Electroless Deposition and Ignition Properties of Si/Fe₂O₃ Core/Shell Nanothermites

Abstract

Thermite, a composite of metal and metal oxide, finds wide applications in power and thermal generation systems that require high-energy density. Most of the researches on thermites have focused on using aluminum (Al) particles as the fuel. However, Al particles are sensitive to electrostatic discharge, friction, and mechanical impact, imposing a challenge for the safe handling and storage of Al-based thermites. Silicon (Si) is another attractive fuel for thermites because of its high-energy content, thin native oxide layer, and facile surface functionality. Several studies showed that the combustion properties of Si-based thermites are comparable to those of Al-based thermites. However, little is known about the ignition properties of Si-based thermites. In this work, we determined the reaction onset temperatures of mechanically mixed (MM) Si/Fe₂O₃ nanothermites and Si/Fe₂O₃ core/shell (CS) nanothermites using differential scanning calorimetry. The Si/Fe₂O₃ CS nanothermites were prepared by an electroless deposition method. We found that the Si/Fe₂O₃ CS nanoparticles (NPs) had a lower reaction onset temperature (∼550 °C) than the MM Si/Fe₂O₃ nanothermites (>650 °C). The onset temperature of the Si/Fe₂O₃ CS nanothermites is also insensitive to the size of the Si core NP. These results indicate that the interfacial contact quality between Si and Fe₂O₃ is the dominant factor for determining the ignition properties of thermites. Finally, the reaction onset temperature of the Si/Fe₂O₃ CS NPs is comparable to that of the commonly used Al-based nanothermites, suggesting that Si is an attractive fuel for thermites.