Packing Configurations of PBX‐9501 Cylinders to Reduce the Probability of a Deflagration to Detonation Transition (DDT)

The detonation of hundreds of explosive devices from either a transportation or storage accident is an extremely dangerous event. This paper focuses on identifying ways of packing/storing arrays of explosive cylinders that will reduce the probability of a Deflagration to Detonation Transition (DDT). The Uintah Computational Framework was utilized to predict the conditions necessary for a large scale DDT to occur. The results showed that the arrangement of the explosive cylinders and the number of devices packed in a “box” greatly effects the probability of a detonation.     

Damage of a High‐Energy Solid Propellant and Its Deflagration‐to‐Detonation Transition

In order to assess the safety of high‐energy solid propellants, the effects of damage on deflagration‐to‐detonation transition (DDT) in a nitrate ester plasticized polyether (NEPE) propellant, is investigated. A comparison of DDT in the original and impacted propellants was studied in steel tubes with synchronous optoelectronic triodes and strain gauges. The experimental results indicate that the microstructural damage in the propellant enhances its transition rate from deflagration to detonation and causes its increased sensitivity. It is suggested that the mechanical properties of the propellant should be improved to reduce its damage so that the probability of DDT might be reduced.     

Deflagration of HMX‐Based Explosives at High Temperatures and Pressures

We measure the deflagration behavior of energetic materials at extreme conditions (up to 520 K and 1 GPa) in the LLNL High Pressure Strand Burner, thereby obtaining reaction rate data for prediction of violence of thermal explosions. The apparatus provides both temporal pressure history and flame time‐of‐arrival information during deflagration, allowing direct calculation of deflagration rate as a function of pressure. Samples may be heated before testing. Here we report the deflagration behavior of several HMX‐based explosives at pressures of 10–600 MPa and temperatures of 300–460 K. We find that formulation details are very important to overall deflagration behavior. Formulations with high binder content (≥15 wt%) deflagrate smoothly over the entire pressure range regardless of particle size, with a larger particle size distribution leading to a slower reaction. The deflagration follows a power law function with the pressure exponent being unity. Formulations with lower binder content (≤10 wt% or less) show physical deconsolidation at pressures over 100–200 MPA, with transition to a rapid erratic deflagration 10–100 times faster. High temperatures have a relatively minor effect on the deflagration rate until the HMX β→δ phase transition occurs, after which the deflagration rate increases by more than a factor of 10.     

The Role of Aluminum in the Detonation and Post‐Detonation Expansion of Selected Cast HMX‐Based Explosives

In order to improve understanding of how aluminum contributes in non‐ideal explosive mixtures, cast‐cured formulations have been analyzed in a series of cylinder tests and plate‐pushing experiments. This study describes the contribution of 15 % aluminum (median size of 3.2 μm) vs. lithium fluoride (an inert substitute for aluminum; <5 μm) in cast‐cured HMX formulations in different temporal regimes. Small cylinder tests were performed to analyze the detonation and wall velocities (1–20 μs) for these formulations. Near‐field blast effects of 58 mm diameter spherical charges were measured at 152 mm and 254 mm using steel plate acceleration. Pressure measurements at 1.52 m gave information about free‐field pressure at several milliseconds. While the observed detonation velocities for all formulations were within uncertainty, significantly higher cylinder wall velocities, plate velocities, and pressures were observed for the aluminum formulations at ≥2 μs. Additionally, hydrocode calculations were performed to determine how non‐ideal behavior affected the plate test results. Collectively, this work gives a clearer picture of how aluminum contributes to detonation on timescales from 1 μs to about 2 ms, and how the post‐detonation energy release contributes to wall velocities and blast effects. The experiments indicate that significant aluminum reactions occur after the CJ plane, and continue to contribute to expansion at late times.     

Effect of Nano‐Aluminum and Fumed Silica Particles on Deflagration and Detonation of Nitromethane

The heterogeneous interaction between nitromethane (NM), particles of nanoscale aluminum (38 and 80 nm diameter), and fumed silica is examined in terms of the deflagration and detonation characteristics. Burning rates are quantified as functions of pressure using an optical pressure vessel up to 14.2 MPa, while detonation structure is characterized in terms of failure diameter. Nitromethane is gelled using fumed silica (CAB‐O‐SIL^®), as well as by the nanoaluminum particles themselves. Use of nanoaluminum particles with fumed silica slightly increases burning rates compared to the use of larger diameter Al particles; however distinct increases in burning rates are found when CAB‐O‐SIL is removed and replaced with more energetic aluminum nanoparticles, whose high surface area allows them to also act as the gellant. Mixtures including fumed silica yield a reduced burning rate pressure exponent compared to neat NM, while mixtures of aluminum particles alone show a significant increase. Failure diameters of mixture detonations are found to vary significantly as a function of 38 nm aluminum particle loading, reducing more than 50% from that of neat nitromethane with 12.5% (by mass) aluminum loading. Failure diameter results indicate a relative minimum with respect to particle separation (% loading) which is not observed in other heterogeneous mixtures.     

Effect of Al/O Ratio on the Detonation Performance and Underwater Explosion of HMX‐based Aluminized Explosives

The performance of detonation and underwater explosion (UNDEX) of a six‐formula HMX‐based aluminized explosive was examined by detonation and UNDEX experiments. The detonation pressures, detonation velocities, and detonation heat of HMX‐based aluminized explosive were measured. The reliability between the experimental results and those calculated by an empirical formula and the KHT code was verfied. UNDEX experiments were carried out on the propagation of a shock wave and a bubble pulse of a 1 kg cylindrical HMX‐based aluminized explosive underwater at a depth of 4.7 m. Based on the experimental results of the shock wave, the coefficients of similarity law equation for the peak pressure and attenuation time constant of shock wave were in acceptable agreement. The bubble motion during UNDEX was simulated using MSC.DYTRAN software, and the radius time curves of bubbles were determined. The effect of the aluminum/oxygen ratio on the performance of the detonation and UNDEX for an HMX‐based aluminized explosive was discussed.     

Thermal Sensitivity of HMX Crystals and HMX‐Based Explosives Treated under Various Conditions

The Five‐Second Explosion Point (5‐SEP) tests and the SEM detections in this research showed that the HMX crystals and the HMX‐based explosives treated under different conditions can possess different thermal sensitivities. That is to say, higher impurity, smaller granularity, and worse integrity of HMX crystals can make them more thermally sensitive. The addition of metal or metal oxide particles, especially nanoparticles to HMX can also enhance its thermal sensitivity. Meanwhile, coating of HMX crystals with polymers to form perfect PBX and to keep them undamaged are helpful to decrease their thermal sensitivity. Furthermore, the thermal sensitivity of temperature‐aged HMX changes differently in terms of the integrity of its particles. Therefore, it can be concluded that conditions which increase the surface energy of HMX crystals or which make the HMX molecules more active to decompose at lower temperature will increase the thermal sensitivity of HMX. Additionally, the variation in the thermal sensitivity of HMX treated under different conditions is generally more temperate than that of its mechanical sensitivity.     

Study of the Effect of Additive Particle Size on Non‐ideal Explosive Performance

Detonation performance of non‐ideal RDX‐based compositions was studied. Charges of phlegmatised RDX containing 30% of two types of aluminium powders, coarse aluminium oxide or fine lithium fluoride particles were tested. The research concerning influence of inert and reactive additives on the detonation velocity and quasi‐static pressure was carried out. To estimate the degree of afterburning of the detonation products and reactive particles, closed explosions were performed in a chamber filled with different atmospheres. Explosion residues were also analysed. Gasdynamical and thermochemical calculations were also performed for the tested explosive compositions.     

New High‐Nitrogen Materials Based on Nitroguanyl‐Tetrazines: Explosive Properties,Thermal Decomposition and Combustion Studies

This paper describes the explosive sensitivity and performance properties of two novel high‐nitrogen materials, 3,6‐bis‐nitroguanyl‐1,2,4,5‐tetrazine ( 1 , (NQ₂Tz)) and its corresponding bis‐triaminoguanidinium salt ( 2 , (TAG)₂(NQ)₂Tz)). These materials exhibit very low pressure dependence in burning rate. Flash pyrolysis/FTIR spectroscopy was performed, and insight into this interesting burning behavior was obtained. Our studies indicate that 1 and 2 exhibit highly promising energetic materials properties.     

Effect of TiH2 Particle Size and Content on the Underwater Explosion Performance of RDX‐Based Explosives

Experiments were conducted to study the underwater explosion performance of titanium hydride/RDX‐based (TiH₂/RDX) composite explosive. Cylinder charges with different TiH₂ particle sizes and contents were prepared and tested. Explosion parameters like peak overpressure, impulse, shock energy, and bubble energy were analyzed. It was notable that underwater explosion performance of TiH₂/RDX composite explosive was promoted by addition of small particle size TiH₂ (D₅₀=0.96 μm), in which case increasing TiH₂ content also showed a favorable effect. The maximum increments of specific initial shock energy, bubble energy, and total energy were 10.5%, 6.4%, and 7.1% respectively. However, with bigger TiH₂ particle sizes (D₅₀=20.78 μm, D₅₀=136.74 μm), the explosion parameters and the TiH₂ content showed a negative relationship, which reveals that TiH₂ particle size plays an important role in determining the reactivity of TiH₂. Meanwhile, the interaction between TiH₂ particle size and content was significant.     

The β‐δ‐Phase Transition and Thermal Expansion of Octahydro‐1,3,5,7‐Tetranitro‐1,3,5,7‐Tetrazocine

Phase behavior of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) is investigated by X‐ray powder diffraction (XRD). The XRD patterns at elevated temperature show that there is a co‐existing temperature range of β‐ and δ‐phase during the phase transition process. Additionally, mechanical forces can catalyze the conversion from δ‐ back to β‐phase. Based on the diffraction patterns of β‐ and δ‐phase at different temperatures, we calculate the coefficients of thermal expansion by Rietveld refinement. For β‐HMX, the linear coefficients of thermal expansion of a‐axis and b‐axis are about 1.37×10⁻⁵ and 1.25×10⁻⁴ °C⁻¹. A slight decrease in c‐axis with temperature is also observed, and the value is about −0.63×10⁻⁵ °C⁻¹. The volume coefficient of thermal expansion is about 1.60×10⁻⁴ °C⁻¹, with a 2.2% change from 30 to 170 °C. For δ‐HMX, the linear coefficients of thermal expansion of a‐axis and c‐axis are found to be 5.39×10⁻⁵ and 2.38×10⁻⁵ °C⁻¹, respectively. The volume coefficient of thermal expansion is about 1.33×10⁻⁴ °C⁻¹, with a 2.6% change from 30 to 230 °C. The results indicate that β‐HMX has a similar volume coefficient of thermal expansion compared with δ‐HMX, and there is about 10.5% expansion from β‐HMX at 30 °C to δ‐HMX at 230 °C, of which about 7% may be attributed to the reconstructive transition.     

Preparation and Properties of An Insensitive Booster Explosive Based on LLM‐105

A new insensitive booster explosive based on 2,6‐diamino‐3,5‐dinitropyrazing‐1‐oxide (LLM‐105) was prepared by a solvent‐slurry process with ethylene propylene diene monomer (EPDM) as binder. SEM (scanning electron microscopy) was employed to characterize the morphology and particle size of LLM‐105 and molding powder. The mechanical sensitivity, thermal sensitivity, shock wave sensitivity, and detonation velocity of the LLM‐105/EPDM booster were also measured and analyzed. The results show that both mechanical sensitivity and thermal sensitivity of LLM‐105/EPDM are much lower than that of conventional boosters, such as PBXN‐5 and A5. Its shock wave sensitivity is also lower than that of PBXN‐5 and PBXN‐7. When the density of charge is 95 % TMD, its theoretical and measured detonation velocities are 7858 m s⁻¹ and 7640 m s⁻¹, respectively. These combined properties suggested that LLM‐105/EPDM can be used as an insensitive booster.     

The Effect of Cook‐Off on the Bulk Permeability of a Plastic Bonded Explosive

Plastic bonded explosives when exposed to prolonged heating environments undergo a variety of changes that affect their bulk chemical, thermophysical, and mechanical properties. During slow heating conditions, referred to as cook‐off, the thermal behavior of the polymeric binder plays an important role in the transformations of these composite energetic materials. The recently introduced Darcian flow hypothesis for PBX‐9501 implies that, during preignition, temperature gradients will lead to pressure gradients which in turn will drive convection of decomposition gases throughout the explosive, thus affecting ignition time and location. Here, we focus on the cook‐off behavior of PBX‐9501 and investigate its effects on bulk permeability to gases produced as a result of thermal decomposition. The concept of Darcian convection through porous media is defined and illustrated in detail by the derivation of the governing equations for a permeameter. Based on a systematic analysis involving: 1) our current understanding about binder behavior as a function of temperature, 2) the physics of the gas permeameter apparatus, 3) the concept of liquid drainage by gas, and 4) the experimental record of four permeameter experiments with cooked PBX‐9501, we conclude that samples heated up to 186 °C were not permeable in the Darcy‐flow sense.     

A DFT Study on the Structures and Energies of Isomers of 4‐Amino‐1,3‐dinitro‐1,2,4‐triazol‐5‐one‐2‐oxide: New High Energy Density Compounds

Isomers of 4‐amino‐1,3‐dinitrotriazol‐5‐one‐2‐oxide (ADNTONO) are of interest in the contest of insensitive explosives and were found to have true local energy minima at the DFT‐B3LYP/aug‐cc‐pVDZ level. The optimized structures, vibrational frequencies and thermodynamic values for triazol‐5‐one N‐oxides were obtained in their ground state. Kamlet‐Jacob equations were used to evaluate the performance properties. The detonation properties of ADNTONO (D=10.15 to 10.46 km s⁻¹, P=50.86 to 54.25 GPa) are higher compared with those of 1,1‐diamino‐2,2‐dinitroethylene (D=8.87 km s⁻¹, P=32.75 GPa), 5‐nitro‐1,2,4‐triazol‐3‐one (D=8.56 km s⁻¹, P=31.12 GPa), 1,2,4,5‐tetrazine‐3,6‐diamine‐1,4‐dioxide (D=8.78 km s⁻¹, P=31.0 GPa), 1‐amino‐3,4,5‐trinitropyrazole (D=9.31 km s⁻¹, P=40.13 GPa), 4,4′‐dinitro‐3,3′‐bifurazan (D=8.80 km s⁻¹, P=35.60 GPa) and 3,4‐bis(3‐nitrofurazan‐4‐yl)furoxan (D=9.25 km s⁻¹, P=39.54 GPa). The  NH₂ group(s) appears to be particularly promising area for investigation since it may lead to two desirable consequences of higher stability (insensitivity), higher density, and thus detonation velocity and pressure.     

Quantitative Schlieren Measurement of Explosively‐Driven Shock Wave Density,Temperature, and Pressure Profiles

Shock waves produced from the detonation of laboratory‐scale explosive charges are characterized using high‐speed, quantitative schlieren imaging. This imaging allows the refractive index gradient field to be measured and converted to a density field using an Abel deconvolution. The density field is used in conjunction with simultaneous piezoelectric pressure measurements to determine the shock wave temperature decay profile. Alternatively, the shock wave pressure decay profile can be estimated by assuming the shape of the temperature decay. Results are presented for two explosive sources. The results demonstrate the ability to measure both temperature and pressure decay profiles optically for spherical shock waves that have detached from the driving explosion product gases.     

Degradation of TNT,RDX, and HMX Explosive Wastewaters Using Zero‐Valent Iron Nanoparticles

The high‐energy explosives 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the high melting explosive octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) are common groundwater contaminants at active and abandoned munitions production facilities causing serious environmental problems. A highly efficient and environmentally friendly method was developed for the treatment of the explosives‐contaminated wastewaters using zero‐valent iron nanoparticles (ZVINs). ZVINs with diameters of 20–50 nm and specific surface areas of 42.56 m² g⁻¹ were synthesized by the co‐precipitation method. The explosives degradation reaction is expressed to be of pseudo first‐order and the kinetic reaction parameters are calculated based on different initial concentrations of TNT, RDX, and HMX. In addition, by comparison of the field emission scanning electron microscopy (FE‐SEM) images for the fresh and reacted ZVINs, it was apparent that the ZVINs were oxidized and aggregated to form Fe₃O₄ nanoparticles as a result of the chemical reaction. The X‐ray diffraction (XRD) and X‐ray absorption near edge structure (XANES) measurements confirmed that the ZVINs corrosion primarily occurred due to the formation of Fe₃O₄. Furthermore, the postulated reaction kinetics in different concentrations of TNT, RDX, and HMX, showed that the rate of TNT removal was higher than RDX and HMX. Furthermore, by‐products obtained after degradation of TNT (long‐chain alkanes/methylamine) and RDX/HMX (formaldehyde/methanol/hydrazine/dimethyl hydrazine) were determined by LC/MS/MS, respectively. The high reaction rate and significant removal efficiencies suggest that ZVINs might be suitable and powerful materials for an in‐situ degradation of explosive polluted wastewaters.     

Preparation,Crystal Structure and Explosive Properties of Copper(II) Perchlorate Complex with 4‐Amino‐1,2,4‐Triazole and Water

A complex from copper(II) perchlorate with 4‐amino‐1,2,4‐triazole (4‐AT, C₂H₄N₄) was synthesized, and elemental composition, molecular structure, and explosive properties were determined. To this end, elemental and X‐ray analyses were carried out, sensitivity to mechanical and thermal stimuli was measured, mechanism of thermal decomposition was investigated, and kinetic parameters of decomposition were determined. In the next step measurements of heat of combustion and detonation velocity were performed. Detonation parameters were also calculated. It was stated that the complex has slightly distorted square bipyramidal (4+2) coordination. The four basal bonds are formed by nitrogen atoms of four 4‐AT molecules. The coordination of the metal is completed by two axial oxygen atoms, one of the perchlorate ion, and one of the water molecule. With respect to explosive properties, tetrakis(4‐AT)copper(II) perchlorate monohydrate belongs to the group of sensitive secondary explosives.     

Synthesis and Characteristics of Bis(nitrofurazano)furazan (BNFF), an Insensitive Material with High Energy‐Density

The insensitive compound bis(nitrofurazano)furazan (BNFF) with high energy‐density was synthesized by three‐step reactions and fully characterized. The key reduction reaction was discussed. BNFF has a high crystal density (1.839 g cm⁻³) and a low melting point (82.6 °C). BNFF is insensitive to impact and friction and has similar detonation velocity (8680 m s⁻¹) and detonation pressure (36.1 GPa) compared to RDX.     

The Synergistic Effect Between Imidazoline‐Based Dissymmetric bis‐Quaternary Ammonium Salts and Thiourea Against CO2 Corrosion at High Temperature

Imidazoline‐based dissymmetric bis‐quaternary ammonium salt (DBA), a type of environmentally friendly surfactant, was compounded with thiourea (TU). The inhibition properties of the compound inhibitor for Q235 steel in a simulated oil field that produced water saturated with CO₂ at high temperature were studied by weight loss measurement, polarization curves, cyclic voltammetry, electrochemical impedance spectroscopy, and observation of surface morphology. Weight loss measurements show that DBA alone has poor inhibition efficiency at high temperature, and TU has a narrow inhibition concentration range. However, DBA and TU together show a synergistic effect, which not only overcomes the short comings when used individually, but also significantly reduces the corrosion rate at reduced dosage. DBA–TU acts as a mixed prohibition inhibitor, and can rapidly form a protective film. The inhibition efficiency decreased slowly with soaking time, which shows it has good substantivity. In conclusion, DBA–TU can be used as high temperature corrosion inhibitor against CO₂ corrosion.