Degradation of TNT,RDX, and HMX Explosive Wastewaters Using Zero‐Valent Iron Nanoparticles

The high‐energy explosives 2,4,6‐trinitrotoluene (TNT), hexahydro‐1,3,5‐trinitro‐1,3,5‐triazine (RDX), and the high melting explosive octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) are common groundwater contaminants at active and abandoned munitions production facilities causing serious environmental problems. A highly efficient and environmentally friendly method was developed for the treatment of the explosives‐contaminated wastewaters using zero‐valent iron nanoparticles (ZVINs). ZVINs with diameters of 20–50 nm and specific surface areas of 42.56 m² g⁻¹ were synthesized by the co‐precipitation method. The explosives degradation reaction is expressed to be of pseudo first‐order and the kinetic reaction parameters are calculated based on different initial concentrations of TNT, RDX, and HMX. In addition, by comparison of the field emission scanning electron microscopy (FE‐SEM) images for the fresh and reacted ZVINs, it was apparent that the ZVINs were oxidized and aggregated to form Fe₃O₄ nanoparticles as a result of the chemical reaction. The X‐ray diffraction (XRD) and X‐ray absorption near edge structure (XANES) measurements confirmed that the ZVINs corrosion primarily occurred due to the formation of Fe₃O₄. Furthermore, the postulated reaction kinetics in different concentrations of TNT, RDX, and HMX, showed that the rate of TNT removal was higher than RDX and HMX. Furthermore, by‐products obtained after degradation of TNT (long‐chain alkanes/methylamine) and RDX/HMX (formaldehyde/methanol/hydrazine/dimethyl hydrazine) were determined by LC/MS/MS, respectively. The high reaction rate and significant removal efficiencies suggest that ZVINs might be suitable and powerful materials for an in‐situ degradation of explosive polluted wastewaters.     

Preparation and Properties of HMX Coated with a Composite of TNT/Energetic Material

To improve the safety of HMX without sacrificing energy properties, the composites of TNT and an energetic material (HP‐1) were used to coat HMX particles by a method of integrating solvent–nonsolvent with aqueous suspension‐melting. SEM (scanning electron microscopy) and XPS (X‐ray photoelectron spectrometry) were employed to characterize the samples. The effect of the processing parameters, such as mass ratio of HP‐1 to TNT (MRHT), stirring speed, and cooling rate, on the quality of coated samples were investigated and discussed. The mechanical sensitivity, thermal sensitivity, thermal decomposition characteristic, and heat of detonation of raw and coated HMX samples were also measured and contrasted. Results show that when MRHT, stirring speed in the second stage and cooling rate are 1 : 5, 1000 r⋅min⁻¹ and 5 °C⋅min⁻¹ respectively, the optimal coating effect is achieved. Compared with that of raw HMX, both impact and friction sensitivity of HMX coated with 2.5 wt.‐% TNT and 0.5 wt.‐% HP‐1 decrease obviously, whereas there is a slight change in their thermal sensitivity and thermal decomposition characteristics. Meanwhile, such surface coating does not result in the decrease of its energy properties.     

Preparation and Characterization of Insensitive HMX/Graphene Oxide Composites

To improve the safety of HMX, a two‐dimensional (2D) graphene oxide (GO) was introduced to HMX by the solvent nonsolvent method. The morphology, composition, thermal decomposition characteristic were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), thermogravimetry (TG) and differential scanning calorimetry (DSC). Compared to the previous reports, GO sheets exhibited better desensitizing effect than [60]Fullerene and CNTs. When 2.0 wt‐% GO sheets were added, the impact sensitivity of raw HMX decreased from 100 to 10 %, and the friction sensitivity reduced from 100 to 32 %. The DSC results proved that GO sheets were compatible with HMX. In addition, by determining the thermal decomposition kinetic parameters of the samples, it was found that the activation energy (E_a) of HMX with 2.0 wt‐% GO increased by 23.5 kJ mol⁻¹, suggesting that GO sheets could improve the thermal stability of HMX.     

Study of the Elaboration of HMX and HMX Composites by the Spray Flash Evaporation Process

The Spray Flash Evaporation (SFE) process invented and developed at the NS3E laboratory allows obtaining different nanosized explosives (TNT, RDX, CL‐20…). This process is based on the very fast evaporation of the solvent due to the drastic modification of pressure and temperature leading to the crystallization of the molecules present in solution into nanometric or submicrometric particles. Here, we show the possibility to prepare pure HMX (Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) or HMX based composites at the nanoscale using this process. This study mainly focuses on the size, morphology and crystallographic phases obtained for HMX and HMX/TNT composites depending on the experimental conditions (temperature, pressure, solution concentration…) used during the elaboration. For this purpose, the results obtained from scanning electron microscopy, X‐ray diffraction and Raman spectroscopy are discussed.     

Nano Cyclotetramethylene Tetranitramine Particles Prepared by a Green Recrystallization Process

The solubility of cyclotetramethylene tetranitramine (HMX) in four ionic liquids (ILs): 1,3‐dimethylimidazolium dimethylphosphate ([Memim]DMP), 1‐butyl‐3‐methylimidazolium chloride ([Bmim]Cl), 1‐hexyl‐3‐methylimidazolium bromide ([Hmim]Br), and 1‐ethyl‐3‐methylimidazolium tetrafluoroborate ([Emim]BF₄) was investigated. Nano‐HMX were produced particles by spraying [Hmim]Br solution into purified ice water. Finally, the particle size, morphology, crystal phase, impact sensitivity, and thermal decomposition properties of nano‐HMX particles were tested and analyzed. All four ILs could dissolve HMX to a greater or lesser extent in the temperature range from 20 °C to 80 °C. The solubility of HMX in [Hmim]Br at 80 °C is up to 0.7 g mL⁻¹. Recrystallized HMX particles are of polyhedral or spherical shape and 40 to 130 nm in size. X‐ray diffraction indicated that nano‐HMX has a similar crystal structure as raw HMX (β‐form). Compared with raw HMX, the nano‐HMX particles have much lower impact sensitivity. However, they are easier to explode than raw HMX under thermal stimulus due to the lower peak temperature and activation energy.     

A Groundbreaking Stepwise Protocol to Prepare HMX from DPT: New Mechanism Hypothesis and Corresponding Process Study

1,3,5,7‐Tetranitro‐1,3,5,7‐tetraazacyclooctane(HMX) is one of the most powerful and widely used explosives. 3,7‐Dinitro‐1,3,5,7‐tetraazabicyclo[3.3.1] (DPT) is an important precursor in the production of HMX. A new reaction mechanism including nitrolysis, nitrosolysis and nitrolysis processes in fuming HNO₃ was put forward. The stable key intermediate 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX) was isolated and characterized. Based on the new mechanism, a stepwise method to prepare HMX from DPT was developed. The influence factors on the yields of MNX such as reaction temperature, loading amounts of HNO₃, NaNO₂ and NH₄NO₃ were investigated. Under the optimized conditions, MNX was obtained with a satisfactory yield of 84.0 %. MNX could be efficiently and smoothly nitrolyzed in fuming nitric acid and afforded pure β‐HMX with excellent yield up to 92.8 %. The overall yield of the stepwise procedure was as high as 78.0 %, much higher than traditional one‐pot nitrolysis protocols.     

Structures and Properties Prediction of HMX/TATB Co‐Crystal

In this study, a new co‐crystal explosive of 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX)/1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) (molar ratio 1 : 1) was designed based on crystal engineering. The crystal structure was predicted using the polymorph predictor (PP) method. The main properties of co‐crystal consisting of mechanical properties, stability, and interaction formats were simulated through molecular dynamics methods. Simulated results indicate that the crystal structure of the HMX/TATB co‐crystal may belong to the P , P2₁2₁2₁ or P2₁/c space group. The calculations of the binding energy and the analysis for radial distribution function show that the two components are connected through electrostatic hydrogen bonding and strong van der Waals interactions. The new co‐crystal has better mechanical properties with the moduli systematically decreased. With the appearance of the new crystal, the trigger bond N NO₂ has little change.     

Energetic Characteristics of HMX‐Based Explosives Containing LiH

The high energy density compound octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) and the strong exothermic compound LiH represent an excellent principal explosive and an active fuel, respectively. Herein, the energetic characteristics of HMX‐based explosives are explored by adding LiH as fuel additive. The detonation parameters of HMX‐based explosives containing LiH were tested with free‐field explosion experiments and compared with those of traditional TNT, HMX, and aluminized explosives. The results show that the explosives exhibit higher energy and present preferable explosion effect when LiH is added as an explosive ingredient. The improvement of impulse is more than 32.8 % at 2 m. The shock wave peak overpressure increases by almost 40 % at a distance of 3 m from detonation center specially for the explosive containing both LiH and Al additives. Elemental H and Li are expected to release tremendous energy to effectively improve the explosives instant damage power, but the detonation duration is shorter than that of Al‐containing mixed explosives, which may limit the advantage over Al in the impulse. Li₂CO₃ powder is the solid product of HMX/LiH, which explains the LiH oxidation during the explosion. The exothermic processes in the formation are the reason for the increased energy of HMX/LiH explosives. These results can provide guidance to a potential energetic system formed by HMX and LiH.     

The Nitrolysis Mechanism of 3,7‐Dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane

Two intermediates, 1,5‐dinitroso‐3,7‐dinitro‐1,3,5,7‐tetraazacyclooctane (DNDS) and 1‐nitroso‐3,5,7‐trinitro‐1,3,5,7‐tetraazacyclooctane (MNX), were isolated and characterized in the synthesis of 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) from the nitrolysis of 3,7‐dinitro‐1,3,5,7‐tetraazabicyclo[3,3,1]nonane (DPT) for the first time. When the nitrolysis of DPT was slowed down, two intermediates were detected with HPLC. It was proposed that electrophilic NO₂⁺ and NO⁺ from HNO₃ and N₂O₄ might attack nitrogen atoms at positions 3 and 7 of DPT to form the cations of the intermediates, then nucleophilic H₂O attacked the bridge carbon atoms of DPT to produce the intermediates, which were oxidized to form HMX.     

Investigation of HMX‐Based Nanocomposites

Advanced munition systems require explosives which are more insensitive, powerful, and reactive. For this reason, nano‐crystalline explosives present an attractive alternative to conventional energetics. In this study, formulations consisting of 95 % octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) and 5 % polyvinyl alcohol (PVOH) were prepared with mean crystal sizes ranging from 300 nm to 2 μm. The process to create these materials used a combination of mechanical particle size reduction and spray drying, which has the advantages of direct control of crystal size and morphology as well as the elimination of ripening of crystals (which occurs during slurry coating of nanomaterials). The basic physical characteristics of these formulations were determined using a variety of techniques, including scanning electron microscopy and X‐ray diffraction. Compressive stress‐strain tests on pressed pellets revealed that the mechanical properties of the compositions improved with decreasing crystal size, consistent with Hall‐Petch mechanics. The 300 nm HMX/PVOH composition demonstrated a 99 % and 129 % greater strength and stiffness, respectively, than the composition with 2 μm HMX. The formulations were subjected to the Small Scale Gap Test, revealing a significant reduction in shock sensitivity with decreasing crystal size. The formulation containing 300 nm HMX registered a shock initiation pressure 1.6 GPa above that of the formulation with 2 μm HMX, a 44 % improvement in sensitivity. These results serve to highlight the relevance of structure‐property relationships in explosive compositions, and particularly elucidate the substantial benefits of reducing the high explosive crystal size to nano‐scale dimensions.     

Encapsulation of Cyclotetramethylenetetranitramine (HMX) by Electrostatically Self‐Assembled Graphene Oxide for Desensitization

To improve the safety of cyclotetramethylenetetranitramine (HMX) particles, a novel strategy was developed for the fabrication of graphene oxide encapsulated HMX (HMX@GO) by electrostatic self‐assembly between graphene oxide and HMX particles. The prepared samples were characterized by optical microscopy, scanning electron microscopy, Raman spectroscopy, X‐ray photon spectroscopy, thermogravimetry, differential scanning calorimetry and water contact angle tests. The results revealed that GO sheets were coated densely and homogeneously on the HMX particles in a HMX@GO composite at a low GO content of about 0.23 wt %. Compared with that of raw HMX, the impact sensitivity of the HMX@GO composite decreased from 100 % to 30 %, and the 50 % probability of required ignition energy (E₅₀) in the electrostatic spark sensitivity test increased from 0.66 J for HMX to 1.12 J for the HMX@GO composite, suggesting that the electrostatically self‐assembled GO coating layer could obviously enhance the safety of HMX.     

Combustion Synthesis and Catalytic Activity of LaCoO3 for HMX Thermal Decomposition

Perovskite‐type LaCoO₃ was prepared by stearic acid solution combustion method and characterized by XRD, DSC‐TG, and XPS techniques. The catalytic activities of LaCoO₃ for HMX (octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine) thermal decomposition were investigated. The as‐prepared LaCoO₃ shows higher activity than the calcined one. This could be due to higher concentration of surface‐adsorbed oxygen and hydroxyl species as well as higher BET surface area of the as‐prepared LaCoO₃.     

Synthesis and Characterization of Energetic 1,2‐Bis(Oxyamino)Ethane Salts

The synthesis, characterization, theoretical calculations, and safety studies of energetic salts based on 1,2‐bis(oxyamino)ethane, (H₂N O CH₂ CH₂ O NH₂), were carried out. The salts were characterized by vibrational (infrared, Raman), multinuclear NMR studies (¹H, ¹³C), differential scanning calorimetry (DSC), elemental analysis, and initial safety testing (impact and friction sensitivity). Single crystal X‐ray diffraction studies were carried out on the mono‐perchlorate and the double nitrate salts, revealing the expected structures.     

非溶剂制备细化HMX及其性能表征

以二甲基亚砜为溶剂,用喷雾重结晶细化法制备了HMX,研究了非溶剂(水、乙醇、氯代烷烃)的种类、溶剂与非溶剂的体积比以及非溶剂的温度对HMX晶体形貌的影响并分析了其影响机理。采用扫描电子显微镜(SEM)、激光粒度分析仪、X射线衍射仪(XRD)、差示扫描热量法(DSC)对其进行了表征和热分析。测试了细化HMX和原料HMX的撞击感度。结果表明,HMX细化最佳工艺条件是以35℃乙醇为非溶剂,溶剂与非溶剂体积比为1∶40,此时可获得中值粒径为616nm、粒径分布均匀、趋于球形且表面光滑的亚微米HMX;亚微米HMX表观活化能比原料HMX降低了13.75kJ/mol,与原料HMX相比具有更好的热安定性,特性落高从34.05cm升至79.10cm,撞击感度显著降低。     

Explosive Strength and Impact Sensitivity of Several PBXs Based on Attractive Cyclic Nitramines

Plastic explosives based on different cyclic nitramines with different polymeric matrices were prepared and studied. The used polymeric matrices were fabricated on the basis of polyisobutylene (PIB), acrylonitrile‐butadiene rubber (ABR), Viton A, and polydimethyl‐siloxane as binders, whereas the nitramines named RDX (1,3,5‐trinitroperhydro‐1,3,5‐triazine), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine), BCHMX (cis‐1,3,4,6‐tetranitrooctahydroimidazo‐[4,5‐d]imidazole) and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane) were used as explosive fillers. Commercial Semtex 10, based on pentaerythritol tetranitrate (PETN), was used for comparison. Impact sensitivity, loading density, ρ, detonation velocity, D, and relative explosive strength (RS) measured by ballistic mortar were determined. It was concluded that plastic BCHMX based on Viton A or PIB‐matrix exhibits higher RS compared with PBXs based on RDX and HMX. Correlations between RS and the impact sensitivity, the ρD² term and the square of the detonation velocity were studied and discussed. The results confirm the well‐known fact that increasing the performance is usually accompanied by an increase in the sensitivity of the explosives. In this connection, Viton A enables achieving a high RS, but with a relatively high sensitivity of the PBXs, whereas the polydimethyl‐siloxane matrix should perhaps give PBXs with optimum explosive strength and sensitivity parameters.     

Chemical Transformation of Octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) Induced by Low Energy Electron Beam Irradiation

The effects of 8.0×10⁻¹⁷ J (500 eV) and 3.2×10⁻¹⁹ J (2 eV) electrons on chemical structure of octahydro‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocine (HMX) were studied in situ, under ultra‐high vacuum conditions using a combination of X‐ray photoelectron spectroscopy (XPS) and quadrupole mass spectrometry. XPS data indicated that electrons impact by 8.0×10⁻¹⁷ J for 30 s caused a decrease in nitro group concentration, and a little shift in the binding energy of the nitrogen 1s peak. Such a phenomenon was found at very low kinetic energy (3.2×10⁻¹⁹ J) with time evolution. Quadrupole mass spectrometry detected gas desorption after electron irradiation included H₂O and H₂ mostly. Microscopy‐IR spectroscopic investigations also proved that the intensity of nitro groups of HMX after irradiation decreased compared with those of the pristine HMX. We attributed the structure changes obtained by XPS and IR spectroscopy result in a chemical transformation, which was associated with low‐energy dissociative electron attachment (DEA) of surface contaminants followed by deoxidization reactions to form the product molecules.     

用LC/APCI/MS方法检测粉尘中的炸药成分

采用高选择性和灵敏度的LC(液相色谱)/APCI(大气压化学电离源)/MS(质谱)方法定量分析粉尘样品中的HMX、RDX、PETN、CE、NQ和TNT。采用ASE萃取,GPC净化浓缩作为前处理方法,在粉尘中分别添加所测炸药组分,用丙酮作为ASE萃取溶剂,乙酸乙酯和环己烷(体积比为1∶1)作为GPC净化时的流动相并抛弃杂质500s,收集1 520s。在LC/MS分析时,通过在流动相中添加1mmol/L甲酸与样品形成[M+HCOO]-的甲酸加合离子。结果表明,HMX、RDX、PETN、CE、NQ、TNT的方法检测限分别为0.78,1.44,1.69,0.77,1.06,1.72ng/mL,回收率为49.0%～88.4%,相对标准偏差为3.5%～10.3%。该方法可以用来系统排查及定量分析爆炸残留物及环境样品中的NQ、RDX、PETN、CE、HMX、TNT成分。     

Study of Plastic Explosives based on Attractive Cyclic Nitramines,Part II. Detonation Characteristics of Explosives with Polyfluorinated Binders

A series of plastic bonded explosives (PBXs) based on Viton A and Fluorel binders were prepared using four nitramines, namely RDX (1,3,5‐trinitro‐1,3,5‐triazinane), β‐HMX (β‐1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane), BCHMX (cis‐1,3,4,6‐tetranitro‐octahydroimidazo‐[4,5‐d]imidazole), and ε‐HNIW (ε‐2,4,6,8,10,12‐hexanitro‐2,4,6,8,10,12‐hexaazaisowurtzitane). The detonation velocities, D, were determined. Detonation parameters were also calculated by means of modified Kamlet & Jacobs method, CHEETAH and EXPLO5 codes. In accordance with our expectations BCHMX based PBXs performed better than RDX based ones. The Urizar coefficient for Fuorel binder was also calculated.     

Selective Extraction of N‐Heterocyclic Precursors of 1,3,5,7‐Tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX) Using Molecularly Imprinted Polymers

N‐heterocyclic compounds are key nitration precursors for some high energy density explosives such as 1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane (HMX). Nitration of 1,3,5,7‐tetraacetyl‐1,3,5,7‐tetraazacyclooctane (TAT) yields HMX in high yields and purity. However, the analogue 1,3,5‐triacetyl‐1,3,5‐triazacyclohexane (TRAT) is easily co‐produced via the condensation of acetonitrile and 1,3,5‐trioxan. To selectively extract TAT from a mixture of TAT and TRAT, the molecular imprinting technology (MIT) was developed in this study. The capacity of the dry polymer is 16 mg g⁻¹ and the recovery surpasses 75 %.     

Kinetic Deuterium Isotope Effects in the combustion of formulated nitramine propellants

The kinetic deuterium isotope effect was used to investigate the rate-limiting process in the combustion of formulated nitramine propellants. Model propellant formulations containing either octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), or their deuteriated analogues were pressed into pellets and burned under nitrogen pressure in a window bomb. The magnitudes of the observed deuterium isotope effects indicate that the HMX and RDX exert significant control over the combustion phenomenon of the propellants studied. Furthermore, assuming a consistent mechanism between decomposition and combustion, the observed isotope effects suggest that a carbon-hydrogen bond rupture in HMX or RDX is the rate-controlling step in the combustion of the model nitramine propellants. Observed isotope effect values for HMX-CW5 and RDX-CW5 formulated propellants at 1000 psig (6.99 MPa) pressure were 1.29 ± 0.09 and 1.24 ± 0.07, respectively, compared to a theoretical estimate of 1.29 for a primary effect due to C H bond rupture at 673 K.