## 3 Results and Discussion
### Benchmark Study
Following the kinetics of the various species in a given reacting unit cell of the system (see Supplementary Information file S3), we observed that at the disruption temperature, only 22% of the Al reservoir is consumed. This is consistent with the fact that Al/CuO is known to produce a lot of gases and possibly fragments or aggregates that continue to burn in the atmosphere. Ferrous oxide (Fe\({}_{2}\)O\({}_{3}\)) is another oxide material of great technological interest due to its high exothermic performance with reduced gas production in thermite couples (0.14 g of gas per 100 g of thermite mixture) [58]. Extensive studies have characterized the Al/Fe\({}_{2}\)O\({}_{3}\) thermite reactions or isolated Fe\({}_{2}\)O\({}_{3}\) reduction finding complex decomposition scenarios that were not found to vary with the stoichiometry of the system. One study in particular by [PERSON] et al., followed by more recent studies, used X-ray diffraction and spectroscopy to analyze the intermediate products present in the reaction [59; 60; 61; 62]. While the main products found were alumina and iron, the significant presence of FeAl\({}_{2}\)O\({}_{4}\) among other intermediate components, led the authors to propose a reduction scheme where Fe\({}_{2}\)O\({}_{3}\) reduces first to both Fe\({}_{3}\)O\({}_{4}\) and FeO, before a final reduction to pure iron. Therefore, similarly to the Al/CuO thermite, our model assumes a two-step decomposition in which Fe\({}_{2}\)O\({}_{3}\) first decomposes into FeO and then further reduces to Fe (see individual reaction equations in the Supplementary Information file S2). Looking at the propagation simulation results plotted in Figure 3b, the Al/Fe\({}_{2}\)O\({}_{3}\) system shows a significantly greater initiation delay (350 ms) and temperature (1994 K) compared to Al/CuO. This is not surprising considering that the diffusion of oxygen species within these species have distinct diffusion kinetics; in our model, we assume decomposition kinetics of the oxidizers to follow inner oxygen diffusion characteristics (see Supplementary Information file S1). Consistent with its diffusion properties, iron oxide is known to have a decomposition temperature, 1808 K,  
Figure 3: Temperature profiles taken at regular time intervals dt and calculated burn rate V\({}_{\rm{SS}}\) for: (**a**) Al/CuO, (**b**) Al/Fe\({}_{2}\)O\({}_{3}\), (**c**) Al/WO\({}_{3}\), and (**d**) Al/Pb\({}_{3}\)O\({}_{4}\). significantly higher than that of CuO (933 K for the bare oxidizer, 1050 K for Al/CuO thermite) [28]. In summary, the ability of iron oxide to release oxygen species dominates the initiation performances, which is radically different from Al/CuO that is driven by oxygen transport through the aluminum oxide barrier layer. Furthermore, the Al/Fe\({}_{2}\)O\({}_{3}\) system has a calculated burn rate in the same range (slightly lower) as the Al/CuO case with a value of 38 cm\(\cdot\)s\({}^{-1}\), with well-established steady-state propagation (see Figure 3b). Considering the lower enthalpy of reaction (281.7 kJ per oxygen atom) compared to that of Al/CuO (397.5 kJ per oxygen atom), some other effects are probably playing an active role in sustaining a relatively high flame velocity (the second highest value of all tested thermites after Al/CuO). On the one side, Al/Fe\({}_{2}\)O\({}_{3}\) combustion can endure a much higher flame temperature due to the high disruption temperature (Al vaporization), which de facto increases all mechanisms kinetics; this effect of the disruption temperature increase leading to a higher burn rate is well-documented in Reference [49] for nanothermites in the form of nanolaminates. On the other side, the thermal conductivity is approximately three times that of Al/CuO, which causes preheating of the non-reacted thermite during the long period of initiation. This process is clearly visible in Figure 3b, as a spatial spreading of the flame front temperature is visible in comparison to that of Al/CuO.