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Thermodynamic assessment of the V-O system
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics. Thermo-Calc Software AB, Norra Stationsgatan 93, Stockholm, Sweden.ORCID iD: 0000-0002-8493-9802
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics.ORCID iD: 0000-0001-5031-919X
2015 (English)In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 51, 144-160 p.Article in journal (Refereed) Published
Abstract [en]

The V-O system was thermodynamically assessed using the CALPHAD method. The available experimental data on thermodynamic and thermochemical properties as well as phase diagram information were critically examined and a self-consistent set of thermodynamic parameters was obtained. In total 20 phases were included in this binary system. Five among them were treated as solid solution phases within the framework of the compound energy formalism. The halite phase was modeled as (V,V+2,V+3,Va)<inf>1</inf>(O-2,Va)<inf>1</inf> covering the solubility of both V and O. Thermodynamic descriptions of two different models for the corundum phase are presented, one of which is more complex to correctly take the defect mechanisms into account. The liquid phase was described by the ionic two-sublattice model with the formula (V+2)<inf>P</inf>(O-2,Va-Q, VO<inf>1.5</inf>,VO<inf>2</inf>, VO<inf>2.5</inf>)<inf>Q</inf>. The stoichiometric Magnéli phases V<inf>n</inf>O<inf>2n-1</inf> (n is an integer between 4 and 8) were modeled as (V+3)<inf>2</inf>(V+4)<inf>n-2</inf>(O-2)<inf>2n-1</inf>. Using the present thermodynamic description reliable experimental phase diagram, thermodynamic and thermochemical data were well reproduced.

Place, publisher, year, edition, pages
2015. Vol. 51, 144-160 p.
Keyword [en]
VANADIUM-OXYGEN SYSTEM, HIGH-TEMPERATURE THERMODYNAMICS, PHASE-EQUILIBRIA, N SYSTEM, 2-SUBLATTICE MODEL, V2O3-VO2 SYSTEM, SOLID-SOLUTIONS, DEGREES K, DEGREES-C, MONOXIDE
National Category
Metallurgy and Metallic Materials
Identifiers
URN: urn:nbn:se:kth:diva-174578DOI: 10.1016/j.calphad.2015.08.003ISI: 000366790500015Scopus ID: 2-s2.0-84942099865OAI: oai:DiVA.org:kth-174578DiVA: diva2:877807
Note

QC 20151208. QC 20160121

Available from: 2015-12-08 Created: 2015-10-07 Last updated: 2017-12-01Bibliographically approved
In thesis
1. Investigation of vanadium-containing oxide systems: CALPHAD and experiments
Open this publication in new window or tab >>Investigation of vanadium-containing oxide systems: CALPHAD and experiments
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Fundamental studies on thermodynamic properties of vanadium-containing oxides systems are essential to understand practical vanadium metallurgical process. The CALPHAD technique is here applied to the thermodynamic modelling of the V-O, Ca-V-O and Ti-V-O systems. The compound energy formalism is used for all the solution phases. All optimization processes and calculations are performed using the Thermo-Calc software package. The present work attempts to develop a self-consistent thermodynamic database of all phases in the studied systems. The obtained datasets can be used to calculate thermodynamic properties, stable as well as metastable phase equilibria and driving forces for oxidation etc.

Steelmaking slag is an important secondary source for vanadium extraction. The phase relationships and vanadium distribution in the CaO-SiO2-MgO-V2O3-Al2O3 synthetic slags, whose compositions were chosen based on the relevance to the steel producers, are also studied. Phase equilibria in the temperature range of 1773 to 1823 K at oxygen partial pressure of 10-10 bar and 0.21 bar were characterized.

An investigation of the volatilization of vanadium oxide was also carried out in the present work. Isothermal evaporation of vanadium pentoxide in the temperature range between 1723 and 1873 K was investigated by Thermogravimetric Analysis under different oxygen partial pressures, viz. oxygen, air or CO2. The Arrhenius activation energy for the evaporation reaction in various atmospheres was calculated from the experimental results. A mathematical model was developed to describe the kinetics of the evaporation process. Evaporation coefficients and enthalpies in various atmospheres were also estimated. The present results may have some implications in recovering vanadium from different vanadium-bearing sources.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. 47 p.
Keyword
Calphad; thermodynamic modelling; compound energy formalism; evaporation kinetics, activation energy, TGA, activity
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:kth:diva-197292 (URN)978-91-7729-169-5 (ISBN)
Public defence
2016-11-25, Sal F3, Lindstedtsvägen 26, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20161202

Available from: 2016-12-02 Created: 2016-12-01 Last updated: 2016-12-02Bibliographically approved

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