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Conceptually new cylindrical charges enveloped by Al foils have been designed and their thermobaric effects, due to simultaneous fragmentation and combustion of the foils, have been experimentally determined. The fragmentation processes of Al foil was supported by numerical simulations. It has been shown that the quasistatic pressures (QSP) for phlegmatized RDX (RDX ph ) enveloped with Al-coated plastic foils are higher than that of the pure RDX ph , due to combustion of these foil fragments in a thermobaric explosion. The QSP generated by Al–Ni foils enveloping RDX ph was found to be much lower than performance of other foils, possibly due to relatively inert nature of Ni. In a small detonation chamber, the charges of RDX ph /Al foil (RDX ph /Alf) produced even higher experimental maximum peak pressure (Δ p max ) than the charges that contained Al powder (Al p ). In a closed bunker, the impulse amplitudes of RDX ph enveloped by aluminized polyethylene (Al-PE) foils and RDX ph enveloped by 100 µm Alf (Alf100) charges are much lower than those of the other charges. It was found that the charges enveloped by Al foils have even larger Δ p max than that of RDX ph /Al p charges, indicating that the Alf could generate better blast performances than the Al p . The simulations indicate that the observed blast enhancement is dependent not on the thickness, but on the size of surrounding space. The thermobaric fire-ball generated by 40 g RDX/Alf charge could sustain combustion up to 40 ms, reaching a maximum radius of about 2.4 m. [ABSTRACT FROM AUTHOR]

Highlights: [•] The thermal behavior of Fluorel bonded explosives (PBXs) containing cyclic nitramines have been investigated. [•] Their decomposition kinetics parameters have been calculated by modified Kissinger–Akahira–Sunose (KAS) method. [•] It has been found that Fluorel matrix has a significant effect on the activation energy distribution of cyclic nitramines. [•] The Fluoropolymer is chemical incompatible cyclic nitramines with crowded molecule such as BCHMX. [Copyright &y& Elsevier]

Highlights: [•] The effects of Viton A binder on the thermal behavior of cyclic nitramines have been investigated by using non-isothermal techniques. [•] The decomposition kinetics parameters have been calculated by modified Kissinger-Akahira-Sunose method. [•] As a thermostable polymer, Viton A could inhibit the initial autocatalysis effect of cyclic nitramines. [•] It would improve the thermal stability of corresponding PBXs containing RDX, β-HMX and ε-CL-20. [Copyright &y& Elsevier]

The crystal structure, thermal behavior, and decomposition kinetics of ε-CL-20, RS-ε-CL-20, α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 were investigated by nonisothermal FTIR, TG, and DSC techniques. It was found that the thermal decomposition of α-CL-20, ε-CL-20/C4, and RS-ε-CL-20/C4 could be considered as a two-step process and the initial step is partly controlled by crystal structure. However, the crystal structure could only affect the initial step of decomposition and the total heat release, and the heat release of RS-ε-CL-20 is the highest compared with α- and normal ε-CL-20. In addition, the activation energy of studied materials was calculated by Kissinger method and modified KAS method, which was compared with the results obtained by other researchers. It was indicated that the obtained activation energy of ε-CL-20 by Kissinger method is about 176.0 kJ mol, which is almost the same with the results from the literatures by STABIL and Noniso-TG methods. It was noticed that the crystal structure has significant effect on the initial activation energy distribution of CL-20, while in case of second stage (α = 0.30-0.85) this effect is relatively small, resulting in identical decomposition mechanism. Moreover, the kinetic compensation effects show that the studied materials could be divided into two groups, one including ε-CL-20, RS-ε-CL-20, α-CL-20, and ε-CL-20/C4 which decompose at solid state and another including ε-CL-20/Formex and RS-ε-CL-20/C4 which decompose at partial liquid state, resulting in different kinetic compensation effects. It reveals that the C4 base could affect the distribution of activation energy of ε-CL-20 and RS-ε-CL-20 in a totally different way. [ABSTRACT FROM AUTHOR]

Over the past 20 years, a number of scientists have conducted numerous fundamental investigations based on quantum chemistry theory into various mechanistic processes that seems to contribute to the sensitivity of energetic materials. A large number of theoretical methods that have been used to predict their mechanical and spark sensitivity are summarized in this article, in which the advantages and disadvantages of these methods, together with their scope of use are clarified. In addition, the theoretical models for thermal stability of explosives are briefly introduced as a supplement. It has been concluded that the current ability to predict sensitivity is merely based on a series of empirical rules, such as simple oxygen balance, molecular properties, and the ratios of C and H to oxygen for different classes of explosive compounds. These are valid only for organic classes of explosives, though some special models have been proposed for inorganic explosives, such as azides. An exact standard for sensitivity should be established experimentally by some new techniques for both energetic compounds and their mixtures. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Abstract: The thermal behavior and decomposition kinetics of C4-bonded PBXs based on some attractive cyclic nitramines were investigated by means of nonisothermal TG and DSC techniques. It has been shown that only a single decomposition process has been observed for RDX-C4 while an obvious two-step process for mixture of BCHMX-C4 CL-20-C4, and HMX-C4. The onset temperature of the exotherms were observed at 216.3, 238.7, 279.2 and 236.7°C with the peak temperatures of 235.1, 279.0, 231.2 and 233.7°C for RDX-C4, BCHMX-C4, HMX-C4 and CL-20-C4, respectively. Their corresponding exothermic decompostion processes were covered by energy changes of 1749, 1938, 1213 and 2639Jg−1, which are lower than that of their pure cyclic nitramines. It was also proved that C4 matrix has significant effect on the activation energy distribution of RDX, BCHMX and CL-20, whose initial autocatalysis effect was inhibited or weakened. With regard to HMX-C4, the activation energy of its initial step is much lower than that of the second step. [Copyright &y& Elsevier]

Abstract: As an attractive new energetic material, cis-1,3,4,6-tetranitrooctahydroimidazo-[4,5-d]imidazole (BCHMX) and its polymer bonded explosive (PBX) with styrene-butadiene rubber (SBR) binder (Formex type) have been investigated with regard to its thermal decomposition kinetics and reaction models by using DSC, TG and SEM techniques. It was found that the decomposition of BCHMX in dynamic nitrogen could be divided into two steps, while there is only one step for its Formex bonded explosive. The activation energy for decomposition of BCHMX/Formex was obtained to be 221.7±4.99kJmol−1 by modified KAS method, while the mean activation energies for pure BCHMX are calculated as 233.0±2.1kJmol−1 for first step and 186.0±0.92kJmol−1 for the second step. It was further proved that the first decomposition step of BCHMX is autocatalytic, during which the crystal of BCHMX could dissolve in the liquid phase of its thermolysis products on the surface. Besides, the JMA and AC models were found to be appropriate to interpret the two-step decomposition of pure BCHMX and JMA model for BCHMX/Formex, the parameterized reaction models for BCHMX could be established as f(α)= α 0.45(1− α)1.51 and f(α)=2.33×(1− α)[−ln(1− α)]0.57, while for BCHMX/Formex as f(α)=2×(1− α)[−ln(1− α)]1/2. [Copyright &y& Elsevier]

Abstract: In this paper, several fundamental investigations published over the past decades with regard to the thermal analysis of polymer-based explosives (PBXs) have been briefly reviewed. A number of explosive fillers and polymer bases that were used as their main ingredients of PBXs are summarized herein. In addition, the calculation methods for their decomposition kinetics and thermal stability parameters are also introduced in detail. It was concluded that only PBXs based on HMX, RDX and TATB have been widely investigated, and that some other PBXs containing innovative fillers, such as CL-20, TNAZ, NTO and BCHMX are at the design stage. The isoconversional methods and model fitting procedures are usually used to analyze the discrete thermolysis processes of PBXs. In addition, their thermal stability parameters such as shelf life, explosion delay, critical temperature, thermostability threshold, 500-day cookoff temperature and approximate time to explosion could be calculated easily from the kinetic data. [Copyright &y& Elsevier]

The zero-order reaction rates (specific rate constants) of isothermal decomposition at 120 °C of plastic bonded explosives (PBXs) in the first six hours of decomposition were measured by means of the Czech vacuum stability test, STABIL. The PBXs were filled by RDX (1,3,5-trinitro-1,3,5-triazinane), β−HMX (β−1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX and ϵ-CL20 (ϵ-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane, ϵ-HNIW) and, in one case, on a mixture of BCHMX and 3-nitro-1,2,4-triazol-5-one (NTO), in a 1:1 wt. ratio. These nitramines were bonded by 9% by wt. of softened polyisobutylene matrix, 13% by wt. of softened polystyrene-butadiene matrix, 18% by wt. of crosslinked hydroxyl-terminated polybutadiene, 12% by wt. of polydimethylsiloxane and by 40% of TNT. The relationships of specific rate constants with experimental detonation velocities, impact and friction sensitivities of these PBXs are shown and discussed. It is postulated that this approach provides results which are applicable to studies of initiation reactivity of energetic materials and which are fully comparable with those of other methods of investigation in this area. [ABSTRACT FROM AUTHOR]

[Display omitted] • AuNCs-engineered nanofibrous film was fabricated for the detection of explosives. • The dual-emitting AuNCs exhibit rapid response, high sensitivity and specificity for CL-20 and TNT. • The "BUF" and "NOT" logic gates were designed based on distinct response patterns. • The sensing film enables visual and quantitative detection of CL-20 and TNT. Development of reliable sensors for explosive detection is important to reduce explosion-related safety risks and mitigate widespread environmental concerns. However, it remains highly challenging to achieve on-site detection of multiple analytes in a simple yet efficient way. Herein, a flexible electrospun film-based sensing platform by engineering with dual-emitting gold nanoclusters (AuNCs) has been fabricated for the simultaneous fluorescent detection of two representative explosives, hexanitrohexaazaisowurtzitane (CL-20) and trinitrotoluene (TNT). Particularly, two types of AuNCs with different emission colors (green and red) and surface chemistry are designed, which can specifically respond to trace amounts of two explosives separately. While the presence of CL-20 can remarkably enhance the green emission of l -arginine/6-aza-2-thiothymine-protected AuNCs, the presence of TNT can efficiently quench the red emission of glutathione-protected AuNCs. Consequently, ratiometric fluorescent sensing of CL-20 and TNT can be achieved with these dual-emitting AuNCs (G/R-AuNCs), which exhibits a detection limit down to 0.55 and 2.38 µM, respectively. The distinct "turn on" and "turn off" response patterns of G/R-AuNCs towards two explosives could be harnessed to construct fluorescent "BUF" and "NOT" logic gates. Moreover, the present AuNCs-based explosive sensors were deposited into flexible electrospun nanofibrous film for visual and quantitative detection of CL-20 and TNT, which exhibit good mechanical property and promising sensing performance. This work provides a new approach to design explosive sensing platform by coupling the attractive features of fluorescent AuNCs to the electrospun nanofibrous film, which holds great potential for further practical applications. [ABSTRACT FROM AUTHOR]