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Deposition and characterization of reactive magnetron sputtered zirconium carbide 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, Inorganic Chemistry.
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2013 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 232, 876-883 p.Article in journal (Refereed) Published
Abstract [en]

Zirconium carbide films have been deposited on silicon (100) substrates using direct current magnetron reactive sputtering using CH4 as a carbon source. The films exhibit a typical nanocomposite structure consisting of nanocrystalline ZrCx (nc-ZrC) grains embedded in a matrix of amorphous carbon (a-C) at low carbon content. Almost no crystalline phase can be found for carbon contents above 86 at.%. The mechanical, tribological and electrical properties of the films showed a significant dependency on the amount of the a-C in the nanocomposite structure. A larger amount of a-C gives rise to reduced hardness and higher resistivity of the film. However, both friction coefficient and wear resistance are improved by increasing the content of the surplus a-C. The influence of binding state of excess a-C phase on the properties has also been investigated. A larger sp(2)/sp(3) ratio was beneficial to relax the stress and improve the electrical properties. The Zr-based films exhibited lower friction coefficients than nanocomposites films based on e.g. Ti suggesting a potential application for this material in sliding contacts.

Place, publisher, year, edition, pages
2013. Vol. 232, 876-883 p.
Keyword [en]
Zirconium carbide, Mechanical properties, Friction and wear, Electrical resistivity, Magnetron sputtering
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:uu:diva-214005DOI: 10.1016/j.surfcoat.2013.06.116ISI: 000327691300113OAI: oai:DiVA.org:uu-214005DiVA: diva2:683797
Available from: 2014-01-06 Created: 2014-01-06 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Synthesis, Characterization, and Evaluation of Ag-based Electrical Contact Materials
Open this publication in new window or tab >>Synthesis, Characterization, and Evaluation of Ag-based Electrical Contact Materials
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Ag is a widely used electrical contact material due to its excellent electrical properties. The problems with Ag are that it is soft and has poor tribological properties (high friction and wear in Ag/Ag sliding contacts). For smart grid applications, friction and wear became increasingly important issues to be improved, due to much higher sliding frequency in the harsh operation environment. The aim of this thesis is to explore several different concepts to improve the properties of Ag electrical contacts for smart grid applications.

Bulk Ag-X (X=Al, Sn In) alloys were synthesized by melting of metals. An important result was that the presence of a hcp phase in the alloys significantly reduced friction coefficients and wear rates compared to Ag. This was explained by a sliding-induced reorientation of easy-shearing planes in the hexagonal structure. The Ag-In system showed the best combination of properties for potential use in future contact applications. 

This thesis has also demonstrated the strength of a combinatorial approach as a high-throughput method to rapidly screen Ag-based alloy coatings. It was also used for a rapid identification of optimal deposition parameters for reactive sputtering of a complex AgFeO2 oxide with narrow synthesis window. A new and rapid process was developed to grow low frictional AgI coatings and a novel designed microstructure of nanoporous Ag filled with AgI (n-porous Ag/AgI) using a solution chemical method was also explored. The AgI coatings exhibited low friction coefficient and acceptable contact resistance. However, under very harsh conditions, their lifetime is too short. The initial tribotests showed high friction coefficient of the n-porous Ag/AgI coating, indicating an issue regarding its mechanical integrity.

The use of graphene as a solid lubricant in sliding electrical contacts was investigated as well. The results show that graphene is an excellent solid lubricant in Ag-based contacts. Furthermore, the lubricating effect was found to be dependent on chemical composition of the counter surface. As an alternative lubricant, graphene oxide is cheaper and easier to produce. Preliminary tests with graphene oxide showed a similar frictional behavior as graphene suggesting a potential use of this material as lubricant in Ag contacts.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2017. 98 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1517
Keyword
electrical contact, bulk, coating, Ag-based alloys, Ag-based delafossite, AgI, graphene, graphene oxide, combinatorial material science, dc magnetron sputtering, friction, wear, hardness, contact resistance
National Category
Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320235 (URN)978-91-554-9915-0 (ISBN)
Public defence
2017-06-08, Room 2001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
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Supervisors
Available from: 2017-05-18 Created: 2017-04-18 Last updated: 2017-06-07

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Meng, Qingnan N.Mao, FangNedfors, NilsJansson, Ulf

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