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Synthesis, structure and properties of Ni-alloyed TiCx-based thin films
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Inorganic Chemistry. (oorganisk kemi)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Materials Chemistry, Structural Chemistry. (strukturkemi)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
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2010 (English)In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 28, 5950-5960 p.Article in journal (Refereed) Published
Abstract [en]

By using non-reactive sputter deposition at low temperatures metastable solid solution phases in the Ti–Ni–C system were synthesized. Produced thin films were either single phase carbides or nanocomposite of nanocrystalline carbide and amorphous C. In the Ni-containing samples a supersaturated solid solution phase (Ti1−xNix)Cy was identified, and was present either as single phase or in a nanocomposite with amorphous C. By modification of the chemical stability of the carbide phase, the addition of Ni was found to strongly promote the formation of amorphous carbon phase in the coatings. Samples have been microstructurally analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Mechanical properties have been evaluated through nanoindentation and pin-on-disc measurements; electrical properties were determined by measurement of the resistivity and the contact resistance. Alloyed nanocomposite coatings were also found to exhibit enhanced tribological and electrical properties, with a decreased resistivity and friction. This makes these thin films very interesting for application in sliding electrical contacts. The mechanisms responsible for the reductions remain to be determined.

Place, publisher, year, edition, pages
2010. Vol. 20, no 28, 5950-5960 p.
National Category
Inorganic Chemistry Engineering and Technology
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-109034DOI: 10.1039/c0jm00592dISI: 000279565900025OAI: oai:DiVA.org:uu-109034DiVA: diva2:245932
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
In thesis
1. Design of carbide-based nanocomposite coatings
Open this publication in new window or tab >>Design of carbide-based nanocomposite coatings
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis research on synthesis, microstructure and properties of carbide-based coatings is reported. These coatings are electrically conducting, and can be tailored for high hardness, low friction and wear, along with load-adaptive behaviour. Tailoring these properties is achieved by controlling the relative phase content of the material. Coatings have been synthesised by dc magnetron sputtering, and their structures have been characterised, mainly by X-ray photoelectron spectroscopy and X-ray diffraction.

It has been shown that nanocomposites comprising of a nanocrystalline transition metal carbide (nc-MeCx, Me = Ti, Nb or V) and an amorphous carbon (a-C) matrix can result in low contact resistance in electrical contacts. Such materials also exhibit low friction and high resistance to wear, making them especially suitable for application in sliding contacts. The lowest contact resistance is attained for small amounts of the amorphous carbon phase.

It has been shown that specific bonding structures are present in the interface between nc-TiCx and the a-C phases in the nanocomposite.  It was found in particular that Ti3d and C2p states are involved, and that considerable charge transfer occurs across the interface, thereby influencing the structure of the carbide.

Further design possibilities were demonstrated for TiCx-based nanocomposites by alloying them with weakly carbide-forming metals, i.e., Me = Ni, Cu or Pt.  Metastable supersaturated solid solution carbides, (T1-xMex)Cy, were identified to result from this alloying process. The destabilisation of the TiCx-phase leads to changes in the phase distribution in the deposited nanocomposites, thus providing further control over the amount of carbon phase formed. Additional design possibilities became available through the decomposition of the metastable (Ti1-xMex)Cy phase through an appropriate choice of annealing conditions, yielding either more carbon phase or a new metallic phase involving Me. This alloying concept was also studied theoretically for all 3d transition metals using DFT techniques.

It has also been demonstrated that Ar-ion etching (commonly used in the analysis of carbide based nanocomposites) can seriously influence the result of the analysis, especially for materials containing metastable phases. This implies that more sophisticated methods, or considerable care are needed in making these analyses, and that many of the earlier published results could well be in error.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2009. 83 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 682
Keyword
chemistry, thin film, dc magnetron sputtering, carbide, nanocomposite, PVD, solid solution
National Category
Chemical Sciences Inorganic Chemistry
Research subject
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-109427 (URN)978-91-554-7636-6 (ISBN)
Public defence
2009-11-27, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2009-11-06 Created: 2009-10-15 Last updated: 2014-01-21Bibliographically approved
2. Nanocomposites for Use in Sliding Electrical Contacts
Open this publication in new window or tab >>Nanocomposites for Use in Sliding Electrical Contacts
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis nanocomposite materials for use in high performance electrical contacts are tested. Self mating silver as coatings on cupper substrates are the most used material combination in power connectors today. In this work two new concepts were tested. The first one was to change one of the mating surfaces to a hard thin coating and keep the other surface made of silver. Tested coatings were nanocomposites with hard carbides in a matrix of amorphous carbon. TiC/a-C and  Ti-Ni-C/a-C were tested both electrically and tribologically. The total amount of carbon and the amount of carbon matrix was important, both for the electrical and the tribological properties. The Ti-Ni-C coating also showed that substituting Ti in TiC with the weak carbide former Ni changed the stability of the carbides. The substitution resulted in more a-C matrix and less C in the carbides. Thin coatings of nc-TiC/a-C and  Ti-Ni-C/a-C showed high potential as material candidates for use in electrical contacts.

The other tested concept was to modify the used silver instead of replacing it. This was done by embedding nanoparticles of solid lubricant IF-WS2 in the silver. The results from reciprocating sliding displayed low friction and high wear resistance. The modified silver surfaces lasted for 8000 strokes with a friction of about 0.3 while at the same time allowing for a low contact resistance. The results for surfaces of pure silver coating displayed a friction of 0.8-1.2 and that the silver was worn through already after 300 strokes.

A new method to investigate inherent hardness and residual stress of thin coatings, on complex geometries or in small areas, was also developed. An ion beam was used to create stress free coating as free standing micro pillars. Hardness measured on the pillars and on as-deposited coating were then used to calculate the residual stress in the coatings.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 49 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 879
Keyword
tribology, materials science
National Category
Materials Engineering Other Materials Engineering Composite Science and Engineering
Research subject
Materials Science; Engineering Science with specialization in Materials Science; Engineering Science with specialization in Tribo Materials
Identifiers
urn:nbn:se:uu:diva-160809 (URN)978-91-554-8219-0 (ISBN)
Public defence
2011-12-09, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 10:15 (Swedish)
Opponent
Supervisors
Available from: 2011-11-18 Created: 2011-11-01 Last updated: 2011-11-23Bibliographically approved

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Lewin, ErikUrbonaite, SigitaWiklund, UrbanJansson, Ulf

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