Sensitive nanoenergetic powders, such as nanothermites, have traditionally been processed by ultrasonic mixing of very low solids loaded suspensions in organic solvents, which has restricted their use and application due to high solvent content and associated handling issues. In this work, we report on the performance and mixing quality of nanothermite mixtures prepared in a LabRAM resonant mixer at high solids loadings as compared to ultrasonic mixing. Specifically, the aluminum‐bismuth(III) oxide (Al/Bi2O3) system processed in the polar solvent N,N‐dimethylformamide (DMF) was investigated. It was found that the performance and overall quality of mixing was strongly correlated to the volumetric solids loading during processing; increasing volumetric solids loading decreases separation of particles, leading to more particle interaction and more intimate mixing. The measured performance of this system processed at 30 vol‐% was similar to traditionally ultrasonicated mixtures. Increasing the solids loading above 30 vol‐% yielded diminishing returns in performance and may introduce additional safety concerns since dry powders are very sensitive to electrostatic discharge. This mixing approach uses significantly less solvent than traditional ultrasonic mixing, results in a higher density final material, and is amenable to scaling. In addition, solvent wetted nanothermite mixed at 30 vol‐% solids loading can be mixed and deposited from a single applicator and was observed to be over five orders of magnitude less sensitive to electrostatic discharge than dry powders. This relative insensitivity enables the safe deposition of high density nanothermite ink onto devices.

Nanothermites are a promising replacement energetic for many devices but their use has been limited by high sensitivity during processing, hazardous processing solvents, and time consuming deposition. Incorporating processing and deposition into a single step, especially if no organic solvents were used, could allow nanothermites to be applied safely in a wider range of applications. This work reports on the performance and characterization of direct‐deposited water processed nanothermite inks on semiconductor bridge (SCB) initiators. Specifically, it investigates the replacement of nanothermites processed by resonant mixing (Resodyn LabRAM) in the solvent N,N‐dimethylformamide (DMF) with nanothermites processed in water. Processing safety and mixture performance were then characterized. It was found that water processed nanothermites were stable for up to 480 min in a water bath at 50 °C only if both metal and metal oxide particles were coated with palmitic acid. In addition, water processed nanothermites were found to have better mixing intimacy, which resulted in better performance than nanothermite processed in DMF. Direct deposition of water processed nanothermites also mitigates electrostatic discharge (ESD) sensitivity, while the material remains wetted, improving processing safety dramatically. For the system investigated, it was found that processing at a solids loading of 30 vol.% resulted in a high density, high performance ink that was deposited directly onto the SCBs. This resulted in a 25 % reduction in the all fire threshold over traditional energetics. This mixing approach uses an environmentally friendly mixing medium, can result in a higher density final material, and allows safe one‐step mixing and deposition.

Although nanotechnology advancements should be fostered, the environmental health and safety (EHS) of nanoparticles used in technologies must be quantified simultaneously. However, most EHS studies assess the potential implications of the free nanoparticles which may not be directly applicable to the EHS of particles incorporated into in-use technologies. This investigation assessed the aquatic toxicological implications of copper oxide (CuO) nanospheres relative to CuO nanorods used in nanoenergetic applications to improve combustion. Particles were tested in both the as-received form and following combustion of a CuO/aluminum nanothermite. Results indicated nanospheres were more stable in water and slowly released ions, while higher surface area nanorods initially released more ions and were more toxic but generally less stable. After combustion, particles sintered into larger, micrometer-scale aggregates, which may lower toxicity potential to pelagic organisms due to deposition from water to sediment and reduced bioavailability after complexation with sediment organic matter. Whereas the larger nanothermite residues settled rapidly, implying lower persistence in water, their potential to release dissolved Cu was higher which led to greater toxicity to Ceriodaphnia dubia relative to parent CuO material (nanosphere or rod). This study illustrates the importance of considering the fate and toxicology of nanoparticles in context with their relevant in-use applications.