Titania Nanocrystalline Prepared by Detonation Method and Calculation of Detonation Parameters

As a promising method for synthesizing nanosized materials, detonation method was used to prepare TiO₂ nanoparticles. A new method for predicting the Chapman‐Jouguet (C‐J) detonation parameters of C_aH_bO_cN_dTi_e explosives, such as detonation heat, detonation temperature, and detonation pressure, was introduced according to the approximate reaction equations of detonation. The coefficient of oxygen balance of explosive was also calculated according to the specific detonation synthesis experiment. The calculation method was more useful in predicting the formation processes of detonation products and optimizing the experimental procedure. It could also support theory foundation for further experiments to some extent.     

Experimental study on the effect of titanium hydride content on the detonation performance of emulsion explosives

In order to improve the explosion characteristics of emulsion explosives, titanium hydride was added to emulsion explosives to produce a new type of hydrogen storage emulsion explosives. Charges with different contents of titanium hydride were evaluated through underwater explosion experiments and detonation velocity tests. The tests on underwater explosion and detonation velocity reveal that compared to pure emulsion explosives, the detonation parameters of emulsion explosives containing titanium hydride showed a trend of first increasing and then decreasing. When the mass ratio of titanium hydride in the emulsion explosive is 1 % to 3 %, all detonation parameters have been improved to a certain extent. When the mass ratio of titanium hydride in the emulsion explosive is 3 % to 10 %, only part of the detonation parameters (specific impulse, specific shock energy, specific total energy and volume energy density) has been improved. The maximum increase of specific impulse, specific shock energy, specific total energy and volume energy density of emulsion explosive containing titanium hydride is 7.06 %, 8.95 %, 3.97 % and 8.22 %, respectively. Based on the analysis, it is evident that though powdered TiH₂ participates in the detonation reaction process of the emulsion explosive, the majority of TiH₂′s energy is released during the secondary reaction occurring after the detonation wave front. Therefore, the detonation performance of emulsion explosives can be effectively improved by adding a certain mass ratio of titanium hydride.     

Reactive Flow and the Size Effect

The detonation reaction rate in μs⁻¹ is derived from Size Effect data using the relation – DU_s(∂U_s/∂y)⁻¹, where y =1/R_o, where U^s is the detonation velocity for a ratestick of radius R^o and D is the infinite‐radius detonation velocity. These rates are generally not constant with radius and have pressure exponents ranging from <−5 to > 5. JWL++, a simple Reactive Flow code, is run with one rate constant on many samples to compare its rates. JWL++'s pressure exponents vary from about 0.5 to 2.5, and failure occurs outside this range. There are three classes of explosives: (1) those for which the pressure exponent is between 1 and 2 and the rate is nearly constant (e.g. porous urea nitrate); (2) higher pressure explosives with a concave‐down shape and large positive pressure exponents (dense TNT); and (3) explosives with negative pressure exponents and concave‐up shapes (porous PETN). JWL++ fits only the first class well and has the most trouble with class 3. The pressure exponent in JWL++ is shown to be set by the shape of the Size Effect curve – a condition that arises in order to keep a constant reaction rate for all radii. Some explosives have too much bend to be modeled with one rate constant, e.g. Comp. B near failure. A study with creamed TNT shows that the rate constant need not be changed to account for containment. These results may well be pertinent to a larger consideration of the behavior of Reactive Flow models.     

Size Effect and Detonation Front Curvature

A simple theory relates the size effect (decrease of the detonation velocity with decreasing radius) of a cylinder with its average sonic reaction zone length, 〈x_e〉, i.e. the distance from first reaction to the sonic plane. The size effect is described by where R₀ is the radius, U_s and D the detonation velocities at R₀ and at infinite size and σ is a function describing the extent of wall motion, which is calibrated using four explosives. In this theory, the cylindrical symmetry imposes a quadratic shape to the detonation front. The lag distance at the edge of the cylinder, L₀, is related to the reaction zone length by 〈x_e〉 ≈︁ L₀. Collected results are presented for 56 measured curvatures on 26 explosives, with reaction zone lengths varying from 0.1 mm to 30 mm.     

Predicting the Detonation Velocity of CHNO Explosives by a Simple Method

A simplified method is shown, based on a semi‐empirical procedure, to estimate the detonation velocities of CHNO explosives at various loading densities. It is assumed that the product composition consists almost of CO, CO₂, H₂O and N₂ for oxygen‐rich explosives. In addition solid carbon and H₂ are also counted for an oxygen‐lean explosive. The approximate detonation temperature, as a second needed parameter, can be calculated from the total heat capacity of the detonation products and the heat of formation of the explosive by PM3 procedure. The detonation velocities of some well‐known CHNO explosives, calculated by the simple procedure, fit well with measured detonation velocities and the results from the well‐established BKW‐EOS computer code.     

Partial Reparametrization of the BKW Equation of State for DNAN‐Based Melt‐Cast Explosives

DNAN‐based melt‐cast explosives are a type of new, insensitive munitions (IM) explosives. Quickly determining munitions’ explosive properties is extremely important during the formulation design stage. The aim of this study was to partially reparameterize BKW‐EOS (only β and κ were reparameterized on the basis of the parameters (α , β , κ , and θ ) of classical BKW‐RDX set and BKW‐TNT set) to more accurately predict the properties of DNAN‐based melt‐cast explosives. A new set of parameters β and κ was obtained (β =0.19, κ =9.81) according to measured detonation velocity and detonation pressure for ideal DNAN‐based melt‐cast formulations (DNAN/RDX and DNAN/HMX). For non‐ideal DNAN‐based melt‐cast formulations (DNAN/RDX/Al and DNAN/HMX/Al), aluminum oxidation degree was first determined according to the measured detonation heat; then, another new set of parameters β and κ was obtained in the same way as the ideal formulations (β =0.24, κ =8.5). The predicted detonation properties with BKW reparametrization for DNAN‐based melt‐cast explosives agreed with the measured data.     

Modification of W/O Emulsions by Demilitarized Composition B

A series of W/O emulsion explosives containing 30–50 wt‐% of the demilitarized mixture RDX/TNT (Composition B 50/50) was prepared. Detonation velocities and relative explosive strengths of these mixtures were determined and their detonation characteristics were calculated according to the EU standard methods for commercial explosives. Thermal reactivities of the most reactive components of these W/O mixtures were examined by means of differential thermal analysis and outputs were analyzed according to the Kissinger method. The reactivities, expressed as the E_a ⋅ R⁻¹ slopes of the Kissinger relationship, correlate with the squares of the detonation velocities of the corresponding explosive mixtures. It was found that fortification of the W/O emulsions by the demilitarized mixture RDX/TNT allows modification of detonation velocities of the resulting emulsion explosives within relatively broad limits. However, the effect of this admixture on the relative explosive strength is not well defined. Nevertheless, fortification in this sense can give rock‐blasting explosives with a performance on the level of industrial powdered amatols.     

Detonation Failure Characterization of Homemade Explosives

Typically characterizing home made explosives (HMEs) requires many large scale experiments, which is prohibitive given the large number of materials in use. A small scale experiment was developed to characterize HMEs such as ammonium nitrate‐fuel oil mixtures. A microwave interferometer is applied to small scale confined transient experiments, yielding time resolved characterization of a failing detonation that is initiated with an ideal explosive booster charge. Experiments were performed with ammonium nitrate and two fuel compositions (diesel fuel and mineral oil). It was observed that the failure dynamics were influenced by factors such as the chemical composition, confiner thickness, and applied shock wave strength. Thin steel walled confiners with 0.71 mm wall thickness experienced detonation failure and decoupling of the shock wave from the reaction zone. Confiners with a wall thickness of 34.9 mm showed a decrease in propagation speed and a steady reactive wave was achieved. Varying the applied shock strength by using an attenuator showed corresponding changes in the initial overdriven reactive wave velocity in the HMEs. The distance to detonation failure was also shown to depend on the attenuator length when thin wall confinement was used. This experimental method is shown to be repeatable and can be performed with little required material (about 2 g). The data obtained could be useful to model development and validation, as well as quantifying detonability of materials.     

Calculation of the Wave-Shaper Effects on Detonation Wave in Shaped Charges

Results are presented from two-dimensional computations simulating the development of detonation for various configurations of shaped charges containing inert elements. These calculations were performed using the nonlinear explicit finite-difference computer code PISCES 2D ELK. The numerical model employed represented the high explosives by a finely zoned Lagrangian mesh and used JWL (Jones-Wilkins-Lee) equation of state with C-J (Chapman-Jouguet) burn model. The inert elements were modeled by Lagrangian grids and used Mie-Grueneisen equations of state with a linear relationship between the shock velocity (U_s) and particle velocity (U_p) fitting the Hugoniot data of the inert materials. The development of detonation waves all around the wave-shaper are shown in contour plots of pressure at various time steps during the calculations. Mesh plots of the different configurations are also reported. Our simulations are compared with previous radiographic and numerical results for a slab of explosive with an aluminium confinement and with recent not yet published streak-camera tests on a particular shaped charge configuration with hemispherical wave-shaper. Our numerical results appear to be in good agreement with the experimental data.     

理想混合炸药模型的提出及其应用

通过建立“理想混合炸药”模型 ,发现理想混合炸药的爆速 Did与纯组分炸药的爆速 Di和质量分数 Wi之间存在着定量关系 ,据此发展了一种计算混合炸药爆速的新方法。对大量混合炸药的计算结果表明 ,爆速计算值与实验值的一致性令人满意 ,平均误差 1.37%。本文方法的提出 ,不仅提供了一种预测混合炸药爆速的方法 ,而且对高爆速混合炸药的研究具有一定的指导意义     

Detonation of a thin explosive layer in evacuated tubes

Detenation of thin layers of dispersed primary and secondary high explosives (HE) on the outer surface of glass and plastic tubes 0.6–3 mm in diameter was examined at an initial air pressure inside the tube of 0.1 MPa to 30 Pa. It is shown that, under these conditions, the air practically does not influence the detonation velocity, which for secondary explosives (PETN, RDX, and HMX), is lower than or approximately equal to the Chapman-Jouguet detonation velocityD _CJ for a homogeneous mixture of the same substances. Experiments with a primary HE (lead azide) revealed regimes with a wave velocity higher thanD _CJ and a varying reaction zone pattern. When tubes containing a layer of a secondary HE were filled with an explosive gas mixture, waves of a hybrid detonation with a velocity both higher and lower than that in the evacuated tubes was observed. In tubes with diameter 2–3 mm, detonation proceeded in a spinning regime over the entire range of the initial pressure and at a velocity higher thanD _CJ. It is concluded that in the evacuated tubes with a thin HE layer on the walls, ignition is transferred by the stream of hot detonation products moving at the head of the detonation wave. Translated fromFizika Goreniya i Vzryva, Vol. 36, No. 4, pp. 56–67, November–December 1998     

Effect of an inert high-modulus ceramic wall on detonation propagation in solid explosive charges

The effect of an intert high-modulus ceramic wall on detonation propagation in charges of a solid heterogeneous explosive was investigated experimentally and numerically. Subdetonation pressures occurred at the boundary between the wall and the explosive for the conditions investigated. Here the detonation velocity increased, and the mass velocity and the pressure at the detonation front decreased, which is explained by the indirect effect of an overtaking wave into the unreacted explosive and the chemical reaction zone. Transverse waves, which affect the detonation parameters, propagate perpendicular to the detonation front with a velocity of ∼6 km/sec. The initial decomposition rate of the explosive directly after the compression shock determines the degree of the transverse-wave effect. Novosibirsk State Technical University. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 5, pp. 107–114, September–October, 1994.     

Energy release of mixed explosives during propagation of a nonideal detonation under conditions similar to the operation conditions of a blasthole charge

Detonation experiments were performed in a specially developed explosive device simulating a blasthole using charges of fine-grained and coarse-grained (granular) 30/70 TNT/ammonium nitrate mixtures of identical density 0.89 g/cm³ in steel shells with an inner diameter of 28 mm and a wall thickness of 3 mm at detonation velocities of 4.13 and 2.13 km/sec, respectively. Despite significant differences in detonation velocity (pressure), identical expansion of the charge shells was observed. On the other hand, numerical simulations of detonation propagation in the explosive device with the corresponding velocities ignoring the possibility of energy release behind the shock front show that the expansion of the charge shell is always greater in the case of a high-velocity regime. It is concluded that under the conditions simulating detonation propagation and the work of explosion products in a blasthole, effective additional energy release occurs behind the low-velocity (nonideal) detonation front. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 4, pp. 111–120, July–August, 2007.     

Analytic Model of Reactive Flow

A simple analytic model allows prediction of rate constants and size effect behavior before a hydrocode run, if size effect data exist. It utilizes detonation velocity, average detonation rate, pressure and energy at infinite radius. This allows the derivation of a generalized radius, which becomes larger as the explosive becomes more non‐ideal. The model is applied to near‐ideal PBX 9404, in‐between ANFO and most non‐ideal AN. The power of the pressure declines from 2.3, and 1.5 to 0.8 across this set. The power of the burn fraction, F, is 0.8, 0 and 0, so that an F‐term is important only for the ideal explosives. The size effect shapes change from concave‐down to nearly straight to concave‐up. Failure is associated with ideal explosives when the calculated detonation velocity turns in a double‐valued way. The effect of the power of the pressure may be simulated by including a pressure cut‐off in the detonation rate. The model allows comparison of a wide spectrum of explosives providing that a single detonation rate is feasible.     

New Method for Prediction of the Gurney Energy of High Explosives

An empirical new correlation is used to calculate the Gurney velocity as an important parameter for the estimation of explosive energy output without considering the heat contents of explosives and detonation products. The number of nitrogen molecules as well as the ratios of oxygen to carbon and hydrogen to oxygen are the fundamental factors in the new method. The new correlation may be applied to any C_aH_bN_cO_d explosive, in which b is nonzero, at any loading density. The calculated Gurney velocity for both pure and explosive formulations shows good agreement with respect to measured values. Moreover, there is no need to use any assumed decomposition reaction.     

Estimating Heats of Detonation and Detonation Velocities of Aromatic Energetic Compounds

A new method is introduced to predict reliable estimation of heats of detonation of aromatic energetic compounds. At first step, this procedure assumes that the heat of detonation of an explosive compound of composition C_aH_bN_cO_d can be approximated as the difference between the heat of formation of all H₂O CO₂ arbitrary (H₂O, CO₂, N₂) detonation products and that of the explosive, divided by the formula weight of the explosive. Overestimated results based on (H₂O CO₂ arbitrary) can be corrected in the next step. Predicted heats of detonation of pure energetic compounds with the product H₂O in the liquid state for 31 aromatic energetic compounds have a root mean square (rms) deviation of 2.08 and 0.34 kJ g⁻¹ from experiment for (H₂O CO₂ arbitrary) and new method, respectively. The new method also gives good results as compared to the second sets of decomposition products, which consider H₂, N₂, H₂O, CO, and CO₂ as major gaseous products. It is shown here how the predicted heats of detonation by the new method can be used to obtain reliable estimation of detonation velocity over a wide range of loading densities.     

An empirical confinement model for ANFO explosive

Ammonium-nitrate-fuel-oil (ANFO) explosive, one of the most used mining explosives, exhibits highly non-ideal behaviour. The non-ideality of the detonation is manifested in the strong dependence of the detonation velocity on the charge radius and existence and the characteristics of confinement. This can lead to the detonation velocities as low as one-third of the ideal velocity. The literature reported experimental detonation velocities of cylindrical ANFO charges confined in different confiners (aluminium, copper, steel, polymethyl methacrylate, and polyvinyl chloride) are analysed in this paper. An empirical confinement model, which relates the detonation velocity to the charge radius and the mass of the confiner to the mass of explosive ratio per unit length, is proposed. The model predicts the detonation velocity of unconfined and confined ANFO charges with a mean average percentage error of 8.8 %.     

Explosive Strength and Impact Sensitivity of Several PBXs Based on Attractive Cyclic Nitramines

Plastic explosives based on different cyclic nitramines with different polymeric matrices were prepared and studied. The used polymeric matrices were fabricated on the basis of polyisobutylene (PIB), acrylonitrile‐butadiene rubber (ABR), Viton A, and polydimethyl‐siloxane as binders, whereas the nitramines named RDX (1,3,5‐trinitroperhydro‐1,3,5‐triazine), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine), BCHMX (cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole) and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane) were used as explosive fillers. Commercial Semtex 10, based on pentaerythritol tetranitrate (PETN), was used for comparison. Impact sensitivity, loading density, ρ, detonation velocity, D, and relative explosive strength (RS) measured by ballistic mortar were determined. It was concluded that plastic BCHMX based on Viton A or PIB‐matrix exhibits higher RS compared with PBXs based on RDX and HMX. Correlations between RS and the impact sensitivity, the ρD² term and the square of the detonation velocity were studied and discussed. The results confirm the well‐known fact that increasing the performance is usually accompanied by an increase in the sensitivity of the explosives. In this connection, Viton A enables achieving a high RS, but with a relatively high sensitivity of the PBXs, whereas the polydimethyl‐siloxane matrix should perhaps give PBXs with optimum explosive strength and sensitivity parameters.     

Detonation velocity of an emulsion explosive sensitized with polymer microballoons

This paper presents the results of investigation of the detonation velocity of an emulsion explosive sensitized with Expancel polymer microballoons in a wide range of initial density of 0.14–1.33 g/cm³. It is shown that at a density of the emulsion explosive less than 0.4 g/cm³, detonation with an unstable front characteristic of liquid explosives is possible.     

Theoretical Investigation of Several 1,2,3,4‐Tetrazine‐Based High‐Energy Compounds

The enthalpies of formation of six 1,2,3,4‐tetrazine‐based compounds were calculated according to the Density Functional Theory BOP/TNP method and by using homodesmotic reaction designs. Their detonation performances, including detonation velocity and pressure, were predicted in terms of the Stine equations. The 1,2,3,4‐Tetrazine‐based compounds labeled A, B, C, D, and F are powerful high‐energy compounds. The detonation performances of A and B, including detonation velocity, and detonation pressure, are superior to that of the current high‐energy explosive CL‐20. The detonation velocity, detonation pressure, and oxygen balance of 1,2,3,4‐tetrazine related oxo derivatives can be improved by partial oxidation of the nitrogen atoms in the tetrazine ring, but further oxidation causes reduction of the enthalpies and specific impulses of the oxo derivatives. Calculation of the molecular resonance energies indicated that E [C₆N₁₂] and F have more negative values, i.e, the ring strain energies of their configurations are high, whereas the resonance energies of C and D are low, only compound B has a very positive resonance energy. Considering energy and stability, B is a promising compound for practical use with both high energy and low sensitivity.