Mixed Explosives Research Articles

Improved method for prediction of detonation velocity for C−H−N−O based pure, mixed and aluminized explosives

AbstractAn improved method is presented for the prediction of detonation velocity of C−H−NO based pure, mixed, and aluminized explosives. The new empirical relation is based on calculated values of the heat of detonation and the number of moles of gaseous detonation products. A constant of the empirical relation has been found using regression analysis of 74 data points of pure and mixed explosives as well as 22 data points of aluminized explosives. The value of the constant is found to be 1.00 with R2 value of 0.96. Proposed empirical relation has been validated by comparing predicted values of detonation velocities with measured values for TNT, HMX/RDX‐TNT‐Al and HMX‐TNT based explosives. Experimental measurement of detonation velocity has been carried out using pin‐ionization method on cylindrical explosive charges of diameter 50 mm and height 150 mm. The predicted values of detonation velocities are in good agreement with measured values with a root mean square error of 1.28 %. The validation of the new relation has also been carried by comparing calculated values of detonation velocities using present and literature methods with reported experimental values.

Effects of aluminum particle size on metal acceleration for CL-20-based aluminized explosives

The addition of aluminum (Al) powder to CL-20 significantly enhances the overall energy of mixed explosives. Nonetheless, the metal acceleration ability of explosion after Al addition shows unpredictable behavior due to the unclear reaction characteristics of Al in CL-20 detonation products. This study utilizes a plate push test employing CL-20-based aluminized explosives to acquire the reaction degree formulation for Al powder with varying particle sizes in a CL-20 detonation environment. Moreover, it elucidates the reaction mechanism of microsized Al particles during the initial phase of afterburning. Additionally, this reaction formulation enhances the equation of state (EOS) for CL-20-based aluminized explosives. Subsequently, the new EOS is implemented in LS-DYNA to simulate the metal flyer acceleration process. Consequently, the impact of Al particle size on the metal acceleration capability of aluminized CL-20 is examined. The results indicate that for CL-20-based aluminized explosives with 15 % Al content, an optimal Al particle size of 34.12 μm exists when the particle size exceeds 10 μm. This optimum increases the speed of the driving metal plate by 7.4 % compared to CL-20/LiF explosives.

Determination of hexogen recovered from scrapped 2-chlorobenzalmalononitrile mixed explosives by gas chromatography

This study focuses on the extraction of Hexogen (RDX) from decommissioned CS mixed explosives using the Soxhlet extraction method. Recrystallization using a solution of rtnanol is utilized to purify the extract and remove impurities, such as CS. Qualitative analysis is conducted using Fourier transform infrared spectroscopy and a melting point tester. Additionally, gas chromatography is employed for qualitative and quantitative analysis of the recovered RDX. The experimental results demonstrate that the recovered RDX exhibits a strong linear relationship at concentrations ranging from 500 mg/L to 6000 mg/L, with a correlation coefficient of r = 0.9999 and a relative standard deviation (RDS) of ≤5% (n = 6). Furthermore, the purity of the recovered RDX can reach 100% through secondary recrystallization using ethanol. The quantitative analysis of RDX by gas chromatography offers the advantages of operating cylinder, high accuracy and high sensitivity.

Rapid identification of cocrystal components of explosives based on Raman spectroscopy and principal component analysis

Energetic cocrystal materials are considered to be one of the important directions for the development of energetic materials, due to their high energy density and low sensitivity. However, there is still a lack of effective methods to carry out rapid structural and purity identification. Herein, we explored a method for rapid identification and identification of unknown components extracted from CL-20/MTNP and CL-20/HMX cocrystal processes based on Raman spectroscopy combined with principal component analysis (PCA). Thirty sets of cocrystal and 30 sets of mixed explosives were randomly selected as the training set and 10 sets each as the validation set. The principal components were extracted by dimensionality reduction of the collected Raman spectra using the principal component sub-featured clustering algorithm of chemometrics. The region identification structure formed by different principal components allows intelligent output of whether the sample was cocrystal or not. The results show that the cumulative contribution rate of the three principal components in the sample set was 98.7 %. The confidence ellipses of the validation set were all well distributed within the confidence ellipses of the training set. And the structure identification results of explosive cocrystals were output quickly, accurately and intelligently. Therefore, this method shows good potential application value in the rapid structural identification of other complex mixtures such as energetic even pharmaceutical cocrystals.

Comprehensive atomic insight into the whole process of thermolysis of HMX/CL-20 mixed explosives based on a brand-new layered model of mixed explosives

Comprehensive atomic insight into the whole process of thermolysis of HMX/CL-20 mixed explosives based on a brand-new layered model of mixed explosives

Research on inhibitory effect of mixed suppressants CaCO3, KCl, and K2CO3 on coal dust explosion pressure

To discuss the inhibitory effect of micrometer scale coal dust explosion pressure, three types of explosion suppressants are selected for mixed explosion suppression. The results indicate that the coal dust explosion process includes three stages: accelerated and decelerated energy release, as well as energy dissipation. When using explosive suppressants, K2CO3 has the greatest inhibitory effect on coal dust explosion, followed by KCl, and CaCO3 has the smallest effect. The K2O, K2O2, and KOH generated by the thermal decomposition of K2CO3 can also block the heat transfer of coal dust, playing a good role in suppressing explosions. The explosion suppression effect of mixing CaCO3 and K2CO3 is better than that of mixing CaCO3 and KCl, and is worse than the explosion suppression effect of using K2CO3 alone. The synergistic effect of KCl and K2CO3 mixed explosion suppression makes the suppression effect better than using K2CO3 alone. This is because KCl generates K2O during pyrolysis, promoting the dynamic equilibrium of K2CO3 explosion suppression process. This makes mixed explosion suppression more worthy of attention and adoption when considering purchase costs.

Selection of the optimal composition and analysis of the detonating characteristics of low-density mixed explosives applied to break thin ore bodies

Purpose is to select the optimal composition of the mixed low-density explosive (Es) applied in the form of blasthole charges which provide high efficiency of blasting operations while mining of thin ore deposits. The abovementioned becomes possible while studying features of the foamed polystyrene chemical decomposition and gasification; role of additional water components as well as catalyzator being sodium carboxymethyl cellulose; and analysis of explosive characteristics of the compositions. Methods. The research involved lab-based experiments to define application efficiency of the recommended low-density blasting agents through identification of the basic explosive characteristics of the model mixed Es. Findings. The optimal composition of the mixed low-density Es has been developed. It consists of ammonia nitrate, diesel fuel, granulated foamed polystyrene, water, and sodium carboxymethyl cellulose to be used to break thin ore bodies. Owing to it, the possibility has arisen to control over a wide range both detonation velocity and pressure of blasting fumes during the charge density increasing or decreasing. The main detonative characteristics of the proposed compositions of low-density Es have been determined helping perform explosive rock mass loading in terms of extremely low values of both energy and explosive characteristics. The developed composition of the mixed low-density Es makes it possible to control quantity of Es energy in a volume well unit by means of increase or decrease in the charge energy concentration depending upon the changes in the rock mass resistance; in such a way, efficient breakage of thin ore bodies is provided inclusive of less dilution indicators. Originality. For the first time, dependence of the relative efficiency of the mixed low-density Es upon the foamed polystyrene volume content has been identified as well as dependence of pressure of blasting fumes upon the charging density. Practical implications are the development of procedures for blasting operations while thin ore body mining. The procedures are based upon formulating of the optimal composition of low-density Es differing in its simplicity, safety, and efficiency; and helping reduce prime cost of the extracted mineral at the expense of the decreased degree of the ore dilution. An empiric formula to define specific consumption of the low-density Es has been proposed for Akbakay mine.

Experimental study on gas and coal dust explosive overpressure and flame dynamic characteristics in an engineering-level test roadway

The continuous development of coal science and technology has made gas and coal dust explosion disasters an important factor that restricts efficient and intelligent coal mining, which seriously threatens the safe production process of coal mines. To explore the gas and coal dust explosive overpressure and flame propagation characteristics in an actual roadway, the dynamic characteristics of gas and coal dust mixed explosion propagation and evolution laws of explosion flames were investigated using an integrated explosion test system and a high-speed image acquisition system in an engineering-level test roadway with a length of about 700 m and a cross-sectional area of 7.2 m2. Experimental results showed that the peak overpressure measured at each measuring point during the propagation process of explosion shock wave in the roadway did not rise or fall monotonously but fluctuated. The power of explosion shock wave was significantly strengthened by adding coal dust, while the flame propagation speed sharply increased in a certain zone, which generally showed a first increasing and then declining trend. In addition, the flame was blue white after the gas in the roadway was ignited, developed in an irregular shape, and ignited the surrounding combustible gas soon, which further ignited the coal dust under the combined action of pressure wave and flame front. In this case, the flame was deep yellow on the whole. The gas and coal dust explosion flame propagated along the longitudinal section above the roadway, and the flame propagated at an accelerated speed on the transverse section due to the disturbance of obstacles. The study results will provide an important theoretical basis for the R&D of technical active explosion suppression equipment in coal mines and the improvement in their installation technologies.

Properties of Mixed Crystal Coprecipitation Substances of Ammonium Nitrate and Potassium Perchlorate Prepared by the Evaporative Solvent Method.

Ammonium perchlorate (AP) has been widely used as an oxidizer in propellants and military mixed explosives in recent years. However, its high characteristic signal, environmental pollution, and poor detonation performance have prompted the industry to seek alternatives to AP. Ammonium nitrate (AN) is a suitable substitute due to its low characteristic signal, lack of pollution, and excellent detonation performance. However, its room-temperature phase transition and hygroscopicity affect its practical use. In this work, we prepared mixed crystal coprecipitation (MCC) materials of AN and potassium perchlorate (KP) using the evaporative solvent method. The characterization of AN/KP MCCs was carried out by combining TG-DSC, XRD, FT-IR, and SEM analysis, revealing that the formation of MCCs by AN and KP is due to ion exchange between the two components. AN/KP MCCs not only solve the problem of room-temperature phase transition in AN but also reduce its hygroscopicity. Furthermore, AN/KP MCCs have mechanical sensitivity, explosive performance, and specific impulse similar to pure AN, but compared to AN, AN/KP MCCs have higher density, effective oxygen content, and thermal stability. Compared with existing oxidizers AN, AP, and KP, AN/KP MCCs with high density, low sensitivity, high oxygen content, and high safety have obvious advantages and have good prospects in the application of oxidizers in solid propellants and military mixed explosives.

Following the Decomposition of Hydrogen Peroxide in On-Site Mixture Explosives: Study of the Effect of the Auxiliary Oxidising Agent and Binder.

The issues of safety and its impact on both human health and the environment are on-going challenges in the field of explosives (EXs). Consequently, environmentally-friendly EXs have attracted significant interest. Our previous work, dedicated to on-site mixed (OSM) EXs utilising concentrated hydrogen peroxide (HTP) as an oxidising agent, revealed that the gradual decomposition of HTP may be harnessed as an additional safety measure, e.g., protection from theft. The rate of HTP decomposition is dependent on the OSM components, but this dependence is not straightforward. Relevant information about the decomposition of HTP in such complex mixtures is unavailable in literature. Consequently, in this work, we present a more detailed picture of the factors influencing the dynamics of HTP decomposition in EXformulations. The relevant measurement and validation methodology is laid out and the most relevant factors for determining the rate of HTP decomposition are highlighted. Among these, the choice of auxiliary oxidising agent is of particular relevance and it can be seen that the choice to use ammonium nitrate (AN), made in previous works dealing with HTP-based EXs, is sub-optimal in terms of maintaining the stability of HTP. Another important finding is that glass microspheres are not as inert to HTP as would be expected, as replacing them with polymer microspheres significantly slowed the decomposition of HTP in the investigated OSM samples.

Application of TNBA-based low eutectic mixture in melt-cast explosives

ABSTRACT In this work, two TNBA-based low eutectic mixtures, TNBA/TNAZ (TZ) and TNBA/DNTF (TD), as well as eight TNBA-based melt-cast explosives, TNBA/TNAZ/RDX (TZR), TNBA/TNAZ/HMX (TZH), TNBA/TNAZ/TKX-50 (TZT), TNBA/TNAZ/CL-20 (TZC), TNBA/DNTF/RDX (TDR), TNBA/DNTF/HMX (TDH), TNBA/DNTF/TKX-50 (TDT) and TNBA/DNTF/CL-20 (TDC), were developed as structural models. A molecular dynamics approach was used to model the cohesive energy density, binding energy, and mechanical properties of these explosives. Moreover the thermal decomposition properties and mechanical sensitivity were characterized via DSC and mechanical sensitivity tests. Finally, the EXPLO-5 software predicted the detonation properties and detonation products of the aforementioned 10 mixed explosive systems. The results showed that the four mixed explosives of TDT, TDH, TZC, and TDR had excellent performance in cohesive energy density, binding energy, and material rigidity, respectively. The temperature difference was comparatively significant between the melting temperature and decomposition temperature of the eight types of mixed explosives, up to 170.60 K, with TDH and TZH having the highest thermal decomposition temperature at approximately 520 K. The six kinds of mixed explosives of TZR, TZH, TZT, TDR, TDH, and TDT had moderate mechanical sensitivities. . The five types of mixed explosives, TZT, TZC, TDH, TDT, and TDC, had the greatest detonation velocity.

Study on the Multiphase Flow Mechanism of Coupling Gas-dust Coupling Explosion in Open and Closed Vessels

In order to study the flame propagation characteristics and influencing factors of gas-coal dust mixed explosion in containers, this paper quantitatively explores the effect mechanism of two-phase concentration ratio and closed section restraint mode on gas-coal dust coupling explosion by numerical simulation, comprehensively considering the coal pyrolysis model and the two-phase mass and heat transfer model. The current research results show that: in closed pipeline, with the increase of pulverized coal concentration, the gas explosion intensity of lean fuel shows a trend of first increase and then decrease. Under the methane concentration of 7%, the optimal concentration of pulverized coal is 100 g/cm3; a similar trend also occurs in the open pipe. Secondly, the two-phase flame propagation speed in the closed pipe is faster than that in the open pipe. The research results of this paper can provide scientific guidance for the prevention and control of coal mine explosion accidents.

The effect of Mg(BH4)2 on the energy characteristics of RDX based aluminized explosives

This paper mainly discusses the effect of Mg(BH4)2 on RDX-based aluminized explosives' energy characteristics. RDX/Mg(BH4)2, RDX/Al/Mg(BH4)2, RDX/AP/Al/Mg(BH4)2 mixed explosives were prepared by molding power method. The influence of energy storage materials on the performance of mixed explosives was discussed by adjusting the proportion of Mg(BH4)2. The impact sensitivity, friction sensitivity, detonation heat experiment, and XPS experiment were carried out for the mixed explosive. The mechanical sensitivity, energy characteristics, and the products after the explosion of the mixed explosive were analyzed. Through the above experiments, it is concluded that Mg(BH4)2 can effectively improve the energy characteristics of RDX, but its safety will become worse after being prepared by a simple mixing method, and the use of the molding power method can effectively reduce the sensitivity. As the mass fraction of Mg(BH4)2 increases and Al decreases, the detonation heat of explosives decreases gradually. Mg(BH4)2 made the oxygen balance of mixed explosives more negative has been considered as a potential reason. Analysis of the detonation heat solid products by XPS found that, unlike our expected results, the product contained a large amount of low calorific value of B2O2 instead of B2O3, which may be a crucial reason. This paper provides a reference for the application of Mg(BH4)2 in energetic materials and is of great significance for the development and application of new materials in energetic materials.

Atomic insights into the thermal decomposition mechanism and cluster growth law of nanoscale HMX and LLM-126 mixture: A ReaxFF-lg molecular dynamics study

In this paper, the thermal decomposition process and cluster growth law of the HMX/LLM-126 nanoscale mixture system were studied by ReaxFF-lg combined with DFT, and the thermostability of the mixture system with a molar ratio of 1:1 was investigated. The results show that clusters can be formed between HMX and LLM-126 in the mixture system, which effectively delays the cracking speed of the HMX structure. Meanwhile, NO2 generated from the initial decomposition of HMX will accelerate the denitration process of LLM-126. The decomposition process of HMX is mainly a continuous denitration until the structural ring-opening disintegration, the initial decomposition step is C4H8O8N8 => C4H8O6N7 + NO2. In contrast, the initial decomposition of LLM-126 is dominated by intramolecular hydrogen transfer reactions and the generation of dimer clusters, followed by the detachment of nitro and bitter amino groups, and finally the cleavage of the pyridine ring. The intramolecular hydrogen transfer process of LLM-126 is the transfer of H on -NH- to the adjacent nitro group. After LLM-126 was added to the HMX system, the oxygen balance of the system increased, and the N content, exothermic rate, and the number of final products decreased significantly compared with the HMX pure component system. Also, the number of clusters generated, and the maximum cluster weight increased significantly. These phenomena are important reasons for the improved thermostability of the mixture system compared to the pure HMX system. This work can provide a theoretical basis for the design and application of nanoscale high-energy thermostable mixed explosives.

Study on the Crystal Structure and Properties of a New Crystal Form: ζ-HMX

HMX is often used in military explosives and propellants due to its superior explosive properties. There already exist five different crystal forms of HMX. This paper synthesized a new form of ζ-HMX, in which the crystal is a trigonal system, and the space group is R3̅c. The crystal density is 1.330 g cm–3, and the calculated porosity is 31.0%, which provides the possibility for adsorption inside molecules and coating of military explosives. The crystal structure was tested by an X-ray single-crystal diffractometer. The thermal analysis, infrared spectroscopy, powder X-ray diffraction (XRD), explosion performance, and safety performance were compared with the most stable-state β-HMX. The detonation velocity of ζ-HMX is 7530 m s–1, and the detonation pressure is 20.03 GPa. It has certain advantages in sensitivity, and this experimental result is in good agreement with the theoretical calculation of the crystal structure and electronic energy. This study has a certain reference value for HMX application in mixed explosives and propellants.

Experiments and simulations on cookoff characteristics of a DNAN based cast explosive

AbstractIncidents caused by fire and combat operations can heat energetic materials that may lead to thermal explosion and result in structural damage and casualty, thus understanding the response of energetic materials to thermal insults is crucial for the safety design and assessment of insensitive munitions. In the present work, cookoff characteristics of a new DNAN‐based cast explosive ROL‐1 are systematically analyzed. Small‐scale slow cookoff experiments were performed and an overall reaction kinetic model including the melt‐ignition model for DNAN was developed and implemented in FLUENT. The simulated results agree well with the experimental data, which verifies the validity of the model. The large‐scale fast cookoff experiment and simulation were then performed. Ignition behaviors as well as the reaction mechanism of ROL‐1 under slow and fast cookoffs are investigated. The heat generation rates are highly correlated to the temperature gradient, liquid phase fraction, and ignition behaviors in ROL‐1. The ignition of ROL‐1 happens at around 550 K, delaying the ignition temperature of the HMX (493 K) by nearly 60 K, indicating the potential substitution of NTO for HMX. The safety of ROL‐1 has proven to stand out in comparison to a range of mixed explosives.

Multi-aspect simulation insight on thermolysis mechanism and interaction of NTO/HMX-based plastic-bonded explosives: a new conception of the mixed explosive model.

Reactive molecular dynamics (RMDs) calculations were used to determine, for the first time, the process of thermolysis of the mixed explosives, including 3-nitro-1,2,4-triazol-5-one (NTO) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoline (HMX). Significantly, this is the first time that a layered model for mixed explosives, which is an extreme innovation of mixed explosive models was adopted. It is shown that a large amount of NO2 in the HMX and OH groups generated by the decomposition of HNO2 has a favorable effect on the thermolysis of NTO, as further validated by a reduction in the activation energy of NTO/HMX. The amount of H2O and N2 in the resulting products increased significantly, but the amount of NH3 changed slightly. The analysis results correspond to the change in chemical bonds. Whenever there is an increase in temperature, the time for the maximum number of clusters to appear is shortened accordingly. In addition, the acidity of NTO has been considered. An independent gradient model based on Hirshfeld partition (IGMH) and atoms in molecule (AIM) analysis of NTO/HMX was implemented. The relatively strong hydrogen bonds indicate that HMX can inhibit the acidity of NTO and is beneficial for the wide application of NTO/HMX-based plastic-bonded explosives (PBXs).

Study on the prediction and inverse prediction of detonation properties based on deep learning

The accurate and efficient prediction of explosive detonation properties has important engineering significance for weapon design. Traditional methods for predicting detonation performance include empirical formulas, equations of state, and quantum chemical calculation methods. In recent years, with the development of computer performance and deep learning methods, researchers have begun to apply deep learning methods to the prediction of explosive detonation performance. The deep learning method has the advantage of simple and rapid prediction of explosive detonation properties. However, some problems remain in the study of detonation properties based on deep learning. For example, there are few studies on the prediction of mixed explosives, on the prediction of the parameters of the equation of state of explosives, and on the application of explosive properties to predict the formulation of explosives. Based on an artificial neural network model and a one-dimensional convolutional neural network model, three improved deep learning models were established in this work with the aim of solving these problems. The training data for these models, called the detonation parameters prediction model, JWL equation of state (EOS) prediction model, and inverse prediction model, was obtained through the KHT thermochemical code. After training, the model was tested for overfitting using the validation-set test. Through the model-accuracy test, the prediction accuracy of the model for real explosive formulations was tested by comparing the predicted value with the reference value. The results show that the model errors were within 10% and 3% for the prediction of detonation pressure and detonation velocity, respectively. The accuracy refers to the prediction of tested explosive formulations which consist of TNT, RDX and HMX. For the prediction of the equation of state for explosives, the correlation coefficient between the prediction and the reference curves was above 0.99. For the prediction of the inverse prediction model, the prediction error of the explosive equation was within 9%. This indicates that the models have utility in engineering.

Effects of heat transfer mechanism on methane-air mixture explosion in 20 L spherical device

This study developed a model of methane one-step combustion mechanism based on the CFD code GASFLOW-MPI to understand the influence mechanism and degree of influence of heat transfer mechanism on methane explosion. Moreover, this study proposed the addition of heat transfer mathematical models using GASFLOW-MPI, including thermal radiation and convection heat transfer. Further, the effects of thermal radiation and convective heat transfer on the shock wave during a methane explosion in a 20 L spherical explosion tank were studied through numerical simulation and the results were compared with the experimental data. The numerical simulation results were found to reasonably predict the peak pressure value and pressure decay process of a methane explosion. In addition, through comparisons of the effects of adiabatic and numerical simulations considering heat loss, the peak pressure of gas explosion calculated via adiabatic simulation were found to be overestimated. Moreover, during the methane-air mixed explosion experiment in the 20 L spherical device, the heat loss was observed to be primarily caused by heat radiation, accounting for more than 76.01% of the total heat loss, followed by convection heat transfer, accounting for 23.99% of the total heat loss. The research results showed that heat loss significantly influenced the methane explosion process. Additionally, for the methane-air mixture explosion experiment in a 20 L spherical device, thermal radiation was the most critical factor that resulted in heat loss in the methane explosion process. Therefore, the influence of thermal radiation and convective heat transfer mechanism on methane explosion must be considered in the numerical simulation of a methane explosion.

Temperature and Pressure Effects on HMX/Graphene via ReaxFF Molecular Dynamics Simulations

Studying the thermal decomposition of energetic materials at high temperatures can provide detailed reaction and mechanistic information, which is critical for understanding the reactivity of energetic materials, designing mixed explosives, and achieving improved safety. In this work, the effects of temperature and pressure on graphene (Gr)-based HMX crystals were investigated using ReaxFF molecular dynamics simulations. The thermal decomposition processes of perfect HMX crystals, HMX crystals with (001), (010), or (100) crystal planes, and HMX/Gr mixed systems were studied at high temperatures and pressures. In the mixed systems, different configurations of HMX molecules adsorbed on the Gr surface were confirmed by theoretical calculation methods. With the pressure ranging from atmospheric pressure to 31 GPa, 3, 5, and 3 configurations of HMX adsorbed on the Gr surface were identified for the (001)/Gr, (010)/Gr, and (100)/Gr systems, respectively. The time-dependent curves for the evolution of fragments, intermediates, and pyrolysis products were analyzed. The rate constant for the thermal decomposition of HMX was found to be significantly affected by the addition of Gr. In particular, the thermal decomposition reaction was strongly inhibited in the (010)/Gr system. This result indicates that Gr promotes an anisotropic thermal effect, resulting from the steric hindrance of the NO2 functional groups and the interaction between Gr and HMX molecules. Gr also affected the initial reaction pathway of homolytic N–NO2 bond cleavage, with C=O, C–OH, and C–OC bonds on the Gr surface participating in the formation of nitro radicals and HONO.