Hydrostatic Compression Curve for Triamino‐Trinitrobenzene Determined to 13.0 GPa with Powder X‐Ray Diffraction

Using powder X‐ray diffraction in conjunction with a diamond anvil cell (DAC), the unit cell volume of triamino‐trinitrobenzene (TATB) has been measured from ambient pressure to 13 GPa. The resultant isotherm is compared with previous theoretical (Byrd and Rice and Pastine and Bernecker) and experimental (Olinger and Cady) works. While all reports are consistent to approximately 2 GPa, our measurements reveal a slightly stiffer TATB material than reported by Olinger and Cady and an intermediate compressibility compared with the isotherms predicted by the two theoretical works. Analysis of the room temperature isotherm using the semi‐empirical, Murnaghan, Birch–Murnaghan, and Vinet equations of state (EOS) provided a determination of the isothermal bulk modulus (K_o) and its pressure‐derivative (K_o′) for TATB. From these fits to our P–V isotherm, from ambient pressure to 8 GPa, the average results for the zero‐pressure bulk modulus and its pressure derivative were found to be 14.7 GPa and 10.1, respectively. For comparison to shock experiments on pressed TATB powder and its plastic‐bonded formulation PBX 9502 (95% TATB, 5% Kel‐F 800), the isotherm was transformed to the pseudo‐velocity U_s–u_p plane using the Rankine–Hugoniot jump conditions. This analysis provides an extrapolated bulk sound speed, c_o=1.70 km s⁻¹, for TATB and its agreement with a previous determination (c_o=1.43 km s⁻¹) is discussed. Furthermore, our P–V and corresponding U_s–u_p curves reveal a subtle cusp at approximately 8 GPa. This cusp is discussed in relation to similar observations made for the aromatic hydrocarbons anthracene, benzene and toluene, graphite, and trinitrotoluene (TNT).     

Divergent Detonation Wave Processes in PBX Based on RDX

In order to characterize the initial phase of the divergent detonation wave in PBX, a hemispheric explosive sample was initiated by a long cylindrical charge of the same explosive. The tested PBX is composed of 85 wt% of RDX and 15 wt% of binder based on HTPB. This PBX‐RDX presents an effective density of 1.57 g/cm³, and a detonation velocity of 7.90 mm/μs.     

Optical Properties of Energetic Materials: RDX,HMX, AP,NC/NG,and HTPB

Optical properties of RDX, HMX, AP, HTPB/IPDI and a catalyzed NC/NG propellant (N5) were obtained from 2.5 μm to 18 μm using FTIR transmission spectrometry. Scattering-corrected KBr pellet methodology was used for the crystalline materials. Absorption index (k) was measured directly and refractive index (n) was deduced using dispersion theory. At 10.600 μm the absorption coefficients were AP, 190 cm⁻¹ (240 cm⁻¹ at 10.6036 μm); HTPB/IPDI, 360 cm⁻¹; N5, 510 cm⁻¹; RDX, 2800 cm⁻¹; and HMX, 5670 cm⁻¹.     

Preparation and Performances of Castable HTPB/CL‐20 Booster Explosives

HTPB/CL‐20 castable booster explosives were prepared successfully by a cast‐cured process. Scanning electron microscope (SEM) and the charge density test were employed to characterize the molding effect of HTPB/CL‐20 explosives. The propagation reliability, detonation velocity, mechanical sensitivity, thermal decomposition characteristics and thermal stability of the HTPB/CL‐20 explosives were also measured and analyzed. The results show that, when CL‐20 content is less than 91 wt.‐%, the charges with better molding effect were obtained easily. The critical diameter of HTPB/CL‐20 explosives is less than 1 mm, which exhibits good propagation reliability. When the density of HTPB/CL‐20 charge with 91 wt.‐% CL‐20 is 1.73 g cm⁻³, its detonation velocity can reach 8273 m s⁻¹. Moreover, this kind of explosives has low mechanical sensitivity and good thermal stability.     

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.     

Density Distributions in TATB Prepared by Various Methods

The density distribution of two legacy types of 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) particles were compared with TATB synthesized by new routes and recrystallized in several different solvents using a density gradient technique. Legacy wet (WA) and dry aminated (DA) TATB crystalline aggregates gave average densities of 1.9157 and 1.9163 g cm⁻³, respectively. Since the theoretical maximum density (TMD) for a perfect crystal is 1.937 g cm⁻³, legacy TATB crystals averaged 99% of TMD or about 1% voids. TATB synthesized from phloroglucinol (P) had comparable particle size to legacy TATBs, but significantly lower density, 1.8340 g cm⁻³. TATB synthesized from 3,5 dibromoanisole (BA) was very difficult to measure because it contained extremely fine particles, but had an average density of 1.8043 g cm⁻³ over a very broad range. Density distributions of TATB recrystallized from dimethylsulfoxide (DMSO), sulfolane, and an 80/20 mixture of DMSO with the ionic liquid 1‐ethyl‐3‐methyl‐imidazolium acetate (EMImOAc), with some exceptions, gave average densities comparable or better than the legacy TATBs.     

Thermochemical,Sensitivity and Detonation Characteristics of New Thermally Stable High Performance Explosives

The M06‐2X/6‐311G(d,p) and B3LYP/6‐311G(d,p) density functional methods and electrostatic potential analysis were used for calculation of enthalpy of sublimation, crystal density and enthalpy of formation of some thermally stable explosives in the gas and solid phases. These data were used for prediction of their detonation properties including heat of detonation, detonation pressure, detonation velocity, detonation temperature, electric spark sensitivity, impact sensitivity and deflagration temperature using appropriate methods. The range of different properties for these compounds are: crystal density 1.51–2.01 g cm⁻³, enthalpy of sublimation 346.4–424.7 kJ mol⁻¹, the solid phase enthalpy of formation 500.4–860.6 kJ mol⁻¹, heat of detonation 13.64–17.57 kJ g⁻¹, detonation pressure 33.0–37.0 GPa, detonation velocity 8.5–9.5 km s⁻¹, detonation temperature 5488–6234 K, electric spark sensitivity 7.89–9.47 J, impact sensitivity 21–38 J, deflagration temperature 560–586 K and power [%TNT] 207–276. The results show that two novel energetic compounds N,N′‐(diazene‐1,2‐diylbis(2,3,5,6‐tetranitro‐4,1‐phenylene))bis(5‐nitro‐4H‐1,2,4‐triazol‐3‐amine) (DDTNPNT3A) and 1,1′‐(diazene‐1,2‐diylbis(2,3,5,6‐tetranitro‐4,1‐phenylene))bis(3‐nitro‐1H‐1,2,4‐triazol‐5‐amine) (DDTNPNT5A) can be introduced as thermally explosives with high detonation performance.     

A Novel Insensitive High Explosive 3,4‐Bis (Aminofurazano) Furoxan

A novel insensitive high explosive 3,4‐bis (aminofurazano) furoxan (BAFF) was prepared using 3‐amino‐4‐acylchloroximinofurazan (ACOF) as a precursor. The molecular and crystal structures of BAFF were characterized by IR, MS, ¹H NMR, ¹³C NMR, elemental analysis, and single crystal X‐ray diffraction. The single crystal structure of BAFF recrystallized from water is monoclinic, space group P 21/c, and ρ_c=1.745 g cm⁻³, and that recrystallized from ethanol is triclinic, space group P 1, and ρ_c=1.737 g cm⁻³. BAFF has multiple crystal forms. The calculated detonation velocity by BKW code is 8100 m s⁻¹ (ρ=1.795 g cm⁻³, theoretical density calculated by quantum chemistry) and the experimental value is 7177 m s⁻¹ (ρ=1.530 g cm⁻³, charge density). The tested values of impact, friction, and electrostatic spark sensitivity show that BAFF is insensitive.     

Characterization of 4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine

4,6‐Diazido‐N‐nitro‐1,3,5‐triazine‐2‐amine (DANT) was prepared with a 35 % yield from cyanuric chloride in a three step process. DANT was characterized by IR and NMR spectroscopy (¹H, ¹³C, ¹⁵N), single‐crystal X‐ray diffraction, and DTA. The crystal density of DANT is 1.849 g cm⁻³. The cyclization of one azido group and one nitrogen atom of the triazine group giving tetrazole was observed for DANT in a dimethyl sulfoxide solution using NMR spectroscopy. An equilibrium exists between the original DANT molecule and its cyclic form at a ratio of 7 : 3. The sensitivity of DANT to impact is between that for PETN and RDX, sensitivity to friction is between that for lead azide and PETN, and sensitivity to electric discharge is about the same as for PETN. DANT′s heat of combustion is 2060 kJ mol⁻¹.     

Evaluation of Nano‐Co3O4 in HTPB‐Based Composite Propellant Formulations

Different propellant compositions were prepared by incorporating nano‐sized cobalt oxide from 0.25 % to 1 % in HTPB/AP/Al‐based composite propellant formulations with 86 % solid loading. The effects on viscosity build‐up, thermal, mechanical and ballistic properties were studied. The findings revealed that by increasing the percentage of nano‐Co₃O₄ in the composition, the end of mix viscosity, the modulus and the tensile strength increased, whereas the elongation decreased accordingly. The thermal property data envisaged a reduction in the decomposition temperature of ammonium perchlorate (AP) as well as formulations based on AP. The ballistic property data revealed an enhanced burning rate from 6.11 mm s⁻¹ (reference composition) to 8.99 mm s⁻¹ at 6.86 MPa and a marginal increase in pressure exponent from 0.35 (reference composition) to 0.42 with 1 % nano‐cobalt oxide.     

Tetrakis(nitratoxycarbon)methane (Née CLL‐1) as a Potential Explosive Ingredient: a Theoretical Study

Ab initio electronic structure calculations at the MP2/cc‐pVTZ level predict the vibrational stability of the theoretical molecule tetrakis(nitratoxycarbon)methane, designated CLL‐1. The gas phase enthalpy of formation, predicted to be +1029.3 kJ mol⁻¹ using the G3(MP2) method, and the estimated density of 1.87 g cm⁻³ are used to predict the explosive performance properties using the equilibrium thermochemical code CHEETAH. The predicted detonation velocity (8.61 km s⁻¹) and pressure (33.1 GPa) are similar to those of RDX, but with a significantly higher detonation temperature (6740 K). Finally, the stability of this theoretical molecule is investigated by calculating the lowest energy unimolecular decomposition pathways of the HCO₃N model compound as well as barriers to rearrangement upon interaction of two HCO₃N molecules.     

The Shock Initiation Threshold of HNS as a Function of its Density

The shock initiation threshold of hexanitrostilbene (HNS) pellets with different densities has been investigated by performing small‐scale gap tests. As the sensitivity of HNS strongly depends on the density of the pellet, the density was varied in a range that the pellet material can be expected to be insensitive by means of no initiation at pressure loads of 2.6 GPa. In the case of HNS we observed that the material became insensitive at densities larger than 1.65 g cm⁻³. Further, we found that the pressure loads can be increased from 2.6 GPa to 3.29 GPa for densities increasing from ϱ=1.65 g cm⁻³ to ϱ=1.70 g cm⁻³ (98% TMD) without detonation of the HNS pellet.     

Predicted Anisotropic Thermal Conductivity for Crystalline 1,3,5‐Triamino‐2,4,6‐trinitobenzene (TATB): Temperature and Pressure Dependence and Sensitivity to Intramolecular Force Field Terms

The anisotropic thermal conductivity of the layered molecular crystal 1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB), an insensitive secondary high explosive, is determined using classical molecular dynamics on the P=0.0 GPa isobar for temperatures 200 K≤T≤700 K and on the T=300 K isotherm for pressures 0.0 GPa≤P≤2.5 GPa. Sensitivity of the predicted (300 K, 0.0 GPa) conductivity to intramolecular terms in the force field is investigated. Two conduction directions are considered, one nominally within and the other exactly perpendicular to the stacked planar single‐molecule‐thick layers comprising the TATB crystal. The thermal conductivity λ(T,P) along both directions is found to decrease approximately as λ∝1/T with increasing temperature and increase approximately linearly λ ∝ T with increasing pressure. The temperature dependence is found to be highly anisotropic with nearly twice as large a reduction in absolute conductivity within the molecular layers (Δλ=−0.67 W m⁻¹ K⁻¹) compared to between them (Δλ=−0.35 W m⁻¹ K⁻¹). Anisotropy in the conductivity is predicted to decrease with increasing temperature; the P=0.0 GPa conductivity is 68 % greater within the layers than between them at 200 K, but only 49 % greater at 700 K. The pressure dependence is also anisotropic, with a 51 % and 76 % increase in conductivity within and between the layers, respectively. Predicted values for the conductivity are found to differ by less than 12 % for several instructive modifications to the intramolecular force field. Completely eliminating high‐frequency N H bond vibrations using the SHAKE algorithm leads to an isotropic reduction in the conductivity that scales as the corresponding reduction in the classical heat capacity, indicating that optical phonons are likely significant contributors to the total conductivity. Replacing harmonic bond potential energy functions with anharmonic Morse functions results in an isotropic ≈6 % reduction that is likely due to stronger phonon‐phonon coupling and corresponding reduction in the phonon mean free path.     

High‐Pressure Vibrational Spectroscopy of Hexahydro‐ 1,3,5‐Trinitro‐1,3,5‐Triazine (RDX)

The molecular‐level response of RDX to hydrostatic compression was examined in a diamond anvil cell using Raman spectroscopy. The pressure‐induced alterations in spectral profiles of the C N stretching mode (886 cm⁻¹) were studied up to 8.3 GPa. At pressures near 4.4 GPa, several changes of the C N stretching mode become immediately apparent in Raman spectrum, such as large frequency shifts, line broadening, mode splitting, and intensity changes, which are associated with the α–γ phase transition and rearrangement between the RDX molecules. The high pressure Raman spectra changes of the C N stretching mode are indicative of an α–γ phase transition, and also suggest the lowering of molecular symmetry and crystal symmetry, which are expected to provide some insight into RDX molecular stability and decomposition.     

Mechanical properties of HTPB-IPDI-based elastomers

A polyurethane elastomer having mechanical and adhesive properties suitable for liner applications in solid rocket propellants was developed using HTPB as the prepolymer and IPDI as the curing agent. The effects of the NCO/OH ratio (R value) and the trio/diol ratio on the mechanical properties of the polyurethane matrix were investigated. The reaction of HTPB and IPDI is followed by monitoring the changes in the IR absorption bands of the NCO stretching at 2255 cm⁻¹ and the CO stretching at 1730 cm⁻¹. It was found that the rate of the polyurethane formation obeys an overall second-order kinetics. At an R value of 1.15, the elastomer shows the maximum tensile strength and 200% elongation at break. The hardness, elongation, and the tensile strength reach a steady value around the same R value. The elastomers having a triol/diol ratio less than 0.03 show a decrease in the tensile strength and modulus with a concomitant increase in elongation. At a triol/diol ratio greater than 0.05, the tensile strength increases to about the same value for the liner composition without any triol component. The elongation reaches a steady level at a triol/diol ratio of 0.10 and one observes a steady increase in hardness up to 0.5. The modulus for the compositions having a triol/diol ratio greater than 0.1 is about 50% higher than that for the composition without triol. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2347–2354, 1997     

Design and Synthesis of Hydrolytically Stable N‐Nitrourea Explosives

A series of high energy density compounds (HEDCs) based on N‐nitrourea were designed and their theoretical performances were calculated using the Gaussian programs. The predicted values of the energy density of these compounds are in the range 1.848–1.93 g cm⁻³, and their calculated VODs are in the range 6700–8305 m s⁻¹. Tetranitrodiglycoluril (TNDGU) ( 1 ) and tetranitrotriglycoluril (TNTGU) ( 2 ) were synthesized and characterized by NMR (¹H, ¹³C) and IR spectroscopy as well as elemental analyses. The structure of the aminolysis product ( 7 ) of TNDGU was further confirmed by single‐crystal X‐ray diffraction, which indicated that the structure belongs to P2₁/c space group in the monoclinic system.     

1,3,5‐Trinitroperhydro‐1,3,5‐triazine (RDX)‐Based Sheet Explosive Formulation with a Hybrid Binder System

A plastic‐bonded explosive (PBX) in the form of a sheet was formulated comprising of 1,3,5‐trinitroperhydro‐1,3,5‐triazine (RDX) and an hybrid binder system containing a linear thermoplastic polyurethane and a fluoroelastomer (Viton). The effect of a fluoroelastomer on the explosive as well as mechanical properties and thermal behavior of sheet explosive formulations were investigated and compared with a control formulation containing 90 % of RDX and 10 % of natural rubber (ISNR‐5). The replacement of 10 % natural rubber by a hybrid binder system led to an increase in the velocity of detonation (VOD) of the order of 250–950 m s⁻¹ and better mechanical properties in terms of tensile strength (1.9–2.5 MPa) compared to the control formulation (RDX/ISNR‐5 (90/10)). The compatibility of ingredients and thermal decomposition kinetics of selected sheet explosive formulations were investigated by vacuum stability tests and differential scanning calorimetry (DSC). The results suggested better compatibility of RDX with the hybrid binder system (polyurethane/Viton), which is useful to reduce potential hazards in handling, processing, and storage.     

The Influence of Temperature and Composition on the Operation of Al Anodes for Aluminum‐Air Batteries

The influence of composition and temperature on the anode polarization and corrosion rate of pure Al and Al‐In anodic alloys in 8M NaON electrolyte has been investigated. High current density (more than 800 mA cm⁻²) and faradaic efficiency over 97% were observed for all investigated alloys at 60 °C. Lower temperature provides lower current density (200–300 mA cm⁻² at 40 °C, and less than 100 mA cm⁻² at 25 °C). Different formation of the product reaction layers was observed for pure aluminum and Al–0.41In alloy, leading to the different polarization character of the samples. The comparison of two Al‐In alloys with similar composition has been carried out. Al–0.45In alloy having a coarse‐grained structure had a more positive no‐current potential and lower value of anode limiting current (200 mA cm⁻² vs. 300 mA cm⁻²) compared with the fine‐grained Al–0.41In alloy, as well as greater parasitic corrosion rate and greater no‐current corrosion. The current‐voltage, power and discharge characteristics of the aluminum‐air cell with Al–0.41In anode and gas diffusion cathode have been investigated. Open circuit voltage of the cell is 1.934 V and the maximum power density of the cell is 240 mW cm⁻² at the voltage of 1.3 V.     

The Synthesis and Energetic Properties of 5,7‐Dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide (DNBTDO)

Energetic tetrazine‐1,3‐dioxide, 5,7‐dinitrobenzo‐1,2,3,4‐tetrazine‐1,3‐dioxide ( DNBTDO ), was synthesized in 45 % yield. DNBTDO was characterized as an energetic material in terms of performance (V_det 8411 m s⁻¹; p_{C J} 3.3×10¹⁰ Pa at a density of 1.868 g cm⁻³), mechanical sensitivity (impact and friction as a function of grain size), and thermal stability (T_dec 204 °C). DNBTDO exhibits a sensitivity slightly higher than that of RDX , and a performance slightly lower (96 % of RDX ).     

The Insensitive Energetic Material Trifurazano‐oxacycloheptatriene (TFO): Synthesis and Detonation Properties

The high‐energy insensitive compound trifurazano‐oxacycloheptatriene (TFO) was first by synthesized through special etherification. The reaction mechanism and reaction conditions were discussed. TFO has a low melting point (78.6 °C) and good compatibility. TFO is insensitive to impact and friction and has similar detonation velocity (7.7 km s⁻¹) and detonation pressure (35.6 GPa) to RDX.