Explosive Reaction Research Articles

Control of Explosive Chemical Reactions by Optical Excitations: Defect-Induced Decomposition of Trinitrotoluene at Metal Oxide Surfaces.

Interfaces formed by high energy density materials and metal oxides present intriguing new opportunities for a large set of novel applications that depend on the control of the energy release and initiation of explosive chemical reactions. We studied the role of structural defects at a MgO surface in the modification of electronic and optical properties of the energetic material TNT (2-methyl-1,3,5-trinitrobenzene, also known as trinitrotoluene, C7H5N3O6) deposited at the surface. Using density functional theory (DFT)-based solid-state periodic calculations with hybrid density functionals, we show how the control of chemical explosive reactions can be achieved by tuning the electronic structure of energetic compound at an interface with oxides. The presence of defects at the oxide surface, such as steps, kinks, corners, and oxygen vacancies, significantly affects interfacial properties and modifies electronic spectra and charge transfer dynamics between the oxide surface and adsorbed energetic material. As a result, the electronic and optical properties of trinitrotoluene, mixed with an inorganic material (thus forming a composite), can be manipulated with high precision by interactions between TNT and the inorganic material at composite interfaces, namely, by charge transfer and band alignment. Also, the electron charge transfer between TNT and MgO surface reduces the decomposition barriers of the energetic material. In particular, it is shown that surface structural defects are critically important in the photodecomposition processes. These results open new possibilities for the rather precise control over the decomposition initiation mechanisms in energetic materials by optical excitations.

Hydrothermal liquefaction of soybean straw: Effect of steam explosion pretreatment and reaction media

In this study, soybean straw (SS) was subjected to a steam explosion to produce pretreated soybean straw (PSS). Food waste was used to make a liquor with a lower layer (LL) and an upper layer (UL). Hydrothermal liquefaction (HTL) of SS and PSS was performed in deionized water (DW), LL, and UL at 320 °C for 30 min. The highest bio-oil yield was obtained by conducting HTL in the UL, with SS accounting for 31.30 wt% yield and PSS accounting for 31.77 wt% of the bio-oil yield; this result may be due to the high gas content of the UL. Moreover, conducting HTL in the LL produced lowest bio-oil yield, which was only 15.30 wt% bio-oil yield for PSS. Bio-oil is not suitable for direct use as a fuel because of its high nitrogen content. However, bio-oil consists mainly of ketones and phenols and is therefore a promising feedstock for the production of high-value-added chemicals. PSS is high in lignin and therefore produces more hydrochar than SS. The hydrochar produced from PSS has a higher heating value (HHV) ranging from 27 to 28 MJ/kg and can be used as green biocoal. PSS could also be used as a feedstock to reduce the gaseous product yield, especially the water-soluble product yield. The gaseous products mainly consisted of CO2, CO, H2, N2, CH4, and C2H6, among which CO2 and CO accounted for more than 95 %. Compared to the products obtained by HTL from PSS, there were more acetic acid, ketones and fewer phenolic substances in the water-soluble products obtained by HTL from SS.

Influence of Dust Layers in Connecting Pipes on Explosion Propagation Characteristics of Flake Aluminum Powder in Cylindrical Interconnected Vessels.

Aluminum dust explosion has become an important type of dust explosion accident. In the present work, an interconnected system is established to study the influence of accumulated dust layers in connecting pipes on explosion propagation characteristics. A high-precision computational fluid dynamics (CFD) method is applied to study the overpressure and flame development of aluminum powder explosion under the central ignition condition of two cylindrical vessels with a volume ratio of 1:5. The results show that pressure build-up in the secondary container is mainly due to the oscillating pressure wave. Moreover, compared with the ignition container, the thickness of the dust layer has a more obvious enhancement effect on the peak overpressure for the secondary container. When the ignition occurs in a large container, the dust layer is lifted in the connecting pipe under the action of the precursor pressure wave. After the jet flame enters the connecting pipe, the lifted aluminum dust participates in the explosion reaction, which significantly increases the explosion intensity. With the participation of the accumulated dust layer, the maximum overpressure of the explosion of flake aluminum dust in the interconnected system is higher than 30 bar, and the jet flame velocity is increased by 3 times. The present work can provide reference for the safety design of process equipment involving dust.

TESTE E AVALIAÇÃO DE FORÇA DOS MEMBROS INFERIORES EM ATLETAS DE KUNG FU

ABSTRACT Introduction “Popularization and improvement” has been a solid guideline for developing kung fu in China for decades. Objective Test and evaluate the lower limb strength in juvenile kung fu athletes. Methods 10 young volunteer athletes were selected, including six males and four females. A three-dimensional dynamometer and a multifunctional jumping system measure the F-T curves of different bounces. Explosive force, reaction force, and proprioceptive capacity of the lower limbs were evaluated, measured, and statistically treated. Results In the experiment, the athletes in the experimental and control groups showed no increase in muscle volume or lower limb circumference, and there were no significant changes in other body lengths and thicknesses (P > 0.05). However, the relative peak power of the experimental group and the control group showed statistically remarkable differences (P < 0.05). Conclusion Young kung fu athletes should pay attention to the combination of strength and proprioception training while performing dedicated and technical training. Level of evidence II; Therapeutic studies - investigation of treatment outcomes.

Study on inhibition effect and mechanism of NH4H2PO4 on explosion of titanium powder

In order to effectively inhibit the explosion of titanium powder, this study used the Hartmann tube experimental system and the 20 L explosion tank experimental system to carry out flame propagation and explosion overpressure experiments, respectively, and the effect of NH4H2PO4 on the explosion suppression of titanium powder was studied. The results show that when the addition of NH4H2PO4 powder is 50%, the flame propagation velocity and explosion pressure can be reduced to the minimum, and the explosion pressure can be basically suppressed. Finally, the inhibition mechanism of NH4H2PO4 on the explosion of titanium powder was analyzed. The endothermic decomposition of NH4H2PO4 absorbed the energy needed by the explosion of titanium powder. Oxides produced by the decomposition of NH4H2PO4 powder cover the surface of titanium powder, increase the thickness of the oxide film, and play a role of heat insulation; the gaseous water produced by the decomposition of NH4H2PO4 powder reduces the concentration of oxygen in the air and increases the difficulty of the explosion reaction. NH4H2PO4 powder traps the free radicals needed for the explosion to block the chain reaction.

Thermal explosion synthesis of Cr2AlB2 materials

Abstract Ternary conductive ceramic Cr2AlB2 phase has been widely studied because of its unique physical and chemical properties. However, the preparation of conventional synthetic Cr2AlB2 requires expensive raw materials or higher equipment cost, which is not conducive to its synthesis and promotion. Hence, we synthesized high-content Cr2AlB2 by thermal explosion reaction, a technology with low-energy consumption. Cr2AlB2 was synthesized by thermal explosion reaction from Cr/Al/B mixed powders. The effects of different ignition materials and diamond additive on Cr2AlB2 synthesis were studied systematically. Results showed that the Cr/Al/B system did not undergo a thermal explosion reaction. An aluminothermic reaction between Al and Cr2O3 occurred by introducing a small amount of Cr2O3. The main phase of the thermal explosion products of the Cr/Al/B/Cr2O3 green body was CrB. The addition of an appropriate amount (7.5 % and 10 %) of diamond in the raw material can obviously promote Cr2AlB2 synthesis. The main phases of the product were Cr2AlB2 and CrB. The samples were composed of a large number of fine Cr2AlB2 lath grains. Finally, the mechanism of Cr2AlB2 formation by thermal explosion reaction was proposed.

Dust explosion in fusion reactors: Explosion characteristics and reaction mechanism of tungsten micro-powder

The explosion of in-vessel dusts, mainly produced by energetic plasma and wall interaction, will pose a great threat to the safe operation of a fusion reactor. Unlike dust explosions in traditional industrial systems, dust explosion in tokamak devices has the unique characteristics, including dust composition (tungsten is one of the main components), initial conditions of explosion, etc. However, the experimental data on this aspect are very few, which is not enough to support the safety assessment of fusion reactors. In this work, the experiments were used to study the explosion characteristics and mechanism of the micro-tungsten in a 20 L spherical vessel. Results showed that the lower explosion limit (LEL) of 2 µm tungsten dust was in the range of 250–500 g/m3, and the maximum explosion pressure would reach 0.46 MPa at 3000 g/m3. The factors related to fusion reactor environment, including initial pressure, ignition energies and the ignition delay time, were studied to demonstrate a significant effect on explosion parameters. The explosion product changed from WO3 to WO2.72 with the increase of nominal dust concentration. A combustion mechanism for single mirco-tungsten particle was established. Based on the experimental data, the explosion possibility and hazard of tungsten dust in fusion reactor were also dicussed.

Experimental study on the multi-level suppression of N2 and CO2 on hydrogen-air explosion

The multi-level suppression of the hydrogen-air explosion by non-premixed N2 and CO2 in a closed duct was experimentally investigated. The multi-level suppression effect of inert gas on hydrogen-air explosion was discussed by comparing explosion parameters such as explosion pressure, the rate of pressure rise, combustion duration and flame propagation. The results showed that the inert gas adjacent to the explosion zone played a major role in explosion suppression. Compared to single-level explosion suppression, the multi-level explosion suppression was not obvious for inhibitors on the same side, while the multi-level explosion suppression was most efficient for inhibitors on different sides. Moreover, the turbulent development of the flame would exacerbate the explosive reaction, which could not be avoided. The experiment in this paper had great practical significance, and the experimental results could provide data support and theoretical guidance for the safe utilization of hydrogen and the effective suppression of hydrogen-air explosion.

Iron and Copper Doped Zinc Oxide Nanopowders as a Sensitizer of Industrial Energetic Materials to Visible Laser Radiation.

The development of methods ensuring reliable control over explosive chemical reactions is a critical task for the safe and efficient application of energetic materials. Triggering the explosion by laser radiation is one of the promising methods. In this work, we demonstrate a technique of applying the common industrial high explosive pentaerythritol tetranitrate (PETN) as a photosensitive energetic material by adding zinc oxide nanopowders doped with copper and iron. Nanopowders of ZnO:Fe and ZnO:Cu able to absorb visible light were synthesized. The addition of one mass percent nanopowders in PETN decreased the threshold energy density of its initiation through Nd:YAG laser second harmonic (2.33 eV) by more than five times. The obtained energetic composites can be reliably initiated by a CW blue laser diode with a wavelength of 450 nm and power of 21 W. The low threshold initiation energy and short irradiation exposure of the PETN-ZnO:Cu composite makes it applicable in laser initiation devices. PETN-ZnO:Cu also can be initiated by an infrared laser diode with a wavelength of 808 nm. The proposed photochemical mechanism of the laser-induced triggering of the explosion reaction in the studied energetic composites was formulated. The results demonstrate the high promise of using nanomaterials based on zinc oxide as a sensitizer of industrial energetic materials to visible laser radiation.

Reaction mechanism of core–shell Al@SiO2 nanoparticles from molecular dynamics simulations

Nanothermites play an important roles in both civil and military fields. In this paper, using molecular dynamics simulations with reactive force field (ReaxFF), we study the thermally induced reactions of core–shell Al@SiO2 nanoparticles to elucidate the underlying reaction mechanism between Al and a metallic oxide. Core–shell Al@SiO2 nanoparticles undergo a four-stage explosive reaction after being heated to the ignition temperature. They are, in sequence: (i) Heat is released from the core–shell interface to Al core, and Al core begins to melt. (ii) The melted Al core accelerates the redox exothermic reaction, producing a pure Si shell. (iii) The Si shell moves towards the center of the system under electric field induction, and the distorted AlnO (n = 4, 5) clusters are ejected from the system’s surface. (iv) The detonation of the nanoparticles, and the formation of final products. Notably, the electric-field-induced Al atoms diffuse faster than the O atoms throughout the reaction. Our findings provide a reference guide for the reactions of nanothermites.

Flow process and energy release of hydrogen in fluorine

Hydrogen is a clean energy source and fluorine is a strong oxidant. The chemical reaction between the two will make the utilization of hydrogen energy significantly improved, which is a new way to develop and utilize hydrogen energy. In this study, the ANSYS Fluent software is used to solve the reaction kinetics process, which has great advantages in the simulation of combustion and chemical reaction flow, and Computational fluid dynamics (CFD) adopts numerical methods to solve the Navier-Stokes (N–S) partial differential equation. Here, the CFD code ANSYS Fluent is performed to calculate the two-dimensional compressible reaction flow, therefore, we use the methods to explore the flow process and reaction energy release of hydrogen in fluorine and a new ways of hydrogen energy development is explored. The initial stage of the explosion for F2 filling into H2/air in the pipeline is volatile. Chemical reactions for F2 filling into H2/air in the pipeline interact with flows for F2 filling into H2/air in the pipeline. Energy release of hydrogen in fluorine depends on the flow and mixing process. When F2 is filled into a premixed H2/air in the pipeline with a length of 0.9 m and a diameter of 0.1 m, the explosion pressure reaches 0.307MPa–0.408 MPa and the explosion temperature reaches 2698 K–3107 K. The explosion reaction is very rapid and only takes about 40 ms to reach equilibrium. The higher the incident pressure at the pressure inlet, the smaller the peak pressure and temperature are, when the reaction reaches equilibrium.

Contribution of arm explosive power hand reaction speed to badminton smash ability

This research aims to discover these problems, (1) Is there a contribution of arm power explosive to the smash ability of UM Palopo badminton athletes (UKM)? (2) Is there any contribution of hand reaction speed to the smash-hitting ability strength of UM Palopo badminton athletes (UKM)? (3) Is there any contribution of arm explosive power to hand reaction speed to the smash ability of UM Palopo badminton athletes (UKM)? Two independent variables and one dependent variable form this research. It is a descriptive research Sample and the population is athletes from UKM Badminton UM Palopo, by random sampling, 40 people were obtained. The data analysis technique used is Regression-Test (R). (1) Arm explosive power makes a sizable contribution to the smash-hitting ability of badminton Where the obtained value = 0.512 (p < 0.05), with a contribution or contribution of 57. 80% (2). There is a significant contribution of hand reaction speed to the ability to smash in badminton. The value = -0.4 61 (p < 0.05), with a contribution or contribution of 54.20 % (3). There is a significant contribution of explosive power, and arm reaction speed, to the smash ability of badminton. Where the value of Ro = 0.854 (P < 0.05), with a contribution or contribution of 72.90%.

Effect of multi-component gaseous fuel on the explosion behaviors and mechanism of aluminum dust

Hydrogen/ethylene/aluminum dust hybrid mixture may pose a potential explosion risk in the production process of triethyl aluminum. To investigate the effect of multi-component gaseous fuel on the hybrid explosion, the flame propagation behaviors and explosion characteristics of hydrogen/ethylene/aluminum dust hybrid mixtures were studied in a confined space. The explosion residues were analyzed, and the reaction mechanism was further established. The results show that the effect of hydrogen-rich fuel on increasing the maximum flame propagation velocity of two-phase fuel was more obvious than that of ethylene-rich fuel. Ethylene-rich fuel can promote the explosion intensity of aluminum dust only in an oxygen-rich environment, while hydrogen-rich fuel can promote aluminum dust explosion in both an oxygen-rich and oxygen-deficient environment. A modified formula for predicting the lower explosion limit of the hybrid mixtures is proposed, and the accuracy of the formula is significantly improved by introducing effective coefficients. The hydrogen-rich gaseous fuel mainly regulated H and OH production through R2 (H2 +O <=> H + OH) and R3 (H2 + OH <=> H + H2O) reactions to dominate the explosion reaction, while the ethylene-rich gaseous fuel affected the explosion reaction through R69 (O + CH3<=>H + CH2O) and R205 (C2H4 + M <=> H2 + C2H2 + M) reactions to regulate the degree of participation of C–C, C–H, and C–O. These results can provide corresponding reference for preventing and reducing the explosion hazard of multi-component gaseous and dust hybrid mixtures.

Effect of particle size distribution on explosion intensity of aluminum powder

AbstractIn order to effectively prevent the occurrence of aluminum powder explosion accidents, the statistical analysis method was used to analyze the differences between all the groups and between any two groups in relation to the explosion intensity parameters (Pex, [dP/dt]ex, Kst, t1 and t2) of aluminum powder samples. The results show that small particle size aluminum powder components play a major role in the explosion reaction rate, while large particle size aluminum powder components have relatively little effect. Among the nine factors D10–D90, the top three particle size parameters with the most relevance to Pex are D10 (0.708*), D3,2 (0.686*), and D30 (0.646*) in turn. The top three particle size parameters with the most relevance to t1 are D10 (0.903**), D20 (0.898**), and D30 (0.873**) in turn. The top three particle size parameters with the greatest relevance for (dP/dt)ex and Kst are SSA (0.963**), D30 (−0.748*), and PSS (−0.744*). The top three particle size parameters with the greatest relevance for t2 are D30 (0.962**), D20 (0.960**), and D4,3 (0.936**). Therefore, D10, D20, D30, D3,2, D4,3, PSS and SSA have important effects on the explosion parameters, and they are important reference indicators for assessing explosion risk.

Effect and mechanism analysis of wires explosion-proof material on ethylene-air explosion

To further study the explosion effect and mechanism of explosion-proof material on olefin gas, the 6.5% ethylene-air explosion experiments and simulation results were analyzed after filling with different wires. The experiments show that wires can effectively inhibit ethylene explosion. In addition, the inhibition effect of iron wire is better than that of nickel wire, followed by aluminum wire and copper wire. The wires mainly make the explosion end in advance, promoting the early termination of chain reaction and reducing explosion pressure. The simulation results show the key free radicals and the main reaction routes affecting the explosion reaction. The ferromagnetic iron wire direct affects the movement of oxygen molecules and weakens the reaction between ·O, ·OH, and ethylene. It provides the significance of reference and guidance for the future development of new explosion-proof materials.

Explosion behaviors of IPN/air mixture at high temperature and high pressure

PurposeThe reaction dynamics of combustible clouds at high temperatures and pressures are a common form of energy output in aerospace and explosion accidents. The cloud explosion process is often affected by the external initial conditions. This study aims to numerically study the effects of airflow velocity, initial temperature and fuel concentration on the explosion behavior of isopropyl nitrate/air mixture in a semiconstrained combustor.Design/methodology/approachThe discrete-phase model was adopted to consider the interaction between the gas-phase and droplet particles. A wave model was applied to the droplet breakup. A finite rate/eddy dissipation model was used to simulate the explosion process of the fuel cloud.FindingsThe peak pressure and temperature growth rate both decrease with the increasing initial temperature (1,000–2,200 K) of the combustor at a lower airflow velocity. The peak pressure increases with the increase of airflow velocity (50–100 m/s), whereas the peak temperature is not sensitive to the initial high temperature. The peak pressure of the two-phase explosion decreases with concentration (200–1,500 g/m3), whereas the peak temperature first increases and then decreases as the concentration increases.Practical implicationsChain explosion reactions often occur under high-temperature, high-pressure and turbulent conditions. This study aims to provide prevention and data support for a gas–liquid two-phase explosion.Originality/valueSustained turbulence is realized by continuously injecting air and liquid fuel into a semiconfined high-temperature and high-pressure combustor to obtain the reaction dynamic parameters of a two-phase explosion.

The ionic salts with super oxidizing ions O2 + and N5 +: Potential candidates for high-energy oxidants.

As an important component of energetic materials, high-energy oxidant is one of the key materials to improve their energy. The oxidizability of oxidant directly determines the intensity of combustion or explosion reaction. It is generally believed that when the nature of reductant is certain, the stronger the oxidizability, the more intense the reaction. Dioxygenyl cation (O2 +) and pentazenium cation (N5 +) are two kinds of super oxidizing ions, which oxidizability are comparable to that of fluorine. A series of high energetic ionic salts with O2 +, N5 + and various anions as active components are designed, and the results show that: 1) Most ionic salts have appropriate thermodynamic stability, high density (up to 2.201 g/cm3), high enthalpy of formation (up to 1863.234 kJ/mol) and excellent detonation properties (up to 10.83 km/s, 45.9 GPa); 2) The detonation velocity value of O2 (nitrotetrazole-N-oxides) and O2B(N3)4 exceed 10.0 km/s, and the detonation pressure exceed 45.0 GPa because of the O2 + salts have higher crystal density (g/cm3) and oxygen balance than that of N5 +salts; 3) With a higher nitrogen content than O2 +, the N5 + salts have higher enthalpy of formation, which exceed 330 kJ/mol than that of O2 + salts; 4) The linear spatial structure of N5 + leads the salts to reduce their density. Encouragingly, this study proves that these super oxidizing ions have the potential to become high-energy oxidants, which could be a theoretical reference for the design of new high energetic materials.

Control of Large‐Scale Single‐Phase Ni Silicide Formation from Reactive Multilayers

The Ni/Si reactive multilayer (RML) is full of application potentials including reactive joining, igniters, and power sources. Here, the Ni/Si RMLs with atomic ratios of Ni and Si (2:1, 1:1, and 1:2) are studied, where the bilayer thickness and the total thickness are controlled to be 53 nm and 2 μm, respectively. After laser ignition, a rapid explosive reaction is observed where there are two self‐propagation wavefronts and their velocities reach 7.20 and 11.93 m s−1. The uniform, small grains, and single‐phase Ni silicides are obtained and controlled by tuning growth parameters. From the understanding of the Gibbs free energy diagram, the first wavefront comes from the solid‐state amorphization reaction between the Ni and a‐Si. The formation of the final Ni silicide causes the second wavefront. The entire reaction is described by a transient heat transfer model. It proposes a key parameter called heat loss rate, which explains the importance of RML thickness and the thermal diffusivity of the substrate. It allows to accurately control the reaction rate, which masters the final silicide phase. Thus, the oxidation of samples downgrades the reliability as the self‐propagation velocity of the two wavefronts dropped to 1.34 and 1.91 m s−1 in samples after 200 h of oxidation.

Research on performance of PBT/Bu-NENA low-vulnerability propellant

Large-size program temperature controller was used to carry out the slow cook-off test study of PBT, Bu-NENA, PBT/Bu-NENA mixture and PBT/Bu-NENA propellant in the range of gram and kilogram scale. The comprehensive performance of PBT/Bu-NENA propellant was carried out evaluation, including energy performance, mechanical performance, and low vulnerability performance (including fast cook-off test, slow cook-off test, shaped charge jet impact test and bullet impact test). The test results show that the slow cook-off response temperature of gram-weigh PBT, Bu-NENA and PBT/Bu-NENA mixture are 178.5°C, 142.3°C, and 139.0°C, respectively, while that of kilogram-weigh PBT/Bu-NENA propellant is 121.9°C. Analysis believes that high volatility of Bu-NENA plasticizers the main reason for the response temperature to drop from 139.0°C to 121.9°C. The PBT/Bu-NENA propellant has low vulnerability characteristics. Among them, the shaped charge jet impact test has the highest degree, which is an explosive reaction, and the sympathetic detonation test has the lowest response degree, which is below the burning. The theoretical special impulse of the PBT/Bu-NENA propellant is greater than 267 s,the density is greater than 1.80 g/cm3, the glass transition temperature (Tg) is less than -66°C, and the mechanical properties in the range of -60°C ∼ +70°C are excellent.

Explosion behaviors of vapor–liquid propylene oxide/air mixture under high-temperature source ignition

Propylene oxide (PO) is widely used in fuel–air explosive (FAE) and pulse detonation engines (PDE). The explosion process of PO/air mixture in a 20 L spherical container under high-temperature source ignition was studied through experiment and numerical simulation. A good agreement was observed between the experimental and simulation results. The ignition temperature (1100–2500 K) and initial droplet size (10–200 μm) had no obvious effect on the maximum explosion pressure (Pmax) at a nominal concentration of 130 g/m3. Explosion time (te) and reaction time (tr) of PO aerosol explosion increased with the increase in initial droplet size. The flame propagation process in the direction of 90° was not the same as that of 45°. Explosion flame propagated from the center to the surrounding area, then sagged along wall facing the center and presented a U-shape. Explosion time at ignition temperature of 1600 K was 29.63 ms, which was the shortest compared with the temperature of 2000 K, 2500 K, and 1100 K. The influence of ignition temperature on te was more obvious than that of initial droplet size. The flame propagation mechanism of droplet sizes of 10 μm and 50 μm was different from that of 100 μm and 200 μm. The time to reach the maximum flame temperature(tf) increased with the increase in droplet size; the flame propagation speed decreased with the increasing droplet size, and the maximum flame velocity can reach 6.07 m/s.