The controllable incorporation of multiple immiscible elements into a single nanoparticle merits untold scientific and technological potential, yet remains a challenge using conventional synthetic techniques. We present a general route for alloying up to eight dissimilar elements into single-phase solid-solution nanoparticles, referred to as high-entropy-alloy nanoparticles (HEA-NPs), by thermally shocking precursor metal salt mixtures loaded onto carbon supports [temperature ~2000 kelvin (K), 55-millisecond duration, rate of ~10 K per second]. We synthesized a wide range of multicomponent nanoparticles with a desired chemistry (composition), size, and phase (solid solution, phase-separated) by controlling the carbothermal shock (CTS) parameters (substrate, temperature, shock duration, and heating/cooling rate). To prove utility, we synthesized quinary HEA-NPs as ammonia oxidation catalysts with ~100% conversion and >99% nitrogen oxide selectivity over prolonged operations.

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Reactive nanolaminates are a high-energy-density configuration for energetics that have been widely studied for their tunable energy release rates. In this study, we characterized Al/CuO nanolaminate reactions with different fuel/oxidizer ratios and bilayer thicknesses using both macro- and microscale high-speed imaging/pyrometry. Under microscopic imaging, we observe significant corrugation (the ratio of the total geometrical length of the flame to the width of the sample in the direction perpendicular to propagation) of the flame, which can increase the reaction surface area by as much as a factor of 3. This in turn manifests itself as an increase in the global burn rate (total nanolaminate film length/total burn time). We find that the global burn rate can be predicted as the product of the microburn rate (local vector burn rate at the microscopic scale) and the corrugation. These corrugation effects primarily impact fuel-rich conditions, resulting in higher global burn rates. We find that the reaction zone has a thickness of ∼150 μm. Finally, we present a 3D rendering of what we believe the reaction zone looks like, based on the results from in-operando observation and SEM cross-sectional imaging.

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