High Melting Explosive Research Articles

Mechanical response characteristics of HMX crystals under resonant acoustic mixing

AbstractUnderstanding the mechanical response characteristics and determining the optimized process conditions is critical to mitigate crystal impacts during resonant acoustic mixing (RAM). Therefore, high‐melting explosive (HMX) crystal collisions with container walls under different RAM accelerations were investigated through simulations and experiments. The HMX crystal damages after RAM were assessed using microscopic imaging, small‐angle X‐ray scattering, and Brunauer–Emmett–Teller tests. Results show that crystal fractures observed in steel containers can be prevented by using low‐modulus polytetrafluoroethylene containers. Rough containers reduce internal damage but increase surface abrasion. Lower RAM accelerations, shorter RAM durations, and low‐modulus containers can mitigate HMX crystal damage.

EFFECT OF HMX CONTENT ON THERMAL SAFETY CHARACTERISTICS OF MODIFIED DOUBLE-BASE PROPELLANTS

In order to explore the thermal safety characteristics of modified double-base propellants, differential scanning calorimetry (DSC) was used to study the thermal decomposition of modified double-base propellants with high melting explosive (HMX) content of 0%, 21%, and 40%, respectively. The thermal decomposition temperatures at the heating rates of 2, 5,10, and 20°C·min<sup>-1</sup> were obtained. The apparent activation energy, pre-exponential factor, reaction rate, Gibbs free energy, activation enthalpy, and activation entropy were calculated by thermal reaction kinetics analysis. The response characteristics of modified double-base propellants with different HMX contents were obtained through slow cook-off, 5 s explosion point, and methyl violet chemical stability tests to characterize the thermal safety of propellants. The insensitivity of modified double-base propellant containing HMX was further studied by flame sensitivity and mechanical sensitivity tests. The results showed that when HMX content was 21%, the apparent activation energy was the highest, the slow cook-off response was the lowest, the 5 s explosion point response temperature was the highest, the methyl violet test paper had the longest discoloration time, and the flame sensitivity and mechanical sensitivity were the lowest; With the increase of HMX content, the first decomposition peak temperature of DSC moves backward, and the apparent activation energy decreases. The slow cook-off response temperature of the double-base propellant moves to the high-temperature direction, and the response level increases accordingly. When the HMX content is 40% or more, the response level is explosive, which cannot pass the slow cook-off test. After HMX component is added into the sample, its 5 s explosion point temperature moves to high temperature, and the trend of rise is obvious. The discoloration time of methyl violet test paper is prolonged, and the thermal stability of modified double-base propellant is improved; The flame sensitivity and the mechanical sensitivity decreased, which was helpful to improve the low vulnerability of the formula.

Parametric Effects on the Mixing Efficiency of Resonant Acoustic Mixing Technology for High-Viscosity Mixture: A Numerical Study

Numerical investigations were conducted on the mixing efficiency of resonant acoustic mixing (RAM) technology using a high-viscosity mixture under vertically forced vibrations. The density distribution was analyzed for a mixture of high-melting explosive (HMX) and trinitrotoluene (TNT). The effects of mixing time, amplitude, frequency, fill level, and mixing vessel geometry were evaluated to determine their influence on the blend homogeneity and the efficiency of the mixing process. The results showed that amplitude and frequency both have significant influences on the mixing efficiency of the RAM process. With higher values of amplitude and frequency, the mixing efficiency was very good, and uniform mixing was achieved in a much shorter time. At the same time, it was seen that geometric changes did not affect the mixing process; in contrast, varying the fill level did have a significant effect. This approach could potentially be used for pharmaceutical blending, cosmetics, and explosive applications, where only small quantities of active particle ingredients (APIs) can change the behavior of the mixture.

Imparting high polymorph transition resistance to cyclotetramethylene-tetranitramine via spherulitic aggregation enabled crystal shape constraint

The high melting explosive (HMX), i.e., cyclotetramethylene-tetranitramine, is plagued by issues such as structural instability, increased sensitivity, and unwanted deflagration at elevated temperatures, which are strongly linked to the microstructural damage generated by its β → δ polymorphic transition around 160–185 °C. An extension of the β form thermal stability is therefore desired. Herein, a new strategy to regulate such β → δ transition via particle-level aggregation is demonstrated. Using polyvinyl pyrrolidone as a growth additive, this study shows that single-crystalline β-HMX can evolve into a unique spherulitic morphology with fine control over particle sizes and compactness. The phase transition is then found sensitive to the spherulitic aggregation while highly correlating with the decrease in particle size. Remarkably, the β-HMX spherulites exhibit an onset transition temperature of up to 205 °C, corresponding to a maximum 20 °C increment as compared with the highest value achieved by its single crystalline counterpart. Mechanistic investigation reveals that the suppressed β → δ transition origins from the restricting of anisotropic expansion of the subunit crystallites in spherulitic aggregates, induced by their unusual radial packing mode. The proposed strategy is expected to be translated to other polymorphic explosives, hence bringing a fresh perspective to future high-performance energetic materials development.

Elastic and phonon-mode anomalies with temperature in the energetic material C6H6N4O8

Temperature-dependent Brillouin and Raman spectroscopic investigations are carried out on energetic material 4,10-Dinitro-2,6,8,12-tetraoxa-4,10-diazatetracyclo $[{5.5.0.0}^{5,9}{.0}^{3,11}]$ -dodecane (TEX; ${\mathrm{C}}_{6}{\mathrm{H}}_{6}{\mathrm{N}}_{4}{\mathrm{O}}_{8}$) from \ensuremath{-}196 to 180 \ifmmode^\circ\else\textdegree\fi{}C, close to its sublimation point, to study its elastic and phonon mode behaviors. Ambient values of experimental shear ($G$) and bulk ($K$) moduli of TEX are obtained as $G=5.6\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$ and $K=17.7\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$. We have computed the elastic tensor and obtained the averaged bulk and shear moduli to compare with the experimentally obtained polycrystalline values. The known lower sensitivity of TEX compared with similar caged secondary explosives as CL-20, Royal Demolition eXplosive, and \ensuremath{\beta}-High Melting eXplosive is reckoned as due to its inherently high bulk modulus. We report direct experimental evidence of rapid reduction in elastic constant of TEX from 20 to 80 \ifmmode^\circ\else\textdegree\fi{}C, much before its melting point. Though there are no phase transitions in this temperature span, all Raman bands exhibit softening behavior around this temperature. We observe two distinct anomalies. Some bending modes such as bending of CNC $(356\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$, in-plane bending of NNO $(552\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$, bending of NCO $(610\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1})$, in-plane bending of NNO (635 $\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$), and in-plane bending of ONO and OCO (712 $\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$) exhibit slight hardening before and after the elastic anomaly. However, the asymmetric stretching modes at 1574 $\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ (asymmetric stretch of NO) and 1590 $\mathrm{c}{\mathrm{m}}^{\ensuremath{-}1}$ (asymmetric stretch of ${\mathrm{NO}}_{2}$) exhibit hardening below 20 \ifmmode^\circ\else\textdegree\fi{}C but soften after 80 \ifmmode^\circ\else\textdegree\fi{}C. This hardening switching over to softening above the anomaly indicates a release of stiffness manifesting from a conformational change to exo-endo and aiding the increasing compressibility. Emergence of new diffraction peaks $\ensuremath{\sim}50{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$ and even observed at 150 \ifmmode^\circ\else\textdegree\fi{}C, which is well above the elastic anomaly, suggests that the material at high temperature may be isostructural to that at low temperature. In this paper, we establish that the high bulk modulus value of TEX contributes to its lower sensitivity; however, we also clearly demonstrate reduction in elastic modulus accompanied by anomalous behavior of Raman modes. This decrease in elastic modulus leading to increased compressibility may result in increased sensitivity of the explosive material just above room temperature.

Comparative study for removal of nitro-heterocyclic explosives using magnetic graphene nanocomposites

In this manuscript, RDX (Royal Demolition eXplosive) and HMX (High Melting eXplosive) were removed from water that is mainly polluted by military activities. Two different forms of magnetic graphene oxide nanocomposites, α-Fe2O3-rGO (hematite-reduced graphene oxide) and nZVI-rGO (nano zero valent iron-reduced graphene oxide) have been evaluated for decontamination of water containing these carcinogenic explosives. Comparative adsorption studies were carried out considering contact time, pH and adsorbent dosage for all the adsorbent–adsorbate systems. Batch adsorption experiments at varied concentrations of RDX and HMX were conducted. The experimental results better fit in pseudo second order model following Freundlich isotherm. Magnetic nature of both adsorbents is suitable for their easy separation from contaminated water in presence of an external magnetic field. α-Fe2O3-rGO showed higher adsorption capacities for HMX and RDX, this was supported by the physio-chemical properties of the adsorbent. Therefore, it could be potentially upscaled and used commercially for purification of water containing explosives.

Aerobic biodegradation of HMX by Planomicrobium flavidum.

In this report, aerobic biodegradation of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine or high melting explosive (HMX), a highly explosive chemical by Planomicrobium flavidum strain S5-TSA-19, an isolate from an explosive-contaminated soil, was investigated. The isolate S5-TSA-19 degraded 70% of HMX in 20days during which time nitrite ion was produced with the subsequent formation of metabolites, viz. methylenedintramine and N-methyl-N,N'-dinitromethanediamine with molecular weights 136Da and 149Da, respectively. The degradation mechanism was found to follow first-order kinetics with a half-life of 11.55days and formation of above intermediates indicate single nitrite elimination pathway. The proliferation of isolate S5-TSA-19 in the absence of nitramines indicates the cometabolic degradation of HMX. Isolate S5-TSA-19 can thus be used as futuristic microbe for degradation of HMX at explosive-contaminated site.

Boron-doped graphene for fast electrochemical detection of HMX explosive

Ultrasensitive explosive sensors are significant in anti-terrorism and related environment issues. Herein, we proposed a novel boron-doped graphene (B-GE) modified glassy carbon electrode (GCE) applied as a simple, sensitive electrochemical high melting explosive (HMX) sensor. The morphology and structure features of B-GE were characterized. The electrochemical behaviors of HMX on the B-GE modified GCE were investigated by cyclic voltammetry (CV). Under the optimized conditions, CV was used for the quantitative detection of HMX, and the reduction peak current exhibited good linear dependence with the concentration of HMX in the ranges of 2∼20μM and 20∼100μM. The low detection limit (LOD) was calculated as 0.83μM (245.81ppb). Furthermore, the B-GE/GCE showed satisfactory repeatability, high selectivity and stability. The reduction reaction mechanism of HMX on B-GE modified electrode was explored by computational theoretical analysis. Additionally, the differences of the reduction mechanisms from nitroaromatic explosives were discussed.

Pilot-scale in situ bioremediation of HMX and RDX in soil pore water in Hawaii

A nine-month in situ bioremediation study was conducted in Makua Military Reservation (MMR) in Oahu, Hawaii (USA) to evaluate the potential of molasses to enhance biodegradation of royal demolition explosive (RDX) and high-melting explosive (HMX) contaminated soil below the root zone. MMR has been in operation since the 1940's resulting in subsurface contamination that in some locations exceeds USEPA preliminary remediation goals for these chemicals. A molasses-water mixture (1 : 40 dilution) was applied to a treatment plot and clean water was applied to a control plot via seven flood irrigation events. Pore water samples were collected from 12 lysimeters installed at different depths in 3 boreholes in each test plot. The difference in mean concentrations of RDX in pore water samples from the two test plots was very highly significant (p < 0.001). The concentrations differences with depth were also very highly significant (p < 0.001) and degradation was greatly enhanced at depths from 5 to 13.5 ft. biodegradation was modeled as first order and the rate constant was 0.063 per day at 5 ft and decreased to 0.023 per day at 11 ft to 13.5 ft depth. Enhanced biodegradation of HMX was also observed in molasses treated plot samples but only at a depth of 5 ft. The difference in mean TOC concentration (surrogate for molasses) was highly significant with depth (p = 0.003) and very highly significant with treatment (p < 0.001). Mean total nitrogen concentrations also differed significantly with treatment (p < 0.001) and depth (p = 0.059). The molasses water mixture had a similar infiltration rate to that of plain water (average 4.12 ft per day) and reached the deepest sensor (31 ft) within 5 days of application. Most of the molasses was consumed by soil microorganisms by about 13.5 feet below ground surface and treatment of deeper depths may require greater molasses concentrations and/or more frequent flood irrigation. Use of the bioremediation method described herein could allow the sustainable use of live fire training ranges by enhancing biodegradation of explosives in situ and preventing them from migrating to through the vadose zone to underlying ground water and off-site.

Molasses enhanced phyto and bioremediation treatability study of explosives contaminated Hawaiian soils

A 15-week treatability study was conducted in a greenhouse to evaluate the potential effects of molasses on the bioremediation and phytoremediation potential of Guinea Grass (Panicum maximum) for treating energetic contaminated soil from the open burn/open detonation area of the Makua Military Reservation, Oahu, HI (USA). The energetics in the soil were royal demolition explosive (RDX) and high-melting explosive (HMX). Among the 6 treatments employed in this study, enhanced removal of RDX was observed from treatments that received molasses and went to completion. The RDX degradation rates in treatments with molasses diluted 1:20 and 1:40 were comparable suggesting that the lower dose worked as well as the higher dose. Treatments without molasses degraded RDX slowly and residuals remained after 15 weeks. The bacterial densities in molasses-treated units were much greater than those without molasses. Phytoremediation alone seems to have little effect on RDX disappearance. For HMX, neither bioremediation nor phytoremediation was found to be useful in reducing the concentration within the experimental period. The concentrations of nitrogen and phosphorous in the soil did not change significantly during the experiment, however, a slight increase in soil pH was observed in all treatments. The study showed that irrigating with diluted molasses is effective at enhancing RDX degradation mainly in the root zone and just below it. The long term sustainability of active training ranges can be enhanced by bioremediation using molasses treatments to prevent RDX deposited by on-going operations from migrating through the soil to groundwater and off-site.

Computational Studies on Nitro Derivatives of 1-Hydroxy-1,2,4-triazole

Thermodynamic properties and energetics of the nitro derivatives of 1-hydroxy-1,2,4-triazole, viz. 1-hydroxy-3-nitro-1,2,4-triazole (A), 1-hydroxy-5-nitro-1,2,4-triazole (B), and 1-hydroxy-3,5-dinitro-1,2,4-triazole (C), are considered for a detailed computational study during the present investigation using a density functional theory B3LYP/6-311G(d,p) method as implemented in the Gaussian 03 suite of programs. Heats of formation and other thermodynamic properties for all of the compounds considered were determined. Studies revealed that these compounds possess the requisite properties for use as high-density energetic materials. Detonation velocity (D) and detonation pressure (P) of the title compounds were evaluated using the Kamlet-Jacobs method based on the crystal densities calculated at the DFT(B3LYP)/6-311G(d,p) level incorporating the electrostatic interaction. Calculation showed that these compounds yielded a detonation pressure and detonation velocity in the range of 27–35 GPa and ∼8 km/s, respectively, at loading densities of 1.60–1.90 g/cm3. The calculated values are comparable to the values determined for powerful commercial explosives such as Research Department Explosive (RDX) (34.10 GPa, 8.75 km/s, 1.80 g/cm3), High Melting Explosive (HMX) (39.00 GPa, 9.11 km/s, 1.89 g/cm3), and Trinitrotoluene (TNT) (21.00 GPa, 6.93 km/s, 1.64 g/cm3).

Accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) exposure in the green anole (Anolis carolinensis)

Environmental contamination by energetic compounds is an increasing international concern, although little is known of their accumulation in and affect on wildlife. Reptiles are often good models for contaminants studies due to natural history traits that increase their potential for exposure. We report a study to assess accumulation and effects of octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX, High Melting Explosive) in green anoles (Anolis carolinensis). Acute oral toxicity (LD(50)) was estimated to exceed 2000 mg/kg body weight in adult male and female anoles using a standard up-and-down method. Accumulation of HMX was assessed in adult females via dietary exposure and into eggs by two routes (directly from the soil and via maternal transfer). HMX readily accumulated into adult females in a dose-dependent manner and into eggs following both exposure pathways. However, total HMX in soil-exposed eggs was up to 40-times greater than those exposed via maternal transfer. Although there was a suggestion of an HMX-induced reduction in body weight in adult females, overall there were no effects observed over the 12 week exposure period. The only significant effect on eggs was a 50% reduction in hatching success for eggs exposed to 2000 mg/kg HMX in the soil during incubation. Growth and survival of hatchlings was not affected by HMX exposure. Our results demonstrate that HMX accumulates through the food chain and into eggs from the soil, but likely poses minimal threat to lizards except to hatching success in eggs incubated in soils with HMX levels near maximum environmental concentrations.

Toxicity of Octahydro-1,3,5,7-Tetranitro-1,3,5,7-Tetrazocine (HMX) in Three Vertebrate Species

The explosive, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine or high-melting explosive (HMX), has been found in soils in areas used for testing and training by the military. Many of these areas contain habitat for valued wildlife species. In an effort to better understand the environmental consequences from exposure, a reptilian (western fence lizard [Sceloporus occidentalis]), an amphibian (red-backed salamander [Plethodon cinereus]), and a mammalian species (rabbit [Oryctolagus cuniculus]) were exposed to HMX under controlled laboratory conditions. Lizards and rabbits were exposed to HMX by way of corn oil through gavage, and salamanders were exposed to HMX in soil. Two deaths occurred from acute oral exposures to lizards to 5000 mg HMX/kg BW. Histological and gross pathologic assessment suggested gut impaction as a possible cause of death. Salamanders exposed to concentrations of HMX in soil < or = 1970 mg HMX/kg soil for 10 days did not show adverse effects. Rabbits, however, showed neurologic effects manifested as hyperkinetic events with convulsions at > 24 h after oral exposures. An LD(50) for rabbits was calculated as 93 mg/kg (95% confidence interval 76-117). A subacute 14-day testing regime found a lowest observed effect level of 10 mg/kg-d and a no observed adverse effect level of 5 mg/kg-d based on hyperkinesia and seizure incidence, although changes suggesting functional hepatic alterations were also found. These data suggest that physiologic differences between species, particularly in gastrointestinal structure and function, can affect the absorption of HMX and hence lead to marked differences in toxicity from exposure to the same compound.

Numerical study of blast characteristics from detonation of homogeneous explosives

A new robust numerical methodology is used to investigate the propagation of blast waves from homogeneous explosives. The gas-phase governing equations are solved using a hybrid solver that combines a higher-order shock capturing scheme with a low-dissipation central scheme. Explosives of interest include Nitromethane, Trinitrotoluene, and High-Melting Explosive. The shock overpressure and total impulse are estimated at different radial locations and compared for the different explosives. An empirical scaling correlation is presented for the shock overpressure, incident positive phase pressure impulse, and total impulse. The role of hydrodynamic instabilities to the blast effects of explosives is also investigated in three dimensions, and significant mixing between the detonation products and air is observed. This mixing results in afterburn, which is found to augment the impulse characteristics of explosives. Furthermore, the impulse characteristics are also observed to be three-dimensional in the region of the mixing layer. This paper highlights that while some blast features can be successfully predicted from simple one-dimensional studies, the growth of hydrodynamic instabilities and the impulsive loading of homogeneous explosives require robust three-dimensional investigation.

Bioremediation of nitroexplosive wastewater by an yeast isolate Pichia sydowiorum MCM Y-3 in fixed film bioreactor

Nitroexplosives are essential for security and defense of the nation and hence their production continues. Their residues and transformed products, released in the environment are toxic to both terrestrial and aquatic life. This necessitates remediation of wastewaters containing such hazardous chemicals to reduce threat to human health and environment. Bioremediation technologies using microorganisms become the present day choice. High Melting Explosive (HMX) is one of the nitroexplosives produced by nitration of hexamine using ammonium nitrate and acetic anhydride and hence the wastewater bears high concentration of nitrate and acetate. The present investigation describes potential of a soil isolate of yeast Pichia sydowiorum MCM Y-3, for remediation of HMX wastewater in fixed film bioreactor (FFBR). The flask culture studies showed appreciable growth of the organism in HMX wastewater under shake culture condition within 5-6 days of incubation at ambient temperature (28 +/- 2 degrees C). The FFBR process operated in both batch and continuous mode, with Hydraulic Retention Time (HRT) of 1 week resulted in 50-55% removal in nitrate, 70-88% in acetate, 50-66% in COD, and 28-50% in HMX content. Continuous operation of the reactor showed better removal of nitrate as compared to that in the batch operation, while removal of acetate and COD was comparable in both the modes of operation of the reactor. Insertion of baffles in the reactor increased efficiency of the reactor. Thus, FFBR developed with baffles and operated in continuous mode will be beneficial for bioremediation of high nitrate and acetate containing wastewater using the culture of P. sydowiorum.

Bioremediation of HMX-Contaminated Soil Using Soil Slurry Reactors

Soil in some parts of the Iowa Army Ammunition Plant in Burlington, Iowa, was contaminated with cyclotetramethyleneter-anitramine, commonly known as high melting explosive (HMX). A laboratory treat-ability study was conducted to find out the ability of the native soil bacteria present in the contaminated site to degrade HMX. The results indicated that the HMX can be removed effectively from soil by native soil bacteria through a co-metabolic process. Molasses, identified as an effective co-substrate, is inexpensive, and this factor makes the treatment system cost-effective. The successful operation of aerobic-anoxic soil slurry reactors in batch mode with HMX-contaminated soil showed that the technology can be scaled up for field demonstration. The HMX concentration in the contaminated soil was decreased by 97% in 4 months of reactor operation. The advantage of the slurry reactor is its simplicity of operation. The method needs only mixing and the addition of molasses as co-substrate.