ADNII (NH4–ON(O)NNO2) and the four ADNII conformers, which are minimal clusters of anion and cation in molten ADN. In the initial stage of decomposition, the ADNII decomposes to NO2∙ and NNO2NH4. Following the initial decomposition, NNO2NH4∙ decomposes to N2O, NH3, and OH∙, and the OH∙ combines NO2∙ to yield HNO3. This decomposition can be written using one global formula: ADN → N2O + NH4NO3 (NH3 + HNO3).

Initial Decomposition Pathways of Aqueous Hydroxylamine Solutions

This work examined the reaction pathways involved in the initial decomposition of aqueous hydroxylamine solutions via the overall reaction, 2NH2OH → NH3 + HNO + H2O, using quantum chemistry calculations incorporating solvent effects. Several possible decomposition mechanisms were identified and investigated: three neutral-neutral bimolecular, two water-catalyzed, one neutral trimolecular, two ion-neutral bimolecular, and one cation-catalyzed. Optimized structures for the reactants, products, and transition states were obtained at the ωB97XD/6-311++G(d,p)/SCRF = (solvent = water) level of theory, and the total electron energies of such structures were calculated at the CBS-QB3 level of theory. The cation-catalyzed reaction 2NH2OH + NH3OH+ → NH4+ + HNO + H2O + NH2OH (maximum energy barrier (ΔE0‡) = 53.6 kJ/mol) and the anion-neutral bimolecular reaction NH2OH + NH2O- → NH3 + 1NO- + H2O (ΔE0‡ = 79.0 kJ/mol) were both found to be plausible candidates for the dominant step in the initial decomposition. The results of this study indicate that both acidic and basic conditions can affect the thermal stability of hydroxylamine in water.

Analysis of the thermal hazards of 1-butyl-3-methylimidazolium chloride mixtures with cellulose and various metals

Ionic liquids (ILs) are a relatively new class of environmentally benign and comparatively safe solvents and are expected to have numerous applications in chemical processes. Although pure ILs are thermally stable, the presence of impurities can affect their thermal stability and decomposition behavior. In addition, ILs decomposition products include flammable gases that may present a fire hazard. When designing safer processes and operating conditions, it is therefore important to investigate IL thermal properties and decomposition products in combination with additives. The present work focused on cellulose dissolution which is promising application of ILs to obtain better understanding of thermal hazards. Mixtures of cellulose, iron (III) oxide (Fe2O3), copper(II) oxide (CuO), chromium, and nickel with 1-butyl-3-methylimidazolium chloride (BmimCl) were examined, using differential scanning calorimetry, high-sensitivity calorimetry, and thermogravimetry–differential thermal analysis–mass spectrometry. The addition of CuO was found to generate an exothermic reaction below the decomposition temperature of BmimCl and also to lower the decomposition temperature. BmimCl/CuO mixtures also produced extremely flammable gases below the decomposition temperature of pure BmimCl.