Nitrocellulose (NC) is typically synthesized by nitrating cellulose from cotton linter using a mixed acid of H2SO4 and HNO3. Okara, a soybean-processing byproduct often disposed of as waste, contains approximately 40 wt% of insoluble dietary fiber rich in cellulose, making it a promising alternative raw material for NC. In this study, NC was synthesized from okara under different pretreatment and nitration conditions. Light yellow powder (okara NC) was obtained with a maximum crude yield of 18.0%. Elemental analysis and Fourier transform infrared spectroscopy revealed that the chemical structure of okara NC was comparable to that of the reference NC, with a nitrogen content of approximately 12%. When NaOH-pretreated okara was used as the raw material, the resulting product exhibited a structure that more closely resembled that of the reference NC. In this case, thermal analysis indicated a heat amount of 2.20 kJ g(-1) and a decomposition temperature of 143.6 degrees C. Hot water washing after nitration increased the decomposition temperature; however, it remained lower than that of the reference NC.
Miniaturization of exploding foil initiator (EFI) system with micron-sized bridge foil (similar to 200x200 mu m(2)) may provide substantial improvement on detonator reliability and safety as well as manufacturing cost by lowering all-fire operational voltage and relieving many constraints on system design and fireset components. This numerical modeling study presents thermomechanical modeling on plastic flyer acceleration after bridge foil burst by pulsed energy input and high-speed flyer impact detonation initiation of HNS-IV explosive charges in such microscale EFI systems and low-energy fireset circuit. The compensation of deviation from linear bridge vapor expansion is introduced and detonation initiation criteria is recalibrated based on firing test results with thin flyer thickness in present modeling. The computational results on flyer velocity is well validated against the firing test measurements of EFI system with copper bridge foil and polyimide flyer. The influences of bridge and flyer thicknesses on detonation threshold are thoroughly investigated and the combined range of bridge and flyer thicknesses could be suggested for optimal EFI design of micron-sized bridge foil in terms of minimization of threshold charging voltage.
Carbonates have been used as only pyrotechnic colorants with other oxidisers. But it was considered that the using carbonates which did not contained chloride, nitrogen oxides, and sulfur as oxidiser in pyrotechnics composition is one of the solution methods for reducing of toxic and harmful ingredients and smoke. Calcium carbonate (CaCO3), which produces an orange flame in fireworks and not typically used as the main component in pyrotechnic compositions, was tested to be used as oxidiser in combination with Ti in this study for developments of carbonates-based pyrotechnics composition. And the substitution of commercial CaCO3 powder with eggshell, with calcium carbonate as their major component, was tested for making effective use of a food waste product. The mixture between CaCO3 and Ti was ignited under argon atmosphere as traditional pyrotechnics composition. The reaction products of the mixture which were TiC and CaTiO3 were determined, and the equation of combustion reaction was summarised. The mixture exhibited continuous combustion and low sensitivity, demonstrating the potential to be used in pyrotechnics. The spark generation was found to be enhanced on substituting CaCO3 with eggshell powder.
Trinitrotoluene (TNT) equivalency converts an explosive into the weight of TNT that will result in the same explosive power, which can then be used to calculate its blast parameters. However, the blast parameters of an explosive charge depend on not only its weight but also its shape. In this study, field experiments were conducted using cylindrical emulsion explosive (EMX) charges with weights of 1-80 kg. The height between the center of the EMX charge and ground surface was fixed, and the explosion was initiated from the center of the top face. The blast parameters of the peak overpressure and scaled positive impulse were then used in empirical equations based on hemispherical and cylindrical TNT charges to estimate the explosive power of the EMX charges. The differences of the TNT equivalencies based on the peak overpressure and scaled positive impulse were 18.8% using the hemispherical TNT and 2.5% using the cylindrical TNT, respectively. When the shape, height above the ground surface, and initiation point of the TNT and EMX charges were similar, their blast waves had similar characteristics, and the TNT equivalency of the EMX charge was almost independent of the blast parameter used (i.e., peak overpressure or scaled positive impulse). These results emphasize the necessity of ensuring that the experimental conditions for two types of explosives match as closely as possible to compare their explosive powers.
Based on the HTPB/IPDI propellant formulation system, the compatibility of three solidifiable catalysts TPB, TEPB and TS-01 with the main component of the propellant, their respective morphological characteristics and rheological properties of the propellant slurry were analyzed by differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and ARES rheometer. Combined with the curing catalytic mechanism, the influence of three curing catalysts on HTPB propellant process and mechanical properties were studied. The result show that the three curing catalysts have good compatibility with the main propellant component. TEPB and TS-01 have higher catalytic activity than TPB, which can accelerate the curing reaction process of propellant system and shorten the curing cycle of propellant. After adding TS-01, the properties of propellant were not much different from those of TPB-containing systems, and the tensile strength of propellant increased by about 0.1 MPa compared with TPB-containing propellant under the same curing conditions. Mechanical properties of TS-01-containing propellant were maintained at virtually a similar level at activity conditions of 50 degrees C, 4 days and 40 degrees C for 5 days as TPB-containing propellant at activity conditions of 60 degrees C, 8 days and 50 degrees C for 10 days.
Recently, many small satellites have been developed due to the miniaturization and integration of onboard devices. The satellites' transportation capacity is greatly affected by the propulsion performance of upper-stage motors, such as solid kick motors, which must have higher performance. One of the methods is to increase the nozzle expansion ratio of solid rocket motor, which can be easily achieved by adjusting the nozzle throat diameter and suppressing the burning rate of solid propellants. One way to suppress the burning rate is to add catalysts. In this study, the burning rate was measured by mixing negative catalysts that reduce the burning rate of the solid propellant. The results were used to verify the effectiveness of the propellant in enhancing propulsion performance by reducing its burning rate. From the combustion test results, it was determined that mixing the selected negative catalysts reduced the burning rate of the solid propellant. As a result of the theoretical analysis based on the obtained characteristic values of the burning rate, the theoretical total impulse was enhanced when 10 parts of the negative catalysts were mixed with the propellant. These results indicate that propulsion performance can be enhanced by reducing the burning rate.
To clarify the effects of wall regression on the internal flow characteristics of solid rocket motors (SRMs) with complex grain geometries, three-dimensional numerical simulations were performed using the building cube method (BCM) and an Immersed Boundary Method (IBM) to clarify the effects of wall regression on the internal flow characteristics of SRMs. Four grain configurations, including three star-shaped grains representing different stages of combustion and one cylindrical reference model, were analyzed to examine the influence of changes in chamber geometry on flow acceleration and vortex formation. The simulations showed that the star-shaped grains, particularly in the early combustion stages, induced stronger flow acceleration toward the nozzle owing to the narrow chamber and pronounced surface protrusions. The transition region between the grain and nozzle formed cavity-like structures that triggered local flow separation and vortex generation. The Q-criterion visualizations and vorticity magnitude analyses revealed that these vortices were most intense in the early stages and gradually weakened as the chamber geometry became more uniform with continued combustion. The results demonstrate that the time-varying grain geometry significantly affects the internal flow field and vortex behavior within the SRMs. The insights from this study will contribute to the development of optimized grain designs for improved thrust performance and combustion stability.
Understanding the explosive characteristics of nitromethane (NM) under various confinement conditions is a crucial aspect of optimizing the practical applications of this compound. This study investigated the effects of the containment vessel material, diameter and wall thickness on the explosive pressure generated by NM once initiated. Higher pressures were obtained in vessels made of the rigid material stainless steel, whereas explosions were less intense in mortar and poly (methyl methacrylate) containers. Different reaction modes, ranging from deflagration to possible detonation, were observed upon slight changes in the confinement conditions. These findings provide new insights into the complex decomposition mechanism of NM together with a better understanding of the effect of confinement on the explosive power of this compound. The work reported herein is expected to advance the state of controlled energy release technologies, paving the way for safer and more efficient applications in various industries.
Technologies that modify the combustion of the propellant components are crucial for developing novel high-energy propellants. Amide compounds function as fuels and also act as melting point depressants for ammonium dinitramide (ADN)-based energetic ionic liquids (EILs). A formulation comprising ADN, monomethylamine nitrate (MMAN), and urea in a 40/40/20 weight ratio (AMU442) has demonstrated potential as a hydrazine substitute. However, AMU442 faces limitations in terms of its ignitability and reactivity. In this study, the flame structure of acetamide (AA), which exhibits superior reactivity with ADN compared with urea in the liquid phase, was investigated. AA was combined with ADN/MMAN to function both as a fuel and melting point depressant. The influence of amide compounds on the combustion process was systematically explored. Burning rates and combustion temperatures of two mixtures with varying oxygen balances (ADN/MMAN/AA, denoted as AMA) were assessed using strand burners. The results indicated that AMA992 and AMA442 exhibited significantly higher burning rates at 68 mm s(-1) and 5.5 mm s(-1), respectively, compared to 2.7 mm s(-1) for AMU442. The combustion temperature profiles revealed six stages: liquid phase, gas-liquid phase, 1st flame region, two constant temperature plateaus (primary and secondary), and 2(nd) flame region. Both AMU442 and AMA992 exhibited the secondary plateau during the 2(nd) flame stage. The maximum flame temperature of AMA992 exceeded 1800 degrees C, surpassing 1684 degrees C of AMU442, while AMA442 reached a lower maximum of approximately 900 degrees C. In AMA442, ADN and AA predominantly reacted in the liquid phase, and the primary plateau was attributed to the endothermic decomposition of MMAN. In AMA992, ADN decomposed in the gas phase and reacted with MMAN to generate a high-temperature flame. The liquid-phase reaction between ADN and AA contributed to a higher burning rate than that observed in AMU442. Furthermore, the heat released in the AMA992 flame enhanced the burn rate. These findings suggest that selecting a fuel that both lowers the melting point and reacts effectively with ADN in the liquid phase, such as AA, offers a promising approach to overcome the low reactivity limitations of AMU.
In this study, reference functions were derived for the relationship between the mass-scaled distance (Z) and the negative-phase blast wave parameters, including the negative peak overpressure (P -), scaled negative impulse (I -), and scaled negative duration (T-). A blast wave was generated in field experiments using a right cylindrical cast trinitrotoluene (TNT) charge with a weight of 16.16-160 kg and a burst scaled height of approximately 0.18 m kg -1/3. Each pressure profile was measured using piezoelectric pressure sensors installed at a height of 1 m in the range of 2.53148.9 m kg (-1/3). The blast parameters were corrected for ambient pressure and temperature. Additionally, P- and I were fitted using an equation inversely proportional to Z, while T- was assumed to be constant with respect to Z, and a constant was derived. Compared to the surface explosion of hemispherical TNT, P- and I- were similar, whereas Twas larger.
A "blast-wave trap" in an L-shaped tunnel section was studied to mitigate blast pressure outside an underground or subsurface magazine. Small-scale blast measurement experiments, utilizing a square tube model and a 100-mg test explosive, were conducted to evaluate how the trap length, without cushioning materials, affects the waveform and blast pressure parameters outside the tube. When the trap was long enough, the blast wave outside the tube formed a two-wave structure, and the peak overpressure was mitigated significantly. Even with the two-wave structure outside, the waveform near the tube exit inside did not clearly show two wave structures; the second wave steepened rapidly after leaving the tube. The trap's effect on mitigating blast pressure was assessed by "without trap equivalency," setting the case without the trap as 1. Under the experimental conditions with a two-wave structure outside, the equivalencies based on peak overpressure were approximately 0.2 to 0.4, and those from the positive scaled impulse were approximately 0.7 to 0.9. Installing a sufficiently long trap effectively mitigated blast pressure outside the tube.
Underwater shock waves generated by explosives provide superior processing range and precision due to their high energy density, outperforming other shock-wave-based material processing methods. However, practical applications require minimizing explosive usage for safety and efficiency. Detonators contain the smallest amount of explosive for practical use. A major challenge in underwater detonator explosions is the rapid pressure attenuation caused by the three-dimensional expansion of shock wave energy. To mitigate this, shock wave reflections from walls can be utilized to control propagation direction and reduce pressure attenuation, thereby improving processing efficiency. Depending on the wall geometry, the shock wave front can be flattened while maintaining high pressure, ensuring uniform force application and enhancing processing quality. This study developed a numerical model using Ansys Autodyn to simulate underwater detonator explosions. The propagation of shock waves captured through high-speed imaging and the measured pressure closely matched the simulation results, validating the model's accuracy. These findings provide a foundation for optimizing reflective wall designs, contributing to enhanced material processing techniques and improved shock wave convergence applications.
Controlling rock fragmentation and ground vibration is essential in rock blasting to ensure resource uniformity and mitigate environmental impacts. The air-deck blasting method, which incorporates an air gap into the blasthole, has been widely employed to address these challenges. Building on prior research, we developed a modified air-deck charging technique utilizing a paraffin-waxed paper tube to create a stable air gap, demonstrating reductions in vibration levels and enhanced fragment uniformity. Despite its practical advantages, the mechanisms underlying this method remain partially understood. To investigate these mechanisms, we applied three-dimensional combined finite-discrete element method (3-DFDEM) simulations, analyzing mainly rock fragmentation, and ground vibration patterns. The comparative results between conventional and air-deck blasting provide valuable insights into the method's performance and potential applications.
This study investigates the effect of ambient pressure on ignition delay for B/KNO3 using laser ignition. Experiments were conducted in air with ambient pressure as a parameter, and the influence of the generated gas was examined by comparing vertical and horizontal laser irradiation. The results showed that in vertical irradiation, ignition delay increases as ambient pressure rises. This is because the generated gas interferes with the laser, and the gas density increases with pressure, reducing laser intensity and heat transfer to the ignition charge. At lower pressures, gas density decreases due to diffusion, leading to less laser attenuation and shorter ignition delays. In horizontal irradiation, the range of the ignition delay range with respect to the ambient pressure is much smaller than that of vertical irradiation. The generated gas moves upward due to buoyancy, reducing interference between the gas and the laser. These findings indicate that ambient pressure significantly affects ignition delay by influencing gas generation and laser attenuation.
Theoretical design of molecular hybrids of 2-(dinitromethylene)-1,3-diazacyclopentane (DNDZ) (a derivative of FOX7) was done by linking the DNDZ to known energetic materials via a -CH 2- chain. A total of 12 novel molecular hybrids of DNDZ were designed, and their performance parameters were studied computationally. All the calculations for the molecules were done successfully to obtain these properties, which were further compared with DNDZ and RDX. Molecule 1, a hybrid of DNDZ and 2,3,4,5-tetranitro-1H-pyrrole, performed way better than the rest of the molecules and even better than DNDZ and RDX. As much as this molecule has the best detonation parameter, it is very sensitive to impact with the calculated impact sensitivity (IS) of 6 J. Molecule 12 has detonation performance better than all the molecules except molecule 1, and it has a good balance between detonation performance and impact sensitivity as compared to molecule 1.
In fields of agriculture, ammonium nitrate is the most often used chemical fertilizer. Its physicochemical qualities are also applied in the explosive sector because of its affordability and ease of accessibility. But for anti-social objectives, this characteristic has made it more appealing. In order to avoid this, scientists have concentrated on adding different compounds to the ammonium nitrate synthesis process in order to lower its enthalpy. The primary focus of this study was on the effects of ammonium nitrate on the plant's ability to reduce nitrogen concentration and minimize caking phenomena. The plant's ability to absorb heavy metals was not affected by the addition of zinc borate and magnesium nitrate, as evidenced by the significantly reduced results of calorimetry tests. The findings of the instrumental examination showed that even with the addition of 0.1% of the study's ingredients & horbar; zinc borate, and magnesium nitrate & horbar;considerably enhanced the crushing strength of ammonium nitrate. With the results in this instance, it can be said that ammonium nitrate's inclination to deteriorate reduces and its shelf life improves. It was discovered that the reaction medium with the highest crushing strength is the one to which all three chemicals are introduced, even if their crushing strengths are comparable when applied separately. The peak heights in the ammonium nitrate content in anion and cation analysis in ion chromatography, however, show that the low quantities of boron content & horbar;a heavy metal of the chemicals used & horbar;are the cause of this. According to nitrogen analysis, there is no impact on the nitrogen concentration of ammonium nitrate when it comes to agricultural use. It was discovered that boron compounds significantly lowered the enthalpy of ammonium nitrate when DSC analysis was carried out as a calorimetric value. It was discovered that the tendency to detonate was greatly decreased when all three chemicals were added since there was no exothermic peak in the combustion reactions. An electron microscope was used to assess surface porosity, another component influencing the detonation process. The addition of all three compounds to the ammonium nitrate surface results in the smallest and least number of porosity when compared to the surface where each compound is added separately. It has been discovered that reducing surface porosity may change reactivity but it does not lower detonation enthalpy.
Detonation is a high-speed combustion phenomenon in which shock waves and chemical reaction waves interact, leading to rapid temperature and pressure increases that drive chemical reactions. Stability in detonation propagation is highly sensitive to the equivalence ratio (Phi) and the initial droplet size distribution, both of which significantly impact energy release and combustion efficiency. This study investigates two-phase detonation behavior using a two-dimensional Eulerian-Eulerian model under high-temperature and high-pressure ignition conditions. The effects of varying equivalence ratios and liquid fuel droplet distributions on detonation wave propagation were analyzed. The results indicate that wider droplet size distributions improve detonation stability by reducing fluctuations associated with incomplete combustion and droplet fractionation. These findings provide insights into optimizing fuel injection strategies for advanced propulsion systems, including rotating detonation engines, where stable and efficient wave propagation is essential.
The electrolytic ignition of an energetic ionic liquid (EIL) composed of a binary mixture of ammonium dinitramide (ADN) and hydroxylethylammonium nitrate (HEHN) was investigated. A voltage was applied to the ionic liquid (ADN/ HEHN) using six different cathode electrode materials (Mo, Fe, Pt, Ni, and Ta), and the time from voltage application to ignition and current immediately after voltage application was compared. The results demonstrated that the current measured immediately after voltage application and the reciprocal of the ignition delay time for each electrode material followed the order: Fe>Ni>Mo>Pt>Ta and Fe>Mo>Pt>Ni>Ta. The current exhibited a volcano-shaped trend with respect to the d-band center of the transition metal elements, reaching its maximum at a specific d-band center. The reciprocal of the ignition delay time presented a trend similar to that of the current, with the highest value observed for Fe and the lowest for Ta. However, a clear volcano-shaped trend was not observed, likely due to the influence of the pyrolysis reaction that proceeds simultaneously with the electrolysis reaction. This study demonstrates that electrode materials with an optimal d-band center can enhance the electrolytic response immediately after the application of voltage.
HEGPs (High energetic green propellants), the liquid monopropellants based on energetic ionic liquid including Hydroxyl ammonium nitrate (HAN) or Ammonium dinitramide (ADN) are considered promising candidates of alternatives to conventional hydrazine. Yet, insufficient atomization due to the high viscosity of the HEGPs causes a lack of thruster performance, and many parts of the atomization mechanism of the green monopropellants, notably the break-up behavior in the initial part of the injection, remain unexplained. This paper conducts a series of injection experiments with green monopropellants in various conditions, following up with a visual investigation of the injected propellant flow behavior. After explaining the methodology of the visual analysis, it reports the influence on the temporal transitions of the injection, depending on the spray characteristics, the effect of the ambient pressure, and the superheat level.
In this study, the novel method was used to visualize the detonation initiation process by the high-speed spherical projectile using the soap bubble filled with the combustible mixture. The experiments were conducted using the stoichiometric hydrogen-oxygen mixtures with three argon dilution ratios of 40%, 50%, and 70% (2H(2) + O-2 + 2Ar, 2H(2) + O-2 + 3Ar, and 2H(2) + O-2 + 7Ar) in order to investigate the effect of the effective activation energy of the mixture on the criteria of detonation initiation by the projectile. The combustion phenomena around the projectile were observed using the shadowgraph optical system and the high-speed camera. The observation using the soap bubble indicated that the detonation initiation process included the multiple detonation initiations around the projectile that eventually developed into the spherical self-sustained detonation, when the Mach number of the projectile was lower than the Chapman-Jouguet (C-J) detonation Mach number. The initiation criteria based on the detonation cell width was consistent in the 2H(2) + O-2 + 2Ar and 2H(2) + O-2 + 3Ar mixtures, however, the detonation initiation was not observed even if the condition well above the criticality of other two mixtures in the 2H(2) + O-2 + 7Ar mixture, which indicated that the reduction of effective activation energy due to the high argon dilution ratio had the effect to reduce the capability of detonation initiation by the high-speed projectile. Two dimensionless parameters, which characterized the rapidness of the exothermic reaction and the induction length behind the shock wave, were applied to separate the conditions between the shock-induced combustion and the detonation initiation regardless of the argon dilution ratio, and the dimensionless parameters was able to separate the conditions for the detonation initiation, which could not be separated by the cell width.
