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First-principles based calculation of binary and multicomponent phase diagrams for titanium carbonitride
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.ORCID-id: 0000-0002-9920-5393
KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad materialfysik.
2008 (Engelska)Ingår i: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 32, nr 3, s. 543-565Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In this paper we have used a combined first principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on the vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x + y <= 1). Results from earlier Monte Carlo simulations of the low-temperature binary phase diagrams are used in order to formulate sublattice models for TiCxNy within the compound energy formalism (CEF) that are capable of describing both the low temperature ordered and the high-temperature disordered state. We parameterize these models using first-principles calculations and then we demonstrate how they can be merged with thermodynamic descriptions of the remaining Ti-C-N phases that are derived within the Calphad method by fitting model parameters to experimental data. We also discuss structural and electronic properties of the ordered end-member compounds, as well as short range order effects in the TiCxNy phase.

Ort, förlag, år, upplaga, sidor
2008. Vol. 32, nr 3, s. 543-565
Nyckelord [en]
First-principles calculations; CALPHAD; Titanium carbonitride; Order-disorder reactions; Phase diagrams
Nationell ämneskategori
Den kondenserade materiens fysik Fysikalisk kemi Keramteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-6891DOI: 10.1016/j.calphad.2008.04.007ISI: 000260324400014Scopus ID: 2-s2.0-51649091367OAI: oai:DiVA.org:kth-6891DiVA, id: diva2:11731
Anmärkning
QC 20100622Tillgänglig från: 2007-03-14 Skapad: 2007-03-14 Senast uppdaterad: 2017-12-14Bibliografiskt granskad
Ingår i avhandling
1. From the Electronic Structure of Point Defects to Functional Properties of Metals and Ceramics
Öppna denna publikation i ny flik eller fönster >>From the Electronic Structure of Point Defects to Functional Properties of Metals and Ceramics
2007 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

Point defects are an inherent part of crystalline materials and they influence important physical and chemical properties, such as diffusion, hardness, catalytic activity and phase stability. Increased understanding of point defects enables us to tailor the defect-related properties to the application at hand. Modeling and simulation have a prominent role in acquiring this knowledge. In this thesis thermodynamic and kinetic properties of point defects in metals and ceramics are studied using first-principles calculations based on density functional theory. Phenomenological models are used to translate the atomic level properties, obtained from the first-principles calculations, into functional materials properties. The next paragraph presents the particular problems under study.

The formation and migration of vacancies and simple vacancy clusters in copper are investigated by calculating the energies associated with these processes. The structure, stability and electronic properties of the low-oxygen oxides of titanium, TiOx with 1/3 < x < 3/2, are studied and the importance of structural vacancies is demonstrated. We develop an integrated first-principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on vacancy-induced ordering of the substoichiometric

carbonitride phase, TiCxNy (x+y < 1). The possibility of forming higher oxides of plutonium than plutonium dioxide is explored by calculating the enthalpies for nonstoichiometric defect-containing compounds and the analysis shows that such oxidation is only produced by strong oxidants. For ceria (CeO2) doped with trivalent ions from the lanthanide series we probe the connection between the choice of a dopant and the improvement of ionic conductivity by studying the oxygen-vacancy formation and migration properties. The significance of minimizing the dopant-vacancy interactions is highlighted. We investigate the redox thermodynamics of CeO2-MO2 solid solutions with M being Ti, Zr, Hf, Th, Si, Ge, Sn or Pb and show that reduction is facilitated by small solutes.

The results in this thesis are relevant for the performance of solid electrolytes, which are an integral part of solid oxide fuel cells, oxygen storage materials in automotive three-way catalysts, nuclear waste materials and cutting tool materials.

Ort, förlag, år, upplaga, sidor
Stockholm: Materialvetenskap, 2007
Nyckelord
first principles, ab initio, density functional theory, Calphad, point defects, diffusion, solid electrolytes, oxygen storage materials
Nationell ämneskategori
Övrig annan teknik
Identifikatorer
urn:nbn:se:kth:diva-4309 (URN)978-91-7178-590-9 (ISBN)
Disputation
2007-03-30, F2, Lindstedtsvägen 26, Stockholm, 10:00
Opponent
Handledare
Anmärkning
QC 20100622Tillgänglig från: 2007-03-14 Skapad: 2007-03-14 Senast uppdaterad: 2012-03-22Bibliografiskt granskad

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