Cyclotetramethylene Tetranitramine Research Articles

Analysis of the biodegradation and phytotoxicity mechanism of TNT, RDX, HMX in alfalfa (Medicago sativa)

The aim of this study was to reveal the mechanism underlying the toxicity of TNT (trinitrotoluene), RDX (cyclotrimethylene trinitroamine), and HMX (cyclotetramethylene tetranitramine) explosives pollution in plants. Here, the effects of exposure to these three explosives were examined on chlorophyll fluorescence, antioxidant enzyme activity, and the metabolite spectrum in alfalfa (Medicago sativa) plants. The degradation rates for TNT, RDX, and HMX by alfalfa were 26.8%, 20.4%, and 18.4%, respectively, under hydroponic conditions. TNT caused damage to the microstructure of the plant roots and inhibited photosynthesis, whereas RDX and HMX induced only minor changes. Exposure to any of the three explosives caused disturbances in the oxidase system. Non-targeted metabolomics identified a total of 6185 metabolites. TNT exposure induced the appearance of 609 differentially expressed metabolites (189 upregulated, 420 downregulated), RDX exposure induced 197 differentially expressed metabolites (155 upregulated and 42 downregulated), and HMX induced 234 differentially expressed metabolites (132 upregulated and 102 downregulated). Of these differentially expressed metabolites, lipids and lipid-like molecules were the main metabolites induced by explosives poisoning. TNT mainly caused significant changes in the alanine, aspartate, and glutamate metabolism metabolic pathways, RDX mainly caused disorders in the arginine biosynthesis metabolic pathway, and HMX disrupted the oxidative phosphorylation metabolic pathway. Taken together, the results show that exposure to TNT, RDX, and HMX leads to imbalances in plant photosynthetic characteristics and antioxidant enzyme systems, changes the basic metabolism of plants, and has significant ecotoxicity effects.

Fast estimation on the pressure of detonation products of cyclotetramethylene tetranitramine through molecular dynamics simulations

The equation of states (EOS) that correlates the pressure, volume and temperature (PVT) of detonation products is indispensable in the numerical modeling of blasting performances of energetic materials. Based on extensive molecular dynamics simulations on the mixtures of CO2, H2O, N2, CO and H2, which are the main components of detonation products of cyclotetramethylene tetranitramine (HMX), the relation of pressure with density, temperature and composition is derived in the range of 1.4–2.2 g/cm3 for density, 3000–4400 K for temperature and 8–40 GPa for pressure. The proposed EOS exhibits good general applicability under the studied conditions and reasonable agreement with the experimentally established Becker–Kistiakowsky–Wilson (BKW) equation. Although several approximations are applied in the computations and some deviations remains, it suggests an effective and feasible approach to establish the EOS for detonation products of energetic materials by means of molecular modeling.

Complete Equations of State for Cyclotetramethylene Tetranitramine

AbstractComplete equations of state for the volumetric deformation of the β‐polymorph of cyclotetramethylene tetranitramine (β‐HMX) have been derived from its Helmholtz free energy. Dispersion‐corrected density functional theory calculations were used to compute the dependence of the frequencies of the vibrational normal modes on specific volume. The normal mode frequencies were used directly to generate both a tabular equation of state and an approximate model where the sum over normal mode frequencies is replaced by a set of five Debye models. Both the tabular and Debye model‐based equations of state use the same cold curve, which is parameterized to the isothermal compression data of Yoo and Cynn [C. S. Yoo and H. Cynn, J. Chem. Phys., 1999, 111, 10229]. The two equations of state are applied to the calculation of the thermophysical properties of β‐HMX required for continuum‐level hydrodynamic simulations and are compared in detail.

Near-infrared (NIR-II) luminescence for the detection of cyclotetramethylene tetranitramine based on stable Nd-MOF

Near-infrared-emissive materials as novel materials have drawn much attention for their unique properties of deep tissue penetration, high spatial resolution and low light damage to biological tissues. Lanthanide MOFs (Ln-MOFs) with high stability and near-infrared emission located in the near-infrared-II window (1000–1700 ​nm) is urgently needed to be developed in recent years. To tackle this challenge, a near-infrared-emissive lanthanide-based metal-organic frameworks (Nd-MOF-Y) [Nd(L-F4)1.5(L-N) (H2O)]n [L-F4 ​= ​2,3,5,6-Tetrafluoroterephthlonic acid, L-N ​= ​1.10-phenanthroline] based on mixed ligands strategy has been successfully prepared. The stability measurements show that Nd-MOF-Y possesses high water stability, chemical stability (pH ​= ​3–11), thermal stability (below 80 ​°C) and mechanical stability (vacuum environment). Luminescence performance studies exhibit the near-infrared-II emission characteristics and Nd-MOF-Y can detect cyclotetramethylene tetranitramine in the near-infrared range with high sensitivity, selectivity, cyclicality and low detection limit. Taking advantages of the stability and NIR-II emission, Nd-MOF-Y can be suitable for the biomedical applications in future.

Experimental Performance Assessment of Layered Thermobaric Explosive in an Explosion Chamber

AbstractExplosion experiments of cyclotetramethylene tetranitramine (HMX) based layered thermobaric explosive (TBX) were carried out in an explosion chamber. The layered TBX was prepared by combination of both press and cast procedures, and the shock overpressure, quasi‐static pressure (QSP), heat flux, and oxygen concentration data were obtained. The results show that the corresponding parameters of TBX are significantly larger compared with TNT, which indicates obvious thermobaric effects of TBX. To correctly evaluate the performance of the layered TBX, the TNT equivalent model based on the overpressure and QSP of TBX was established, which could reflect the two stages of detonation and post combustion effects of the TBX.

Synthesis and Effects of Two Novel Rare-Earth Energetic Complexes on Thermal Decomposition of Cyclotetramethylene Tetranitramine (HMX).

In order to explore the effect of the energetic complex on the thermal decomposition HMX, two new rare-earth energetic complexes [La(tza)(NO3)2(H2O)4]n (1) and [Ce(tza)(NO3)2(H2O)4]n (2) (Htza = tetrazole-1-acetic acid) were prepared by a solvent evaporation method. The obtained products were structurally characterized by Fourier-transform infrared spectroscopy (FTIR), elemental analysis, powder X-ray diffraction (PXRD), single crystal X-ray diffraction (XRD), and thermogravimetric analysis coupled with differential scanning calorimetry (TG-DSC). In addition, the compatibility of complex 1 with cyclotetramethylene tetranitramine (HMX) was studied by DSC and FTIR, respectively. Structural analysis suggested that complex 1 exhibits an orthorhombic, P 21 21 21 space group, and the La (III) ion was 10-fold coordinated in a distorted double-capped antiprism configuration. Complex 2 featured a one-dimensional, right-handed helical infinite chain. The effect of complexes 1 and 2 on the thermal decomposition of HMX was investigated by DSC, which revealed that complex 1 showed a slightly better effect than 2 on the thermal decomposition of HMX and released more heat. Furthermore, complex 1 had good compatibility with HMX, indicating that it may act as a combustion promoter for nitrate ester plasticized polyether (NEPE) solid propellant.

Anisotropic mechanical-thermal-phase transformation response of cyclotetramethylene tetranitramine (HMX) single crystal under ramp loading

A thermomechanical consistent model for cyclotetramethylene tetranitramine (HMX) is developed, which considers material anisotropy, nonlinear thermoelasticity, dislocation-based plasticity, shear cracking induced damage and physical-based phase transformation. The proposed model is employed to investigate the mechanical-thermal-phase transformation response of oriented HMX single crystals under isentropic compression ramp loading at pressures up to ~50GPa for the first time. The proposed model could well reproduce the anisotropic three-wave structure profiles for loading on (0 1 0) and (0 1 1) orientations, including the isentropic elastic limit and stress relaxation after phase transformation. The incorporated inelastic deformation mechanism (plasticity, damage) and phase transformation are responsible for the calculated anisotropic thermomechanical response. Specifically, damage outstands for loads on (0 1 0) orientation while plasticity is more prominent for loads on (0 1 1) orientation. Pressure-temperature-relative volume relation is directly obtained, which agrees well with experimental result from Hooks et al. (2006). Phase transformation response and its effect on thermomechanical behavior are quantified.

Synthesis, crystal structure and thermal behavior of magnesium 5,5′-bistetrazole-1,1′-diolate hexahydrate complex

ABSTRACT A new energetic green burning rate catalyst, magnesium 5,5′‒bistetrazole‒1,1′‒diolate hexahydrate complex ([Mg(BTO)(H2O)6], 1) was synthesized based on 5,5′‒bistetrazole‒1,1′‒diolate dehydrate (BTO, 2) by the metathesis reaction, and it was characterized by FTIR spectroscopy, elemental analysis (EA), Scanning Electron Microscopy (SEM) and single X-ray diffraction. The thermal decomposition processes of magnesium complex 1 and compound 2 were studied utilizing the TG‒DTA and TG‒MS technologies. Moreover, the sensitivity tests were carried out to evaluate the stability of compound 1 and compound 2. Besides, the DSC was used to evaluate the catalytic effect of magnesium complex 1 on thermal decomposition of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), hexanitrohexaazaisowurtzitane (CL‒20) and dihydroxylammonium 5,5′-bistetrazole −1,1′-diolate (TKX‒50). The thermal behaviors indicate that the gaseous products such as NO, CO, N2 are checked from the decomposition of the complex at 320°C. Sensitivity results show that compound 1 is more insensitive to mechanical stimuli than compound 2. The results from DSC and the target line method analyses indicate that [Mg(BTO)(H2O)6] have no effect on the thermal decomposition of RDX, HMX, CL‒20 except for TKX‒50.

Ignition and Combustion Developments of Granular Explosive (RDX/HMX) in Response to Mild‐Impact Loading

AbstractThe experimental analyses of ignition and burning responses of mild‐impacted granular explosive, namely, cyclotrimethylene trinitramine (RDX) and cyclotetramethylene tetranitramine (HMX), were performed based on an optimized drop‐weight system equipped with a High‐Speed Camera (HSC). It has been found that jetting phenomena observed by HSC is the result of the energy released by gaseous products, which push the pulverized or melted explosives to splash radially. Jetting is the only and the most obvious difference between reactive and inert particles prior to combustion so that it can be regarded as the sign of ignition more accurately than other ways. For RDX sample, the molten phase plays an important role in the hot‐spots formation. After a piece of waxed paper is put on the glass anvil, the jetting of molten‐phase RDX will be limited due to the high‐roughness of waxed paper. Moreover, ignition growth to burning probability of RDX particles is increased compared with the non‐waxed paper case. Radial deformation velocity, jetting velocity, and flame propagation velocity have been estimated via image processing, making it possible to quantify the violence of mechanical deformation and chemical reaction.

Dislocation energy and line tension in molecular crystal cyclotetramethylene tetranitramine (β-HMX)

Cyclotetramethylene tetranitramine (β-HMX) is an energetic molecular crystal often used in plastic bonded explosives. Its decomposition reaction may be triggered by plastic deformation. Efforts have been made in recent years to evaluate the mechanisms of plasticity in these crystals and to develop constitutive descriptions that can be used to represent plastic deformation on the microstructural level. In this work, we use atomistic simulations to evaluate the dislocation self-energy, core energy, and line tension in four slip systems previously identified as being the most active. The cores are compact and the anisotropic elasticity solution applies at distances from the dislocation line larger than approximately one Burgers vector. Core energies between 0.3 and 0.5 eV/Å result. The line tension varies rapidly when the character of the dislocation is modified due to the strong elastic anisotropy of the crystal, with maxima at approximately ±40° relative to the screw orientation. The line tension also varies from slip system to slip system. These quantities enter many models of elementary mechanisms of dislocation motion such as cross-slip, dislocation nucleation from stress concentrators, the strength of dislocation junctions and other dislocation structures, and the critical stress for the operation of Frank–Read dislocation sources. The data reported here can be used to evaluate the conditions in which these processes operate and as an input to dislocation dynamics simulations.

Ranking the Drop-Weight Impact Sensitivity of Common Explosives Using Arrhenius Chemical Rates Computed from Quantum Molecular Dynamics Simulations.

Drop-weight impact tests are used routinely to characterize the handling safety of explosives. Numerous studies have sought to connect various physical and chemical properties of the energetic molecules and materials to their measured impact sensitivities. Wenograd in the early 1960s demonstrated that there is a strong dependency of the drop-heights on the critical temperatures required for explosives to undergo prompt reactions. Reactive quantum molecular dynamics simulations with the lanl31 density functional tight binding model have been used to compute the delay time before the thermal explosion of the secondary explosives erythritol tetranitrate (ETN), pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), trinitrotolune (TNT), and 3,3'-diamino-4,4'-azoxyfurazan (DAAF) as a function of the initial temperature and pressure. The delay time to explosion data are consistent with Arrhenius chemical kinetics, which is expected for thermally activated processes in materials and in accord with experimental measurements. The critical temperatures required for the materials to undergo prompt explosions display the same dependence on drop height as was observed by Wenograd. Hence, quantum-based reactive molecular dynamics simulations are potentially a tool for ranking the drop-weight impact sensitivity and handling safety of explosives.

The Effect of Metal Film Thickness on Ignition of Organic Explosives with a Laser Pulse.

The results of numerical ignition simulation of pentaerythritol tetranitrate (PETN), cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX) and 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) by aluminium (Al) and molybdenum (Mo) films heated by nanosecond laser pulses in a three-layer system: glass–metal–explosive material (EM) are presented. Influence of metal film thickness on the time of EM ignition delay was considered. A non-linier dependence of time of delay of ignition of EM from thickness of a metal film is shown. The greatest critical thicknesses of Al and Mo metallic films at which ignition of EM is still possible were determined. It was established that the greater the thickness of the metal film and heat resistance of EM, the greater the heat reserve needed in EM ignition film. It was established that the ignition delay time of EM increases in the sequence of PETN, RDX, HMX and TATB.

Graphene oxide–silver nanocomposite SERS substrate for sensitive detection of nitro explosives

Here, we carried out the sensing of nitro amine explosives through surface-enhanced Raman scattering (SERS) employing silver nanoparticle (Ag NP)-decorated reduced graphene oxide (rGO) nanocomposite substrate. In situ reduction process has been utilized to prepare the reduced graphene oxide–silver nanocomposite. The areal distribution and structural properties of Ag NPs have been studied. The fabricated nanocomposite was characterized using microscopic, spectroscopic and thermogravimetric methods. Moreover, the electrochemical properties of rGO–Ag nanocomposites were analysed using electrochemical methods. Raman spectra show the enhancement in the Raman signal of rGO-decorated Ag NPs with an intensity enhancement factor of 12.5 for D peak and 9 for G peak. The Ag NP-enriched rGO has also demonstrated strong SERS activity towards the detection of cyclotetramethylene tetranitramine and cyclotrimethylenetrinitramine up to 10−12 M as the limit of detection with SERS enhancement of 109. Thus, the synthesized nanocomposite shows potential applications for sensing of explosives.

Indentation fracture behavior of energetic and inert molecular crystals

Abstract

Modelling Microstructural Deformation and the Failure Process of Plastic Bonded Explosives Using the Cohesive Zone Model.

A microstructure finite element method combining the cohesive zone model (CZM) is used to simulate the mechanical behavior, deformation, and failure of polymer-bonded explosive (PBX) 9501 under quasi-static loading. PBX 9501 consists of Cyclotetramethylene tetranitramine (HMX) filler particles with a random distribution packaged in a polymeric binder. The particle is treated as elastic and the binder as viscoelastic. Cohesive elements with a bilinear softening law are inserted into the particle/binder interface, the HMX particle, and the binder to study the interface’s debonding and failure evolution. Macroscopic stress–strain curves homogenized across the microstructure under tension and compression with different strain rates are basically consistent with the experimental data. The interface debonding approximately vertical to the loading direction is the primary failure mechanism under tension, while shear failure along the interfaces and particle fracture plays a significant role under compression. The effects of interface strengths and strain rates on the performance of PBX 9501 are also evaluated. The tensile and compressive strengths are dependent on the interface strength and strain rate, but the failure paths are insensitive. This model is shown to accurately predict macroscopic responses and improve our understanding of the relationship between the mechanical behavior and microstructure of PBX 9501.

Dislocation cross slip in molecular crystal cyclotetramethylene tetranitramine (β-HMX)

In this work, we explore the mechanism of cross-slip in the low symmetry molecular crystal cyclotetramethylene tetranitramine (β-HMX)—a secondary explosive. Cross-slip is well studied and understood in high symmetry crystals but virtually uninvestigated in molecular crystals. To this end, we use molecular simulations and observe that only screw dislocations with the [100] Burgers vector may cross-slip effectively. The process involves the (011), (010), (001), and (011¯) planes and takes place in both the positive and negative directions of dislocation motion in each of the respective slip systems. Resolved shear stresses larger than ∼0.6 of the critical resolved shear stress are necessary in at least two of the planes in order to activate cross-slip. The application of pressure does not prevent cross-slip from taking place. The phenomenon occurs at elevated pressures in the same slip systems as at zero pressure. However, due to the limited number of slip systems involved, cross-slip does not appear to be of central importance in β-HMX and, of course, remains relevant only as long as the dislocation-based mechanism of plasticity is not replaced by the shear localization mode, which becomes dominant at high pressure, under strong shock conditions.

Cross slip not key deformation in explosive molecular crystal

Simulations show cross slip is not a very important deformation mechanism for the widely used explosive cyclotetramethylene tetranitramine.

Synthesis of HMX/SiO2 nanoenergetic composite and application in ignition charge

The nanoparticles of cyclotetramethylene tetranitramine (HMX) have many potential advantages, such as high energy release rate, low sensitivity, etc. Silica (SiO2) xerogel matrix with tridimensional reticular structures, which has huge specific surface area and superior impact resistance, was taken as a template to synthesize HMX/SiO2 nanocomposite by sol-gel method, and the loaded HMX was up to 80 wt.% of the HMX/SiO2 nanocomposite. The structures and properties of HMX/SiO2 nanocomposite were characterized by SEM, TEM, XRD, DSC, etc. The results revealed that the particle size of HMX in SiO2 matrix is below 100 nm. The initial and the peak decomposition temperatures of HMX/SiO2 nanocomposite were decreased with the increase of SiO2 content. A new type of ignition composition containing HMX/SiO2 nanocomposite was prepared. The results showed that the ignition composition particles are smaller than 100nm without agglomerate. Its thermal behavior was improved and mechanical sensitivities were reduced significantly, but the heat of combustion was increased properly compared with the mixture of the same components. Briefly, with the introduction of SiO2 matrix, HMX can exist in the form of nanoparticles and the comprehensive properties of the ignition composition can be improved.

Comparison of the interfacial bonding interaction between GAP matrix and ionic/non-ionic explosive: Computation simulation and experimental study

Experimental has been performed on the interfacial interaction between glycidyl azide polymer (GAP) and the novel ionic explosive 5,5′-bistetrazole-1,1′-diolate (TKX-50) in contrast with the most commonly used non-ionic explosive cyclotetramethylene tetranitramine (HMX). Stronger adhesion energy was exhibited for TKX-50/GAP through interfacial tension, static and dynamic mechanical studies. To further reveal the interaction mechanism, the morphology surfaces have been predicted with the most stable (011) surfaces for both crystals. It was found that the binding energy between GAP and TKX-50 was stronger than HMX and stronger hydrogen bonds and van der Waals interaction exist between interface of GAP molecules and TKX-50 surfaces owing to the polar azide groups with least steric hindrace and the positively NH3OH+ cations.

Van der Waals Density Functional Theory vdW-DFq for Semihard Materials

There are a large number of materials with mild stiffness, which are not as soft as tissues and not as strong as metals. These semihard materials include energetic materials, molecular crystals, layered materials, and van der Waals crystals. The integrity and mechanical stability are mainly determined by the interactions between instantaneously induced dipoles, the so called London dispersion force or van der Waals force. It is challenging to accurately model the structural and mechanical properties of these semihard materials in the frame of density functional theory where the non-local correlation functionals are not well known. Here, we propose a van der Waals density functional named vdW-DFq to accurately model the density and geometry of semihard materials. Using β -cyclotetramethylene tetranitramine as a prototype, we adjust the enhancement factor of the exchange energy functional with generalized gradient approximations. We find this method to be simple and robust over a wide tuning range when calibrating the functional on-demand with experimental data. With a calibrated value q = 1.05 , the proposed vdW-DFq method shows good performance in predicting the geometries of 11 common energetic material molecular crystals and three typical layered van der Waals crystals. This success could be attributed to the similar electronic charge density gradients, suggesting a wide use in modeling semihard materials. This method could be useful in developing non-empirical density functional theories for semihard and soft materials.