V. V. Nedel'ko

Comparative Investigation of Thermal Decomposition of Various Modifications of Hexanitrohexaazaisowurtzitane (CL-20)

The thermal decomposition kinetics of different polymorphs of CL-20 (α, γ and e) has been investigated by thermogravimetry, IR spectroscopy and optical and electronic microscopy. The reactions proceed with self-acceleration and can be described by a kinetic law of first order with autocatalysis. Already at the earliest stages of decomposition (≤1%) phase transitions take place from αγ and from eγ. For this reason the observed decomposition is related to the decomposition of γ-CL-20. On the other hand, the kinetics of decomposition depends on the initial polymorphic state, so that the thermal decomposition increases in the series: α<γ<e. Experiments with different samples of α-CL-20 demonstrate that different rates of decomposition are observed for the same polymorph depending on the mean size and the size distribution of the crystals and their morphological features. In some cases the thermal stability of α-CL-20 can be increased by previous annealing. It is concluded that the thermal decomposition of CL-20 is purely a solid-state process. Microscopical and spectroscopical analysis of the condensed CL-20 decomposition product (formed after prolonged heating at high temperature) show that it has a network structure and consists mainly of carbon and nitrogen.

Kinetics of thermal decomposition of hexanitrohexaazaisowurtzitane

Thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW) in the solid state and in solution was studied by thermogravimetry, manometry, optical microscopy, and IR spectroscopy. The kinetics of the reaction in the solid state is described by the first-order equation of autocatalysis. The rate constants and activation parameters of HNIW thermal decomposition in the solid state and solution were determined. The content of N2 amounts to approximately half of the gaseous products of HNIW thermolysis. The thermolysis of HNIW and its burning are accompanied by the formation of a condensed residue. During these processes, five of six nitro groups of the HNIW molecule are removed, and one NO2 group remains in the residue, which contains amino groups and no C−H bonds.

Synthesis and thermal decomposition of ditetrazol-5-ylamine

Ditetrazol-5-ylamine (DTA) was synthesized from cyanuric chloride in four steps. The thermal decomposition of DTA in the solid state was studied by thermogravimetry, volumetry, mass spectrometry, IR spectroscopy, and calorimetry. Under isothermal conditions at 200–242 °C, thermal decomposition obeys the first order autocatalytic kinetics. The kinetic and activation parameters of DTA decomposition were determined. The composition of gaseous reaction products and the structure of condensed residue were studied. The thermal effect of thermal DTA decomposition is 281.4 kJ mol−1. The nitrogen content in a mixture of gaseous products formed by the reaction in a temperature interval of 200–242 °C exceeds 97 vol.%.

Thermal decomposition ofC-iodotetrazoles

Thermal decomposition of 1-substitutedC-iodotetrazoles in melt and solutions has been investigated. Thermal stabilities, kinetic and activation parameters, and compositions of products of thermolysis ofC-iodotetrazolcs depend on the substituent nature. The scheme of thermolysis ofC-iodotetrazoles has been suggested.

Thermal decomposition of 1-ethyl-5-iodotetrazole

The thermal decomposition of 1-ethyl-5-iodotetrazole in a melt and in solutions was studied using thermogravimetry, manometry, pyrolytic mass spectrometry, and IR spectroscopy. The kinetic and activation parameters of the process and the nature of the decomposition products were determined. The reaction mechanism is assumed to involve equilibrium tautomeric rearrangement of the tetrazole to azidoazomethine form followed by homolytic cleavage of the C-I bond.

THERMAL DECOMPOSITION OF NITROUREA

The thermal decomposition of nitrourea in the solid phase proceeds with a pronounced self-acceleration, the maximum reaction rate being reached at extremely high extents of conversion. A significant increase in the specific surface is simultaneously observed: the specific surface increases 33-fold by the time when the maximum reaction rate is reached, and the mean particle size becomes equal to 230 Å. In a closed system an increase in the pressure of the gas evolved is followed by an abrupt decrease. A mechanism for the process, in which an intermediate, isocyanic acid, and the heterogeneous character of the reaction play the key role is proposed on the basis of kinetic measurements and data on the composition of the decomposition products.

Density evolution of the energy-rich compound furazano[3,4-e]tetrazine-4,6-dioxide as stability indicator during prolonged storage

Pycnometric method, powder X-ray diffraction analysis, and IR spectroscopy were used to study the fundamental aspects of how the density of energy-rich compound furazano[3,4-e]tetrazine-4,6-dioxide varies during its prolonged storage. It was shown that the density grows during the first stage with length of up to 14 days due to the recrystallization. In further storage during eight years, the density gradually falls due to the buildup of stresses in the crystal lattice, created by thermal decomposition products. The degree of decomposition at 22°C during 8 years, evaluated by extrapolation of the Arrhenius dependence, is 0.24%. The observed decrease in the density is attributed to the anomalously weak hampering effect of the crystal lattice.

The role of additional anions in microporous aluminosilicates with cancrinite-type framework

Microporous framework aluminosilicates with the cancrinite- and sodalite-type structures containing NO3−, CO32−, SO42− and PO43−, as extra-framework anions were synthesized under hydrothermal conditions at temperatures from 160 to 200°C. SO42− exhibits the highest affinity to cancrinite structure at the competition of various X anions. Chemical composition, X-ray diffractometry characteristics, and IR spectra of the compounds obtained, as well as kinetics and mechanism of thermal transformations of nitrate counterpart of cancrinite, were studied.

Kinetics and Mechanisms of Cation Exchange and Dehydration of Microporous Zirconium and Titanium Silicates

The kinetics of ion-exchange reactions of 6 minerals with heteropolyhedral framework structures [heterosilicates: sitinakite, KNa2Ti4Si2O13(OH)·4H2O, penkvilksite, Na4Ti2Si8O22·5H2O, zorite, Na6Ti(Ti,Nb)4(Si6O17)2O(OH)4·11H2O, terskite, Na4ZrSi6O15(OH)2·H2O, gaidonnayite, Na2ZrSi3O9·2H2O, and kuzmenkoite-Mn, K2Mn(Ti,Nb)4(Si4O12)2(OH,O)4·nH2O], and so-called zirfesite, an amorphous product of natural hydrolysis of eudialyte, with aqueous solutions of salts of Cs, K, Sr and Cu was investigated by the dynamic calorimetry method. The effect of temperature, salt concentration as well as preliminary leaching on the kinetic low and activation energies of ion-exchange reactions was investigated. Na-deficient terskite can concentrate and keep fast U and Th that could have a practical use for the immobilization of these elements. Structural transformations accompanying cation-exchange processes and thermal dehydration of natural titano-, niobo- and zirconosilicates have been investigated by means of single-crystal X-ray diffraction, Rietveld and full-profile IR spectroscopy methods. In particular, crystal chemistry of Rb-, Sr-, Ba-, Ca- and Pb-exchanged forms of natural hilairite are investigated using single-crystal X-ray diffraction data.