An Arrhenius-Wescott-Stewart-Davis (AWSD) reactive burn model is applied to describe shock initiation and detonation properties of the HMX-based high explosive LX-04. The parameters in the model are calibrated to data from multiple sources. The thermodynamic equations of state used in the model are calibrated to a combination of thermochemical calculations for HMX and LX-04 as well as experimentally-measured cylinder expansion results for LX-04. The kinetic parameters are calibrated to velocity data from gas gun experiments performed using EDC-32-a high explosive with the same chemical composition as LX-04 but different structural properties, and scaled rate stick data for PBX 9012. The AWSD model is shown to accurately describe the shock initiation and propagation of LX-04. Very good agreement is observed between the available experimental data and the AWSD model output. The presented results constitute an accurate LX-04 reactive burn model for use in engineering-scale models and simulations.
Plastic-bonded explosive (PBX) formulations are physical mixtures of polymers with explosive solids, and their mechanical strength is heavily dependent on the adhesion between polymer and explosive. The surface chemistry of the explosive can limit the strength of this bond. This paper explores the capability of atomic layer deposition (ALD) to successfully coat a representative explosive powder (triaminotrinitrobenzene, TATB) to generate a new surface functionality without degrading the explosive crystal. ALD is a thin film deposition technique designed to coat high aspect ratio materials conformally with sub-nm level precision by utilizing alternating exposures of gaseous species to form monolayer reaction sequences on the substrate of interest's surface. X-ray photoelectron spectroscopy of a batch of TATB crystals coated with 20 deposition cycles of aluminum oxide reveal the presence of the Al 2s and 2p peaks, as well as oxygen peaks, consistent with successful aluminum oxide deposition. Transmission electron imaging after focused ion beam lift-out reveals the presence of approximately an 80 nm coating after 200 ALD cycles, corresponding to a deposition rate of about 4 & Aring;/cycle. Finally, small-scale safety testing for thermal, impact, spark, friction, and chemical aging were performed on TATB processed with 20 cycles of aluminum oxide ALD. Coated TATB was demonstrated to be insensitive with some slight increase thermal aging mediated degradation. In summary, this shows that ALD is likely usable on explosives without catastrophic chemical effects, and the effects of the surface changes will be useful for PBX formulation processes.
ABSTRACT Ammonium nitrate (AN) is a prominent environment‐friendly oxidizer, but it suffers from drawbacks such as combustion instability, hygroscopicity, and phase transitions at room temperature. To address these challenges, an extensive, combined theoretical and experimental study was performed on ammonium‐nitrate/ammonium‐perchlorate (AN/AP) composite solid propellants to assess the impact of a dual‐oxidizer formulation containing AN and AP with cobalt nitrate hexahydrate (CNH) as a catalytic additive. Propellant formulations were evaluated using NASA CEA thermochemical calculations, x‐ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, high‐pressure burn‐rate tests, mechanical characterization (including Young's modulus), density measurements, heat‐of‐combustion determinations, chloride‐ion analysis, and detailed kinetic modeling. The optimized AN/AP/CNH formulation exhibited a 1419.87% increase in burn rate at 4.14 MPa and a 24.85% increase in Young's modulus relative to pure AN‐based propellant. Addition of CNH to the dual‐oxidizer matrix also reduced the experimentally measured chloride content by 22.8% compared with AP‐only propellants. Thermal decomposition kinetic analysis showed that the activation energy was also drastically decreased with CNH, showing that their decomposition behavior is improved. Based on the overall results, it is concluded that the combined incorporation of AP and CNH is associated with improved ballistic, thermo‐mechanical, and combustion performance of AN‐based propellants, which makes it promising for high‐performance solid rocket applications with reduced toxicity.
Resonant mixing is a promising processing approach to manage mixing of materials with high solids content and has shown strong performance for mixing powders and pastes in energetic materials. This has led to the exploration of the approach for granulation of primary particles into millimeter-sized agglomerates, including for generating energetic material prill. Despite some demonstrations of the ability to form prill, little work has been done to understand how the resonant mixing process parameters, such as the acceleration, applied vacuum, and mixing time, impact the properties of the prill. Here we systematically examine these process parameters through a design of experiments approach, evaluating the critical quality attributes including prill size, span, and roundness as well as the granule yield as the response variables. We find that the amount of time spent in the first stage where vacuum is applied, has a significant effect on the granule yield, while the magnitude of the vacuum in the second stage where vacuum is applied, is important for the particle size and roundness. We also examined the porosity in depth using microcomputed tomography, showing that a strong applied vacuum leads to a more porous prill. With these results, this study highlights key process parameters and provides future directions for optimization of resonant mixing granulation for different formulations.
To address the safety and environmental concerns of conventional water jets in hydroxyl-terminated polybutadiene (HTPB) propellant processing, a high-pressure liquid CO2 jet is proposed for fragmentation. An experimental platform was established to systematically investigate the effects of jet pressure, standoff distance, and nozzle diameter via single-factor and Taguchi orthogonal experiments. Results indicate that impact efficiency increases with jet pressure, with depth and area rising sharply beyond 25 MPa and 30 MPa, respectively. Efficiency decreases with standoff distance; increasing it from 5 to 11 mm reduces maximum depth and area by 51% and 62%. Nozzle diameter enlarges the damaged area, while depth peaks at 1.5 mm. Orthogonal analysis reveals the dominant parameter for depth is pressure > nozzle diameter > standoff distance (optimal: 35 MPa, 5 mm, 1.5 mm), and for area is nozzle diameter > standoff distance > pressure (optimal: 35 MPa, 5 mm, 2.0 mm). Compared to water jets, liquid CO2 jets produce a damaged area up to 248.2 mm(2), approximately 4.9 times larger, confirming its feasibility and advantages for safe, eco-friendly propellant disposal.
