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Modeling of iron diffusion in the iron oxides magnetite and hematite with variable stoichiometry
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.ORCID iD: 0000-0002-4521-6089
2011 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 59, no 1, 53-60 p.Article in journal (Refereed) Published
Abstract [en]

The vacancy model of diffusion is applied to magnetite and hematite, and mathematical expressions for the iron flux in the lattice-fixed frame of reference, as a function of the defect structure, are presented The defect structures, i e the vacancy content on the different type of sites, and the thermodynamic factors are calculated from the available Calphad type of thermodynamic descriptions for the oxides Expressions for Fe tracer diffusion coefficients are derived and the relations between mobility and tracer diffusivity are given The mobilities are fitted by a least-squares optimization to experimental data on tracer diffusion from the literature For magnetite, an excellent representation of the experimental tracer data is achieved together with a satisfactory description of the sparse chemical diffusion data available For hematite, the experimental scatter is very large and anomalous large frequency factors and activation energies have been reported In the present report a compromise is suggested.

Place, publisher, year, edition, pages
2011. Vol. 59, no 1, 53-60 p.
Keyword [en]
Lattice defects, Thermodynamics, Bulk diffusion, Kinetics, Binary oxides
National Category
Materials Engineering
Identifiers
URN: urn:nbn:se:kth:diva-27694DOI: 10.1016/j.actamat.2010.08.032ISI: 000284789200006Scopus ID: 2-s2.0-78049529140OAI: oai:DiVA.org:kth-27694DiVA: diva2:380239
Note

QC 20101221

Available from: 2010-12-21 Created: 2010-12-20 Last updated: 2017-12-11Bibliographically approved
In thesis
1. On high temperature oxidation resistance: Towards the materials genome of high temperature alloys
Open this publication in new window or tab >>On high temperature oxidation resistance: Towards the materials genome of high temperature alloys
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The efficiency of a heat engine increases with increasing service temperature. This leads to a demand for material that can withstand aggressive environments and sometimes also high load at higher and higher temperature. That is the rationale for the work of this thesis. It is divided into two parts, both addressing model alloy systems for components used in oxidizing high temperature environments. In the first part the phase equilibria and phase diagrams of Ni-Ru and Al-Ni-Ru are investigated from a thermodynamic point of view using the well known Calphad method. In particular, the debated existance of a miscibility gap between the aluminides NiAl and RuAl is considered. This led to a combined ab initio/Calphad approach and it is suggested that there is a miscibility gapat low temperature. In the second part, first of its kind diffusion simulations in oxides are performed in the technologically important Fe-O and Cr-O systems. In the simulations, the moving phase boundary problem is solved with use of temperature and composition dependent diffusion coefficients, that are evaluated for complex oxide phases modeled with up to four sublattices. This type of simulations attracts a lot of interest and it looks very promising for future extension to higher order systems.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. vii, 32 p.
National Category
Metallurgy and Metallic Materials
Research subject
Materials Science and Engineering
Identifiers
urn:nbn:se:kth:diva-154227 (URN)978-91-7595-313-7 (ISBN)
Public defence
2014-11-14, B2, Brinellvägen 23, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20141222

Available from: 2014-10-22 Created: 2014-10-15 Last updated: 2014-10-23Bibliographically approved

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