Controlling the morphology and particle size distribution is a proven strategy for preparing energetic materials that achieve both high energy output properties and high safety performance. In this study, we developed a modular microfluidic crystallization system for the preparation of ultrafine spherical CL-20 with regulated morphology and particle size. By optimizing the process parameters, the optimal conditions for preparing spherical CL-20 were determined to be a solvent-to-non-solvent flow rate ratio of 1:10, a mixing disc size of 60 & times;105 mu m, a solution concentration of 0.35 g/mL, and a reaction temperature of 25 degrees C. Under these optimal conditions, CL-20 with a mean particle size of 0.49 mu m, minimal surface defects, and high sphericity were successfully produced. Simultaneous control of CL-20's morphology and particle size significantly enhances its thermal decomposition properties and mechanical safety. This study offers a practical strategy for tailoring CL-20's microstructure and experimental guidance for optimizing other energetic materials.
This study systematically investigated the metal-free oxidative debenzylation of 2,6,8,12-tetraacetyl-4,10-dibenzyl-2,4,6,8,10,12-hexaazaisowurtzitane to 2,6,8,12-tetraacetyl- 2,4,6,8,10,12-hexaazaisowurtzitane using an H2O2/HBr system was systematically optimized by response surface methodology. A face-centered central composite design enabled reliable modeling of the reaction within experimentally feasible boundaries. The resulting quadratic model showed high statistical significance and predictive accuracy, with analysis of variance confirming that H2O2 concentration, H2O2 equivalents, HBr equivalents, and reaction temperature all significantly influence the reaction outcome. Notably, reaction temperature exhibited a pronounced curvature effect, defining an optimal operational window beyond which the yield decreased. Numerical optimization predicted optimal conditions of approximately 60% H2O2, 20 equivalents of H2O2, 10 equivalents of HBr, and a reaction temperature of similar to 53 degrees C, corresponding to a predicted yield of about 79%. Experimental validation under these conditions provided reproducible yields of 76-77%, confirming the robustness and reliability of the developed model. Overall, this work establishes an efficient, metal-free, and environmentally compatible strategy for the oxidative debenzylation of TADBIW under mild conditions.
This study investigates the influence of Hydroxyl-Terminated Polybutadiene (HTPB) molecular weight (Mn), hydroxyl value, polydispersity index, and functionality on the mechanical and combustion properties of composite solid propellants (CSPs). Five samples (CSP-A to E) were prepared using HTPB grades with Mn ranging from 2462 to 4226 Da at a constant 68 vol% solid loading. Results revealed that moderate-molecular-weight HTPB formulations demonstrate optimal overall performance. Specifically, CSP-C (Mn = 3253 Da) exhibited the highest energetic output, with increases of approximately 5-7% in specific impulse (271.3 s), 7-10% in density impulse (458.5 s), and similar to 15% in heat of decomposition (7.08 MJ/kg), respectively, compared to other samples. While lower molecular weight and higher functionality enhanced tensile strength (up to 6.81 kgf/cm(2)) through increased crosslink density, excessive crosslinking led to reduced ductility. These findings highlight the importance of optimizing intrinsic HTPB characteristics to tailor CSP performance.
In the pursuit of high-efficacy, low-visibility infrared illuminants, three distinct formulations were developed: I-1, composed of nitrocellulose (NC); I-2, containing glycidyl azide polymer (GAP); and I-3, a composite of NC and GAP. Among these, formulation I-3 demonstrated an exemplary equilibrium, achieving a burn duration of 62 seconds coupled with enhanced irradiance. Molecular dynamics simulations revealed that the rigid structure of nitrocellulose and the flexible chains of glycidyl azide polymer amalgamate to form a dense microarchitecture (with a free volume of 13.17% and a cohesive energy density of 464.0 J/cm & sup3;). This microstructural arrangement significantly contributes to improved combustion stability and radiative efficiency. This investigation offers essential mechanistic insights that advance the development of high-performance, low-signature pyrotechnics.
This study investigates the influence of aluminum powder content on the metal-driving capability and underwater explosion energy of HMX/RDX-based aluminized explosives. Through the preparation of polymer-bonded explosives (PBX) with aluminum content ranging from 0 to 15%, we conducted explosive-driven metal plate test and established JWL-Miller equation of state model incorporating aluminum secondary reactions for underwater explosion simulations using LS-DYNA. Experimental results demonstrated that increasing aluminum content in aluminized explosives resulted in a gradual decline in metal-driving capability, with an 8% reduction observed at 15% aluminum content. Underwater explosion simulations revealed that where the aluminum-oxygen ratio reached 0.15, the shock wave energy achieved 1.846 MJ/kg. Bubble energy showed positive correlation with aluminum content, when the 15% aluminum formulation exhibited prolonged bubble pulsation period (249.6 ms) and expanded bubble radius (107.4 cm). The research validates the effectiveness of the JWL-Miller equation in modeling non-ideal detonation characteristics of aluminized explosives, the impact of aluminum powder on explosive performance is not only reflected in its heat value but also in the timing of energy release. These findings provide critical theoretical guidance for the design of high-energy explosive systems requiring optimized performance.
This study investigates the shock initiation mechanisms of covered high explosive (HE) subjected to shaped charge jet (SCJ) penetration. With varying cover plate thicknesses and SCJ velocities, the impact and initiation processes exhibit complex dynamic behaviors. The initiation mechanisms for different jet velocities and cover plate configurations were analyzed. A theoretical model was established to describe the initiation process, accounting for the dynamic coupling between the precursor shock wave (PSW) and bow shock wave (BSW). The model's predictive accuracy was validated against experimental data from prior studies. The influence of SCJ velocity and cover plate thickness on shock initiation was systematically examined. Results demonstrate that, for a given SCJ with a velocity of 7500 m/s, the initiation of covered HE is induced solely by the PSW when the cover plate thickness is below 20 mm. At moderate thicknesses (20-60 mm), initiation results from the dynamic coupling between the PSW and BSW. When the cover plate thickness exceeds 60 mm (up to 120 mm), where the PSW attenuates below the critical threshold, initiation occurs exclusively due to the BSW.
To investigate the influence of cracks on the response characteristics of explosive columns under drop-weight impact, a finite element simulation model of a drop-weight impacting an RDX-based aluminized explosive column was established. Columns without cracks, with a close fit, with 1 mm cracks, and with 1.5 mm cracks were prepared, and drop-weight impact loading experiments were conducted. The computational results indicate that the crack edge is the point of maximum stress during drop-weight loading, and the radial displacement of nodes around the crack is significant. Compared to intact and close-fit columns, columns with cracks exhibit a significant increase in the internal maximum stress, stress rate, strain, strain rate, and radial flow velocity, with the magnitude of increase being greater for wider cracks. Drop-weight loading experiments show that the ignition thresholds for aluminized explosive columns under impact are essentially equivalent under no-crack and close-fit conditions. When a crack is present, the ignition threshold under impact significantly decreases. A flow phenomenon of internal material from high-density to low-density regions was observed at the half-radius position along the column axis. The experimental results show good consistency with the simulation results.
Spherical reactive composite powders with narrow size distributions are desired as feedstocks for printable reactive inks. Emulsion-assisted milling (EAM) yields such powders for a range of materials. Earlier work established certain relationships between the EAM process parameters and material properties for one material system. This study aims to expand the applicability of such relations to different materials. A stoichiometric Al & centerdot;Fe2O3 composite thermite powder was prepared by EAM. When the EAM process parameters are not optimized, the product contains both spherical and irregularly shaped composite particles. Optical microscopy and image analysis served to separate the EAM-produced thermite particles into spherical and irregular classes. Thermal analysis was used to quantify the reactivity of the prepared powders. The morphological characteristics of the powders, their composition (from XRD), and their reactivity descriptors were correlated with both the EAM process parameters and the powders' quality metrics. At least some of the process-property correlations for EAM apply similarly to different materials. Correlations between the powder morphology and its reactivity are indirect.
This study systematically investigates the effects of fluorinated graphite (FG) on 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX) through an integrated approach combining theoretical calculations and experimental validation. Static theoretical analyses, encompassing frontier orbital theory, electrostatic potential mapping, interaction region analysis, and bond order calculations, were conducted. These analyses collectively revealed that fluorinated graphite enhances the reactivity of HMX while concurrently preserving its intrinsic safety profile. This theoretical finding was further substantiated by vacuum gas evolution tests, which confirmed the absence of any detrimental impact on HMX's safety characteristics. Furthermore, thermal molecular dynamics simulations provided insights into the modulation of HMX thermal decomposition by FG with varying fluorination degrees. The simulations indicated a distinct mechanistic difference: low-fluorination-degree FG primarily promotes decomposition through the dissociation of its participating fluorine atoms, while high-fluorination-degree FG acts as a direct catalyst for the decomposition process. In parallel, experimental techniques including Differential Scanning Calorimetry (DSC), combustion pressure tests, and combustion residue characterization were employed. The results from these experiments consistently and conclusively verified the combustion-promoting effects of fluorinated graphite on HMX. Therefore, this comprehensive work lays a solid theoretical and experimental foundation for the potential application of fluorinated graphite in solid propellant formulations.
This study examines the impact of mass percentages of fine and coarse particles in PBX compositions on mechanical properties, performance, and sensitivity, as well as the influence of temperature on these factors. The findings indicate that the density measurement test alone is insufficient to definitively identify voids in pressed PBXs, and that the mass percentages of fine and coarse particles do not significantly affect impact and friction sensitivity. Additionally, a decrease in packing density correlates with an increase in linear thermal expansion coefficients, as shown by TMA tests. Compression tests reveal that mechanical properties (stress and strain) decrease with increasing mass percentages of coarse particles, with variations due to density changes at different temperatures. Furthermore, higher mass percentages of fine or coarse particles lead to reduce in packing density and performance at ambient temperatures, while performance is significantly impacted by temperature variations as packing density decreases. Notably, as packing density approaches optimal levels the effect of temperature on performance diminishes. Overall, the study highlights that variations in particle mass percentages significantly influence mechanical properties and performance through changes in packing density, and that initial temperature of PBXs result in notable variations in performance and mechanical properties due to the presence of voids.
This study investigates the influence of structural parameters on the energy release characteristics of warheads with aluminum/polytetrafluoroethylene (Al/PTFE) energetic casings. This study adopted a numerical simulation method to compare the performance of an Al/PTFE-cased warhead against a bare explosive charge. The simulations demonstrated that the energetic casing significantly enhances the shockwave overpressure with an average increase of 24.7% compared to bare charges. Field tests were conducted to validate the numerical model. The comparison between simulated and experimental overpressure data yielded maximum and minimum relative errors of 23% and 2.58%, respectively. The results indicate that at shorter distances from the detonation center, higher length-to-diameter (L/D) ratios generate greater overpressure. Conversely, at greater distances, warheads with lower L/D ratios show a slower attenuation of overpressure. For the parameters investigated, the optimal configuration for maximizing peak overpressure was identified as an L/D ratio of 2.0 combined with a casing thickness of 0.12D, where D is the charge diameter. Furthermore, a distinct bimodal relationship between casing thickness and overpressure was identified, with a local optimum at 0.04D and a global optimum at 0.12D. These results offer critical guidance for the structural design of Al/PTFE energetic-cased warheads, while providing a basis for designing optimized warheads.
A comparative thermomechanical study of nitrile butadiene rubber (NBR)-based high-energy composite propellants was conducted to clarify formulation-dependent deformation and damage mechanisms. Two compositions, Type I (78 wt.% solids) and Type II (79 wt.% solids), were examined through uniaxial tensile testing (5-1000 mm & centerdot;min-& sup1;) at -20, 27, and 55 degrees C, supported by dynamic mechanical analysis (-80 to 80 degrees C). Stress-strain behavior exhibited three regimes linear elasticity, de-wetting, and strain hardening governed by binder continuity and filler packing. Type I, with higher binder content, demonstrated superior ductility, sustained strain hardening, broader failure boundary envelope, and matrix-dominated damage across loading conditions. Type II showed increased modulus, greater strain-rate sensitivity, and interface-controlled failure marked by accelerated de-bonding. Time-temperature superposition and cumulative damage modeling quantified rheo-kinetic sensitivity and durability limits. The results define formulation-specific thermomechanical operating envelopes, highlighting the trade-off between stiffness and damage tolerance critical for propellant structural reliability.
This study reports the development and characterization of a novel solid composite propellant formulated with hydroxyl-terminated polybutadiene (HTPB) and potato-starch nitrate (NPS) as an energetic bio-based additive. The effect of NPS incorporation at different loadings (10%, 30%, and 50%) on the physicochemical and energetic properties of the binder system was systematically investigated. Thermochemical simulations predicted a marked increase in specific impulse upon NPS doping, highlighting its potential to enhance propulsion performance. Structural and chemical interactions were examined by Fourier Transform Infrared Spectroscopy (FTIR), while density measurements revealed a progressive increase in binder density with increasing NPS content. Scanning Electron Microscopy (SEM) confirmed a homogeneous morphology and acceptable dispersion of NPS within the HTPB matrix. Differential Scanning Calorimetry (DSC) demonstrated improved thermal stability and increased exothermicity, indicating enhanced energetic performance. Overall, the incorporation of NPS significantly improves the physicochemical and energetic-related properties of HTPB-based propellants, making this modified binder a promising candidate for advanced and sustainable energetic formulations.
Optimizing the fuel phase in bulk emulsions for open-pit and underground mining enhances safety and efficiency. In this study, gas-to-liquid (GTL) fuels have been studied due to their low viscosity readily biodegradable nature, and low odor and toxicity. Single- and double-salt emulsions were prepared with two GTL fuels, G85 and G100, different in boiling range but identical in hydrocarbon composition targeting at 95/5%m/m oxidizer/fuel (O/F) ratio. GTL emulsions were compared to a standard 94/6%m/m O/F ratio emulsion prepared with White Oil, as well as common polyisobutylene succinic anhydride (PIBSA) emulsifiers. Viscosity and microscopy data demonstrated good emulsification and stability, even with reduced fuel content (5% vs. 6%m/m). Decrease in density with time during chemical gassing with NaNO2 was also evaluated, pointing to differences between fuel phases, which was ascribed to the highly paraffinic nature of the fuel, as well as the varying viscosities. Further, it was demonstrated that the reduce fuel content did not impact velocity of detonation (VoD) significantly, showing values around 4500 m/s in unconfined tests in plastic pipes with two diameters. This work demonstrated that GTL fuel phases offer advantages over mineral oils while maintaining emulsion stability and performance, offering economic and safety benefits.
