Explosive decomposition of slightly compacted powders of lead azide over a wide range of laser pulse length

Abstact  Initiation of slightly compacted powders of lead azide of density not greater than 1.2 g/cm³ by laser radiation with a wavelength of 1.06 μm was studied experimentally over a wide range of pulse lengths (10⁻⁵–10⁻³ sec). It is shown that the ignition threshold of the slightly compacted samples does not change as the laser pulse length is increased. It is found that the explosion products contain molten lead particles whose sizes are an order of magnitude larger than the sizes of similar particles from explosion of samples of density 4.0 g/cm³. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 98–100, September–October, 2008.     

Multistage mechanism of thermal decomposition of hydrogen azide

A kinetic mechanism for combustion of hydrogen azide (HN₃) comprising 61 reactions and 14 flame species (H₂, H, N, NH, NH₂, NNH, NH₃, HN₃, N₃, N₂H₂, N₂H₃, N₂H₄, N₂, and Ar) was developed and tested. The CHEMKIN software was used to calculate the flame speed at a pressure of 50 torr in mixtures of HN₃ with various diluents (N₂ and Ar), as well as the self-ignition parameters of HN₃ (temperature and pressure) at a fixed ignition delay. The modeling results of the flame structure of HN₃/N₂ mixtures show that at a 25–100% concentration of HN₃ in the mixture, the maximum temperature in the flame front is 25–940 K higher than the adiabatic temperature of the combustible mixture. Analysis of the mechanism shows that burning velocity of a HN₃/N₂ mixture at a pressure of 50 torr is described by the Zel’dovich-Frank-Kamenetskii theory under the assumption that the burn rate controlling reaction is HN₃ + M = N₂ + NH + M (M = HN₃) provided that its rate constant is determined at a superadiabatic flame temperature. The developed mechanism can be used to describe the combustion and thermal decomposition of systems containing HN₃.     

Initiation of lead azide using an electron pulse

A thermal model of the initiation of lead azide by means of an electronic pulse is studied. The heattransfer equations, which take into account the burnup of the sample, are solved numerically. Equations are derived for the ignition criterion and for the delay times in the ignition of condensed explosive materials. It is shown that the thermal ignition cannot explain the short delay time in the lead azide initiation by means of an electron pulse. Kemerovo. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 5, pp. 63–66, September–October, 1993.     

Criteria of excitation of explosive decomposition of silver azide by pulsed radiation

The process of explosive decomposition of silver azide in a pulsed electron radiation field was studied by the method of high-speed time-resolution optical spectroscopy. The criteria of excitation of explosive decomposition were determined. It is shown that in the case of short pulses, the critical parameter is the integral energy of the exciting pulse, whereas with the use of long pulses it is the pulse energy flux density.Published for purposes of discussionKemorovo. Translated from Fizika Goreniya i Vzryva, Vol. 28, No. 4, pp. 87–90, July–August, 1992.     

Explosive decomposition of silver azide single crystals for various diameters of the irradiated area

The threshold pulsed laser energy for initiating the explosive decomposition of silver azide single crystals was studied experimentally for various diameters of the irradiated area. It was found that, as the diameter of the irradiated area was decreased from 1000 to 10 µm, the threshold energy density of explosion initiation increased by more than an order of magnitude. It is shown that this dependence cannot be explained by light scatter, diffusion of reactants, or heat transfer from the reaction zone.     

Co-Precipitation Studies on Lead Azide with Tetrazole Derivatives-a search for lead azide substitute

Co-precipitation of lead azide with various tetrazole and nitrophenol derivatives is discussed. Thermal behaviour of lead azide before and after co-precipitation is studied suing DSC. Thermal study indicated that the co-precipitation of lead azide with other flame sensitive compounds produced an intimate mixture of lead azide and lead salts of tetrazole and nitrophenyl derivatives but not a single compounds. Explosive properties evaluation indicated that the co-precipitation process not only improves the flame sensitivity of lead azide but also eliminates the hazardous process of physical mixing of lead azide with flame sensitive materials. A good correlation between thermal sensitivity and flame sensitivity is noticed. Both thermal and flame sensitivity decreases.     

三水合乙酸铅在空气气氛下的热分解特性

通过热重分析技术(TG-DTA)和热重红外联用分析技术(TG-FTIR)等热分析技术研究三水合乙酸铅晶体在空气气氛条件下的热分解过程。其热分解过程中主要存在二氧化碳、丙酮和乙酸等中间产物。热解过程的关键转变温度为61.4℃、204.9℃、256.8℃、293.6℃、348.7℃。焙烧后铅粉的氧化度能够达到95%以上,视密度比传统球磨氧化铅粉低,吸水值高于传统的球磨氧化铅粉。研究结果对于三水合乙酸铅作为前体制备铅粉提供了参考依据。     

Determining the width of the reaction wave front in the explosive decomposition of silver azide

A procedure was developed and used to determine the width of the reaction wave in the explosive decomposition of single crystal whiskers (υ = 1.2 ± 0.2 km/s and l = 230 ± 30 μm) and a pressed powder (υ = 4.0 ± 0.4 km/s and l = 110 ± 10 μm) of silver azide. It is shown that in the mode of reaction propagation at a rate of 1.2 ± 0.2 km/s, the decomposition wave is almost symmetric, in contrast to the detonation wave.     

Critical initiation-energy density as a function of single-crystal size in explosive decomposition of silver azide

The dependence of the critical initiation-energy density of explosive decomposition of silver azide on the sample size was studied experimentally for the first time. The dependence of the critical energy density was found to be determined by the diffusion of the reactants to the crystal surface, where their recombination rate far exceeds the bulk rate. The diffusion coefficient and the rate constant of bulk electron-hole recombination obtained for the explosive decomposition agree within the experimental error with those determined earlier in photoconductivity studies. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 2, pp. 76–78, March–April, 2008.     

Thermal decomposition of poly(glycidyl azide) as studied by high-temperature FTIR and thermogravimetry

Thermal decomposition of poly(glycidyl azide) (PGA) has been studied by using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and high-temperature FTIR spectrometry. By using DSC and TGA techniques, the first stage weight loss of PGA due to exothermic decomposition of pendant azide ( N₃) groups was explained in terms of the energy released at every stage of decomposition. From the glass transition temperature (T_g) measurements, it was observed that T_g values of PGA increased with increasing quantity of decomposed  N₃ groups. The course of the decomposition reaction was also studied by taking successive FTIR spectra. It was observed that during the first stage weight loss process of PGA, the main chain was not decomposed thermally; inter- and intramolecular linking reactions accompanied the side chain decompositions. © 1996 John Wiley & Sons, Inc.