Thermite reactions with oxides of iron and silicon during combustion of magnesium with lunar and Martian regolith simulants

Abstract

It has been shown recently that mixtures of JSC-1A lunar regolith simulant with magnesium are combustible. Thermite-type reactions in these mixtures could be used for in situ production of construction materials on the Moon. Because of complex composition of lunar regolith, however, the mechanisms of these reactions are not well understood. Also, for Mars mission applications, it is important to explore the possibility of using Martian regolith in such mixtures. In the present paper, combustion of two Martian regolith simulants (JSC-Mars-1A and Mojave Mars) with magnesium is studied using thermodynamic calculations and combustion experiments. To understand the reaction mechanisms in these mixtures as well as in the mixtures of JSC-1A lunar regolith simulant with magnesium, thermoanalytical experiments are also conducted. It has been shown that the Martian regolith simulants form combustible mixtures with magnesium. The measured combustion temperatures and identified product compositions are in reasonable agreement with thermodynamic predictions. The mixtures of JSC-Mars-1A with magnesium at 20-30 wt% Mg exhibit higher temperatures and burn more vigorously than mixtures based on Mojave Mars, which is explained by the higher content of iron oxide in JSC-Mars-1A. For Mojave Mars, combustion is accompanied by oscillations in the front motion and by the formation of a layered structure of the product. This effect is more significant at lower concentrations of Mg. Thermoanalytical studies have shown that iron oxide plays a dominant role in the combustion of JSC-Mars-1A simulant with magnesium. However, Mg/SiO 2 mixture ignites at a temperature lower by approximately 100°C than for Mg/Fe 2 O 3 . For Mojave Mars material and JSC-1A lunar regolith simulant, which include more silica and less iron oxide, silica exhibits a significant effect on the combustion, promoting reactions at lower temperatures.

Mechanically activated combustion synthesis and shockwave consolidation of magnesium silicide

“…The effect of changing the particle volume during the reaction is negligible according to the calculations based on the densities of Mg, Si, and Mg 2 Si (1.74 g/cm 3 , 2.32 g/cm 3 , and 1.99 g/cm 3 , respectively). Note that swelling was also observed in recent experiments on combustion of lunar and Martian regolith simulants with magnesium [41,46,47].…”

“…During SHS, however, increased Mg vapor pressure expands the material in the localized, relatively thin combustion front and the expanded material simply pushes the above products upward. The layered structure of the SHS product has been observed previously [41,[46][47][48] and explained by thermal instability (pulsations) of the combustion wave in low-exothermic mixtures [49,50].…”

Magnesium: properties and rich chemistry for new material synthesis and energy applications

“…However, SF 6 in particular has a global warming impact 23 900 times that of CO 2 . 53 Molten Mg can react with iron oxides in a thermite reaction, which can increase reaction temperatures over 2473 K. 54 Furthermore, molten Mg has a high affinity for water (H 2 O). In the event where it is exposed to H 2 O, it can expand to about 1000 times its original volume.…”

Prioritization of habitat construction materials on Mars based on multi-criteria decision-making

“…In a study by Delgado, Cordova and Shafirovich [120], the possibility of using Martian regolith has been explored to understand the effect of iron oxide and magnesium contents on reaction mechanisms. However, more research needs to be conducted on this cement.…”