Abdellatif Laarich
This is where a general scientific background will be useful to you.
Let’s take the question in stages:
• The oxidation. Magnetite can be equated to a mixed Fe (II) and Fe (III) compound. Or alternatively FeO.Fe2O3. Thus, the oxidation can be shown as:
4Fe3O4 + O2 → 6Fe2O3
There will be a weight gain here when the reaction takes place. This can be followed by TGA. See: https://www.sciencedirect.com/topics/earth-and-planetary-sciences/maghemite where we see that 'Maghemite (γFe2O3) is the ultimate low-temperature oxidation or weathering product of magnetite...... It is unstable and when heated inverts to rhombohedral hematite (αFe2O3) at temperatures between 250 and 750°C'.
• Thermodynamics. Using the Ellingham diagram for iron oxides we see that the above reaction is exothermic but needs high temperatures (or high pressures) to accomplish this. You can find the Ellingham diagram for iron oxides in many places. I attach one from:
https://www.uobabylon.edu.iq/eprints/publication_12_25331_298.pdf
https://www.researchgate.net/publication/345467436_Iron_production_by_hydrogen_plasma
• A knowledge of solid-solid diffusion tells you that you could only have small (let’s say micron or smaller) particles present in atomized aerosols. If you’re dealing with powders the high temperatures will give you a mass of fused post- and sub-micron particles. See for example this webinar (registration required):
Adhesion and cohesion
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W180725AdhesionCohesion
Dispersion and nanotechnology
https://www.malvernpanalytical.com/en/learn/events-and-training/webinars/W190528DispNanoMat
• A corollary of the above is the reaction kinetics will be diffusion controlled – that is getting oxygen into the unreacted Fe (II), FeO
• In general terms reactivity is proportional to specific surface area (SSA) or proportional to 1/d2 where d is the particle size. The usual determinant of SSA is via the BET isotherms or chemisorption experiments. Thus, SSA via BET or O2 chemisorption will give you some indicator of what ‘fused solid mass’ of magnetite may be more reactive. In the ACS paper below we have a proposed kinetic model with the SSA included
• Notwithstanding the above then Google Scholar searches will aid you. I have come up with this list:
• Kinetics of Magnetite (Fe3O4) Oxidation to Hematite (Fe2O3) in Air for Chemical Looping Combustion
https://pubs.acs.org/doi/10.1021/ie501536s
• Open access: Investigation of Magnetite Oxidation Kinetics at the Particle Scale
https://link.springer.com/article/10.1007/s11663-018-1459-5
here are a few articles that discuss the impact of particle size on magnetite oxidation:
These articles should provide you with a good starting point for exploring the impact of particle size on magnetite oxidation.
Zakaria Elmaddahi, Thank you for you answer, However I could not find any article from the ones you mentioned above. could you please tell me where I can find them ?
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