Condensed-phase kinetics of cyclotrimethylenetrinitramine by modeling the T-jump/infrared spectroscopy experiment

Abstract

During the combustion of solid propellants, explosives, or pyrotechnics, the condensed phase experiences heating rates that may exceed 20,000 K/s. At such high heating rates, the thermal decomposition behavior of the energetic material could be affected by its rate of decomposition. To simulate the high heating rate environment, the T-jump experiment was developed for use with Fourier-transform infrared spectroscopy. The T-jump experiment utilizes electrical resistance heating of a thin Pt filament on which a small amount of the energetic test sample is placed. This work describes a heat transfer model of the filament and sample, a model of the current's control circuit, and global decomposition and heat release mechanisms of Cyclotrimethylenetrinitramine (RDX), which is an energetic ingredient .used in propellants and explosives. Comparisons of model calculations with experimental data reveal an excellent agreement. Similarly, the predicted time to rapid heat release for the highly energetic RDX sample also shows a good agreement with experimental results. Thus the use of the developed model in conjunction with experiments should be a useful tool in studying the thermal decomposition behavior of energetic materials under combustion-like conditions. NomenclatureA = pre-exponential factor A f = cross-sectional area of filament c, c p -specific heat E -activation energy gi, 82 = gains of electronic circuit h = heat transfer coefficient h g = enthalpy of gas = current = thermal conductivity = length of sample ' -mass = number of species = Nusselt number = heat transfer = Rayleigh number = universal gas constant = temperature -time time constants of electronic circuit = internal energy = voltage drop across filament -width of filament = axial coordinate = species mass fraction = thermal diffusivity or coefficient of electrical resistivity = thermal expansion coefficient = heat of formation i k L s m Af Nu q Ra R u T t *d u V w x Y a t c2 = A/i/ e = emissivity v = kinematic viscosity p e = resistivity of filament p f = density of filament p s = density of sample cr = Stefan-Boltzmann constant aj" = species production Subscripts av = average cond = conduction conv = convection e = electrical ex = time to explosion / = filament g = gas i = ith species in = initial / = liquid Ig = liquid to gas max = maximum rad = radiation ref = reference quantity s = sample set = set or prescribed condition sur = surroundings 0 = sample location Superscripts ' = per unit length ± = left (-) or right (+) side at x = L s

Kinetics of thermal decomposition of ε-hexanitrohexaazaisowurtzitane by TG-DSC-MS-FTIR

“…Fig. 5 represents the mass spectra of the gaseous products from HNIW decomposition, which shows the m/z 14,16,17,18,26,27,28,29,30,32,43,44,45,46 and 52 were detected. The onset, peak and end temperatures for the main ion numbers and the possible assignments are summarized in Table 2.…”

“…Two types of reaction pathways are suggested for the initial thermal decomposition of cyclic nitramines: (i) ring-opening reactions accompanied by a concerted C-N bond ring fission, (ii) homolytic cleavage of a N-N bond accompanied by the elimination of the -NO 2 group [3]. Brill and his co-workers [29] believed that there is a competition between these two pathways for thermal decomposition of cyclic nitramines. In the case of RDX, the first detected primary products are CH 2 O and N 2 O if the initial reaction pathway is a concerted C-N bond ring fission, and HCN and HONO for the N-N bond cleavage [30].…”

Decomposition kinetics of manganese tris (carbohydrazide) perchlorate (MnCP) derived from the filament control voltage of the T-jump/FTIR spectroscopy

“…(1). The intercept, γ , is not the conventional Arrhenius preexponential factor A, but is assumed to be about − ln A s [19]. Values of E s and ln A s are chosen to give the cumulative decomposition rate.…”

Kinetics of the exothermic decomposition reaction of flash pyrolysis of KNTO⋅H2O

“…The filament temperature had been calibrated under each pressure using compounds with standard melting points. The power supply was set to about 2000 • C s −1 , but heat transfer effects limited the heating rate of the sample to about 800 • C s −1 [19,20].…”