Bulletin of the American Physical Society
22nd Biennial Conference of the APS Topical Group on Shock Compression of Condensed Matter
Volume 67, Number 8
Monday–Friday, July 11–15, 2022; Anaheim, California
Session V02: Metalized Explosives, Thermites, Hydrides, and NanoenergeticsFocus Recordings Available
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Chair: Jennifer Jordan, Los Alamos National Laboratory Room: Anaheim Marriott Platinum 6 |
Thursday, July 14, 2022 2:00PM - 2:30PM |
V02.00001: Reactive Metal Nanopowders via Wet Sonochemical Methods Invited Speaker: Albert Epshteyn Techniques have been developed for the wet sonochemical synthesis and stabilization of single, as well as mixed-metal, reactive metal nanopowders (RMNPs) that exhibit unique characteristics, including combined high energy density and relative stability towards handling in non-inert environments under ambient conditions. Processes have been developed for making various RMNPs, including those containing early transition metals, such as Ti, Zr, and Hf, as well as other high-energy elements, such as Al, B, C, and H. The focus of each process design is on the appropriate selection of starting materials, solvent, process conditions, byproduct salt removal, and powder post-processing techniques to obtain final product powders with the most desirable characteristics. Experiments examining the combustion of select RMNPs show unique and interesting burn characteristics. |
Thursday, July 14, 2022 2:30PM - 2:45PM |
V02.00002: Energy release mechanisms of solid-state hydride containing hybrid propellant systems Prithwish Biswas, Michael Zachariah Solid-state hydrides possess higher enthalpy of combustion than commonly employed fuels in energetic materials such as Al, Ti, Si, and Mg, on both gravimetric and molar basis. Ammonia borane (NH3BH3/AB) possesses the highest gravimetric hydrogen content and has the potential to release high amount of energy from the oxidation of its energetic elemental constituents (B and H). We have characterized AB-nanoflakes, synthesized by anti-solvent crystallization method, using various techniques such as in-situ time-of-flight mass spectrometry, FTIR, TGA/DSC, and NMR, accompanied by DFT calculations, to study the reaction mechanism of AB with different solid-state oxidizers (KClO4, CuO, Bi2O3, AP). We found that AB/AP reaction pathway differs from the reaction mechanism of AB with all other oxidizers. This alternative reaction route causes the AB/AP system to exhibit remarkably higher energy release rates over that of AB/KClO4 (∼27x) and the standard Al/AP propellant (∼7x). These findings motivated us to use aerosol route to synthesize a hybrid propellant composite consisting of Al/AP/AB, with optimized gravimetric and volumetric energy release profile, having a ~400 K lower ignition onset than Al/AP system. |
Thursday, July 14, 2022 2:45PM - 3:00PM |
V02.00003: Macroscopic and microscopic imaging of aluminum-HTPB in a counter flow system Erik Hagen, Haiyang Wang, Michael Zachariah Evaluation of solid-fuels for air breathing applications is inherently complicated due to the interplay of fluid mechanics, heat and mass transport to the burning surface. Counter-flow systems offer a quasi- 1-D geometry which significantly decreases the complexity while still maintaining the key operational parameter space of a non-premixed fuel oxidizer system. Hydroxyl-terminated polybutadiene (HTPB) is the most common binder in a solid propellant, but there is interest in increasing energy density though the addition of metallic fuels. In this study we incorporate nano-Aluminum (nAl) and micron-Aluminum (μAl) into HTPB at various loadings. High-speed macroscopic and microscopic imaging systems were used to characterize the near surface Al burning as a function of oxygen flow and pre-heat. The two imaging techniques revealed the morphology and size of the burning Al agglomerations. The regression rate of the fuel grain increased linearly with increase in the oxidizer flow rate. With the observation of high-speed macroscopic and microscopic imaging, combined with color pyrometry, we found that the agglomeration size of Al particles decreased while their temperature increased as the flow rate of the oxidizer increased. This indicates a more complete reaction of the Al particles with more O2, confirmed by XRD and SEM characterizations. |
Thursday, July 14, 2022 3:00PM - 3:15PM |
V02.00004: Combustion characteristics study of 90 wt% Al/B/Ti-KClO4 loading nanothermites with high-speed videography and pyrometry Yujie Wang, Erik Hagen, Haiyang Wang, Michael Zachariah Nanoscale aluminum, boron and titanium are attractive fuels in the field of energetic materials, therefore understanding the combustion behavior of them is important for their practical application. KClO4 is a strong oxidizer with high oxygen content. We use 3D printing for the preparation of 90 wt% loading of nanoscale aluminum, boron and titanium with KClO4 and study their combustion characteristics with high-speed videography and pyrometry. Different combustion behaviors are observed among the three composites. For Al-KClO4, molten Al droplets with Al2O3 cap form and combine before leaving the burning surface and smoke cloud from the oxidation of Al vapor is present around the burning particles. B-KClO4 and Ti-KClO4 have similar combustion behaviors as coral-shaped agglomerates form on their burning surfaces and spherical burning particles are rarely observed. The combustion behavior characteristics among these three composites are attributed to the melting and boiling point of these metals and their corresponding metal oxides. Three-color pyrometry is utilized to estimate the temperature of the burning particles and the result shows that temperature of molten Al body and Al2O3 cap are higher than the melting point of Al and Al2O3, respectively, but also lower than the boiling points of Al and Al2O3, respectively. Estimated temperature of agglomerates for B-KClO4 is below but near the melting point of B and explains why the agglomerates are non-spherical. The estimated temperature of agglomerates for Ti-KClO4 is higher than the melting point of both Ti and TiO2, and given the agglomeration being non-spherical, Ti2O3 with higher melting point is probably present and dominating the shape of the agglomerates. |
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