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Formation of 2D transition metal dichalcogenides on TiC1-xAx surfaces (A=S, Se, Te): A theoretical study
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - Ångström, Oorganisk kemi.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Fysiska sektionen, Institutionen för fysik och astronomi, Materialteori.
2014 (Engelska)Ingår i: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 29, nr 2, s. 207-214Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Using first principle density functional calculations, we study the formation of 2D transition metaldichalcogenides (TMDs) on TiC1-xAx, (A = S, Se, and Te) surfaces. We examine the structural misfits between chalcogen-containing TiC and different TMDs and demonstrate that the conditions for formation of TMDs are fulfilled in TiC1-xAx. We also demonstrate the influence of chalcogens on the cohesive properties and electronic structure of the carbides. We find that they react with W and form W-dichalcogenides. In the experimentally reported Ti–C–S nanocomposite coatings, the carbide grains are embedded in an amorphous carbon matrix. We discuss here the role ofthis matrix in the reaction. We propose that TiC1-xTex and TiC1-xSex are the favorable sources fordichalcogenide formation and suggest an alternative way to produce 2D materials in general. Furthermore, we argue that using Ti–C–Te or Ti–C–Se in nanocomposite coatings may be more advantageous for tribological applications than that of Ti–C–S.

Ort, förlag, år, upplaga, sidor
2014. Vol. 29, nr 2, s. 207-214
Nationell ämneskategori
Den kondenserade materiens fysik Oorganisk kemi Materialkemi Tribologi (ytteknik omfattande friktion, nötning och smörjning)
Forskningsämne
Materialvetenskap; Kemi med inriktning mot oorganisk kemi; Materiefysik
Identifikatorer
URN: urn:nbn:se:uu:diva-213666DOI: 10.1557/jmr.2013.350ISI: 000332933800005OAI: oai:DiVA.org:uu-213666DiVA, id: diva2:683084
Forskningsfinansiär
Stiftelsen för strategisk forskning (SSF)VetenskapsrådeteSSENCE - An eScience CollaborationKnut och Alice Wallenbergs StiftelseEU, Europeiska forskningsrådet, 247062-ASDTillgänglig från: 2014-01-02 Skapad: 2014-01-02 Senast uppdaterad: 2018-01-11Bibliografiskt granskad
Ingår i avhandling
1. Triboactive Low-Friction Coatings Based on Sulfides and Carbides
Öppna denna publikation i ny flik eller fönster >>Triboactive Low-Friction Coatings Based on Sulfides and Carbides
2014 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

For sustainable development, it is highly important to limit the loss of energy and materials in machines used for transportation, manufacturing, and other purposes. Large improvements can be achieved by reducing friction and wear in machine elements, for example by the application of coatings. This work is focused on triboactive coatings, for which the outermost layer changes in tribological contacts to form so-called tribofilms. The coatings are deposited by magnetron sputtering (a physical vapor deposition method) and thoroughly chemically and structurally characterized, often theoretically modelled, and tribologically evaluated, to study the connection between the composition, structure and tribological performance of the coatings.

Tungsten disulfide, WS2, is a layered material with the possibility of ultra-low friction. This work presents a number of nanocomposite or amorphous coatings based on WS2, which combine the low friction with improved mechanical properties. Addition of N can give amorphous coatings consisting of a network of W, S and N with N2 molecules in nanometer-sized pockets, or lead to the formation of a metastable cubic tungsten nitride. Co-deposition with C can also give amorphous coatings, or nanocomposites with WSx grains in an amorphous C-based matrix. Further increase in coating hardness is achieved by adding both C and Ti, forming titanium carbide. All the WS2-based materials can provide very low friction (down to µ<0.02) by the formation of WS2 tribofilms, but the performance is dependent on the atmosphere as O2 and H2O can be detrimental to the tribofilm functionality.

Another possibility is to form low-friction tribofilms by tribochemical reactions between the two surfaces in contact. Addition of S to TiC/a-C nanocomposite coatings leads to the formation of a metastable S-doped carbide phase, TiCxSy, from which S can be released. This enables the formation of low-friction WS2 tribofilms when a Ti-C-S coating is run against a W counter-surface. Reduced friction, at a moderate level, also occurs for steel counter-surfaces, likely due to formation of beneficial iron sulfide tribofilms.

The studied coatings, whether based on WS2 or TiC, are thus triboactive, with the ability to form low-friction tribofilms in a sliding contact.

 

 

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2014. s. 86
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1183
Nyckelord
coatings, thin films, tribology, tungsten disulfide, transition metal dichalcogenide, nanocomposite, TiC/a-C, tribofilms, PVD, XPS, HAXPES, XRD, SEM, TEM, Raman spectroscopy, nanoindentation
Nationell ämneskategori
Oorganisk kemi
Forskningsämne
Kemi med inriktning mot oorganisk kemi
Identifikatorer
urn:nbn:se:uu:diva-230989 (URN)978-91-554-9041-6 (ISBN)
Disputation
2014-10-31, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (Engelska)
Opponent
Handledare
Tillgänglig från: 2014-10-09 Skapad: 2014-09-02 Senast uppdaterad: 2015-01-23Bibliografiskt granskad

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