Explosive Compositions Research Articles

Effects of Aluminum Powder on Ignition Performance of RDX, HMX, and CL‐20 Explosives

As a kind of high explosives, aluminized explosive cannot release the energy maximumly, which is a key problem. Using DTA‐TG equipment, the ignition performance of three kinds of aluminized explosives (RDX, HMX, and CL‐20) with different mass percentages of aluminum powder (0%, 10 wt.%, 20 wt.%, and 30 wt.%) was investigated. The results showed that the energy release of the HMX/Al composite explosive with 10 wt.%, 20 wt.%, and 30 wt.% aluminum powder was only equivalent to 80%, 65%, and 36% of pure HMX, respectively. It was similar to RDX/Al and CL‐20/Al composite explosives, except the CL‐20/Al mixture with 10% aluminum powder. Rather than participating in the ignition and combustion, the aluminum powder does effect the complete reaction of RDX, HMX, and CL‐20 in the initial stage of ignition or in the lower temperature area of the boundary.

Detonation propagation along percolating cluster in composite explosives

The detonation performance of melt-cast plastic-bonded explosives (PBXs) based on high melting explosive octogen (HMX) was studied in the paper. It has been found that the detonation velocity strongly depends from the dispersion distribution of HMX particles: it changes from 7800 to 8700 m/s. We explain this by the possibility of detonation propagation in PBX through different mechanisms, including detonation front propagation along a percolating cluster formed by filler particles. Thus, varying the particle size distribution can bring about one detonation mechanism or another and hence control the energy release dynamics of melt-cast PBXs to attain high efficiency in practice. Experimental results confirm the assumptions.

Theoretical design and prediction of properties for dinitromethyl, fluorodinitromethyl, and (difluoroamino)dinitromethyl derivatives of triazole and tetrazole.

Fluorine- and oxygen-rich compounds are promising as energetic materials for composite propellants, explosives, and pyrotechnics. As an effective and timesaving tool for screening the structures of potential energetic compounds, computer simulation has been widely used to predict the detonation or physicochemical properties of energetic molecules with relatively high precision. In this study, twelve series of dinitromethyl, fluorodinitromethyl, and (difluoroamino)dinitromethyl derivatives of triazole and tetrazole were designed by C- or N-functionalization. Their properties, including density, heat of formation, and detonation properties, were evaluated extensively using volume-based thermodynamic calculations and density functional theory. Among the investigated compounds, 1-(fluorodinitromethyl)-3-nitro-1,2,4-triazole (B3), 1-(fluorodinitromethyl)-4-nitro-1,2,3-triazole (F3), 4,5-bis(fluorodinitromethyl)-1,2,3-triazole (H3), and 5-(fluorodinitromethyl)-tetrazole (I3) displayed excellent integrated performance, that is, high density (≥1.95 g cm−3), oxygen balance (≥2.97%), detonation velocity (>8900 m s−1), and detonation pressure (>40.0 GPa). These results are expected to facilitate the synthesis of a new generation of fluorine- and oxygen-rich energetic compounds. More importantly, our design strategy of constructing nitrogen-rich molecular skeletons with highly dense substituents and highly positive heats of formation by C- or N-functionalization is a valuable approach for developing novel high-energy-density materials with excellent performance.

Highly soluble cellulose nitrates from unconventional feedstocks

Celluloses isolated by the nitric-acid process from domestic unconventional feedstocks such as Miscanthus, oat hulls, and intermediate flax straw were used herein to produce cellulose nitrates (CNs) with a high solubility. For the synthesis of CNs, a commercial technique was employed that involves nitration of cellulose with mixed acid containing 14 wt.% water followed by high-temperature treatment of the nitration product in acidic, alkaline, and neutral environments. The obtained CNs are similar in physicochemical attributes: 12.04–12.26% mass fraction of nitrogen, 10–14 mPa·s viscosity, and 98% solubility in alcohol– ester mixture. FTIR spectra of CNs had absorption bands (2559–2557, 1646–1631, 1277–1271, 825–812, 747–744, 683–680 cm-1) typical of nitro group vibrations. 13C NMR spectra showed chemical shifts representative of 6-mononitrocellulose, 2,6-dinitrocellulose, 3,6-dinitrocellulose, and 2,3,6-trinitrocellulose. DSC revealed that the resultant CNs were highly chemically pure with an exothermic peak at 209–212°С. The CNs obtained from the said unconventional feedstocks were compared with a commercial, highviscosity, lacquer-grade Colloxylin derived from cotton cellulose, as well as with other commercial Colloxylins, to show that the experimental CNs meet the requirements for comercial grades. Thus, the CNs obtained from the unconventional feedstocks are promising candidates as the component of composite explosives.

火炸药行业危险源辨识标准研究

从人的因素、设备、装置、作业场所、作业活动、作业环境等方面，分析提出了火炸药行业危险源辨识的主要内容。以爆炸品为例，分类列出了危险化学品临界量，为重大危险源辨识提供了量化依据。结合实际应用，采用作业条件危险性评价法，给出了混合炸药实验室危险源辨识标准应用案例。 The main content for hazard identification of explosives and powders is proposed in this paper including the angle of human factor, equipments, installations, working places, activities and environments. The boundary of dangerous chemical quantity is given by giving the example of explosive materials in order to provide the quantization evidences of major hazard. An application case of laboratory identification of hazard of composite explosives is offered by combining practical use of risk evaluating methods.

Comparative studies on structures, mechanical properties, sensitivity, stabilities and detonation performance of CL-20/TNT cocrystal and composite explosives by molecular dynamics simulation.

To investigate and compare the differences of structures and properties of CL-20/TNT cocrystal and composite explosives, the CL-20/TNT cocrystal and composite models were established. Molecular dynamics simulations were performed to investigate the structures, mechanical properties, sensitivity, stabilities and detonation performance of cocrystal and composite models with COMPASS force field in NPT ensemble. The lattice parameters, mechanical properties, binding energies, interaction energy of trigger bond, cohesive energy density and detonation parameters were determined and compared. The results show that, compared with pure CL-20, the rigidity and stiffness of cocrystal and composite models decreased, while plastic properties and ductility increased, so mechanical properties can be effectively improved by adding TNT into CL-20 and the cocrystal model has better mechanical properties. The interaction energy of the trigger bond and the cohesive energy density is in the order of CL-20/TNT cocrystal > CL-20/TNT composite > pure CL-20, i.e., cocrystal model is less sensitive than CL-20 and the composite model, and has the best safety parameters. Binding energies show that the cocrystal model has higher intermolecular interaction energy values than the composite model, thus illustrating the better stability of the cocrystal model. Detonation parameters vary as CL-20>cocrystal > composite, namely, the energy density and power of cocrystal and composite model are weakened; however, the CL-20/TNT cocrystal explosive still has desirable energy density and detonation performance. This results presented in this paper help offer some helpful guidance to better understand the mechanism of CL-20/TNT cocrystal explosives and provide some theoretical assistance for cocrystal explosive design.

Application of paper spray ionization for explosives analysis.

A desired feature in the analysis of explosives is to decrease the time of the entire analysis procedure, including sampling. A recently utilized ambient ionization technique, paper spray ionization (PSI), provides the possibility of combining sampling and ionization. However, an interesting phenomenon that occurs in generating negatively charged ions pose some challenges in applying PSI to explosives analysis. The goal of this work is to investigate the possible solutions for generating explosives ions in negative mode PSI. The analysis of 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) was performed. Several solvent systems with different surface tensions and additives were compared to determine their effect on the ionization of explosives. The solvents tested include tert-butanol, isopropanol, methanol, and acetonitrile. The additives tested were carbon tetrachloride and ammonium nitrate. Of the solvents tested, isopropanol yielded the best results. In addition, adding ammonium nitrate to the isopropanol enhanced the analyte signal. Experimentally determined limits of detection (LODs) as low as 0.06ng for PETN, on paper, were observed with isopropanol and the addition of 0.4mM ammonium nitrate as the spray solution. In addition, the explosive components of two plastic explosive samples, Composition 4 and Semtex, were successfully analyzed via surface sampling when using the developed method. The analysis of explosives using PSI-MS in negative ion mode was achieved. The addition of ammonium nitrate to isopropanol, in general, enhanced the analyte signal and yielded better ionization stability. Real-world explosive samples were analyzed, which demonstrates one of the potential applications of PSI-MS analysis.

A kinetic model of the reaction of dispersed aluminum with water under exposure to hydrocavitation and stabilization of the final product

The reaction of dispersed aluminum with water under the exposure of an A-IX-2 aluminum-containing explosive compound to hydrocavitation has been discussed. A kinetic model of the process has been developed; the chemical reaction rate constant has been determined under experimental conditions. It has been shown that the reaction occurs in an autocatalytic mode and can lead to the complete conversion of aluminum to aluminum hydroxide. A method to stabilize dispersed aluminum during the hydrocavitational extraction of a conversion explosive by using a phosphate buffer has been developed. Experiments have shown that the phosphate buffer has a stabilizing effect and leads to an improvement of the characteristics of the resulting industrial explosive composition.

Procesibilnost livenih kompozitnih eksploziva

Tehnologija izrade livenih kompozitnih PBX eksploziva (Plastic Bonded eXplosive), i procesibilnost, ili preradivost, ovih eksplozivnih smeša, može se sagledati sa više aspekata. U ovom radu sagledan je uticaj sastava, kompatibilnosti komponenata i veličine čestica komponenata na sledeće pokazatelje preradivosti i kvaliteta proizvoda: viskoznost smeše, gustinu i poroznost dobijenih ek-sploziva, kao i na brzinu detonacije kao jedan od najvažnijih parametara efikasnosti eksploziva. Tehnologijom livenja izrađeni su eksperimentalni sastavi sa različitim udelom komponenata: oktogena, amonijumperhlorata, metalnog goriva u prahu (aluminijuma, magnezijuma, bora) i hidroksiter-miniranog polibutadienskog veziva. Kompatibilnost komponenata ispitana je metodom mikrokalorimetrije na uređaju LKB BioMonitor microcalorimeter. Kako pakovanje čestica ima direktan uticaj na gustinu, odnosno poroznost finalnog eksplozivnog punjenja, granulometrijska analiza praškastih komponenata izvršena je koristeći set sita i na Fišerovom podsitovnom analizatoru. Gustine su određene na uzorcima uzetim iz različitih segmenata eksplozivnih punjenja, prema metodi MIL 286C, a potom su određene i poroznosti. Neophodno je da PBX smeša u dovoljno dugom vremenu ima pogodnu livljivost (“pot life”), odnosno da postoji zadovoljavajuća vremenska zavisnost viskoziteta. Ispitano je kako se s vremenom menja viskozitet neumrežene smeše analiziranih sastava, koristeći viskozimetar Brookfield RVT. Brzine detonacije su određene primenom elektrokontaktnih sondi i elektronskog brojača Pendulum CNT-91.

Synthesis of nano-diamond/alumina composite by detonation method

The nano-diamond/alumina composite was prepared by detonation with the boron-nano diamond, the aluminum isopropoxide and the RDX as raw materials in the present paper. The phase, morphology and structure of the explosive products were analyzed by X-ray diffraction, field emission scanning electron microscopy and transmission electron microscopy. The results indicated that the pressure and the temperature generated by explosion led the alumina to tightly coat the nano-diamond particles and to the composite nano-diamond/alumina particles formation, bonding with alumina. The size of the nano-diamond particle remained unchanged at 2–10nm and the composite particle size increased to 50–200nm. The alumina coating layer increased antioxidant properties of nanodiamond, increased the grain size composition of the polycrystalline powder. The Boron element had certain effects onto the oxidation coating, such as the diamond particles oxidation prevention during the preparation, the graphitization losses inversion, the detonation temperature increase and the high-temperature alumina composite particles proportion increase. The aluminum reduced gradually, which could lead to an increase in the density of the explosive composition, the detonation synthesis temperature to be reduced, the high-temperature alumina (such as the alpha-Al2O3) to decrease and all other alumina crystal types to increase.

Electrospray preparation and thermal properties of the composites based on RDX

Composite explosives based on 1,3,5-trinitro-1,3,5-triazinane (RDX) with different additives were prepared by electrospray method. The morphology and particle size, crystal structure and thermal decomposition properties were characterized by the scanning electron microscope, the laser particle size analyzer, the X-ray diffractometer and the differential scanning calorimeter, respectively. In terms of the morphologies of the composites, the particle sizes were in the range of 1–4 μm. The crystal types of the RDX/PVAc, RDX/PVB, RDX/F2604 and RDX/DOS composites were similar to those of raw RDX. The apparent activation energy (145.678 kJ mol−1) and the critical temperature (486.49 K) of the RDX/PVB composites were found to be the lowest among all involved composites. The compatibility of the RDX/F2604 and RDX/DOS composites was both in level A. The thermal stabilities of the composites decreased in the order RDX/F2604 > RDX/DOS > RDX/PVAc > RDX/PVB.

Thermal Behaviors and Their Correlations of Mg(BH4)2-Contained Explosives

ABSTRACTIn order to explore the effect of metal hydride on energetic materials’ thermal behaviors and their correlations, we studied the heats of combustion and detonation of RDX, TNT, and Mg(BH4)2-containing explosives both theoretically and experimentally. The results showed that Mg(BH4)2 can significantly improve the energy of explosive. As the mass fraction of Mg(BH4)2 increases, the combustion heat of composite explosives increases gradually, while the combustion efficiency decreases. When its mass fraction is about 30%, the theoretical heats of detonation of RDX/Mg(BH4)2 and TNT/Mg(BH4)2 reach maximum, which are 7418.47 and 7032.46 kJ/kg, respectively. When we compared the errors between calculation and experimental values, we found that L-C method is more accurate in calculating oxygen-enriched and oxygen-balanced explosives, and that minimum free energy method is more suitable for seriously negative oxygen-balanced explosive. For single explosive, there are three kinds of relationships between heat of combustion and detonation according to the oxygen balance. For Mg(BH4)2-containing explosives, the relationship is in accordance with Boltzmann function.

Nitrato Functionalized Polymers for High Energy Propellants and Explosives: Recent Advances

Future propellants and explosive research focus on developing compositions with less vulnerability without compromising performance. This has provided impetus for research in the area of high energy materials and compounds free from pollution, for safe handling, high performance, reliability and reproducibility. The energetic oxidizers and energetic binders are being developed in this scenario for use in composite propellants and explosives. In a propellant, the binder holds together the matrix containing solid oxidizer particles and finely divided metal particles. It provides structural integrity and aid the combustion of the propellant. Any new development in this area wherein the binder can contribute to the energetic is of immense importance. This can be achieved by incorporation of energetic groups such as nitrato (−ONO2), azide (−N3) or flurodinitro CF(NO2)2 as side chain or on to the existing polymer backbone. Among these, nitrato functionalized energetic binders can find application in myriad areas like boosters, plastic bonded explosives, gas generators and pyrogen igniters. The present article is a concise review on various types of nitrato binders; their synthesis, properties and their propellant studies. Copyright © 2017 John Wiley & Sons, Ltd.

Effect of the Al/O ratio on the Al reaction of aluminized RDX-based explosives

Aluminum (Al) powders are used in composite explosives as a typical reducing agent for improving explosion performance. To understand energy release of aluminum in aluminized RDX-based explosives, a series of thermal measurements and underwater explosion (UNDEX) experiments were conducted. Lithium fluoride (LiF) was added in RDX-based explosives, as a replacement of aluminum, and used in constant temperature calorimeter experiments and UNDEXs. The influence of aluminum powder on explosion heat () was measured. A rich supply of data about aluminum energy release rate was gained. There are other oxides (CO, CO, and HO) in detonation products besides alumina when the content of RDX is maintained at the same levels. Aluminum cannot fully combine with oxygen in the detonation products. To study the relationship between the explosive formulation and energy release, pressure and impulse signals in underwater experiments were recorded and analyzed after charges were initiated underwater. The shock wave energy (), bubble energy (), and total energy () monotony increase with the Al/O ratio, while the growth rates of the shock wave energy, bubble energy, and total energy become slow.

Laser‐induced Deflagration for the Characterization of Energetic Materials

Standard propellant and detonation tests typically performed to characterize the performance of energetic materials require large quantities of material (at least tens of grams) and can be expensive and time-consuming. This work introduces a method for characterizing the deflagration of energetic materials in a laboratory setting, using only 15–20 mg of energetic material. Temperature, energy release and emission signatures were measured and analyzed for the laser-induced deflagration of 8 different conventional military explosives. Graphite nanoparticles and micron-sized aluminum powder were added to the explosive compositions to investigate their effect on the emission signatures. A high-speed color camera recorded the deflagration events and was utilized as a full-color pyrometer to calculate the average temperatures and image hotspots; the temperatures maps were compared to those measured by conventional two-color pyrometry. The laboratory-scale method presented here can be applied to novel energetic materials under development that may be available only in limited quantities to evaluate their potential as propellants or reduced emission signature explosives prior to scale-up.

Influence of hot rolling on the interface microstructure and mechanical properties of explosive welded Mg/Al composite plates

Abstract

A computational study on new oxidizers as replacements for ammonium perchlorate: tetranitroacetimidic acid and tetranitroacetamide

High energetic materials tetranitroacetimidic acid (TNAA) and tetranitroacetamide (NTNAA) with positive oxygen balance (OB = 30%) are highly potential replacements for ammonium perchlorate (AP). Tautomerization from TNAA to NTNAA is feasible, reflected by the activation energy of 160.2∼170.0 kJ/mol. No transition state appears on the C–NO2 bond breaking, which triggers pyrolysis of two compounds. The C–NO2 bond dissociation energies are 116.1∼167.2 kJ/mol and 120.4∼174.6 kJ/mol for TNAA and NTNAA, respectively. The chemical stabilities of TNAA and NTNAA are higher than that of the insensitive explosive 1,1-diamino-2,2-dinitroethylene. TNAA and NTNAA possess lower impact sensitivities (h50 ≥ 77.51 cm) than AP does. Detonation properties of the composite explosives containing TNAA or NTNAA are comparable with that of the composite explosives containing AP. The acceptable stabilities, highly positive OB, environmentally friendly decomposition products, and the comparable ability to improve detonation performance of composite explosives show that TNAA and NTNAA are potential replacements for AP as an oxidizer used in composite explosives.

Studies of Confined Explosions of Composite Explosives and Layered Charges

Studies of Confined Explosions of Composite Explosives and Layered Charges

Investigation of Fireball Temperatures in Confined Thermobaric Explosions

AbstractNew composite metalized explosives were studied. The explosives consisted of two different types of macroscopic granular multi‐component RDX‐based formulations. In a 0.15 m3 explosion chamber, fireball temperature histories for numerous cylindrical pressed and layered charges made from the composites were determined using optical spectroscopy. For comparison, charges consisting of simple mixtures instead of the composites as well TNT and RDX phlegmatized (RDXph) charges were also studied. The influence of the structure of the macroscopic granular composite, the charge type (pressed charge or layered charge with an RDXph core), oxygen availability (air or argon atmosphere) and aluminum particle size on the fireball temperature and the combustion of the aluminum powder were determined. The measured temperatures were compared with the theoretical ones calculated by assuming different activity of the aluminum fuel.

Point measurements of ambient biological noise before, during, and after multiple underwater detonation events over coral substrate off the southern coast of Oahu, Hawai

Measurements were taken of background noise at the U.S. Navy's Pu‘uloa Underwater Detonation Range off the south coast of O‘ahu during a U.S. Navy underwater explosive training exercise in shallow water (10-18 m) where distance from the detonation site, charge size, and explosive composition were controlled. The autonomous recording unit was deployed approximately 1500 m from the detonation location. The combined data from the paired low (-220 dB re 1 V /μPa) and high (-170 dB re 1 V /μPa) sensitivity hydrophones gives an approximately 100 dB dynamic range view of each event. Each trial consisted of three replicate events per charge weight (2.2, 4.5, and 8.6 kg) for a total of nine explosive events over the coral substrate. An analysis of the background noise environment immediately before and after each replicate is presented using metrics such as spectral probability density. Results are considered in the context of typical coral reef noise including discussion of snapping shrimp noise (one of the dominant features of the soundscape) before and after each event. [Work supported by U.S. Pacific Fleet.]