Decomposition Of HMX Research Articles

Adsorption and catalysis of Bi-doped Fe2O3 on gas products of HMX decomposition: A DFT study

To clarify the role of Bi-doped Fe2O3(001) in the decomposition process of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane(HMX), the effect of Bi-Fe2O3(001) on the gas products of HMX(NO, NO2, N2O, H2O, CH2O) was emphatically investigated using density functional theory (DFT) calculation. The adsorption configuration, energy, electronic properties and possible reactions of gas products were considered. All of these gases are adsorbed on the Fe-top site of Bi-Fe2O3 surface in molecular form, resulting in the orbital hybridization and electron transfer. NO2 and CH2O interacting with Bi are of higher adsorption energy comparing with gas adsorbed on pure Fe2O3(001). Since the reaction of NO2 with CH2O and the dissociation of NO2 play an important role in the subsequent decomposition of HMX, the effects of Bi doping on these two reactions were investigated. TS search shows that the activation energy of these two reactions are all decreased on Bi-Fe2O3 surface, which may accelerate the consumption of NO2, indicating that Bi doping can promote the reaction of NO2 and CH2O, thus accelerating the subsequent decomposition of HMX.

Ammonium Percholorate/HMX Co-crystal: Bespoke Energetic Materials with Tailored Decomposition Kinetics via Dual Catalytic Effect

ABSTRACT Ammonium perchlorate (AP)/HMX co-crystal with dual catalytic effect was developed. Proper integration of AP particles into the HMX matrix was verified with the evolution of novel crystalline structure. AP/HMX co-crystal demonstrated an increase in HMX decomposition enthalpy by + 57.5%. HMX demonstrated activation energy of 343.2 and 354.4 kJ/mol using Kissinger and KAS models, respectively. AP/HMX co-crystal demonstrated a decrease in HMX activation energy by −75% and −76%, correspondingly. AP could act as an active point with the release of reactive gases that could boost HMX decomposition. HMX experienced a catalytic effect with the disappearance of AP endothermic phase transition.

Synthesis, Crystal Structure and Catalytic Performance of a novel Five‐Coordinated Energetic Copper(II) Compound

AbstractEnergetic copper (II) compound was synthesized based on 2,4,6‐trinitrobenzoic acid (TNBA) and imidazole (IMI), which characterized by elemental analysis and FT‐IR characterization. Single‐crystal X‐ray diffraction analysis revealed that [Cu(IMI)2(H2O)(TNBA)2] (1) belongs to monoclinic, pertains to P21/c space group, β=95.230(2)° and Dc=1.790 g cm−3. The five bonds formed by the central copper atom are derived from the two oxygen atoms and nitrogen atoms in the two TNBA and IMI ligands, and the oxygen atom in the water molecule, which present a novel five‐coordination model and a unique pyramid structure and show a typical single tooth coordination pattern. Catalytic effects on the thermal decomposition of ammonium perchlorate (AP), RDX and HMX of complexe 1 were investigated in detail by employing the DSC technique. Complex 1 shows an outstanding catalytic activity. The non‐isothermal kinetics parameters were calculated by the Kissinger's, Ozawa's and Starink's method, respectively. In the end, impact sensitivity was also determined by standard method. All the experimental data results supported the potential applications of the energetic complexes as additives of solid rocket propellants.

The Impact of Metastable Intermolrecular Nanocomposite Particles on Kinetic Decomposition of Heterocyclic Nitramines Using Advanced Solid‐Phase Decomposition Models

Surface oxygen of oxide catalyst has low coordination number; they are negatively charged. Surface oxygen can act active site for decomposition of energetic nitramines (i.e. HMX). Additionally hydrous catalyst surface can release active OH radicals. Colloidal oxide particles can fulfil these requirements. Furthermore oxide particles can induce thermite reaction with aluminium particles. This study reports on the facile fabrication of colloidal ferric oxide particles of 5 nm average particle size. Aluminium nanoplates of 100 nm particle size were dispersed in ferric oxide colloid. Colloidal Fe2O3/Al binary mixture was integrated into HMX matrix via co-precipitation technique. SEM micrographs demonstrated uniform dispersion of nanothermite particles into energetic matrix. Naonothermite particles experienced dramatic change in HMX thermal behaviour with increase in total heat release by 63% using DSC. The impact of thermite particles on HMX kinetic decomposition was evaluated via an integral isoconversional method using KAS, and Kissinger models. The mean value of apparent activation was reduced by 23.5 and 24.3% using Kissinger and KAS models respectively. This dramatic change in HMX decomposition could be ascribed to ferric oxide reactivity. Facile integration of colloidal thermite particles into HMX can secure high interfacial surface area.

The significant impact colloidal nanothermite particles (Fe2O3/Al) on HMX kinetic decomposition

ABSTRACT HMX is one of the most powerful energetic materials; however, HMX experience low sensitivity and high activation energy. Whereas ferric oxide particles can act as catalyst for HMX decomposition with change in its decomposition kinetics from C-N bond cleavage to hydrogen atom abstraction; ferric oxide can induce vigorous thermite reaction with aluminum particles. Consequently, thermite particles can catalyze HMX decomposition, and enhance its decomposition enthalpy. This study reports on the fabrication and of ferric oxide nanoparticles of 5 nm particle size. Ferric oxide NPs and aluminum nanoplates of 100 nm were effectively integrated into HMX via co-precipitation technique. Elemental mapping was performed using EDAX detector; uniform dispersion of nanothermite particles was confirmed. Nanothermite particles experienced enhanced HMX decomposition enthalpy by 53%, with decrease in decomposition temperature by 13°C. The impact of nanothermite particles on HMX kinetic decomposition was evaluated using two different analysis models including differential isoconversional method of model-free Friedman analysis, and integral isoconversional method of Ozawa. Thermite nanoparticles demonstrated drastic decrease in HMX activation energy by 24 and 30% using Friedman and Ozawa models, respectively. The developed colloidal nanothermite particles demonstrated superior catalytic effect with enhanced decomposition enthalpy.

Biodegradation and physiological response mechanism of Bacillus aryabhattai to cyclotetramethylenete-tranitramine (HMX) contamination

This study aims to reveal the biodegradation and interaction mechanism of cyclotetramethylenete-tranitramine (HMX) by a newly isolated bacteria. In this study, a bacterial strain (Bacillus aryabhattai) with high efficiency for HMX degradation was used as the test organism to analyze the changes in growth status, cell function, and mineral metabolism following exposure to different stress concentrations (0 and 5 mg L−1) of HMX. Non-targeted metabonomics was used to reveal the metabolic response of this strain to HMX stress. The results showed that when the HMX concentration was 5 mg L−1, the removal rate of HMX within 24 h of inoculation with Bacillus aryabhatta was as high as 90.5%, the OD600 turbidity was 1.024, and the BOD5 was 225 mg L−1. Scanning electron microscope (SEM) images showed that the morphology of bacteria was not obvious Variety, Fourier transform infrared spectroscopy (FTIR) showed that the cell surface –OH functional groups drifted, and ICP-MS showed that the cell mineral element metabolism was disturbed. Non-targeted metabonomics showed that HMX induced the differential expression of 254 metabolites (133 upregulated and 221 downregulated). The main differentially expressed metabolites during HMX stress were lipids and lipid-like molecules, and the most significantly affected metabolic pathway was purine metabolism. At the same time, the primary metabolic network of bacteria was disordered. These results confirmed that Bacillus aryabhattai has a high tolerance to HMX and can efficiently degrade HMX. The degradation mechanism involves the extracellular decomposition of HMX and transformation of the degradation products into intracellular purines, amino sugars, and nucleoside sugars that then participate in cell metabolism.

Synergistic Catalytic Effect of Thermite Nanoparticles on HMX Thermal Decomposition

Even though HMX is one of the most vigorous energetic materials for solid propellants, explosives, and pyrotechnics; it has high thermal stability and low sensitivity to common catalysts. Metal oxides with hydrous surface can release active $$\dot{\text{{O}}}$$ H radicals at low temperature. These active radicals could attack HMX heterocyclic ring and alter HMX decomposition mechanism form C-H bond cleave to hydrogen atom abstraction. This study reports on the facile synthesis of Fe2O3 nanoparticles (NPs) of 8 nm average particle size. Aluminum NPs of 80 nm was employed in combination with Fe2O3 NPS; this nanothermite binary mixture can induce not only catalytic effect but also vigorously-exothermic thermite reaction with high heat output. Colloidal thermite mixture Fe2O3/Al was effectively-integrated into HMX crystals via co-precipitation technique. Uniform distribution of nanothermite particles into HMX was confirmed via elemental mapping using EDAX. Nanothermite mixture as high energy density material offered an increase in HMX total heat release by 82% using DSC. Furthermore, nanothermite particles offered superior catalytic effect with decrease in HMX activation energy by 25% using Kissinger method. Kinetic decomposition parameters using KAS model were found to be in good agreement with Kissinger's model. Colloidal nanothermite particles can act as high energy density material, and as a catalyst with decrease in required activation energy.

Synthesis, crystal structure, and properties of energetic copper(II) compound based on 3,5-dinitrobenzoic acid and imidazole

Energetic copper(II) compound was synthesized based on 3,5-dinitrobenzoic acid (HDNBA) and imidazole (IMI), and characterized by elemental analysis and FTIR characterization. Single-crystal X-ray diffraction analysis revealed that [Cu(IMI)2(DNBA)2] (1) belongs to monoclinic, pertains to P21/c space group, β= 96.195(2) and Dc= 1.742 g cm–3. Cu(II) ion was coordinated to a plane tetragon, by two oxygen atoms and two nitrogen atoms from different DNBA ions and IMI ligands, which of them present typical monodentate coordination mode. Differential scanning calorimetry (DSC) was applied to assess the thermal decomposition behavior of 1. The non-isothermal kinetics parameters were calculated by the Kissinger’s method, Ozawa’s method and Starink’s method, respectively. Impact sensitivity and friction Sensitivity were also determined by standard method. In the end, the catalytic effects on the decomposition of ammonium perchlorate (AP), HMX and RDX of 1 were studied by DSC. All results supported the potential applications of the energetic complex 1 as additive of solid rocket propellant.

Mechanism of Two Typical Binders BR and F2604 on Thermal Decomposition of HMX.

DSC–TG–FTIR–MS coupling technology was used to study the mechanism of two typical binders, that is, BR and F2604, on the thermal decomposition behavior of the HMX crystal. The results show that both BR and F2604 can induce premature decomposition of HMX and increase the activation energy of HMX. Especially in the case of HMX/BR particles, the decomposition temperature is the lowest, but the activation energy is the highest. Based on the results of DSC–TG–FTIR–MS, it is found that the rapid mechanism of binder and active intermediate products inhibits the reaction of relatively inert intermediate products and prolongs the continuous generation time of gas products in the composite particles, which delays the decomposition of HMX to a certain extent. This study is helpful for us to better understand the thermal decomposition behavior of HMX composite particles and provides reference for the application of high-energy composites.

Three-Dimensional Mechanical–Thermal–Chemical Coupled Mesoscopic Simulation of the Collapse of an Air Bubble in an HMX Crystal

Octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is extensively employed in military weapons as the main constituent of HMX-based polymer-bonded explosives (PBXs). It is known that the safety of PBXs is closely related to their microstructures. Discontinuities in PBXs, such as micron-sized pores, air bubbles, and interfaces between the explosive crystal and polymer bonds, may transform into hot spots when subjected to impact. Herein, a three-dimensional mechanical–thermal–chemical coupled mesoscopic model is proposed to study the collapse of an air bubble in an HMX crystal under impact. A viscoplastic constitutive model and the Birch–Murnaghan equation of state are employed for the HMX crystal to predict its mechanical response. Thermal decomposition of HMX is taken into account by using multistep thermal decomposition equations. The viscoplastic model yields results that reasonably agree with data obtained in the plane shock experiment. The influence of the edge length of the mesh elements on simulation results is analyzed. Then more simulations are conducted for studying the feasibility of using the viscoplastic model for different orientations of the HMX lattice. Afterwards, the coupled model is applied to study the collapse of an air-bubble/pore in the HMX crystal for different impact velocities.

Isothermal decomposition of HMX before and after thermally induced β–δ crystal transformation

The β–δ crystal transformation of HMX is examined using a self-made constant temperature decomposition gas measuring device, and the isothermal decomposition kinetic parameters of HMX with different crystal phases are obtained.

Thermal Decomposition Mechanism of 1,3,5,7-Tetranitro-1,3,5,7-tetrazocane Accelerated by Nano-Aluminum Hydride (AlH3): ReaxFF-Lg Molecular Dynamics Simulation.

ReaxFF-low-gradient reactive force field with CHONAl parameters is used to simulate thermal decomposition of 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) and AlH3 composite. Perfect AlH3 and surface-passivated AlH3 particles were constructed to mix with HMX. The simulation results indicate HMX is adsorbed on the surface of particles to form O–Al and N–Al bonds. The decomposition of HMX and AlH3 composite is an exothermic reaction without energy barrier, but the decomposition of pure HMX needs to overcome the energy barrier of 133.57 kcal/mol. Active nano-AlH3 causes HMX to decompose rapidly at low temperature, and the primary decomposition pathway is the rupture of N–O and C–N bonds. Adiabatic simulation shows that the energy release and temperature increase of HMX/AlH3 is much larger than those of the HMX system. Surface-passivated AlH3 particles only affect the initial decomposition rate of HMX. In HMX and AlH3 composites, the strong attraction of Al in AlH3 to O and the activation of the intermediate reaction by H2 cause HMX to decompose rapidly. The final decomposition products of pure HMX are H2O, N2, and CO2, and those of HMX/AlH3 are H2O, N2, and Al-containing clusters dominated by C–Al. The final gas production shows that the specific impulse of HMX/AlH3 is larger than that of HMX.

Coupling effect of high temperature and pressure on the decomposition mechanism of crystalline HMX

The coupling effect of temperature and pressure plays a significant role in the behavior of energetic materials. Energetic materials present extremely complex behavior at high temperatures. Handling difficulties and safety risks have restricted detailed experimental studies on their decomposition mechanisms, especially for less-stable configurations of energetic materials. This has necessitated theoretical studies particularly under the coupling effect. A combinational strategy based on density functional tight-binding molecular dynamics (DFTB-MD) simulations and the density functional theory (DFT) was applied to study the effects of temperature and pressure on the initial decomposition and reaction activation barrier of α-octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) and δ-HMX. A comprehensive analysis of HMX in each system indicated that while the initial decomposition mechanism was not dependent on pressure at high temperatures, the initial reaction rate and activation barrier were highly dependent on pressure. The initial decomposition mechanisms of α-HMX at 1500 ​K and δ-HMX at 1200 ​K under pressures of 1–3 ​GPa involved unimolecular C–H bond breakage and N–NO2 homolysis, respectively. Pressure inhibited the decomposition of α-HMX, but accelerated that of δ-HMX. The decompositions of α-HMX and δ-HMX occurred via first-order reactions. The classical Arrhenius form indicated that pressure (1–3 ​GPa) increased and decreased the decomposition barriers of α-HMX at 1500 ​K and δ-HMX at 1200 ​K, respectively. These findings provide a new understanding of the thermal decomposition and reaction mechanisms of HMX under the coupling effect of temperature and varying pressures.

The potentials of TiO2 nanocatalyst on HMX thermolysis

Even though HMX is one of the most powerful highly explosive materials; HMX-based propellants demonstrated complexity of burning rate control as well as high pressure exponent (n). In addition, HMX is insensitive to common catalyst. TiO2 can offer novel catalyzing ability for HMX. Highly-crystalline, mono-dispersed TiO2 NPs of 5.0 nm particle size with proper surface area (26.87 ± 0. 36 m2/g) were fabricated using hydrothermal processing. TiO2 NPs were re-dispersed in organic solvent and effectively-integrated into HMX via co-precipitation technique; the impact of TiO2 NPs on HMX thermal behavior was investigated using DSC and TGA. TiO2 NPs exposed superior catalytic performance; the endothermic phase change of HMX at 187 °C was decreased by 43.3%. The main exothermic decomposition peak was decreased by 10 °C with enhanced total heat release by 46.7%. The catalytic performance of TiO2 NPs could be ascribed to the release of active surface ȮH radicals that could induce HMX decomposition via hydrogen abstraction. Furthermore, TiO2 NPs could adsorb evolved NO2 on its surface with surge in total heat release in condensed phase.

Performance optimization of core-shell HMX@(Al@GAP) aluminized explosives

The energy release of aluminized explosives was impeded by the aggregation of aluminum powders, especially for nano-aluminum powders. The core-shell HMX@(Al@GAP) explosives with 5 wt% to 15 wt% aluminum were fabricated, with systematical investigation of morphology, mechanical properties, thermal decomposition, combustion and detonation properties. Compared with the physical mixtures, the aluminized explosives with core-shell microstructure showed better creep resistance and mechanical strength. The thermal decomposition of HMX in core-shell HMX@(Al@GAP) was slightly advanced due to good dispersion of Al@GAP particles. Delayed but more vigorous and longer burning during combustion process was witnessed for the core-shell explosive. For HMX@15 wt%(Al@GAP) aluminized explosives, the detonation velocity and specific kinetic energy was 8567 m/s and 1.412 kJ/g, which was 1.3% and 5.1% higher than the corresponding physical mixtures. The reaction of the core-shell HMX@(Al@GAP) and the physical mixtures were calculated by ReacFF-/g force field, showing remarkable dependent of the average temperature on the microstructure. Present research might provide new insight for synergistically improvement of mechanical and detonation properties in aluminized explosives.

Reinforced combustion of the ZrH2-HMX-CMDB propellant: The critical role of hydrogen

Metal hydrides, which are capable of producing H2 and release much energy efficiently via combustion, are regarded as promising high-energy fuels for future advanced solid propellants. Here, we report our first attempt on the application of a high-density hydride ZrH2 in CMDB propellants containing the high-energy explosive HMX and the revelation of the combustion mechanism of ZrH2 in HMX-CMDB propellants. ZrH2 was found to be capable of enhancing the combustion of HMX-CMDB propellants effectively. Especially, hydrogen in ZrH2 was determined to play a critical role during both its intrinsic combustion and the combustion in propellants. Upon ignition, ZrH2 dehydrogenates to produce Zr and H2, followed by combustion of the decomposition products. Interestingly, H2 release results in particle fragmentation either, promoting the combustion of hydride. As for the combustion of propellant with ZrH2, in the condensed phases, the Hδ+-Hδ− interaction promotes the thermal decomposition of HMX, leading to enhanced reaction rates. The ZrH2 combustion in propellant also starts with the hydrogen-release process, followed by melting and combusting of the newly generated metallic Zr on the burning surface. Thus, the heat feedback is greatly reinforced and the reactions in the condensed phases are further speeded up. The other dehydrogenation product, H2, participates in the gaseous combustion reactions. The insights into the effects of metal hydrides on propellant combustion are believed to be of great importance for developing novel hydride fuels for solid propellants.

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.

Evaluation of reaction kinetics models for meso-scale simulations of hotspot initiation and growth in HMX

Meso-scale modeling of heterogeneous energetic materials requires accurate description of the chemical reaction model that governs the decomposition of solid energetic crystals to gaseous products. For HMX, various 1-step and multi-step Arrhenius based chemical kinetic models are available; these chemical kinetics models for HMX have been calibrated against macro-scale experimental data under different ranges of pressure and temperature conditions, which may lie outside the ranges that arise during void collapse. Therefore, depending on the reaction model, the predicted meso-scale hotspot initiation and growth behavior can vary. Here, we examine the effects of five global HMX reaction kinetics models on predictions of void collapse induced hotspots, viz. the Henson-Smilowitz 1-step (HS1), Menikoff 1-step (M1), Tarver-Nichols 3-step (TN3), Henson-Smilowitz 9-step (HS9) and a 7-step extended Brill-Yetter model (BYS7). Variations in the hotspot behavior predicted using the different models are observed to be significant. A detailed examination of the individual reaction mechanisms of each of these global chemistry models is undertaken to provide insights and understanding of the reaction steps that lead to the differences in the predicted hotspot behavior. For the temperature regime relevant to the void collapse generated hotspots, the differences in the hotspot behavior are attributed to the orders of magnitude variations in the reaction rates that govern the maximum energy release during HMX decomposition. The paper shows that the issue of a suitable kinetics model, even for the commonly used HMX material, remains unsettled.

Adsorption and decomposition properties of HMX on MgH2(1 1 0) surface: A first Principles study

The adsorption and decomposition of HMX (1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane) molecule on the MgH2 (1 1 0) crystal surface were investigated by employing the First Principles computation. With the N-NO2 bond of HMX molecule as a reference, 12 possible adsorption configurations were considered that are either perpendicular (V1 ~ V6) or parallel (P1 ~ P6) to the MgH2 (1 1 0) surface. The adsorption energy, density of states and charge transfer of MgH2(1 1 0)/HMX after adsorption were analyzed. The adsorption energies for all the 12 configurations are positive, suggesting exothermic and stable adsorption. The HMX molecules are chemically adsorbed on MgH2(1 1 0) surface in most cases. The charge analysis shows strong charge transfer between magnesium and oxygen, nitrogen atoms. 8 paths that HMX adsorbs and decomposes on MgH2(1 1 0) surface were determined.

Study on the isothermal decomposition of CL-20/HMX co-crystal by microcalorimetry

The thermal decomposition behavior and kinetics of CL-20/HMX co-crystal were studied by microcalorimetry at the temperature interval of 448.15–468.15 K. The thermal stability of CL-20/HMX co-crystal is mediated by the individual thermal stabilities of pure CL-20 and HMX. CL-20 has a catalytic effect on HMX decomposition. The heat flow curve of CL-20/HMX co-crystal is not a single exothermic peak, and there is an obvious inflection point when the degree of decomposition α = 50 %. The mechanism function and kinetic parameters of CL-20/HMX co-crystal are obtained. Before the inflection point, the model conforms to the Avrami-Erofeev equation, and the activation energy is 166.80 kJ mol−1. After the inflection point, the model conforms to the Jander model, and the activation energy is 174.43 kJ mol−1. The thermal decomposition process of CL-20/HMX co-crystal is not a simple superposition process, but has coupling feature. The decomposition residues are analyzed and identified by high-performance liquid chromatography, Fourier-transform infrared spectroscopy, and scanning electron microscopy, and the isothermal decomposition of CL-20/HMX co-crystal is extensively discussed.