title: Pursuing reliable thermal analysis techniques for energetic materials: decomposition kinetics and thermal stability of dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50).
abstract: Thermal decomposition of a novel promising high-performance explosive dihydroxylammonium 5,5'-bistetrazole-1,1'-diolate (TKX-50) was studied using a number of thermal analysis techniques (thermogravimetry, differential scanning calorimetry, and accelerating rate calorimetry, ARC). To obtain more comprehensive insight into the kinetics and mechanism of TKX-50 decomposition, a variety of complementary thermoanalytical experiments were performed under various conditions. Non-isothermal and isothermal kinetics were obtained at both atmospheric and low (up to 0.3 Torr) pressures. The gas products of thermolysis were detected in situ using IR spectroscopy, and the structure of solid-state decomposition products was determined by X-ray diffraction and scanning electron microscopy. Diammonium 5,5'-bistetrazole-1,1'-diolate (ABTOX) was directly identified to be the most important intermediate of the decomposition process. The important role of bistetrazole diol (BTO) in the mechanism of TKX-50 decomposition was also rationalized by thermolysis experiments with mixtures of TKX-50 and BTO. Several widely used thermoanalytical data processing techniques (Kissinger, isoconversional, formal kinetic approaches, etc.) were independently benchmarked against the ARC data, which are more germane to the real storage and application conditions of energetic materials. Our study revealed that none of the Arrhenius parameters reported before can properly describe the complex two-stage decomposition process of TKX-50. In contrast, we showed the superior performance of the isoconversional methods combined with isothermal measurements, which yielded the most reliable kinetic parameters of TKX-50 thermolysis. In contrast with the existing reports, the thermal stability of TKX-50 was determined in the ARC experiments to be lower than that of hexogen, but close to that of hexanitrohexaazaisowurtzitane (CL-20).
authors.affiliation: Semenov Institute of Chemical Physics RAS, 4, Kosygina Str., 119991 Moscow, Russia. n.v.muravyev@ya.ru.
authors.forename: Nikita V
authors.initials: NV
authors.lastname: Muravyev
authors.affiliation: Semenov Institute of Chemical Physics RAS, 4, Kosygina Str., 119991 Moscow, Russia. n.v.muravyev@ya.ru.
authors.forename: Konstantin A
authors.initials: KA
authors.lastname: Monogarov
authors.affiliation: Zelinsky Institute of Organic Chemistry RAS, 47, Leninsky Ave., 119991 Moscow, Russia and Topchiev Institute of Petrochemical Synthesis RAS, 29, Leninsky Ave., 119991 Moscow, Russia.
authors.forename: Andrey F
authors.initials: AF
authors.lastname: Asachenko
authors.affiliation: Zelinsky Institute of Organic Chemistry RAS, 47, Leninsky Ave., 119991 Moscow, Russia and Topchiev Institute of Petrochemical Synthesis RAS, 29, Leninsky Ave., 119991 Moscow, Russia and Lomonosov Moscow State University, Department of Chemistry, 1/3, Leninskiye Gory, 119991 Moscow, Russia.
authors.forename: Mikhail S
authors.identifier: http://orcid.org/0000-0001-8941-4856
authors.initials: MS
authors.lastname: Nechaev
authors.affiliation: Nesmeyanov Institute of Organoelement Compounds RAS, 28, Vavilova Str., 119991 Moscow, Russia.
authors.forename: Ivan V
authors.initials: IV
authors.lastname: Ananyev
authors.affiliation: Zelinsky Institute of Organic Chemistry RAS, 47, Leninsky Ave., 119991 Moscow, Russia.
authors.forename: Igor V
authors.initials: IV
authors.lastname: Fomenkov
authors.affiliation: Novosibirsk State University, 2, Pirogova Str., 630090 Novosibirsk, Russia and Institute of Chemical Kinetics and Combustion SB RAS, 3, Institutskaya Str., 630090 Novosibirsk, Russia.
authors.forename: Vitaly G
authors.initials: VG
authors.lastname: Kiselev
authors.affiliation: Semenov Institute of Chemical Physics RAS, 4, Kosygina Str., 119991 Moscow, Russia. n.v.muravyev@ya.ru.
authors.forename: Alla N
authors.initials: AN
authors.lastname: Pivkina