Anomalous decomposition of dinitramide metal salts in the solid phase

Abstract

Unusual regularities are observed for decomposition of dinitramide metal salts in the solid phase: the solid-phase reaction is 10--103 times faster than that in the melt, its rate has a sharp peak in the ?egion of eutectics melting with the decomposition product (metal nitrate), and it is instantly inhibited by water vapor. In the inhibited regime, the rate in the solid phase is lower than that in the fiquid phase. No indications of this anomalous behavior are observed for the decomposition of the dinitramide guanidinium salt.It was found in the work I devoted to the study of the thermal decomposition of potassium dinitramide (KN(NO2)2) that on going from the melt to the solid state, the reaction rate does not decrease, as usually takes place for inorganic salts, 2 but, on the contrary, increases sharply. Water vapor inhibits the solid-phase reaction, and the decomposition of solid KN(NO2) ~ in the inhibited regime is considerably slower than in the melt. The study of the mechanism of this unusual reaction, which was named the anomalous decomposition, 1 can be facilitated by a detailed phenomenological description and establishment of its scope and limitations among dinitrarnide (DNA) salts. Therefore, in this work, we studied the liquid-and solid-phase decomposition of several metal DNA metal salts and one onium salt, dinitramide guanidinium.Note. a Calculated from the k values at 160 ~ presented in Ref. 6 assuming that logA/s -1 has the value 15.0 typical of alkaline salts.Data in Ref. 6. c Air pressure (Tort) above the sample, a Data of Refs. I and 3. e At 150 ~

Reactive Molecular Dynamics Study on the Effect of H2O on the Thermal Decomposition of Ammonium Dinitramide

“…The growth rates and amounts of N 2 with time for the ADN with water contents of 2 % and 5 % are similar, which are higher than the other three. The results show that the water contents of 2 % and 5 % can better promote the decay of the ADN, and its degree of decomposition is more thorough, which are almost consistent with the literature [39][40][41][42]. This may be because when the dry ADN combines with H 2 O, water can induce protons to transfer from NH 4 + to N(NO 2 ) 2 À , forming H 3 N…HON(O) NNO 2 * nH 2 O complex and the formation of this complex requires more energy, resulting in an increase in the sublimation enthalpy of ADN.…”

The anomalous solid state decomposition of ammonium dinitramide: a matter of surface polarization

“…Metal and ammonium dinitramides exhibit anomalous decomposition behaviors in the solid state with increased decomposition rates compared to the liquid. [5][6][7] In ADN the rate peaks close to 60 1C, which coincides with the eutectic temperature with ammonium nitrate. 6,7 Furthermore, water in small amounts (o0.5%) is known to act as a stabilizer.…”

“…14 Furthermore, formation of dinitraminic acid cannot explain the decomposition barriers of metal dinitramides, which are similar to ADN. 5 Pavlov and co-workers have suggested that the anomalous decomposition behaviors of metal dinitramide salts and ADN may be attributed to surface effects. 5,6 The dinitramide anions at the surface are not fully coordinated by the ammonium cations, and the non-symmetric coordination of the NO 2 groups leads to polarization and reduced stability.…”

Kinetic Stability and Propellant Performance of Green Energetic Materials

“…Thus, the decomposition barrier for dinitramide anions in low and medium polarity solvents will be in the vicinity of 40 kcal mol À1 , in good agreement with experimental estimates for several solid and molten dinitramide salts. [35] Trinitrogen dioxide: Modeling the kinetic stability of the trinitrogen dioxide anion (c.f. 2 in Scheme 2) is a complex matter, mostly due to the proximity of different spin states.…”