Influence of Stoichiometry on the Thrust and Heat Deposition of On‐Chip Nanothermites

Abstract

Currently, there is very little systematic work quantifying the thrust or heat applied to an electronic circuit or other substrate by a deposited layer of energetic material. A better understanding of the interactions between nanoscale energetic materials and electronic systems, as a function of stoichiometry, is needed. For this purpose, formulations of nAl-CuO and nAl-Bi 2 O 3 nanothermites were prepared at different equivalence ratios and selectively deposited onto electronic circuit analogues (silicon wafers) and the amounts of thrust production and heat deposition were measured. Both nanothermite systems produced maximum thrust near stoichiometric ratios, accom-panied by a shock wave, with minimal thermal effects due to large gas production, which ejects the hot products of the substrates. Conversely, more fuel-rich mixtures led to significantly decreased thrust while increasing heat deposition due to the lower gas production, which allowed more heat to diffuse to the substrates. This shows that the energetic material response can be tuned between thrust or heat deposition by just varying the equivalence ratio. The conductive heat transfer within the silicon substrates from the nAl-CuO system increased more than the nAl-Bi 2 O 3 system at fuel rich conditions due to its higher heat of combustion.

Factors Affecting Substrate Heating with Printed Thermites

“…consider. Previous authors have found evidence that slower flame speeds (expected for larger particles) increase the heating of the substrate [41,46]. Whereas, it has been reported that the heat flux maximizes between the peak burn rate (fuel rich) and flame temp (stoichiometric) compositions [28].…”

“…While hot gases can be important for propagating the reaction, gaseous products are overall detrimental to the heating of the substrate [41,46]. The gaseous reactions above the surface (the flame) liberate their energy remotely from the substrate resulting in little surface heating beyond radiant heating.…”

Progress in Additive Manufacturing of Energetic Materials: Creating the Reactive Microstructures with High Potential of Applications

“…Due to its relative simplicity, direct writing is widely used for RMS production [12,13,63,[116][117][118]; however, the hazardous and viscous natures of energetic compositions present serious challenges. Therefore, a pipette, syringe or pump can be used to deposit the slurry based on hexanitrohexaazaisowurtzitane (CL-20) and the mixture of two solutions, i. e., the aqueous binder solution and the organic solution of another binder.…”

“…Application of liquid media improves safety: the electrostatic discharge sensitivity increases from 10-100 μJ for nanothermites in dry state to above 250 mJ for a water-processed system immediately after deposition [179]. Solvent type is also important as suspensions in polar solvents maintain their stability longer [180], which is advantageous for the mixing of nanoparticles [116]. To improve the uniformity of the ink suspension, dispersants are added, typically nonionic or ionic polymers soluble in a dispersing medium, e. g., Zephrym™ PD 2206 and Solsperse™ 32500 [76].…”

Controllable Electrically Guided Nano-Al/MoO3 Energetic-Film Formation on a Semiconductor Bridge with High Reactivity and Combustion Performance

“…Generally, MICs are regarded as excellent fuels, which generally consist of metal-fuel (e.g., Al, Mg) and oxidizers that include metal oxides (e.g., MoO 3 [5], Fe 2 O 3 [6], polyvinylidene fluoride [7], NiO [8], CuO [9], and iodates [10]). Compared to traditional micro-MICs, nano-structured MICs have been gradually verified as a promising candidate for highly reactive energetic materials or composites due to their higher heat-release properties, greater contact area 2 of 11 between fuels and oxidizers, and faster detonation velocity [11][12][13]. Therefore, there is an emerging research area of interest in designing novel nano-structured MICs via facile techniques.…”