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/Fe 2 O 3 nanothermites and Si/Fe 2 O 3 core/shell (CS) nanothermites using differential scanning calorimetry. The Si/Fe 2 O 3 CS nanothermites were prepared by an electroless deposition method. We found that the Si/Fe 2 O 3 CS nanoparticles (NPs) had a lower reaction onset temperature (∼550 °C) than the MM Si/Fe 2 O 3 nanothermites (>650 °C). The onset temperature of the Si/Fe 2 O 3 CS nanothermites is also insensitive to the size of the Si core NP. These results indicate that the interfacial contact quality between Si and Fe 2 O 3 is the dominant factor for determining the ignition properties of thermites. Finally, the reaction onset temperature of the Si/Fe 2 O 3 CS NPs is comparable to that of the commonly used Al-based nanothermites, suggesting that Si is an attractive fuel for thermites.

Metal–Organic Frameworks as Fuels for Advanced Applications: Evaluating and Modifying the Combustion Energy of Popular MOFs

“…−8700 kJ/mol) that is around 60–65% of the value reported for gasoline and related fuels and a high E v of 36.3 kJ/cm 3 , which exceeds hypergolic rocket fuels MMH and UDMH, and is in the range of popular hydrocarbon fuels (Table ). These values are below those of some actual (aluminum) or proposed (boron) high-energy solid fuels − but already close to those of the magnesium fuel (Table , Figure , also see Supporting Information, Section S9).…”

“…Importantly, we show that the energy density of MOFs can be tuned to approach or even exceed those of kerosene, diesel, magnesium, or hydrazine rocket fuels. Whereas the specific energies and energy densities of herein investigated MOFs are smaller than for high combustion energy solids such as boron, 49,50 the specific energy values are close to those of magnesium and aluminum fuels, with energy density in some cases exceeding that of magnesium. Our study shows that the modular design and the ability to direct the framework topology of ZIFs offer a means to control the energy content in a way that is not accessible to conventional fuels.…”

“…Comparison of E g and E v for herein studied MOFs to those of typical gasoline, hydrazine (MMH and UDMH), and magnesium fuel. ,, Values for carboxylate MOFs are in green and for ZIFs in red.…”

Electroless Metallization of the Elements: Survey and Progress

“…Among the catalyzed substrates, two unique applications are particularly noteworthy. 268 have used EL Fe processes to create nanothermites from Si NPs. 3-aminopropyltriethoxysilanebased (APTES) SAM is chemisorbed onto the native oxide layer on each Si NP and catalyzed with acidic PdCl 2 to bind Pd II to the particle surface.…”

Assembling Hybrid Energetic Materials with Controllable Interfacial Microstructures by Electrospray

“…Compared to changing the formulation of thermites, it seems that assembling energetic materials with organized interfacial structures by new preparation methods is more efficient, such as sol–gel, incorporating with MOFs, sputtering, , arrested reactive milling, and so on. Electrospray, one ramification of electrohydrodynamic atomization, is a mature technology widely used in the realm of mass spectrometry, propulsion system of satellites, encapsulation, particle production, surface coating, and film deposition.…”