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Passive films on nanocomposite carbide coatings for electrical contact applications
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-5516-6388
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
(English)Article in journal (Other academic) Submitted
National Category
Inorganic Chemistry
URN: urn:nbn:se:uu:diva-302061OAI: oai:DiVA.org:uu-302061DiVA: diva2:956179
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29
In thesis
1. Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
Open this publication in new window or tab >>Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Today’s electronic society relies on the functionality of electrical contacts. To achieve good contact properties, surface coatings are normally applied. Such coatings should ideally fulfill a combination of different properties, like high electrical conductivity, high corrosion resistance, high wear resistance and low cost. A common coating strategy is to use noble metals since these do not form insulating surface oxides. However, such coatings are expensive, have poor wear resistance and they are often applied by electroplating, which poses environmental and human health hazards.

In this thesis, nanocomposite carbide-based coatings were studied and the aim was to evaluate if they could exhibit properties that were suitable for electrical contacts. Coatings in the Cr-C, Cr-C-Ag and Nb-C systems were deposited by magnetron sputtering using research-based equipment as well as industrial-based equipment designed for high-volume production. To achieve the aim, the microstructure and composition of the coatings were characterized, whereas mechanical, tribological, electrical, electrochemical and optical properties were evaluated. A method to optically measure the amount of carbon was developed.

In the Cr-C system, a variety of deposition conditions were explored and amorphous carbide/amorphous carbon (a-C) nanocomposite coatings could be obtained at substrate temperatures up to 500 °C. The amount of a-C was highly dependent on the total carbon content. By co-sputtering with Ag, coatings comprising an amorphous carbide/carbon matrix, with embedded Ag nanoclusters, were obtained. Large numbers of Ag nanoparticles were also found on the surfaces. In the Nb-C system, nanocrystalline carbide/a-C coatings could be deposited. It was found that the nanocomposite coatings formed very thin passive films, consisting of both oxide and a-C.

The Cr-C coatings exhibited low hardness and low-friction properties. In electrochemical experiments, the Cr-C coatings exhibited high oxidation resistance. For the Cr-C-Ag coatings, the Ag nanoparticles oxidized at much lower potentials than bulk Ag. Overall, electrical contact resistances for optimized samples were close to noble metal references at low contact load. Thus, the studied coatings were found to have properties that make them suitable for electrical contact applications.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 74 p.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1417
transition metal carbide, amorphous carbon, composite, contact resistance, corrosion, friction, optical properties
National Category
Materials Chemistry Inorganic Chemistry Ceramics Nano Technology Composite Science and Engineering Corrosion Engineering
urn:nbn:se:uu:diva-302063 (URN)978-91-554-9676-0 (ISBN)
Public defence
2016-10-14, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Available from: 2016-09-22 Created: 2016-08-29 Last updated: 2016-09-22

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