Phase transformations and microstructure evolution during combustion of iron powder

Laurine Choisez (Corresponding author), Niek E. van Rooij, Conrad Hessels, Alisson K. da Silva, Isnaldi R. Souza Filho, Yan Ma, Philip de Goey, Hauke Springer, Dierk Raabe

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Abstract

To successfully transition from fossil-fuel to sustainable carbon-free energy carriers, a safe, stable and high-density energy storage technology is required. The combustion of iron powders seems very promising in this regard. Yet, little is known about their in-process morphological and microstructural evolution, which are critical features for the circularity of the concept, especially the subsequent reduction of the combusted oxide powders back to iron. Here, we investigated two iron powder combustion pathways, one in air and one with the assistance of a propane pilot flame. Both processes resulted in spherical hollow particles composed of a complex microstructure of wüstite, magnetite and/or hematite. Partial evaporation is indicated by the observation of nanoparticles on the micro-sized combustion products. The associated gas production inside the liquid droplet could be the origin of the internal porosity and micro-explosion events. Cracking at the end of the combustion process results in mostly open porosity, which is favorable for the subsequent reduction process. With this study, we aim to open the perspective of iron metal fuel from macroscopic combustion analysis towards a better understanding of the underlying microscopic thermodynamic, kinetic, microstructural and thermomechanical mechanisms.
Original languageEnglish
Article number118261
Number of pages13
JournalActa Materialia
Volume239
DOIs
Publication statusPublished - 15 Oct 2022

Funding

We thank Christian Bross, Monika Nellessen and Katja Angenendt for their support to the metallography lab and SEM facilities at MPIE, Benjamin Breitbach for the support to the X-ray diffraction facilities, Herbert Faul for the pycnometer measurement and Daniel Kurz for the chemical analysis of the powders at MPIE. We gratefully acknowledge the support of Pometon S.p.A. LC acknowledges the financial support through the postdoctoral scholarship program of the Max-Planck Society. IRSF acknowledges financial support through CAPES (Coordenação de Aperfeiçoamento de Pessoal de NívelSuperior) & Alexander von Humboldt Foundation (grant number 88881.512949/2020–01). YM acknowledges financial support through Walter Benjamin Programme of the Deutsche Forschungsgemeinschaft (project number 468209039). H.S. acknowledges funding through the Heisenbergprogramm of the Deutsche Forschungsgemeinschaft (grant SP1666/2). TU/e gratefully acknowledges the support of Shell, the European Research Council (grant agreement no. 884916), the European Regional Development Fund and Provincie Noord-Brabant within the OPZUID program.

FundersFunder number
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Shell
Alexander von Humboldt-Stiftung88881.512949/2020–01
H2020 European Research Council884916
Deutsche Forschungsgemeinschaft468209039, SP1666/2
Max-Planck Society
European Regional Development Fund

    Keywords

    • Combustion
    • Iron powder
    • Metal fuel
    • Solidification microstructure
    • Sustainable energy carrier

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