Showing papers in "Journal of Energetic Materials in 2014"

Kinetics of Thermal Decomposition of Ammonium Perchlorate by TG/DSC-MS-FTIR

Abstract: The method of thermogravimetry/differential scanning calorimetry–mass spectrometry–Fourier transform infrared (TG/DSC-MS-FTIR) simultaneous analysis has been used to study thermal decomposition of ammonium perchlorate (AP). The processing of nonisothermal data at various heating rates was performed using NETZSCH Thermokinetics. The MS-FTIR spectra showed that N2O and NO2 were the main gaseous products of the thermal decomposition of AP, and there was a competition between the formation reaction of N2O and that of NO2 during the process with an iso-concentration point of N2O and NO2. The dependence of the activation energy calculated by Friedman's iso-conversional method on the degree of conversion indicated that the AP decomposition process can be divided into three stages, which are autocatalytic, low-temperature diffusion and high-temperature, stable-phase reaction. The corresponding kinetic parameters were determined by multivariate nonlinear regression and the mechanism of the AP decomposition process...

Ignition Temperature of Magnesium Powder and Pyrotechnic Composition

Abstract: Using potassium nitrate, strontium nitrate, and potassium perchlorate as the oxidizing agents, the ignition and combustion behaviors of magnesium powders with different specific surface area were studied. The ignition temperature (Te) was extrapolated using a differential thermal analyzer, and the pyrotechnic spontaneous reaction temperature (Ts) was inferred from the temperature curve by inflection point analysis. The results showed that Ts has much better reproducibility than the extrapolated Te in characterizing the ignition of the pyrotechnic formulations. Increasing the specific surface area of the magnesium powder resulted in decreased Ts of the pyrotechnics.

Microstructured Al/Fe2O3/Nitrocellulose Energetic Fibers Realized by Electrospinning

Abstract: At present, metastable intermolecular composites (MICs) have been widely studied for their potential in high-density energetic materials and nanotechnology, but the relatively low-pressure discharge in a short period of time and the oxidation of Al powders have seriously impeded their applications in rocket solid fuels and explosives. In this work, the authors successfully fabricated microstructured Al/Fe2O3/nitrocellulose (Al/Fe2O3/NC) fibers via simple electrospinning, introducing nitrocellulose (NC), a gas generator to MICs. In view of previous reports, wrapping nAl in NC fibers might reduce their further oxidation during storage. In addition, the thermal properties and elastic modulus of NC fibers were measured before and after adding Al/Fe2O3.

Study of Different Al/Mg Powders in Hydroreactive Fuel Propellant Used for Water Ramjet

Abstract: Experiments were conducted to study the effect of magnesium–aluminum alloy on the combustion performance of hydroreactive fuel propellants. The raw metal powders added to the propellants were ball-milled magnesium–50% aluminum alloy (m-AM), magnesium–50% aluminum alloy (AM), and Al and magnesium (Mg) powders, which were characterized using scanning electron microscopy, X-ray diffraction (XRD), and simultaneous thermogravimetric analysis (TGA). A high-pressure combustor and a metal/steam reactor were used to simulate the two-stage combustion of hydroreactive propellants used for a water ramjet. The combustion performance of the metal powders in propellant was studied experimentally, and the efficiency of the Al reaction in the propellants during the two-stage combustion was calculated. TGA traces in air indicated that the oxidation onset temperature of AM powders is much lower than for both Mg and Al powders. The XRD patterns for the AM and m-AM alloys exhibited Al12Mg17 diffraction peaks. The hydroreactiv...

A Convenient and Efficient Protocol for the Synthesis of HBIW Catalyzed by Silica Nanoparticles under Ultrasound Irradiation

Abstract: 2,4,6,8,10,12-Hexabenzyl-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,9.03,11]dodecane (hexabenzylhexaazaisowurtzitane, HBIW) has been synthesized by the reaction of benzylamine and glyoxal (40% aqueous solution) in acetonitrile as a solvent catalyzed by silica nanoparticles (SiO2 NPs, ca. 42 nm) under ultrasound irradiation. The effects of solvent, catalyst, and ultrasonic power are discussed. With optimized reaction conditions, HBIW was synthesized under the influence of ultrasound irradiation. Compared with conventional methods, the remarkable advantages of this method are the simple experimental procedure, shorter reaction time, and high product yield.

Explosion Power and Pressure Desensitization Resisting Property of Emulsion Explosives Sensitized by MgH2

Abstract: Due to low detonation power and pressure desensitization problems that traditional emulsion explosives encounter in utilization, a hydrogen-based emulsion explosives was devised. This type of emulsion explosives is sensitized by hydrogen-containing material MgH2, and MgH2 plays a double role as a sensitizer and an energetic material in emulsion explosives. Underwater explosion experiments and shock wave desensitization experiments show that an MgH2 emulsion explosives has excellent detonation characteristics and is resistant to pressure desensitization. The pressure desensitization–resistant mechanism of MgH2 emulsion explosives was investigated using scanning electron microscopy.

Effect of Copper Oxide, Titanium Dioxide, and Lithium Fluoride on the Thermal Behavior and Decomposition Kinetics of Ammonium Nitrate

Abstract: Ammonium nitrate (AN) is crystallized along with copper oxide, titanium dioxide, and lithium fluoride Thermal kinetic constants for the decomposition reaction of the samples were calculated by model-free (Friedman's differential and Vyzovkins nonlinear integral) and model-fitting (Coats-Redfern) methods To determine the decomposition mechanisms, 12 solid-state mechanisms were tested using the Coats-Redfern method The results of the Coats-Redfern method show that the decomposition mechanism for all samples is the contracting cylinder mechanism The phase behavior of the obtained samples was evaluated by differential scanning calorimetry (DSC), and structural properties were determined by X-ray powder diffraction (XRPD) The results indicate that copper oxide modifies the phase transition behavior and can catalyze AN decomposition, whereas LiF inhibits AN decomposition, and TiO2 shows no influence on the rate of decomposition Possible explanations for these results are discussed Supplementary materials

Application of Liquid Paraffin in Castable CL-20-Based PBX

Abstract: Hydroxy-terminated polybutadiene (HTPB)/CL-20 castable explosives plasticized with liquid paraffin were processed successfully by a cast-curing method. The compatibility of liquid paraffin with CL-20, influence of liquid paraffin on CL-20 phase transition, and viscosity of the cast mixture were tested and analyzed. The thermal decomposition characteristics, thermal stability, mechanical sensitivity, and velocity of detonation (VOD) of the HTPB/CL-20 plastic-bonded explosives (PBXs) were also measured. The experimental results showed that liquid paraffin was well compatible with CL-20, and it did not have a distinct effect on the ϵ- to γ-phase transition of CL-20. In addition, the casting mixture was free-flowing with sufficiently low viscosity. When the content of CL-20 is 90% by weight, the measured VOD reached 8,775 m/s (density of 1.78 g/cm3), and the PBXs exhibited moderate mechanical sensitivity and good thermal stability.

An Investigation into the Effects of Additives on Crystal Characteristics and Impact Sensitivity of RDX

Abstract: Additives are one of the most important factors that greatly affect the crystal characteristics of the high energy compound hexahydro-1,3,5-trinitro-1,3,5-s-triazine (RDX, C3H6N6O6) and they have an influence on impact sensitivity. In this article, a growth morphology method was applied to obtain the crystal habit of RDX in a vacuum as well as the morphologically important faces, and molecular dynamics simulations were applied to calculate the interaction energy between these crystal faces and additive molecules for prediction of the additive-effect crystal habits of RDX. On this basis, crystal characteristics including crystal morphology, aspect ratio, and total surface charge were investigated. Then the particle size and surface electrostatic voltage of the samples from recrystallization were analyzed experimentally. The impact sensitivity test indicated that acrylamide, which could enhance the regularity and degree of sphericity of RDX crystals and effectively reduce the surface static electricity of R...

The Influence of Magnesium Hydride on the Thermal Decomposition Properties of Nitrocellulose

Abstract: Magnesium hydride is a kind of attractive hydrogen storage material. In this article, the thermal decomposition characteristic of the pure nitrocellulose and the mixture of nitrocellulose with 5% MgH2 was investigated using an accelerating rate calorimeter. The kinetic parameters such as activation energy, Ea; preexponential factor, A; and self-accelerating decomposition temperature, TSADT, were also calculated. We easily showed that the decomposition reaction could be accelerated by adding MgH2, which indicated that MgH2 has an obvious catalytic influence on the decomposition of nitrocellulose. On the other hand, the calculated values of Ea and TSADT showed a decrease in thermal sensitivity with the addition of MgH2. These results were in accordance with our objectives. Therefore, MgH2 is very likely to be an important additive in propellants.

A Successive and Scalable Process for Preparing Spherical Submicrometer-Sized RDX by the SEDS Process

Abstract: The preparation spherical and submicrometer-sized cyclotrimethylene-trinitramine (RDX) is described through the process of solution-enhanced dispersion by supercritical fluids (SEDS). Because SEDS is a successive and scalable process, about 40.5 g RDX particles can be obtained within 70 min and the total yield is about 90.0% under optimized conditions. Submicrometer-sized RDX and original samples were characterized and confirmed by different analysis methods. The results revealed that submicrometer-sized RDX particles are spherical with a mean particle size of 767.7 nm, have high purity, show no crystal structure change, and decompose easily. Mechanical sensitivity tests of submicrometer-size RDX were decreased in comparison to the original RDX.

Synthesis and Reactive Properties of Iron Oxide–Coated Nanoaluminum

Abstract: A homogeneous coating of Fe3O4 on in situ–generated nanoaluminum was accomplished by thermal decomposition of Fe(CO)5 in an aluminum aerosol stream and subsequent oxidation of iron by air bleed. X-ray photoelectron spectroscopy (XPS) investigation revealed that oxygen penetrated through this coating, and Fe3O4 facilitated the formation of an expanded aluminum oxide layer compared to an uncoated aluminum case. Closed cell combustion tests displayed a minor decrease in pressure response for the coated product, which was attributed to the increased aluminum oxide layer. The critical ignition temperature was reduced for the coated product in T-jump fine-wire combustion tests.

Decreasing Friction Sensitivity for Primary Explosives

Abstract: Primary explosives are a group of explosives that are widely used in various initiating devices. One of their properties is sufficient sensitivity to initiating stimuli. However, their sensitivity often introduces a safety risk during their production and subsequent handling. It is generally known that water can be used to desensitize these compounds. The most commonly used industrial primary explosives (lead azide, lead styphnate, tetrazene, and diazodinitrophenol) were mixed with water in various ratios and the sensitivity to friction was determined for all mixtures. It was found that even a small addition of water (5–10%) considerably lowered the friction sensitivity.

Tungsten Combustion in Explosively Initiated W/Zr Mechanical Alloys

Abstract: Tungsten is mechanically alloyed with zirconium and subject to explosive initiation in confined chamber tests. Transient pressure measurements and residue analysis suggest that a majority of the tungsten reacts within 10 ms in alloys containing 33, 57, and 75 w/w W (balance Zr). The product of tungsten oxidation is likely amorphous WO3, because no crystalline tungsten oxides are observed in X-ray analysis of the residues. These results suggest that the chemical energy of tungsten can be extracted efficiently from mechanical alloys containing as little as 25% Zr, resulting in very high-density structural energetics that release chemical energy comparable to TNT on a mass basis.

2,4,6-Tris(2,2,2-trinitroethylamino)-1,3,5-triazine: Synthesis, Characterization, and Energetic Properties

Abstract: A simple and straightforward route for the synthesis of 2,4,6-tris(2,2,2-trinitroethylamino)-1,3,5-triazine (TTET) has been developed. The compound was fully characterized by multinuclear (1H, 13C) magnetic resonance and infrared (IR) spectroscopy, elemental analysis, electron ionization–mass spectrometry, and differential scanning calorimetry (DSC). TTET was found to have good physical properties, such as good thermal stability (Td = 186°C), reasonable impact sensitivity (21.5 J), and high density (1.88 g · cm−3). Additionally, the detonation properties of TTET obtained with the empirical Kamlet-Jacobs equations identify it as a competitively energetic compound, which in some cases is superior to 1,3,5-Trinitroperhydro-1,3,5-triazine.

Study on the Mechanism of the Deflagration to Detonation Transition Process of Explosive

Abstract: We present a numerical study of the mechanisms of the deflagration to detonation transition (DDT) process of explosives to assess its thermal stability. We treated the modeling system as a mixture of solid explosives and gaseous reaction products. We utilized a one-dimensional two-phase flow modeling approach with a space–time conservation element and solution element (CE/SE) method. Simulation results show that in the chemical reaction process a plug area of high density with relatively slow chemical reactions preceeds the new violent reactions and the consequent detonation. We found that steady detonation occurs at the regions where physical characteristics, such as pressure, density, temperature, and velocity, peak simultaneously. These simulation results agree well with high-temperature DDT tube experiments.

Preparation of BAP Composite Particles and Their Effects on Rheological Properties of HTPB/B/AP Slurries

Abstract: Composite particles (BAP) of boron (B) coated with ammonium perchlorate (AP) were prepared by recrystallization and their structures were characterized using Fourier transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), and laser particle size analyses. The results indicated that AP was well coated on the boron surface. The effects of different contents of BAP coated with different amounts of AP on the rheological properties of HTPB/B/AP composite slurries were also studied. The results show that addition of BAP distinctly decreased the slurries’ viscosities and improved their processing properties, which were more obvious when 9.73% AP was coated on the surface of boron and the amount of BAP was 20%.

Thermal Decomposition of Dinitro-chloro-azido Benzenes: A Comparison of Theoretical and Experimental Results

Abstract: 1,2-Dichloro benzene (I) and 1,2,3-trichloro benzene (II) were nitrated under appropriate strong conditions. Nitrated mixtures were reacted with NaN3 in polar solvents. As a result of the nucleophilic substitution, mixtures of nitro-chloro-azido benzene were prepared. After fractional crystallization, two crystalline substances were obtained from the mixtures. These crystalline substances were characterized by infrared (IR), 1H-NMR spectroscopy, mass spectroscopy, and elemental analysis. It was understood that the substance obtained from compound I was 2-chloro-4,6-dinitro azido benzene (III). The crystals of compound III were suitable for single-crystal X-ray diffraction (XRD). The molecular structure of this substance was determined by the mentioned method, XRD. It was revealed that the crystalline substance obtained from compound II was most probably 1,5-dinitro-2,4-diazido-3-chloro benzene (IV). In addition, compounds III and IV were investigated by thermogravimetry (TG) and differential scanning calo...

HPLC-MS Examination of Impurities in Pentaerythritol Tetranitrate

Abstract: Pentaerythritol tetranitrate (PETN) has trace homolog impurities that can be detected by high-performance liquid chromatography–mass spectrometry. Consideration of observed impurity masses and candidate structures based on known pentaerythritol impurities allows identification of 22 compounds in the data. These are all consistent with either fully nitrated homologs or derivatives substituted with methyl, methoxy, or hydroxyl groups in place of a nitric ester. Examining relative impurity concentrations in three starting batches of PETN and six subsequently processed batches shows that it is possible to use relative concentration profiles as a fingerprint to differentiate batches and follow them through recrystallization steps.

A Burning Rate Equation as a Function of Pressure and Temperature for a BTA · NH3/PSAN Mixture

Abstract: The burning rate of propellants is affected by pressure and temperature. The relation between the burning rate and pressure has been well studied. However, the effect of the initial temperature on the burning rate has not been investigated quantitatively. In this study, the burning rate of bis (1H-tetrazolyl) amine ammonium salt and potassium nitrate phase-stabilized ammonium nitrate mixtures was examined and an equation for the burning rate as a function of pressure and temperature was obtained. In general, the burning rates predicted by the regression equations were in good agreement with the observed values. The temperature sensitivities were also predicted using the regression equation and compared with the observed values and good agreement was found between the predicted and observed values.

Oxalylhydrazinium Nitrate and Dinitrate—Efficiency Meets Performance

Abstract: Oxalylhydrazinium nitrate (OHN) and dinitrate (OHDN) were synthesized by protonation of oxalyldihydrazide with nitric acid. The synthesis is extremely cost effective (∼$40/kg at the lab scale) and can be carried out in large scales and very good yields. OHN and OHDN were intensively characterized by low-temperature X-ray diffraction (XRD), nuclear magnetic resonance (NMR) and vibrational spectroscopy. These new organic nitrate salts could be used as powerful ingredients in energetic formulations due to their low sensitivities (measured by Bundesanstalt fur Materialforschung und Profung methods). Their thermal stability was investigated by differential scanning calorimetry (DSC) measurements. Further thermal studies of OHN showed compatibility with TNT (2,4,6-trinitrotoluene), DNAN (2,4-dinitroanisole), and RDX (1,3,5-trinitro-1,3,5-triazinane). The theoretical detonation and propulsion parameters of OHN and OHDN were calculated with the EXPLO5.5 code and compared to well-known insensitive explosives. The ...

Theoretical Investigation of Pyridine Derivatives as High Energy Materials

Abstract: In this work, properties of polynitro-bridged pyridine derivatives were systemically studied at the B3LYP/6-31G(d) level. Gas-phase heats of formation (HOFs) for the designed compounds were calculated using isodesmic reactions, and their solid-phase HOFs were estimated using the Politzer approach. All designed compounds possess large solid-phase HOFs, larger than 700 kJ/mol. Based on the predicted crystal densities, solid-phase HOFs, and chemical energies, detonation properties were evaluated by means of Kamlet-Jacobs empirical equations. The results show that detonation velocities and pressures of all of the designed compounds are above 9.30 km/s and 40.00 GPa, respectively. In addition, bond dissociation energy (BDE) was employed to investigate their thermal stability. Considering solid-phase HOFs, detonation performance, and thermal stability, most of the designed compounds meet the requirements of high energy density materials (HEDMs).

Reaction Characteristic for Various Scale Explosive under Mild Impact

Abstract: This work presents a varying trend of impact ignition threshold denoted by minimum impact velocity to trigger an ignition when the scale of the explosive changes. The effects of explosive scale factors on impact-induced reaction degree were investigated using Steven tests and numerical simulation for polymer-bonded explosive-C03 (a cyclotetramethylene tetranitramine [HMX]-based explosive) impacted by projectiles of various velocities. Two scale factors—that is, axial thickness and radius—were studied through various scale samples including Φ98 mm × 13 mm, Φ98 mm × 39 mm, Φ140 mm × 13 mm, and Φ140 mm × 39 mm. The velocities of projectiles and the impact and ignition processes were analyzed using a high-speed camera. The pressure histories were measured by embedded manganin pressure gauges and poly vinylidene fluoride stress gauges. The reaction overpressures of the explosive were obtained by blast pressure gauges to evaluate the reaction degree. The effects of explosive scale factor on reaction degree and ...

Modeling Shock Desensitization of Composition B Explosive

Abstract: The NOBEL multimaterial adaptive grid Eulerian hydrodynamic code was used to model a shaped charge jet formation, its interaction with a steel plate, and shock formation of a bow shock in front of the jet that shocks and desensitizes a cylinder of composition B explosive so that when the jet arrives it fails to initiate detonation. The jet passes through the composition B explosive cylinder, an air gap, and then initiates propagating detonation in a second composition B explosive cylinder that has not been desensitized by a preshock. The experimental arrangement was studied using X-ray radiography at the Material Research Laboratories in Melbourne, Australia.

Single-Point-of-Failure Mitigation: Prove-Out of a Green Light–Emitting Illuminant Composition in the Handheld Signal Cluster and 40-mm Parachute Configurations

Abstract: The development of handheld signal cluster and 40-mm parachute green light–emitting pyrotechnic compositions is described. Of the new compositions evaluated, one was found to exceed the military requirements in burn time, luminous intensity, dominant wavelength, and spectral purity in both the cluster and parachute configurations. The new illuminant composition is not plagued by single-point-of-failure concerns, as the Laminac 4116/Lupersol binder system has been replaced by the widely available Epon 813/Versamid 140 binder system. In addition, the new illuminant composition was found to be insensitive toward impact, friction, and electrostatic discharge and had a high thermal onset temperature.

Synthesis of Heterocyclic Ylids as Candidates for Energetic Materials

Abstract: Concise syntheses of nitrogen-rich pyridinium and 1,2,4-triazolium N-imides are reported. Substrate scope and various imide-stabilizing electron withdrawing groups are examined. Energetic properties of the target molecules were studied by heats of combustion.

Characterization of Hydrazinium 3,5-Dinitroamine-1,2,4-triazole

Abstract: The structure of hydrazinium 3,5-dinitroamine-1,2,4-triazole (HDNAT) was investigated with infrared (IR), mass spectrometry, 13C-NMR, scanning electron microscopy (SEM), and X-ray crystallography. The crystal density of HDNAT was determined as 1.91 g/cm3 using X-ray diffraction. The crystal belongs to a monoclinic system with the space group P2(1). The thermal decomposition process of HDNAT was investigated via thermogravimetry–differential thermal analysis (TG-DTA) at a heating rate of 10 K/min and differential scanning calorimetry (DSC) under nonisothermal conditions. The decomposition kinetic and thermodynamic parameters were obtained by the Kissinger and Ozawa method. HDNAT can be analyzed by using a C18 high-performance liquid chromatography (HPLC) column with water : acetonitrile : trifluoroacetic acid (97/3/0.1, v/v/v) as the mobile phase and a capacity factor of 1.33.

Study of the Spatial Distribution of Burning Particles in a Pyrotechnic Flame Based on Particle Velocity

Abstract: The burning particles in the pyrotechnic flame play an important role in the ignition and spectral radiance of the pyrotechnic. We used particle image velocimetry (PIV) and high-speed camera (HSC) photography to investigate the 3D spatial pattern and velocity of the burning particles in the flame of pyrotechnics. The original images captured by the HSC were preprocessed through threshold selection, image bivalency, edge detection, and contour extraction and segmentation to obtain the particle coordinates and velocity. Consequently, the particle tracking model was established and the velocity and spatial distribution of the burning particles were obtained. A comparison of the flame flow field with particle image velocimetry demonstrated the typical characteristics of the two-phase flow of the pyrotechnic flame between burning particles and gas. Compared with the convergent gas flow field, the higher velocity burning particles had a discrete distribution in the “comet tail” shape region and showed the same ...

The First-Principle Study on the Crystal Structures of Azido Derivatives of Benzene

Abstract: A molecular mechanics method with COMPASS and Dreiding force fields was used to predict molecular packings for the three title compounds among seven possible space groups (P21/c, P212121, P-1, Pbca, C2/c, Pna21, and P21). Then, periodic band calculations were performed on the predicted crystals using the density functional theory generalized gradient approximation with revised Perdew-Burke-Ernzerhof (DFT-GGA-RPBE) functional method. The obtained density of state (DOS) showed that the C-N3 bonds are possibly the trigger bond during thermolysis. The band gaps (ΔEg) were slightly different and hexaazidobenzene was more sensitive than the two others. Periodic calculation results on DOS were consistent with those obtained from bond dissociation energy calculations on gas molecules.

An Environmentally Friendly Baratol Replacement for Plane Wave Generator Applications

Abstract: The development of low adjustable detonation velocity plastic bonded explosive (PBX) formulations is described. The PBX consists of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), zinc oxide, and Viton A as the binder. We prepared several formulations and determined a range of sensitivity values with respect to impact, spark, friction, and thermal stability for these formulations. Furthermore, we experimentally determined the detonation velocity of each formulation and discovered that a detonation velocity near 5 km/s is attainable using 30 wt% HMX, 60 wt% zinc oxide, and 5 wt% Viton A.