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Deposition and characterization of magnetron sputtered amorphous Cr-C films
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
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2012 (English)In: Vacuum, ISSN 0042-207X, E-ISSN 1879-2715, Vol. 86, no 9, 1408-1416 p.Article in journal (Refereed) Published
Abstract [en]

Thin films in the Cr-C system with carbon content of 25-85 at.% have been deposited using non-reactive DC magnetron sputtering from elemental targets. Analyses with X-ray diffraction and transmission electron microscopy confirm that the films are completely amorphous. Also, annealing experiment show that the films had not crystallized at 500 degrees C. Furthermore, X-ray spectroscopy and Raman spectroscopy show that the films consist of two phases, an amorphous CrCx phase and an amorphous carbon (a-C) phase. The presence of two amorphous phases is also supported by the electrochemical analysis, which shows that oxidation of both chromium and carbon contributes to the total current in the passive region. The relative amounts of these amorphous phases influence the film properties. Typically, lower carbon content with less a-C phase leads to harder films with higher Young's modulus and lower resistivity. The results also show that both films have lower currents in the passive region compared to the uncoated 316L steel substrate. Finally, our results were compared with literature data from both reactively and non-reactively sputtered chromium carbide films. The comparison reveals that non-reactive sputtering tend to favour the formation of amorphous films and also influence e.g. the sp(2)/sp(3) ratio of the a-C phase. 

Place, publisher, year, edition, pages
2012. Vol. 86, no 9, 1408-1416 p.
Keyword [en]
Amorphous, Chromium carbide, Magnetron sputtering, Electrochemical, Nanoindentation
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-174582DOI: 10.1016/j.vacuum.2012.01.021ISI: 000302839400037OAI: oai:DiVA.org:uu-174582DiVA: diva2:529238
Available from: 2012-05-29 Created: 2012-05-22 Last updated: 2017-12-07Bibliographically approved
In thesis
1. Corrosion and Surface Studies of Stainless Steel and Chromium Carbide Thin-Films
Open this publication in new window or tab >>Corrosion and Surface Studies of Stainless Steel and Chromium Carbide Thin-Films
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Although the passive films that form on stainless steels have been extensively studied, the concentration depth profiles are not fully understood. Their thinness makes passive films hard to study, but angle-resolved X-ray photoelectron spectroscopy (ARXPS) is a non-destructive technique that can be used to obtain depth information. An iterative approach to deconvolute ARXPS measurements into depth profiles is discussed, and the chemistry of passive films on a molybdenum-containing 316L stainless steel is investigated. Bipolar electrochemistry, in which the sample is placed along an electric field created by two driving electrodes in an electrolyte, is investigated as a screening tool. It is shown that the method is useful to create corrosion gradients on 304 stainless steel, both under pitting and non-pitting conditions. Chromium carbide thin films were deposited by magnetron sputtering with a variety of deposition parameters on stainless steel, and subsequently analyzed. It is shown that these films present a promising material system for protective coatings to improve the corrosion resistance of stainless steels while also maintaining other useful properties, such as low interfacial contact resistance. Particular attention is given to the electrochemical evaluation of the films, whose high carbon concentrations necessitates different interpretations of the electrochemical results compared to for stainless steels.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 66 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1082
Keyword
corrosion, electrochemistry, thin film, stainless steel, passive film, chromium carbide, carbon oxidation, surface, depth profile, XPS, SEM, EQCM, sputtering
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-208410 (URN)978-91-554-8766-9 (ISBN)
Public defence
2013-11-08, Ångström 2001, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2013-10-18 Created: 2013-09-30 Last updated: 2017-01-20
2. Synthesis and Characterization of Amorphous Carbide-based Thin Films
Open this publication in new window or tab >>Synthesis and Characterization of Amorphous Carbide-based Thin Films
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, research on synthesis, structure and characterization of amorphous carbide-based thin films is presented. Crystalline and nanocomposite carbide films can exhibit properties such as high electrical conductivity, high hardness and low friction and wear. These properties are in many cases structure-related, and thus, within this thesis a special focus is put on how the amorphous structure influences the material properties.

Thin films within the Zr-Si-C and Cr-C-based systems have been synthesized by magnetron sputtering from elemental targets. For the Zr-Si-C system, completely amorphous films were obtained for silicon contents of 20 at.% or higher. Modeling of these films, as well as experimental results suggest that the films exhibit a network-type structure where the bond types influence the material properties. Higher hardness and resistivity were observed with high amounts of covalent Si-C bonds.

Several studies were performed in the Cr-C-based systems. Cr-C films deposited in a wide composition range and with substrate temperatures of up to 500 °C were found to be amorphous nanocomposites, consisting of amorphous chromium carbide (a-CrCx) and amorphous carbon (a-C) phases. The carbon content in the carbidic phase was determined to about 30-35 at.% for most films. The properties of the Cr-C films were very dependent of the amount of a-C phase, and both hardness and electrical resistivity decreased with increasing a-C contents. However, electrochemical analysis showed that Cr-C films deposited at higher substrate temperature and with high carbon content exhibited very high oxidation resistance. In addition, nanocomposite films containing Ag nanoparticles within an amorphous Cr-C matrix were studied in an attempt to improve the tribological properties. No such improvements were observed but the films exhibited a better contact resistance than the corresponding binary Cr-C films. Furthermore, electrochemical analyses showed that Ag nanoparticles on the surface affected the formation of a stable passive film, which would make the Cr-C/Ag films less resilient to oxidation than the pure Cr-C films.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2015. 63 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1239
Keyword
Amorphous, coating, thin film, nanocomposite, sputter deposition, PVD, XPS, SEM, TEM, electrical properties, mechanical properties
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-247282 (URN)978-91-554-9198-7 (ISBN)
Public defence
2015-05-08, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2015-04-16 Created: 2015-03-16 Last updated: 2015-07-07

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Andersson, MatildaHögström, JonasNyholm, LeifJansson, Ulf

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