Thermal Decomposition Behaviors and Burning Characteristics of AN/RDX-Based Composite Propellants Supplemented with MnO2 and Fe2O3

Ammonium nitrate (AN)-based composite propellants have gained popularity because of the clean burning nature of AN as an oxidizer. However, such propellants have several disadvantages such as poor ignition and low burning rate. The burning characteristics of the AN propellant were improved when a portion of this propellant was replaced by an energetic material and the addition of a catalyst. In this study, RDX (1,3,5-trinitroperhydro-1,3,5-triazine) was used as the energetic material, and Fe₂O₃ and MnO₂ were used as catalysts. The burning characteristics of the AN/RDX propellants supplemented with catalysts were investigated, and the effects of the replacement of AN by RDX and the catalyst addition were evaluated.     

Shock Initiation Characteristics of an Aluminized DNAN/RDX Melt-Cast Explosive

Shock sensitivity is one of the key parameters for newly developed, 2,4-dinitroanisole (DNAN)-based, melt-cast explosives. For this paper, a series of shock initiation experiments were conducted using a one-dimensional Lagrangian system with a manganin piezoresistive pressure gauge technique to evaluate the shock sensitivity of an aluminized DNAN/cyclotrimethylenetrinitramine (RDX) melt-cast explosive. This study fully investigated the effects of particle size distributions in both RDX and aluminum, as well as the RDX’s crystal quality on the shock sensitivity of the aluminized DNAN/RDX melt-cast explosive. Ultimately, the shock sensitivity of the aluminized DNAN/RDX melt-cast explosives increases when the particle size decreases in both RDX and aluminum. Additionally, shock sensitivity increases when the RDX’s crystal quality decreases. In order to simulate these effects, an Ignition and Growth (I&G) reactive flow model was calibrated. This calibrated I&G model was able to predict the shock initiation characteristics of the aluminized DNAN/RDX melt-cast explosive.     

Oxalylhydrazinium Nitrate and Dinitrate—Efficiency Meets Performance

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 für Materialforschung und Pröfung 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 aquatic toxicity of OHN was determined by the luminescent bacteria inhibition test, yielding a much lower toxicity than RDX.     

Thermal characterization of mixtures of nitrotriazolone with HMX and RDX

Abstract

Thermal characterization of mixtures of nitrotria-zolone (NTO) with octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) has been carried out by means of differential scanning calorimetry and thermogravimetric analysis. It has been found that HMX decomposition temperature remains constant through the whole composition range. However NTO decomposition temperature decreases as the NTO/HMX ratio decreases. The RDX decomposition temperature keeps constant in all compositions studied. The RDX melting temperature decreases few degrees. The NTO decomposition appears at lower temperatures as the RDX content increases.     

Evaluation studies on partial replacement of RDX by spherical NTO in HTPB-based insensitive sheet explosive formulation

ABSTRACT

Hydroxyl terminated polybutadiene (HTPB)-based sheet explosive incorporating spherical 3-nitro-1,2,4-triazol-5-one (NTO) as a partial replacement of 1,3,5-trinitro-1,3,5-triazinane (RDX) was investigated. The effect of incorporation of NTO on mechanical properties, sensitivity behavior, and velocity of detonation (VOD) was studied in comparison with a sheet explosive formulation containing 82 wt% RDX, both based on an HTPB-binder system. The replacement of 22 wt% of RDX by spherical NTO resulted in reduced vulnerability to shock as well as impact stimuli. The data demonstrated that the NTO-added formulation was found to be higher shock insensitive compared to the RDX-only formulation. However, ~5% decrease in VOD was observed on incorporation of NTO. Further, the sheet explosive formulations were found insensitive toward friction up to 360 N. Also, molecular dynamics simulations were performed to predict the elastic constants of RDX and NTO and the results revealed that the predicted trend correlated with the experimentally obtained mechanical properties of the formulations.     

Symmetry,Conjugated System,and N-oxides in 2,4,6-Trinitro-1,3,5-triazine-1,3,5-trioxides: A New Design Concept for Energetic Oxidizers

A new strategy for an energetic oxidizer, 2,4,6-trinitro-1,3,5-triazine-1,3,5-trioxides (TNTATO), was designed by keeping symmetry and conjugation and introducing N-oxides into 1,3,5-triazine. Molecular mechanics (MM) and density functional theory (DFT) were employed to study the crystal structure, infrared (IR) spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heats of formation, detonation performance, and burning rate of TNTATO. The pyrolysis mechanism and thermal stability were predicted by evaluating the bond dissociation energy (BDE) and activation energy. The calculated results indicate that TNTATO has a symmetric hyperconjugation structure, which contributes to its stability. The BDE (210.64 kJ/mol^?1) and activation energy (27.74 kJ/mol^?1) of the weakest bond C3–N8 show that the C–NO₂ bond is the trigger bond during thermolysis. The detonation velocity (8.51 km/s^?1) and detonation pressure (32.69 GPa) are larger than those of 2,4,6-trinitro-1,3,5-triazine (TNTA). TNTATO exhibits better burning properties than ammonium dinitramide (ADN), indicating that TNTATO may be a potential candidate for a highly energetic oxidizer.     

Detonation Characteristics of Plastic Explosives Based on Attractive Nitramines with Polyisobutylene and Poly(methyl methacrylate) Binders

Four highly brisant nitramines, RDX (1,3,5-trinitro-1,3,5-triazinane), HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane), BCHMX (cis-1,3,4,6-tetranitro-octahydroimidazo-[4,5-d]imidazole), and ?-HNIW (?-2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane), were studied as extruded plastic explosives bonded by two plastic matrices based on polyisobutylene (C4 matrix) and poly-methylmethacrylate (plasticized by dioctyl-adipate) binders. The detonation velocities, D, were measured experimentally. Detonation parameters were also calculated by means of the Kamlet and Jacobs method and CHEETAH and EXPLO5 codes. These detonation parameters showed that plastic-bonded explosives (PBXs) based on BCHMX are more powerful explosives than those based on RDX. The Urizar coefficient for poly(methyl methacrylate) binder was also calculated.     

Studies on energetic compounds part 15 : Transition metal salts of NTO as potential energetic ballistic modifiers for composite solid propellants

Abstract

The combustion of hydroxyl terminated polybutadiene (HTPB) - ammonium perchlorate (AP) composite solid propellants has been studied using transition metal (Mn, Fe, Co, Ni, Cu and Zn) salts of 5-nitro-2,4-dihydro-3H-1,2,4-triazole-3-one (NTO) as energetic burning rate additives. The steady burning rate (r) was considerably enhanced with Cu(NTO)₂ and Fe(NTO)₂ whereas moderately enhanced with Zn(NTO)₂ and Co(NTO)₂ at low concentration (2% by wt.). Activity of these salts has been observed during isothermal decomposition of AP at 260°C. The values of ignition delay (t_iJ), ignition temperature (T_ign.) and activation energy for ignition (E?) for AP has also been lowered when these salts are added to it at 2% wt. concentration. The processing parameters as well as mechanical properties of the propellants with Cu(NTO)₂ as additive have been studied in detail. The r of the propellants (both highly aluminized and less aluminized) with Cu(NTO)₂ as additive at various concentrations, has been determined at high pressures, also shows its activity during combustion, The condensed phase activity of Cu(NTO)₂ during propellant decomposition has also been studied using TG-DTG techniques.     

NTO-Picryl Constitutional Isomers—A DFT Study

The quantum chemical properties and the detonation performance of some new explosives, 5-nitro-4-picryl-2,4-dihydro-3H-1,2,4-triazol-3-one (class A) and 5-nitro-2-picryl-2,4-dihydro-3H-1,2,4-triazol-3-one (class B), and their constitutional isomers have been investigated theoretically using the density functional theory (DFT) 6-31G(d,p) method.

All of the constitutional isomers were found to be more sensitive than 5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one (NTO) and TNT but more insensitive than RDX and HMX. Their detonation performance is higher than that of NTO and TNT and all except two had lower detonation performance than RDX and HMX.     

Thermal Behaviors and Their Correlations of Mg(BH4)2-Contained Explosives

In order to explore the effect of metal hydride on energetic materials’ thermal behaviors and their correlations, we studied the heats of combustion and detonation of RDX, TNT, and Mg(BH₄)₂-containing explosives both theoretically and experimentally. The results showed that Mg(BH₄)₂ can significantly improve the energy of explosive. As the mass fraction of Mg(BH₄)₂ increases, the combustion heat of composite explosives increases gradually, while the combustion efficiency decreases. When its mass fraction is about 30%, the theoretical heats of detonation of RDX/Mg(BH₄)₂ and TNT/Mg(BH₄)₂ reach maximum, which are 7418.47 and 7032.46 kJ/kg, respectively. When we compared the errors between calculation and experimental values, we found that L-C method is more accurate in calculating oxygen-enriched and oxygen-balanced explosives, and that minimum free energy method is more suitable for seriously negative oxygen-balanced explosive. For single explosive, there are three kinds of relationships between heat of combustion and detonation according to the oxygen balance. For Mg(BH₄)₂-containing explosives, the relationship is in accordance with Boltzmann function.     

Nitro Derivatives of 1,3,5-Triazepine as Potential High-Energy Materials

Structure optimization and frequency calculation of six nitro derivatives of 1,3,5-triazepine were performed using a MP2(FULL)/6-311G(d,p) method. In order to obtain reliable energy data, single-point energy and subsequently thermodynamic properties of the species considered were calculated at a fairly high level of theory, CCSD(T)/6-311G(d,p). Solid-phase heats of formation and crystal density were determined using an electrostatic potential (ESP) method utilizing wave function analysis-surface analysis suite (WFA-SAS) code. The result shows that all nitro derivatives possess high positive heats of formation that increase with an increase in the number of nitro groups attached to the ring moiety. The crystal density was found to be in the range of 1.67–1.90 g/cm³. Detonation properties of the compounds were estimated using the Kamlet-Jacobs equation. The results showed that detonation velocity (D) and detonation pressure (P) increased with an increase in the number of nitro groups attached at the ring moiety. It was found that all six nitro derivatives of the title compound had better or comparable performance characteristics than the most widely used commercial explosives, such as TNT, research and development explosives (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The trinitro derivative (1,3,5-trinitro-1,3,5-triazepine, F) yielded detonation pressure (P) and detonation velocity (D) of 45.5 GPa and 9.23 km/s, respectively, at a loading density of 1.90 g/cm³, which are superior to the most powerful available explosive HMX (P = 39.00 GPa and D = 9.11 km/s). The results obtained during the present study show that the title compounds can be used as promising futuristic high-energy-density materials (HEDMs).     

Synthesis and Thermal Decomposition Mechanism of the Energetic Compound 3,5-Dinitro-4-nitroxypyrazole

A novel energetic material, 3,5-dinitro-4-nitroxypyrazole (DNNP), was synthesized via nitration and nucleophilic substitution reaction using 4-chloropyrazole as raw material. The structure of DNNP was characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), and elemental analysis. Its detonation properties were calculated and compared with those of other commonly used energetic compounds. The thermal decomposition mechanism of DNNP was studied by means of thermogravimetry and differential scanning calorimetry coupled with a mass spectrometry (DSC-MS). The results show that the detonation properties of DNNP were better than those of TNT and comparable to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX). In addition, the thermal decomposition mechanism of DNNP was supposed. Initially, the O–NO₂ bond was broken, thereby producing a nitropyrazole oxygen radical. Subsequently, the nitropyrazole oxygen radical was decomposed by free radical cleavage of nitro or isomerized to nitritepyrazole and subsequently decomposed by free radical cleavage of the nitroso group. Finally, pyrazole ring fission occurred and produced N₂, NO, N₂O, and CO₂.     

Compatibility Study of Dihydroxylammonium 5,5′-Bistetrazole-1,1′-diolate (TKX-50) with Some Energetic Materials and Inert Materials

Dihydroxylammonium 5,5′-bistetrazole-1,1′-diolate (TKX-50) emerged as a novel energetic material with low sensitivity and excellent calculated detonation performance. The compatibility of TKX-50 with nitrocellulose (NC), an NC/NG (nitroglycerine) mixture (mass rate: 1.25:1), 2,4-dinitroanisole (DNAN), 2,4,6-trinitrotoluene (TNT), cyclotrimethylenetrinitramine (RDX), ammonium perchlorate (AP), hexanitroethane (HNE), cyclotetramethylenetetranitramine (HMX), hexanitrohexazaisowurtzitane (CL-20), glycidyl azide polymer (GAP), hydroxyl-terminated polybutadiene (HTPB), aluminum powder (Al), boron powder, and centralite was studied by differential scanning calorimetry (DSC). The results show that TKX-50/HNE possesses good compatibility, TKX-50 and HMX have moderate compatibility, and the compatibility of TKX-50 with TNT, CL-20, centralite, NC, AP, Al, and GAP is poor; in addition, TKX-50/RDX, TKX-50/NC + NG, TKX-50/B, and TKX-50/HTPB have poor compatibility.     

Preparation and characterization of RDX/BAMO-THF energetic nanocomposites

ABSTRACT

Novel 1,3,5-trinitro-1,3,5-triazine/3,3-bis (azidomethyl) oxetane-tetrahydrofuran copolymer (RDX/BAMO-THF) energetic nanocomposites were successfully prepared by a facile sol–gel freezing–drying method. The as-prepared RDX/BAMO-THF energetic nanocomposites were characterized by Raman and Fourier transform infrared spectroscopy, which revealed that RDX particles were incorporated into BAMO-THF gel matrix. Scanning electron microscopy was used to characterize the morphology and the particle size of the as-obtained samples. The results showed that RDX particles were trapped in the BAMO-THF gel matrix and the particle sizes were in nanoscale. Differential thermal analyzer (DTA) was performed to determine the thermal decomposition behaviors of BAMO-THF, raw RDX and RDX/BAMO-THF nanocomposites. The results indicated that the thermal decomposition process of RDX/BAMO-THF nanocomposites was enhanced compared with that of BAMO-THF and RDX. The kinetic, thermodynamic and thermal stability parameters were calculated according to DTA analysis. The calculated results revealed that RDX/BAMO-THF nanocomposites presented high thermal reactivity. The results of impact sensitivities for RDX/BAMO-THF nanocomposites indicated the sensitivity was effectively reduced compared to raw RDX.     

Comparison of New and Legacy TATBs

Two newly synthesized versions of the insensitive high explosive (IHE) 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) were compared to two legacy explosives currently used by the Department of Energy. Except for thermal analysis, small-scale safety tests could not distinguish between the different synthetic routes. Morphologies of new TATBs were less faceted and more spherical. The particle size distribution of one new material was similar to legacy TATBs, but the other was very fine. Densities and submicron structure of the new TATBs were also significantly different from the legacy explosives and the densities of pressed pellets were lower. Recrystallization of both new TATBs from sulfolane produced nearly hexagonal platelets with improved density and thermal stability.     

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

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.     

Characterization and Identification of Explosives and Explosive Residues Using GC-MS,an FTIR Microscope,and HPTLC

ABSTRACT

Characterization and identification of explosives and explosive residues collected from different places in India were made using TLC, GC/EI-MS, and GC-FTIR. The explosives used were NG, PETN, TNT, tetryl, RDX, and NH₄NO₃+fuel oil. Quantitative estimation was made using HPTLC. Mass spectra of the samples using selective ion monitoring (SIM) mode based on the relative intensities of the signals X, X + 1 (intensity of the largest fragment X of the explosive, say, RDX [X = 205] was assumed to be 100%, i.e., X = 100%) show no isotopic substitution. The results were confirmed by FTIR spectra. Some physico-chemical aspects of the explosives are discussed.     

Compatibility of 2, 4, 6, 8, 10,12-Hexanitrohexaazaisowurtzitane with a Selection of Insensitive Explosives

Thermal techniques (differential scanning calorimetry (DSC) and the vacuum stability test (VST)), according to STANAG 4147, and non-thermal techniques (Fourier transform infrared (FTIR) spectrometry and X-ray diffractometry (XRD)) were used to examine compatibility issues for 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane (CL-20) with a selection of insensitive explosives, including nitroguanidine (NQ), 2,4,6-trinitrotoluene (TNT), 2,6-diamino-3,5-dinitropyridine-1-oxide (ANPyO), 2,4,6-triamino-1,3,5-trinitrobenzene (TATB), 3-nitro-1,2,4-triazol-5-one (NTO) and 2,6-diamino-3,5-dinitropyrazine-1-oxide (LLM-105). DSC measurements showed that ANPyO, TATB, NTO and LLM-105 were compatible with CL-20. The compatibility of CL-20/NQ, CL-20/TNT, CL-20/ANPyO, CL-20/TATB, CL-20/NTO and CL-20/LLM-105 mixtures was further explored using the VST, which revealed that all the selected insensitive explosives were compatible with CL-20. Possible chemical interactions were suspected for CL-20/TATB from the FTIR results and for CL-20/NTO from XRD analysis. In summary, ANPyO and LLM-105 demonstrated the optimal compatibility with CL-20.     

Synthesis and characterization of sonochemically-aminated 1,3,5-triamino-2,4,6-trinitrobenzene

Abstract

A novel method has been achieved for the preparation of 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) from TCTNB in toluene by animation with ammonium hydroxide solution under the influence of ultrasonic irradiation. Samples of this sonochemically-aminated TATB (FP-TATB) were studied for its powder characteristics. It was found that the arithmetic median diameter (vol%) and BET surface area of FP-TATB are 15 micrometers and 1.2 m²/g, respectively. To evaluate shock initiation, samples of FP-TATB were pressed to high density (1.8g/cc) and subjected to initiation spot-size testing, and the results were compared with those from micronized TATB (UF-TATB), an IHE booster material. Data from this test indicated that the FP-TATB is slightly more sensitive to shock initiation than the UF-TATB as measured by the dent depth of the witness plate.     

Properties and impact sensitiveness of cyclic nitramine explosives containing nitroguanidine groups

Abstract

Some properties of hexahydro-5-nitro-2-(nitroimino)-1,3,5-triazine 1, octahydro-1,3-dinitro-5-(nitroimino)imidazo[4,5-d]imidazole 2, dodecahydro-4,8-dinitro-2,6-bis(nitroimino)diimidazo[4,5-b:4′,5′-e]pyrazine 3 and octahydro-2,5-bis(nitroimino)imidazo[4,5-d]imidazole 4 have been determined. They have acceptable thermal and hydrolytic stability. Compound 3 has greater friction sensitiveness than RDX, however the others are much less sensitive. Rotter impact test data indicate that the cyclic nitroguanidines 1–4 are more easy to initiate than RDX; however, the extent of propagation is less and depends on oxygen balance. Consideration of Hazard Index and Average Powder Explosiveness data indicates that US drop-weight tests, which measure a combination of ease of initiation and extent of propagation, would rank the cyclic nitroguanidines and references explosives in the following order of increasing impact sensitiveness: NQ < 4 < NTO < 1 < RDX, 3 < 2.