Abrupt Transition of Nanothermite Reactivity: The Roles of Loading Density, Microstructure and Ingredients

Area of Science:

• Materials Science
• Chemical Engineering
• Energetic Materials

Background:

• Nanothermites are crucial power sources for microinitiators and pyrotechnics.
• Charge density significantly influences energy storage and reaction kinetics in confined systems.

Purpose of the Study:

• To investigate the combustion and pressurization characteristics of electrosprayed nanothermite-based hybrid energetic materials (THEMs).
• To explore the effects of varying metallic oxides, energetic additives, and loading densities on THEMs' performance.

Main Methods:

• Systematic testing of combustion and pressurization of THEMs with different metallic oxides (Fe2O3, CuO, Bi2O3) and additives (NC, HMX, AP, CL-20).
• Analysis of THEMs across various loading densities, correlating porosity, heat transfer, and reaction kinetics.

Main Results:

• Increased loading density reduced porosity and convective heat transfer efficiency.
• Exceeding a critical density led to decreased peak pressure, drastically reduced pressurization rates, and prolonged combustion duration.
• The critical density for Al/CuO/NC/CL-20 composites was 37.9–43.9% TMD.
• Reactivity order at high loading density: AP > HMX ≈ CL-20 > NC.
• Bi2O3-THEMs maintained high reactivity up to 59.7% TMD due to low ignition temperature and high gas yield.

Conclusions:

• Loading density critically affects nanothermite combustion and pressurization by altering microstructure and heat/mass transfer.
• The choice of metallic oxide and energetic additives significantly impacts THEMs' performance, especially at high densities.
• Bi2O3-based THEMs offer superior high-density performance, providing insights for designing tailored energetic materials.