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Initiation of Ignition in Ammunition
Published in Ajoy K. Bose, Military Pyrotechnics, 2021
The primary explosive lead azide is mostly used in detonators while mercury fulminate and lead styphnate are used for ignition, the latter is also sensitive to electrical initiation. Tetrazene acts as a sensitiser. The presence of tetrazene considerably lowers the stab sensitivity. For example, 5% addition of tetrazene in compositions based on red lead oxide and boron with stab sensitivity of about 200 mJ, the sensitivity falls between 10 mJ and 20 mJ. However, there are some initiatory compositions that do not contain any explosive ingredients. These initiatory compositions are highly sensitive to above external stimuli and provide hot flame, hot gases and incandescent solid particles for ignition. Lead azide is incompatible with copper, copper alloys, zinc and cadmium and, hence, lead azide-based initiatory compositions are pressed in metal cups made of aluminium or aluminium alloys while mercury fulminate is not compatible with aluminium and hence mercury fulminate-based initiatory compositions are pressed in metallic cups of copper duly plated with compatible metal.
Applied Chemistry and Physics
Published in Robert A. Burke, Applied Chemistry and Physics, 2020
Metal azides are inorganic explosive compounds composed of the N3 ion attached to a metal. Heavy metal azides are very explosive when heated or shaken. These include silver azide (AgN3) and lead azide (PbN3). Lead azide is more explosive than other azides and is used in detonators that initiate secondary explosives. Sodium azide, NaN3, decomposes explosively upon heating above 275°C. It releases diatomic nitrogen and is used in airbag and airline escape chute deployment. It is highly toxic and behaves like cyanide inside the body (chemical asphyxiation). Response personnel should be very careful around automobile accidents where airbags have deployed. The white powder residue is likely to contain sodium azide. Most inorganic and organic azides are prepared directly or indirectly from sodium azide. Sodium azide is used in the production of metal azide explosive compounds and as a detonator.
Explosive terrorism characteristics of explosives and explosions
Published in Robert A. Burke, Counter-Terrorism for Emergency Responders, 2017
Metal azides are inorganic explosive compounds composed of the N3 ion attached to a metal. Heavy metal azides are very explosive when heated or shaken. Those include silver azide (AgN3) and lead azide (PbN3). Lead azide is more explosive than other azides and is used in detonators that initiate secondary explosives. Sodium azide, NaN3, decomposes explosively upon heating above 275°C. Sodium azide releases diatomic nitrogen and is used in airbag and airline escape chute deployment. Sodium azide is highly toxic and behaves like cyanide inside the body (chemical asphyxiation). Response personnel should be very careful around automobile accidents where airbags have been deployed. The white powder residue is likely to contain sodium azide. Most inorganic and organic azides are prepared directly or indirectly from sodium azide. Sodium azide is used in the production of metal azide explosive compounds and as a detonator.
Study on the crack propagation behaviour of eccentric uncoupled blasting in a deep-level rock mass
Published in International Journal of Mining, Reclamation and Environment, 2023
Fei Zhang, Liyun Yang, Huanning Hu, Chen Huang, Siyu Chen
The eccentric blasting test specimen is made of PMMA (polymethyl methacrylate), with a geometric size of 315 mm × 285 mm × 5 m, as shown in Figure 7, consider a plane strain model. Related blasting rock test research shows that PMMA can ideally simulate the mechanical behaviour of rock media under dynamic impact load [23,24]. The diameters of the blastholes are 7.5, 10, 12.5, and 15 mm, respectively. Lead azide (Pb(N3)2) was used as the explosive, and the physical parameters are shown in Table 1 [25]. The single blasthole charge is 200 mg. The structure of the specimen and the eccentric uncoupled charge is shown in Figure 7. The explosive package is placed next to the upper blasthole wall. At the same time, to explore the influence of vertical in-situ stress on the effect of eccentric uncoupled blasting. A three-level initial stress was designed. The stress field, σy are 0 MPa, 3 MPa, and 6 MPa, respectively, and the eccentric uncoupled blasting rock working conditions under the effect of the in-situ stress field σy are simulated. The sample number and blasting technical parameters are shown in Table 2.
Influence of stress waves on the propagation behavior of main crack induced by the slotted cartridge blasting
Published in Mechanics of Advanced Materials and Structures, 2022
Chenxi Ding, Chenglong Xiao, Jianhua Chen, Changda Zheng, Genghao Zhang, Shuai You, Songlin He, Wen Chen, Xintong Liang
Polymethyl methacrylate (PMMA) is used as the experimental material in the model experiment. Lead azide (Pb(N3)2) was the explosive used in the experiment. The detonation parameters of Pb(N3)2 and the physical-mechanical parameters of PMMA can be referred to in related literature [24, 25]. In this experiment, not only the influence of the reflected blasting stress wave was studied but also the effect incident blasting stress wave of the adjacent borehole on the main crack propagation behavior was evaluated. The schematic diagram of the specimen is shown in Figure 1. The specimen size was 400 mm × 300 mm × 5 mm. The slotted cartridge with a charge of 120 mg was placed in the circular borehole, and the slit was in the horizontal direction. In addition, a strip-shaped borehole was prefabricated above the circular borehole, and the strip-shaped borehole was placed in a strip of equal length. There are two main purposes for setting the strip-shaped borehole in the experiment. First, to provide a free boundary so that the blasting stress wave of the slotted cartridge is reflected at the strip-shaped borehole to form a reflected stress wave and acts on the main crack. Second, the strip-shaped charge blasting will form a blasting stress wave with a longer pulse time, obliquely entering the crack surface of the main crack and acting on the crack tip.
An elementary model for fast detonations in tubular charges
Published in Combustion Theory and Modelling, 2019
Irina Brailovsky, Leonid Kagan, Peter Gordon, Gregory Sivashinsky
Our explorations of the pertinent two-phase model showed that the precursor-shock and the post-shock rise of temperature survive the distinguished limit combining high initial porosity of the system () with strong disparity between initial solid and gas densities () while keeping the product finite. In particular, the precursor-shock effect is found to be feasible even in the absence of chemical heat release, being sustained exclusively by gasification of the solid phase. Moreover, the precursor-shock effect survives even for the Newtonian limit (adiabatic ) ensuring isothermicity of the system, and therefore may be captured within a model not involving the energy equation. In addition, the model neglects compaction, interphase friction, solid phase compressibility and its motion. The isothermal, high-porosity formulation proved to be highly advantageous for analytical and numerical exploration of the problem. It was found that the precursor-shock emerges when the ignition pressure () exceeds a certain critical value. However, in highly sensitive explosives (low ), the precursor shock does not form (Figure 2), which agrees with experimental studies of two-layer charges involving primary explosives such as lead azide [5].