Micro-Explosion and Recycling of an Iron-Ethanol-Kerosene Slurry Fuel

Metallic iron is explored as a dual-purpose energy carrier and material feedstock by formulating a kerosene-based iron–ethanol slurry that serves both as a micro-explosive fuel where each droplet undergoes rapid internal bubble growth and fragments into many smaller droplets and as a source of recyclable iron. Single-droplet combustion experiments (with 30 wt% iron particles in kerosene + 5 wt% ethanol) demonstrate novel micro-explosion-driven combustion behavior. The addition of ethanol markedly enhances combustion, nearly quadrupling the burning rate and halving the burnout time compared to kerosene alone. Iron particle size is shown to govern the combustion mode: micron-scale iron produces intense, disruptive micro-explosions (with droplet fragmentation rates up to ∼20,000 sec⁻¹) leading to complete burnout in as little as 0.3 s, whereas nano-iron yields more controlled burning (∼1,700 sec⁻¹). Crucially, the hydrocarbon slurry provides an in-situ antioxidant effect, in the sense that the surrounding kerosene liquid acts as a protective barrier that separates the iron particles from oxygen, delaying iron oxidation during combustion and enabling non-oxidative storage of the metal fuel. Following combustion, over 90% of the iron oxide byproduct is recovered and regenerated into metallic iron via hydrogen reduction. The reduced iron is then compacted by Field-Assisted Sintering Technology (FAST), yielding dense iron compacts with fine microstructure and a Vickers hardness of ∼165 HV approximately twice that of conventional pure iron (70–90 HV). This integrated combustion–reduction–sintering cycle highlights a circular iron loop in which the fuel itself becomes a high-value product. The findings showcase a sustainable, energy-efficient metal fuel platform that couples fire-driven micro-explosion phenomena with advanced materials processing, pointing to new opportunities in carbon-free combustion, functional material fabrication, and pyrotechnic applications.