Explosive Particles Research Articles

CL-20 based energetic thin films: Micro-spray molding and micro-detonation

In order to solve the problem of low sample forming efficiency and uncontrollable crystal type in inkjet printing, a formula of explosive ink suitable for micro-spraying is designed by using hexanitrohexaazaisowurtzitane (CL-20) as the main explosive, the compound of polyazide glycidyl ether and ethyl cellulose as the bonding system, ethyl acetate as the solvent, and the refined ε-CL-20 as the seed crystal in this paper. The optimal process conditions were determined, and under the optimal process conditions, the explosive ink is written on an aluminum substrate or a glass substrate by micro-spraying direct writing technology, and CL-20 based energetic thin film forming samples are characterized. The results show that the CL-20 crystal form in the sample is ε type and the molding effect is good. The optimum process conditions are as follows: the nozzle has an air pressure of 0.02 MPa, the height is 40 mm, the spraying rate is 0.4 ml min−1, and the substrate temperature is 50°C. The explosive particles in the energetic thin films are spherical. The particle size is about 10 µm, and the particle size distribution is relatively uniform. The density of the composite is 1.567 g cm−3, and the molding density can reach 80.2% of the theoretical density. The activation energy is 242.07 kJ mol−1. The characteristic drop height H50 is 38.5 cm. When the charge width is 0.8 mm, the critical size of the detonation is 0.8 × 0.03 mm2. The detonation wave formed after the shaped sample is detonated in a small groove with a cross-sectional dimension of 1.0 × 1.0 mm2 can successfully pass through multiple continuous 90° charging corners.

Fabrication of nitrocellulose‐based nanoenergetic composites, study on its structure, thermal decomposition kinetics, mechanism, and sensitivity

AbstractIn order to investigate the thermal decomposition kinetics and mechanism of nitrocellulose (NC) based nitramine explosives nanocomposite energetic materials, this work prepares NC/RDX (cyclotrimethylenetrinitramine), NC/HMX (cyclotetramethylenetetranitramine), and NC/CL‐20 (hexanitrohexaazaisowurtzitane) composites by a combined sol‐gel and the freeze‐drying technology. The structure is systematically investigated and the results reveal that the explosive particles are dispersed, filled, or embedded homogenously in the gel matrix of NC, thereby restricting the crystal growth of RDX, HMX, CL‐20 particles to coarse and achieving submicron/nanometer. The thermal analysis of composites exhibits much lower peak temperature compared with raw explosive crystal, furthermore, the activation energy (Ea) of composites is also lower than that of both NC and explosives. Hence, the unique structure of NC gel matrix embedded explosives inside demonstrated different mechanism of decomposition. Concretely, the rupture of the H‐NCO = O bond in the cross‐linked structure is detected firstly, subsequently, the macromolecular chains’ scission site of gel firstly occurs at ‐C‐O‐C‐ in the ring, and then the scission of ‐NO2 (from NC or explosive crystals) bonds happened. Hence, this study may provide promising fabrication strategy and basic theory for the application of NC‐based nanocomposite energetics in high‐energy propellants and explosives.

Disaster impact assessment of the underground hazardous materials pipeline

In the United States, Canada, the United Kingdom, and other countries with advanced pipeline management, some organizations are responsible for pipeline safety protection management for underground hazardous materials. The security and maintenance of a hazardous material pipeline are serious considerations for urban safety, because the materials transported by underground pipelines contain hazardous goods, such as the flammable or explosive particles of solids, liquids, and gases. Damage to a pipeline by external forces often leads to secondary disasters, such as the leakage of hazardous materials, fires, explosions, and environmental pollution. Such events seriously affect the safety of individuals and their property.Accordingly, this study used seismic scenario analysis with a spatial grid to evaluate earthquake damage to an underground pipeline in an urban area. Damage to underground pipelines was classified, pipeline disaster management procedures were discussed, and improvement measures were proposed, such as establishing a geographic information platform and conducting disaster impact assessments for hazardous material pipelines. Underground hazardous material pipelines were assessed in scenarios including earthquakes. Such assessments are intended to provide disaster reduction plans and disaster prevention drills to improve pipeline safety as well as the planning for pipeline materials to aid seismic resistance.

Explosive vapour/particles detection using SERS substrates and a hand-held Raman detector.

We developed and optimized surface-enhanced Raman spectrometry (SERS) methods for trace analysis of explosive vapour and particles using a hand-held Raman spectrometer in the field. At first, limits of detection (LODs) using SERS methods based on a colloidal suspension of gold nanoparticles were measured under alkaline conditions and are as follows: pentaerythritol tetranitrate (PETN) (1.5 × 10−6 M, 6.9 ng), 1,3,5,7-tetranitro-1,3,5,7-tetrazoctane (HMX), 8.1 × 10−6 M, 35 ng; urea nitrate (UN), 9.2 × 10−4 M, 165 ng; 2,4,6-trinitrotoluene (TNT), 1.1 × 10−7 M, 0.35 ng. We developed SERS substrates that demonstrate the wide applicability of this technique for use in the field for explosive vapour and particles adsorbed on a surface based on Au nanoparticles that were optimal for the detection of the target materials in solution. Au nanoparticles were modified onto quartz fibres or a polyurethane sponge for vapour/particles detection. SERS detection of vapours of 2,4-dinitrotoluene (2,4-DNT) and 1,3-dinitrobenzene (1,3-DNB) was shown by sampling vapours onto Au-modified quartz fibres followed by hand-held Raman analysis with estimated minimum detection levels of 3.6 ng and 54 ng, respectively. The detection of 2,4-DNT using sponge-based SERS decorated with Au nanoparticles was also demonstrated; however, the sensitivity was lower than that observed using quartz fibres. The detection of TNT on a surface was performed by utilizing quartz-fibres precoated with alumina and modified with Au nanoparticles, and the detection of 10 μg (0.53 μg cm−2) of TNT was demonstrated.

In situ identification of TATP and DADP particles collected with transparent tape by Raman spectroscopy and imaging.

Triacetone triperoxide (TATP) and its byproduct diacetone diperoxide (DADP) are commonly used home-made high explosives in bombing cases and terrorist attacks. However, these two peroxide explosives are unstable and prone to thermal decomposition, leading to challenges in sample collection and preparation in bombing cases. Therefore, there is an urgent need to develop an in situ identification method for TATP and DADP. Compared to the solvent-based swabbing methods commonly used for trace explosive collection, the tape lifting method can collect explosive particles and other potential evidence without damaging fingerprints or DNA. This study aims to develop a tape lifting method to collect trace explosive particles in bombing cases and an in situ method to identify TATP and DADP particles on the sticky side of transparent tape directly using laser confocal Raman spectroscopy. One type of fingerprint tape and two types of office tape were used to collect peroxide explosive particles followed by particle fixation on glass slides. Laser confocal Raman spectroscopy was applied to directly identify target particles, without peeling the attached tape off the glass slide. A solid-state laser emitting at 473 nm was suitable for Raman and imaging analysis of TATP and DADP. To mimic the real situation, the synthetic TATP and DADP were passed through a 100-mesh sieve, respectively. Fifty μg of each explosive powder was weighed, mixed and spread on a wooden table with dust in an area of 10 × 10 cm2. Subsequently, the samples were collected with the fingerprint tape. A targeted area of the tape with suspicious particles was imaged for analysis. Based on the difference between the characteristic Raman bands of TATP and DADP, the band ranges of 530-550 cm-1 and 750-770 cm-1 were selected, respectively, for obtaining the distribution information. The combination of Raman technology and the tape lifting method shows great potential for in situ identification of forensic samples by providing chemical and spatial information.

The plutonium isotopes and strontium-90 determination in hot particles by characteristic X-rays

This paper reports the developed non-destructive methods for the plutonium isotopes and strontium-90 content determination in hot particles and other samples. The proposed methods are based on the measurement of the characteristic X-rays accompanying the decay of these radionuclides. For hot particles of NPP accident origin, the proposed method's error limits are 10–15% for hot particles (samples) with activity above 100 Bq and 15–20% for hot particles (samples) with activity less than 100 Bq. For explosive particles, the determination accuracy is 10–15% for activity more than 5 Bq and 20–30% for 0.1–5 Bq activity. The accuracy of the proposed method for determining 90Sr in samples with its specific content of more than 104 Bq/sample is 5%, with ~102 Bq/sample its content is 15–20%. The cost of one sample measurement and the processing time of these methods are significantly reduced compared to traditional studies. The proposed methods are reasonably simple measurement methods and can be carried out even in the field condition. They open up new possibilities for the quick search and study of hot particles and environmental samples.

Size effect of explosive particle on shock initiation of aluminized 2,4-dinitroanisole (DNAN)-based melt-cast explosive

An aluminized melt-cast Duan–Zhang–Kim mesoscopic reaction rate model based on the pore collapse hot-spot ignition mechanism is proposed to characterize the shock initiation behavior as well as size effects of explosive particles on the shock initiation of aluminized melt-cast explosives. For aluminized 2,4-dinitroanisole (DNAN)-based melt-cast R1 explosives [containing 60 wt. % HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine), 30 wt. % DNAN, and 10 wt. % aluminium] with different particle sizes of HMX, both shock initiation experiments and corresponding numerical simulations were performed. The numerical results are found to be in good agreement with the experimental data, by which the mesoscopic reaction rate model is verified and the model parameters for the R1 explosive are determined. It is also found that the smaller the particle size of the granular explosive component, the faster the leading shock wave propagates, and the faster the detonation growth inside the aluminized melt-cast explosive.

Meso-scale failure simulation of polymer bonded explosive with initial defects by the numerical manifold method

Polymer bonded explosive (PBX) is a composite consisting of the polymer binder and embedded explosive particles, along with a large number of the particle/binder interfaces as the third constituent. The particle volume fraction is often higher than 90%. In the present work, a visco-elastic constitutive model, an elastic visco-plastic constitutive model and a bilinear cohesive contact relationship model are implemented into the numerical manifold method (NMM) program, an open source code programmed with C language, to describe the deformations of the polymer binder, the explosive particles and the particle/binder interfaces, respectively. The fracturing of the polymer binder and explosive particles is described based on the maximum tensile stress and the Mohr-Coulomb criteria. Three categories of initial defects, including the initial interfacial debonding, initial voids in the polymer binder, and initial micro-cracks in the explosive particles, are considered in the PBX meso-structures under both uniaxial tensile and compressive conditions. The tension-compression asymmetry, the influence of the initial defects on the meso-structure failure modes/patterns and the macroscopic effective tensile/compressive strength of PBXs are investigated. The factors that cause the differences between the NMM results and other numerical or experimental results are analyzed and discussed. This work enables and proves the NMM to be an robust numerical tool for further simulation studies of the mechanical performances of PBXs, as well as other particle-filled composites, at the meso-scale.

The Ubiquitiformal Characterization of the Mesostructures of Polymer-Bonded Explosives.

A nesting ubiquitiform (NU) approach was developed to characterize the mesostructural features of polymer-bonded explosives (PBXs), and then used to predicate some equivalent physical properties of PBXs, which can also be expected to be extended to other composites with complicated internal mesostructures. To verify the availability, two NU models for two kinds of PBX with different compositions are presented, which are PBX 9501 and LX-17, based on which, the equivalent thermal conductivities were calculated. Particularly, it is so encouraging that an analytical expression of the equivalent thermal conductivity was obtained only under a simply assumption of homogeneity. Moreover, it was found that the numerical results calculated by both the recursive algorithm and the analytical expression were in good agreement with the experimental data. In addition, it is also shown that such a physical property as the equivalent thermal conductivity is indeed independent of the meso-configuration of the location distribution of the explosive particles and the voids inside the PBX, which seems consistent with the common expectations and lays the foundations for the application of ubiquitiform to investigating some equivalent properties of composites.

Coal Dust Blast Isolation by Vortex Inertial Hydrocoagulation

The mathematical model of hydro vortex inertial kinematic coagulation is proposed; the model largely improves energy efficiency of coal dust blast isolation. The graphical model of interaction between liquid drop and explosive aerosol particle at the contact zone at the moment of collision in the liquid-solid system is refined using the theory of added vortexes. The hypothesis on weakening of the wedge effect of a gas medium in the zone of contact between the explosive aerosol particle owing to an added vortex caused by the drop and particle rotation, is put forward and proved. The equations are obtained for calculating energy required for total absorption of explosive aerosol particles, minimum diameter of the particles and wetting angle in hydro vortex inertial coagulation.

In-situ X-ray observations of ultrasound-induced explosive decomposition

High-strain mechanical loading of polymer-bonded explosives can produce significant stress concentrations due to microstructural heterogeneities, resulting in localized thermal “hot spots”. Ultrasound produces similar effects and has been proposed as a tool to study the thermomechanical interactions related to explosive initiation. Detailed observations of the processes governing the generation of heat in these materials are severely lacking, yet they are vital for identifying salient physics, improving the modeling tools used to predict mechanical response, improving explosives safety, and providing insight into the initiation mechanisms of explosion. Here we report on high-speed, high-resolution in-situ observations, obtained via synchrotron X-ray phase contrast imaging and diffraction, of the heating and decomposition of an explosive material under ultrasonic excitation. We demonstrate that interfacial friction is a dominant heating mechanism and can lead to a violent reaction in the explosive particles. Furthermore, sub-surface particle temperatures are estimated via diffraction.

Three-dimensional discrete element technology investigated ignition mechanism of octahydro-1, 3, 5, 7-tetranitro -1, 3, 5, 7-tetrazocine particles under drop hammer impact

The ignition mechanism of the explosive particles under impact has been a hot topic, but the research progress is slow. With the rapid development of computer science, the three-dimensional discrete element technique (DM3) is regarded as an efficient and intuitive method to study the explosive ignition under impact. As is well known, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) is one of the most effective explosive particles in performance, which has high density and energy and thus possesses a significant application. In this paper, the deformation and ignition of HMX particles under impact of drop hammer are investigated based on the three-dimensional discrete element technique. Specifically, the computational process for shock loading as well as chemical reaction is employed in DM3 model through using the state equation of Hugoniot, the reactive model of Arrhenius, the state equation of JWL. The results show that the size, degree of accumulation, defect and the force of drop hammer can definitely influence the ignition and propagation of HMX particles. Under the same shock loading, the particles on a small scale would produce less power. On the same scale of particle, the less the number of particles, the shorter the deformation time is, so the temperature increases more easily. As for the different shapes of single particles, the deformation and ignition first appear from the ‘top’ for the spire particles, and then the deformation and ignition of flat particles happens from ‘shear’. Specifically, there are two results of the internal defect HMX particles under impact: the particles with bigger size (discrete elements 256 × 34 = 8704) have a temperature advantage near the ‘hole’, while the temperature advantage of the particles with the smaller size (discrete elements 93 × 35 = 3814) appears on the ‘top’.

Utilization of ceramic waste by using it as special concrete aggregate

In the article is presented the method ofutilization of ceramic waste by using it as special concrete aggregate for special high temperature resistant concentrates. The research was performed on six empirically designed concrete mixtures of three on aluminous cement with simultaneous aerification with using air entraining admixture respectively at 0, 5 and 10%. In order to compare the results, three Portland cement concrete mixes were prepared which had exactly the same aerification of the mixture. All types of samples were made using recyclable aggregates of sanitary ceramics selected and crushed to 0-4 mm and 4-8 mm. This particular type of aggregate, as proved in previous authors’ workshowed very favorable features in terms of the influence for thermal loads. Selected samples were subjected to a thermal treatment according to the standard curve “temperature-time” for 120 minutes until the furnace chamber temperature reached approximately 1050°C. With interative concrete mixture method design, assuming that the mixture substrates were limited to the commonly used cements and the appropriate amount of air entraining admixture, there were received tight concrete with high strength parameters, which also demonstrates resistance explosive concrete particles’ chipping off under conditions of high temperatures.

Visual study of explosive particles during fast thermal analysis

A study of visual changes occurred during fast thermal analysis of explosive and non-explosive micrometric particles is presented. The experimental setup is based on a microcalorimeter MEMS device which allows linear temperature rising at high heating rates. The micro thermal analysis at high heating rates of ∼500 °C/s was performed on tens of micrometer size particles while observing and filming the process using a digital camera (Sensicam™) operated at a rate of 45 frames per second. The study also employs image subtraction technique which emphasizes the changes occurred between following images. The measurements and image processing reveal that: 1) the observed visual changes are in accordance with the thermal response; 2) thermogram events are well explained by visual observation, thus the last contributes more dimensions to the measurement.

Study of the possibility of increasing the accuracy of measuring the concentration of particles of explosives by remote sensing methods

Most of the existing methods for detection of explosives require sampling and sample preparation, whereas in the search for explosives, it is not always possible to contact the explosive device (ED). In this connection, the methods for remote detection of explosives by detecting their particles present in various quantities near or on the surface of the explosive are of particular interest. The difficulty of detecting such substances lies in the fact that, in addition to full-scale samples, they may be in the package. In addition, it often becomes necessary to detect a trace amount of hazardous substances on packages and contact surfaces. The purpose of the article is to study the possibility of improving the accuracy of lidar measurements of the concentration of particles of explosives, taking into account the width of the laser emission line and the absorption width of the molecule under study.

Preparation of Nano‐DAAF Explosive with Improved Initiation Sensitivity

Abstract3,3′‐diamino‐4,4′‐zoxyfurazan (DAAF) shows fascinating properties and can be practically applied in explosives and solid rocket propellants. Nano‐sized DAAF explosive particles were prepared by a low‐temperature and rapid crystallization process to improve energetic performance. The diameter and morphology of DAAF nanoparticles were characterized by Field emission scanning electron microscopy (FE‐SEM), Atomic force microscopy (AFM) and X‐ray diffraction (XRD). Nano‐DAAF shows irregular spherical nano‐particles with the diameter ranging from 50 to 100 nm. The size and morphology of nano‐DAAF particles can be tuned by temperature difference and DAAF concentration of crystallization process. The thermal properties were also investigated by Differential scanning calorimetry (DSC). For nano‐sized DAAF shows significantly decreased exothermal peak (259.3 °C) and enhanced energy release rate. Deflagration and short impulse shock waves experiments illustrated that nano‐DAAF explosive shows significantly improved initiation sensitivity compared to micro‐particles.

Simulations of meso-scale deformation and damage of polymer bonded explosives by the numerical manifold method

Polymer bonded explosive (PBX) is a particle-matix composite consisting of explosive particles, polymer matrix/binder, and the interface between the particles and the binder, and the particle volume fraction (PVF) in the PBX is extremely high. To simulate the meso-scale deformation and damage behaviors of PBX with the numerical manifold method (NMM), a bilinear cohesive contact relationship (BCCR) model with three parameters is incorporated in the NMM to describe the particle-binder interface, a visco-elastic constitutive model of prony series with 22 parameters is incorporated in the NMM to describe the polymer binder, and a fracturing algorithm based on the maximum tensile stress criterion and the Mohr–Coulomb criterion is employed to describe the fracturing failures of the particles as well as the binder. The PBX meso-scale deformation and damage process of microcrack initiation, crack propagation and formation of crack bands under tensile or compressive conditions are studied through NMM simulations, and the influenes of the PVF and the explosive particle geometrical distribution (PGD) on PBX mechanical performaces are specially investigated. This work enables and proves the NMM to be an promissing roubust numerical tool for further simulation studies of the meso-scale mechanical performances of PBX, as well as other particle-fillled polymer composites.

Detection of microscopic traces of explosive residues on textile fabrics by Raman spectroscopy

AbstractDirect or cross‐contamination of explosive residues on clothing is of high occurrence when handling explosive materials, leading to physically trapped particles between the fibres. In this work, the detection and identification of trace amounts of organic explosives, inorganic explosives, and oxidizing salts trapped between the fibres of dyed and undyed synthetic and natural textile clothing fabrics were studied using two (desktop and portable) confocal Raman microscopes. The results show that, despite the contribution of the textile fabric in terms of fluorescence and vibrational bands coming from the fibres and dyes, detection and identification of the explosive/oxidizing salt particles trapped on highly interfering surfaces was possible. Limits of detection were estimated in the nanogram/picogram range depending on the explosive and fabric. However, problems involving the burning of either some explosive particles or dark cloth textiles were verified, which can cause a destruction of the sample. Also, the analysis of improvised homemade explosives (potassium nitrate mixed with 10 different fuel substances) was studied to evaluate possible interferences.

Study of the adhesion of explosive residues to the finger and transfer to clothing and luggage

It is important to understand the extent of transfer of explosive particles to different surfaces in order to better evaluate potential cross-contamination by explosives in crowded security controls such as those at airports. This work investigated the transfer of nine explosive residues (ANFO, dynamite, black powder, TNT, HMTD, PETN, NH4NO3, KNO3, NaClO3) through fingerprints from one surface to another. First, the extent of adhesion of explosive residues from different surfaces to the bare finger, nitrile and latex gloves was studied. Then, the transfer of explosive residues from one surface to another through fingerprints was investigated. Cotton fabric (hereinafter referred to as cotton) as clothing material and polycarbonate plastic (hereinafter referred to as polycarbonate) as luggage material were chosen for the experiments. These surfaces containing explosive particles were imaged using a reflex camera before and after the particles were transferred. Afterwards the images were processed in MATLAB where pixels corresponding to explosive residues were quantified. Results demonstrated that transfer of explosive residues frequently occurred with certain differences among materials. Generally, the amount of explosive particles adhered to the finger decreased in the following order: skin>latex>nitrile, while the transfer of particles from the finger to another surface was the opposite. The adhesion of explosive residues from polycarbonate to the finger was found to be better compared to cotton, while the amount of particles transferred to cotton was higher.

Quantitative analysis for the determination of aluminum percentage and detonation performance of aluminized plastic bonded explosives by laser-induced breakdown spectroscopy

The aluminized plastic-bonded explosive (PBX) is a composite material in which solid explosive particles are dispersed in a polymer matrix, which includes three major components, i.e. polymeric binder, metal fuel (aluminum) and nitramine explosive. This work introduces a new method on the basis of the laser-induced breakdown spectroscopy (LIBS) technique in air and argon atmospheres to investigate the determination of aluminum content and detonation performance of aluminized PBXs. Plasma emissions of aluminized PBXs are recorded where atomic lines of Al, C and H as well as molecular bands of AlO and CN are identified. The experimental results demonstrate that a good discrimination and separation between the aluminized PBXs is possible using LIBS and principle component analysis, although they have similar atomic composition. Relative intensity of the AlO/Al is used to determine aluminum percentage of the aluminized PBXs. The obtained quantitative calibration curve using the relative intensity of the AlO/Al is better than the resulting calibration curve using only the intensity of Al. By using the LIBS method and the measured intensity ratio of CN/C, an Al content of 15% is found to be the optimum value in terms of velocity of detonation of the RDX/Al/HTPB standard samples.