Explosive RDX Research Articles

The Effects of Material‐Filled Voids on Detonation Wave Shape in Rubberized RDX Explosives

AbstractThe sensitivity of explosives is affected by inhomogeneities within the material. This is evident in the increased shock sensitivity of explosives with slightly lower densities resulting from an increased number of hotspots. The influence of hotspots on explosive initiation has been well studied; however, few studies have been conducted on the effect of intermediate‐sized voids (0.1–10 mm) on a propagating detonation wave. Cylindrical voids filled with air have been studied for diameters ranging from 0.3 mm to 0.8 mm for both 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX) and 1,3,5‐trinitro‐1,3,5‐triazinane (RDX)‐based rubberized explosives. Continuing the investigation into single cylindrical voids, this study examined the effects of 0.5 mm diameter voids filled with different inert cylindrical metals on the detonation wave shape for an RDX‐based rubberized explosive. The metals selected for experiments were 1066 aluminum, brass, copper, and tungsten. The propagation of the detonation wave was captured using a digital streak camera. Experimental results showed that the extent of detonation wave shaping was closely tied to the density differential between the bulk explosive and metal insert. Forty‐four different filler materials, including non‐metals, were simulated using a hydrodynamic code to further analyze material inclusion effects. The main factors hypothesized to be of interest were bulk sound speed, shock impedance, and filler material density. We found that the local detonation delay could be correlated fairly well to a ratio of bulk sound speed and density. Understanding the influence of material inclusions on detonation performance and wave shape allows for tailoring of detonations.

Preparation, characterization, and investigation of thermal behavior of improved HMX and RDX through coating by TNT

ABSTRACT Simultaneous achievement of both low sensitivity and high energy is crucial in practical applications of high energetic materials such as HMX and RDX. In this work, TNT, a low-sensitive explosive, was used to improve sensitivity and thermal stability of HMX and RDX explosives. The method is based on coating HMX and RDX with TNT using solvent-anti-solvent technique. The characterization of samples was done by scanning electron microscopy (SEM), transmission electron microscope (TEM), and X-ray diffraction (XRD). The SEM and TEM images revealed that a layer of TNT was coated on the HMX and RDX surfaces. TG/DSC thermograms for HMX/TNT and RDX/TNT show that decomposition enthalpy change (ΔH) increased to 121.1 and 197.6 J/g compared to pure HMX and RDX, respectively. Fluidity test results showed that the fluidity of the samples improved from medium to good grade after coating. The impact sensitivity for HMX/TNT and RDX/TNT improved to 7.35 and 19.62 J, respectively. Also, friction sensitivity for coated HMX and RDX increased to 210.2 and 196.1 N. The electrostatic discharge experiments showed that HMX/TNT and RDX/TNT were safer than pure HMX and RDX. Therefore, the coated samples will be good candidates for energetic formulations.

Construction and Modification of Nitrogen-Rich Polycyclic Frameworks: A Promising Fused Tricyclic Host-Guest Energetic Material with Heat Resistance, High Energy, and Low Sensitivity.

The construction and modification of novel energetic frameworks to achieve an ideal balance between high energy density and good stability are a continuous pursuit for researchers. In this work, a fused [5,6,5]-tricyclic framework was utilized as the energetic host to encapsulate the oxidant molecules for the first time. A series of new pyridazine-based [5,6] and [5,6,5] fused polycyclic nitrogen-rich skeletons and their derivatives were designed and synthesized. Two strategies, amino oxidation and host-guest inclusion, were used to modify the skeleton in only one step. All compounds exhibit good comprehensive properties (Td(onset) > 200 °C, ρ > 1.85 g cm-3, Dv > 8400 m s-1, IS > 20 J, FS > 360 N). Benefiting from the pyridazine-based fused tricyclic structure with more hydrogen bonding units and larger conjugated systems, the first example of [5,6,5]-tricyclic host-guest energetic material triamino-9H-pyrazolo[3,4-d][1,2,4]triazolo[4,3-b]pyridazine-diperchloric acid (10), shows high decomposition temperature (Td(onset) = 336 °C), high density and heats of formation (ρ = 1.94 g cm-3, ΔHf = 733.4 kJ mol-1), high detonation performance (Dv = 8820 m s-1, P = 36.2 GPa), high specific impulse (Isp = 269 s), and low sensitivity (IS = 30 J, FS > 360 N). The comprehensive performance of 10 is superior to that of high-energy explosive RDX and heat-resistant explosives such as HNS and LLM-105. 10 has the potential to become a comprehensive advanced energetic material that simultaneously satisfies the requirements of high-energy and low-sensitivity explosives, heat-resistant explosives, and solid propellants. This work may give new insights into the construction and modification of a nitrogen-rich polycyclic framework and broaden the applications of fused polycyclic framework for the development of host-guest energetic materials.

Effects of vacuum degree on the detonation characteristics and energy release laws of RDX explosive

To explore the detonation characteristics and energy release laws of RDX explosives under varying degrees of vacuum, the influence of vacuum degree on the fireball characteristic parameters, shock wave propagation laws and detonation performance of columnar RDX charges were studied using the air-blast experiments and AUTODYN simulations, and the fireball temperature distributions were mapped with the colorimetric thermometry technique. The experimental results indicated that as the degree of vacuum increased, the combustion duration and zone area size of the explosive fireball were both extended, while its temperature decay rate was slowed down, making the afterburning effect more pronounced. Furthermore, the peak overpressure and positive impulse of the explosion shock wave showed a downward trend, with the reductions of 56.1 % and 53.5 %, respectively, with the increasing vacuum degree. Numerical simulation was also used to reveal the energy release laws of RDX explosive, and the comparison between the experimental and numerical results showed a good degree of concordance with an average error of 6.45 %. The results of the study could provide a reference for expanding the explosion theory of explosives in plateau environment and improving the performance of explosion-proof equipment.

Exposed Facets and Surface Properties of Highly Explosive RDX Studied by the Crystal-Face-Indexing Method and Theoretical Calculations

Exposed Facets and Surface Properties of Highly Explosive RDX Studied by the Crystal-Face-Indexing Method and Theoretical Calculations

Highly Dense N-N-Bridged Dinitramino Bistriazole-Based 3D Metal-Organic Frameworks with Balanced Outstanding Energetic Performance.

Due to the inherent conflict between energy and safety, the construction of energetic materials or energetic metal-organic frameworks (E-MOFs) with balanced thermal stability, sensitivity, and high detonation performance is challenging for chemists worldwide. In this regard, in recent times self-assembly of energetic ligands (high nitrogen- and oxygen-containing small molecules) with alkali metals were probed as a promising strategy to build high-energy materials with excellent density, insensitivity, stability, and detonation performance. Herein, based on the nitrogen-rich N,N'-([4,4'-bi(1,2,4-triazole)]-3,3'-dial)dinitramide (H2BDNBT) energetic ligand, two new environmentally benign E-MOFs including potassium [K2BDNBT]n (K-MOF) and sodium [Na2BDNBT]n (Na-MOF) have been introduced and characterized by NMR, IR, TGA-DSC, ICP-MS, PXRD, elemental analyses, and SCXRD. Interestingly, Na-MOF and K-MOF demonstrate solvent-free 3D dense frameworks having crystal densities of 2.16 and 2.14 g cm-3, respectively. Both the E-MOFs show high detonation velocity (VOD) of 8557-9724 m/s, detonation pressure (DP) of 30.41-36.97 GPa, positive heat of formation of 122.52-242.25 kJ mol-1, and insensitivity to mechanical stimuli such as impact and friction (IS = 30-40 J, FS > 360 N). Among them, Na-MOF has a detonation velocity (9724 m/s) superior to that of conventional explosives. Additionally, both the E-MOFs are highly heat-resistant, having higher decomposition (319 °C for K-MOF and 293 °C for Na-MOF) than the traditional explosives RDX (210 °C), HMX (279 °C), and CL-20 (221 °C). This stability is ascribed to the extensive structure and strong covalent interactions between BDNBT2- and K(I)/Na(I) ions. To the best of our knowledge, for the first time, we report dinitramino-based E-MOFs as highly stable secondary explosives, and Na-MOF may serve as a promising next-generation high-energy-density material for the replacement of presently used secondary thermally stable energetic materials such as RDX, HNS, HMX, and CL-20.

A Comprehensive Review of Remediation Strategies for Soil and Groundwater Contaminated with Explosives

This study offers an updated overview of the soil and water remediation strategies employed to address the widespread environmental and public health risks associated with explosive compounds, particularly TNT and RDX. Recognizing soil contamination originating from military activities, industrial accidents, and historical land use, this review delves into physical, chemical, and biological approaches to mitigating ecological and human health concerns. While physical methods like excavation and disposal are effective, their applicability is constrained by cost and logistical challenges for large contaminated areas. Chemical methods, such as oxidation and reduction, focus on transforming explosives into less toxic byproducts. Biological remediation utilizing plants and microorganisms emerges as a cost-effective and sustainable alternative. This review highlights challenges, including the persistence of explosive compounds, potential groundwater leaching, and the necessity for long-term monitoring. Emphasizing the need for site-specific strategies, considering the contaminant type, concentration, soil properties, and regulatory requirements, this study advocates for integrated and sustainable remediation approaches in pilot-scale applications. It concludes by evaluating the appropriate solution based on the advantages and disadvantages of the categories of soil and groundwater remediation methods. The duration, the effectiveness, and the cost of available technologies were estimated.

An advanced furoxan-bridged heat-resistant explosive.

Nowadays, thousands of energetic materials have been synthesized, but only a few compounds meet all the high standards of detonation performance comparable to that of the widely used military explosive RDX, thermal stability comparable to that of the most widely used heat-resistant explosive HNS, and impact sensitivity comparable to that of the traditional explosive TNT. Also, as a goal, a novel and unexpected one-step method for constructing the furoxan-bridged energetic compound 3,4-bis(3,8-dinitropyrazolo[5,1-c][1,2,4]triazin-4-amino-7-yl)-1,2,5-oxadiazole 2-oxide (OTF) has been achieved under the conventional TFA/100% HNO3 nitration reaction system from the acetic acid intermediate. In this work, OTF with a high density of 1.90 g cm-3, the highest decomposition temperature of 310 °C (onset) among furoxan-based high explosives to date, superior detonation velocity (DV: 9109 m s-1), and low sensitivity (IS: 25 J) is reported. This work is a giant step forward in the development of advanced high-energy heat-resistant explosives and could improve future possibilities for the design of furoxan-based energetic materials.

Synthesis and detonation characters of 3,4,5-1H-trinitropyrazole and its nitrogen-rich energetic salts.

The development of energetic materials is still facing challenges due to the inherent contradiction between energy and sensitivity. Two new nitrogen-rich energetic salts of 3,4,5-1H-trinitropyrazole (HTNP) were synthesized. They are fully characterized by X-ray diffraction, NMR, MS and IR spectroscopy. The DSC and BAM tests were carried out as well. These TNP salts show high thermostability and high positive heat of formation. Their detonation performances were calculated by the EXPLO5 program. Most noteworthy is that DATr salt exhibits superior sensitivity and detonation performance comparable to secondary explosive RDX, making it promising for use as a new-generation green energetic material.

Strategy for improving the energy output efficiency of TKX-50: introduction of nitroamine explosives

ABSTRACT TKX-50 has attracted the attention of many researchers because of its low sensitivity and high energy characteristics. However, the experimental results show that there is a big gap between the energy level of TKX-50 and the theoretical value. Introducing nitroamine explosives RDX or HMX to stimulate the energy release of TKX-50 is of great significance for improving the energy release efficiency of TKX-50 and expanding its application in the field of energetic materials. In this paper, the properties of different TKX-50/RDX and TKX-50/HMX samples were investigated by thermal analysis and ignition combustion experiments. The results show that RDX has a more obvious catalytic effect on TKX-50. Adding 50% RDX reduces the peak thermal decomposition temperature of TKX-50 from 241.7°C to 218.7°C. At the same time, the flame propagation, maximum combustion pressure, and the pressurization rate of different samples during combustion were analyzed, and the reaction mechanism between RDX (or HMX) with TKX-50 was obtained. Because of the different catalytic effects of RDX and HMX on TKX-50, a strategy was proposed to construct the core-shell structure of TKX-50 to improve the reaction characteristics and energy release efficiency of TKX-50.

A Split Hopkinson Pressure Bar Investigation of Impact-Induced Reaction of HMX, RDX and PETN

We have used a split Hopkinson pressure bar arrangement to investigate impact-induced reaction of the secondary explosives HMX, RDX and PETN in granular form. Sentencing of the experiments was performed by detecting reaction light emission, the spectral analysis of which can also provide information about the temperature of reaction. We measure the fraction of the mechanical energy that passes through the specimens that is absorbed in the run up to reaction, which we refer to as the efficiency factor, and for these experiments is of order 5–10%. We postulate that the efficiency factor is a function of the microstructure. The measured amounts of energy that were absorbed are comparable to those amounts required to bulk heat the samples to their melt points. A critical absorbed energy for reaction implies a minimum duration of loading for a given mechanical power and efficiency factor, and this idea is supported by the observation that the more intense the loading, the shorter the time to reaction. Additionally, we postulate a critical minimum mechanical power below which heat is redistributed faster than it can be accumulated. A minimum mechanical power threshold in turn dictates a minimum pressure threshold; but the idea of a stand-alone critical pressure is not experimentally supported.

Experimental investigation on initiation mechanism, overpressure, and flame propagation characteristics of methane-air mixtures explosion induced by hexogen in a closed pipeline

Gas explosion accidents under shock wave stimulation cause more severe hazards than electric spark ignition. To explore the initiation mechanism and explosion characteristics of methane induced by shock waves. A series of experimental investigations of methane-air mixtures initiated by hexogen (RDX) was performed based on a self-developed closed pipeline. The effects of incident shock wave intensity and methane concentration on the characteristics of methane explosion were studied. The results indicate that methane participating in the reaction can significantly increase the positive pressure duration compared with RDX explosion. With the increase of incident shock Mach number (Ma), methane deflagration pressure increases and counteracts the attenuation of RDX detonation pressure. When the ignition distance is 0 cm, the overpressure inside the pipeline is directly proportional to the methane concentration from 5 vol% to 13 vol%. When the concentration approaches the upper explosion limit, the flame velocity exceeds the theoretical detonation velocity, resulting in the unstable detonation of methane in the pipeline.

Thermostable Insensitive Energetic Materials Based on a Triazolopyridine Fused Framework with Alternating Nitro and Amine Groups

AbstractIn this work, we designed and synthesized a series of novel triazolopyridine fused-ring compounds with alternating nitro and amine groups. Three compounds showed remarkable thermal stability at 256, 310, and 294 °C, respectively, and a low mechanical sensitivity [impact sensitivity (IS) = 40 J, friction sensitivity (FS) = 324 N; IS = 35 J, FS = 240 N; and IS > 40 J, FS = 324 N, respectively]. Significantly, two of these compounds exhibited a better detonation performance [detonation velocity (D) = 8200 and 8335 m s–1, Detonation pressure (P) = 25.6 and 27.2 GPa, respectively] than the widely used heat-resistant explosive hexanitrostilbene (HNS; D = 7612 m s–1, P = 24.3 GPa). Additionally, a nitramine derivative displayed a detonation performance (D = 8569 m s–1, P = 31.3 GPa) similar to that of the high-energy explosive RDX. The superior properties of the materials were further confirmed by X-ray diffraction analysis and by several theoretical calculations (ESP, LOL–π, Hirshfeld surfaces, RDG, and NCI analyses). These results indicated that the three compounds might be potential candidates for use as heat-resistant energetic materials.

Copper Azide-based Complexes without Repulsive Steric Clashes between Azides for Advanced Primary Explosives

Primary explosives are essential energy transfer materials in explosive systems. At present, heavy metal-containing materials, such as lead azide (LA), are still the most widely used primary explosives. Copper azide (CA)-based primary explosives are considered as promising replacements for LA. However, there has little advancement in the high initiation performance and high safety of CA-based primary explosives because of the absence of the relevant theories and structural models. Herein, we report [Cu(N3)(2-bmttz)]n1 with the exceptionally remarkable initiating capability and high safety. Performance tests indicated only 5 mg of 1 can successfully ignite the commercial secondary explosive RDX, as 1/6 priming charge of LA, demonstrating 1 is possibly the most efficient primary explosive known to date. Moreover, 1 possesses the rarely low impact sensitivity (IS = 2.5 J), which is comparable to that of LA and better than most of reported CA-based candidates. Both experimental and theoretical studies have shown that passivation of high-energy primary explosives can be achieved through the coordination between functional ligands and azide ions, in which azide ions without repulsive steric clashes only act as energetic building blocks. This work offers a new insight for designing high performance primary explosives for applications in advanced explosive systems.

Nitraza‐/Oxa‐Propylene‐ and Hydrazonemethylene‐Bridged 1,2,4‐Nitraminotriazoles and Selected Salts

AbstractTwo new bridged nitraminotriazoles with bridging oxapropylene and nitrazapropylene moieties were synthesized, and converted into several salts, as well as from the hydrazonemethylene bridged nitraminotriazole. All compounds were fully characterized by NMR and IR spectroscopy, elemental analysis as well as differential thermal analysis. The sensitivity towards friction and impact were determined according to BAM standard technics and the energetic properties were calculated by using the EXPLO5 computer code. The neutral compounds as well as the various salts were examined in terms of their physicochemical properties and detonation performance to each other and compared to the commonly used secondary explosive RDX.

Reactivity of high active aluminum powder with RDX and HMX mixtures

In order to reveal the interaction law of high active aluminum powder with RDX and HMX mixture, the thermal decomposition behavior of highly active Al powder and its interaction with typical nitramine explosive RDX and HMX were studied by differential scanning calorimetry (DSC), thermogravimetry (TG), thermo-mass spectrometry (TG-DTG-DSC-MS) and CO2 laser ignition technology. Results show that when the nanometer aluminum powder and RDX and HMX respectively, two typical nitramine explosive mixing action is of little influence on the mixing action to respond to the thermal decomposition of HMX, depress RDX points liberation degree of temperature, both the thermal decomposition process of mixed system for random nucleation and subsequent growth process, the ignition delay time decreases with the increase of laser ignition power density. The ignition delay time and ignition energy of the mixture of high active aluminum powder and RDX are greater than that of the mixture of high active aluminum powder and HMX and the high active aluminum powder.

Multiple Hydrogen-Bond Modification of [1,2,5]Oxadiazolo[3,4-b]pyridine 1-Oxide Framework Enables Access to Low-Sensitivity High-Energy Materials.

In this work, a fused-ring [1,2,5]oxadiazolo[3,4-b]pyridine 1-oxide framework with multiple modifiable sites was utilized to develop novel energetic materials with multiple hydrogen bonds. The prepared materials were characterized, and their energetic properties were extensively investigated. Among those studied, compound 3 exhibited high densities of 1.925 g cm-3 at 295 K and 1.964 g cm-3 at 170 K, with high detonation performances (Dv: 8793 m s-1 and P: 32.8 GPa), low sensitivities (IS: 20 J, FS: 288 N), and good thermal stability (Td: 223 °C). N-Oxide compound 4 had higher-energy explosive (Dv: 8854 m s-1 and P: 34.4 GPa) and low sensitivities (IS: 15 J and FS: 240 N). Compound 7 with a high enthalpy group (tetrazole) was determined as a high-energy explosive (Dv: 8851 m s-1, P: 32.4 GPa). Notably, the detonation properties of compounds 3, 4, and 7 were similar to high-energy explosive RDX (Dv: 8801 m s-1 and P: 33.6 GPa). The results indicated that compounds 3 and 4 were potential low-sensitivity high-energy materials.

An Efficient One-Step Reaction for the Preparation of Advanced Fused Bistetrazole-Based Primary Explosives.

The first example of [5,6,5]-tricyclic bistetrazole-fused energetic materials has been obtained through a one-step reaction from commercial and inexpensive 4,6-dichloro-5-nitropyrimidine. This one-step reaction including nucleophilic substitution, nucleophilic addition, cyclization, and electron transfer is rarely reported, and the reaction mechanism and scope is well investigated. Among target compounds, organic salts exhibit higher detonation velocities (D: 8898-9077 m s-1) and lower sensitivities (IS: 16-20 J) than traditional high energy explosive RDX (D = 8795 m s-1; IS = 7.5 J). In addition, the potassium salt of 5-azido-10-nitro-bis(tetrazolo)[1,5-c:5',1'-f]pyrimidin (DTAT-K) possesses excellent priming ability, comparable to traditional primary explosive Pb(N3)2, and ultralow minimum primary charge (MPC = 10 mg), which is the lowest MPC among the reported potassium-based primary explosives. The simple synthesis route, free of heavy metal and expensive raw materials, makes it promising to quickly realize this material in large-scale industrial production as a green primary explosive. This work accelerates the upgrade of green primary explosives and enriches future prospects for the design of energetic materials.

Characterization of Electrospinning Prepared Nitrocellulose (NC)-Ammonium Dinitramide (ADN)-Based Composite Fibers.

Nanoscale composite energetic materials (CEMs) based on oxidizer and fuel have potential advantages in energy adjustment and regulation through oxygen balance (OB) change. The micro- and nanosized fibers based on nano nitrocellulose (NC)-ammonium dinitramide (ADN) were prepared by the electrospinning technique, and the morphology, thermal stability, combustion behaviors, and mechanical sensitivity of the fibers were characterized by means of scanning electron microscope (SEM), transmission electron microscopy (TEM), differential scanning calorimetry (DSC), gas pressure measurement of thermostatic decomposition, laser ignition, and sensitivity tests. The results showed that the prepared fibers with fluffy 3D macrostructure were constructed by the overlap of micro/nanofibers with the energetic particles embedded in the NC matrix. The first exothermic peak temperature (Tp) of the samples containing ADN decreased by 10.1 °C at most compared to that of ADN, and the pressure rise time of all the samples containing ADN moved forward compared to that of the sample containing NC only. Furthermore, ADN can decrease the ignition delay time of NC-based fibers under atmosphere at room temperature from 33 ms to 9 ms and can enhance the burning intensity of NC-based fibers under normal pressure. In addition, compared to the single high explosive CL-20 or RDX, the mechanical sensitivities of the composite materials containing high explosive CL-20 or RDX were much decreased. The positive oxygen balance of ADN and the intensive interactions between ADN and NC can reduce the ignition delay time and promote the burning reaction intensity of NC-based composite fibers, while the mechanical sensitivities of composite fibers could be improved.

Bicyclic High-Energy and Low-Sensitivity Regioisomeric Energetic Compounds Based on Polynitrobenzene and Pyrazoles

With the development of synthetic methodology and crystallography of energetic materials, regiochemistry is becoming popular and vital in the design of versatile energetic compounds as well as in the thorough research on the relationship between structure and property. In this study, two regioisomeric bicyclic energetic compounds based on pyrazole and polynitrobenzene were synthesized simultaneously by a simple synthetic route, and the regioisomers could be purified by a facile approach. It is interesting to note that the ratio of the two compounds changed with temperature. From 80 to 110 °C, the proportion of compound 2 gradually enhanced with the increase in temperature. In addition, the nitramine product of compound 1 was also synthesized. The structural data of compounds 1, 2, and 3 were confirmed by X-ray single-crystal diffraction. The detonation velocities of the new compounds are in the range of 8436–8788 m s–1 and impact sensitivities are between 15 and 27.5 J, of which compounds 2 and 3 not only present superior sensitivities to those of the classical high-energy explosive RDX (7.5 J) but also exhibit comparable detonation velocities to the measured RDX powder (VD = 8796 m s–1), calculated by EXPLO5 as 8788 and 8526 m s–1, respectively. Moreover, compounds 1 and 2 show good thermal stability with decomposition temperatures up to 263 and 287 °C, which is higher than that of RDX (Tdec: 204 °C). All of the above information indicates that these compounds are high-energy, low-sensitivity energetic materials featuring prospective applications.