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Deposition and characterization of MAX phases in the V-Ge-C system
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Materials Chemistry.
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Article in journal (Refereed) Submitted
URN: urn:nbn:se:uu:diva-96303OAI: oai:DiVA.org:uu-96303DiVA: diva2:170834
Available from: 2007-10-19 Created: 2007-10-19Bibliographically approved
In thesis
1. Synthesis and Characterization of Ternary Carbide Thin Films
Open this publication in new window or tab >>Synthesis and Characterization of Ternary Carbide Thin Films
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis reports on synthesis, microstructure and properties of binary and ternary carbide thin films deposited by dc magnetron sputtering. These materials are interesting since they exhibit a wide range of useful properties, such as high hardness, resistance to wear and oxidation, and high electrical conductivity. Here, an early transition metal (M) and carbon (C) have been used as the basis, often with the addition of a second M-element or an A-group element (A). In these systems nanocomposites, metastable solid solutions, multilayers, or Mn+1AXn-phases have been deposited. The Mn+1AXn-phases are a group of nanolaminated compounds with a unique mixture of metallic and ceramic properties. In general X is carbon or nitrogen, although here only carbon has been used.

Epitaxial MAX-phase thin films of Ti2AlC, Ti3AlC2 and V2GeC have been deposited for the first time. They have been studied with emphasis on phase stability, phase composition and nucleation characteristics to gain deeper insights into their growth. The microstructure of the films was characterized by electron microscopy and X-ray diffraction. In addition, bond strength characteristics have been studied by soft X-ray spectroscopy and complementary calculations within DFT. Their mechanical and electrical properties have been studied, and the results are discussed on the basis of their electronic structure. Furthermore, by interleaving the Ti3SiC2 MAX-phase with TiC0.67 a multilayer structure has been formed, for which a new intrusion-type deformation behaviour has been described.

A new concept in the design of nanocomposite films has been developed, whereby a solid solution of a weak carbide-forming element in the carbide structure creates a driving force for surface segregation of C. This concept has been verified both theoretically and experimentally for the Ti-Al-C and Ti-Fe-C systems. It has been shown by pin-on-disc measurements that this surface segregation leads to graphitization and consequently a very low friction coefficient for these films. Finally, it has been demonstrated that low-friction films with tunable magnetic properties can be achieved in the Ti-Fe-C system.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 62 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 353
Chemistry, Thin film, dc magnetron sputtering, tribology, carbide, PVD, MAX-phase, DFT, solid solution, Kemi
urn:nbn:se:uu:diva-8265 (URN)978-91-554-6991-7 (ISBN)
Public defence
2007-11-09, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, 751 21, Uppsala, 10:15
Available from: 2007-10-19 Created: 2007-10-19 Last updated: 2010-09-13Bibliographically approved

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