Change search
ReferencesLink to record
Permanent link

Direct link
Magnetron Sputtering of Nanocomposite Carbide Coatings for Electrical Contacts
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.ORCID iD: 0000-0002-5516-6388
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.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1417
Keyword [en]
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
Identifiers
URN: urn:nbn:se:uu:diva-302063ISBN: 978-91-554-9676-0OAI: oai:DiVA.org:uu-302063DiVA: diva2:956274
Public defence
2016-10-14, Häggsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2016-09-22 Created: 2016-08-29 Last updated: 2016-09-22
List of papers
1. Influence of deposition temperature and amorphous carbon on microstructure and oxidation resistance of magnetron sputtered nanocomposite Cr-C films
Open this publication in new window or tab >>Influence of deposition temperature and amorphous carbon on microstructure and oxidation resistance of magnetron sputtered nanocomposite Cr-C films
Show others...
2014 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 305, 143-153 p.Article in journal (Refereed) Published
Abstract [en]

It is known that mechanical and tribological properties of transition metal carbide films can be tailored by adding an amorphous carbon (a-C) phase, thus making them nanocomposites. This paper addresses deposition, microstructure, and for the first time oxidation resistance of magnetron sputtered nanocomposite Cr C/a-C films with emphasis on studies of both phases. By varying the deposition temperature between 20 and 700 C and alternating the film composition, it was possible to deposit amorphous, nanocomposite, and crystalline Cr C films containing about 70% C and 30% Cr, or 40% C and 60% Cr. The films deposited at temperatures below 300 degrees C were X-ray amorphous and 500 C was required to grow crystalline phases. Chronoamperometric polarization at +0.6 V vs. Ag/AgCl(sat. KG) in hot 1 mM H-2 SO4 resulted in oxidation of Cr C, yielding Cr203 and C, as well as oxidation of C. The oxidation resistance is shown to depend on the deposition temperature and the presence of the a-C phase. Physical characterization of film surfaces show that very thin C/Cr2O3/Cr C layers develop on the present material, which can be used to improve the oxidation resistance of, e.g. stainless steel electrodes. (C) 2014 Elsevier B.V. All rights reserved.

Keyword
Chromium carbide, Magnetron sputtering, Nanocomposite, Deposition temperature, Carbon oxidation
National Category
Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-227992 (URN)10.1016/j.apsusc.2014.03.014 (DOI)000336525400020 ()
Available from: 2014-07-04 Created: 2014-07-02 Last updated: 2016-08-29
2. Growth and characterization of chromium carbide films deposited by high rate reactive magnetron sputtering for electrical contact applications
Open this publication in new window or tab >>Growth and characterization of chromium carbide films deposited by high rate reactive magnetron sputtering for electrical contact applications
Show others...
2014 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 260, 326-334 p.Article in journal (Refereed) Published
Abstract [en]

Chromium carbide films with different phase contents were deposited at 126±26 °C by industrial high rate reactivemagnetron sputtering, using both direct current magnetron sputtering (DCMS) and high power impulsemagnetron sputtering (HiPIMS). Film structure and properties were studied by SEM, XRD, TEM, XPS, NRA, Raman spectroscopy, nanoindentation, unlubricated reciprocating sliding experiments, and a laboratory setup to measure electrical contact resistance. The films consisted of amorphous a-CrCy, a nanocrystalline minority phase of metastable cubic nc-CrCx, and a hydrogenated graphite-like amorphous carbon matrix (a-C:H). The DCMS and HiPIMS processes yielded films with similar phase contents and microstructures, as well as similar functional properties. Low elastic modulus, down to 66 GPa, indicated good wear properties via a hardness/elastic modulus (H/E) ratio of 0.087. Unlubricated steady-state friction coefficients down to 0.13 were obtained for films with 69 at.% carbon, while the electrical contact resistance could be reduced by two orders of magnitude by addition of a-C:H phase to purely carbidic films. The present films are promising candidates for sliding electrical contact applications.

Place, publisher, year, edition, pages
Elsevier: , 2014
Keyword
Direct current magnetron sputtering, High power impulse magnetron sputtering, Reactive sputtering, Amorphous chromium carbide, Solid lubricant, Contact resistance
National Category
Physical Chemistry Condensed Matter Physics Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-240742 (URN)10.1016/j.surfcoat.2014.06.069 (DOI)000347584300045 ()
Conference
The 41st International Conference on Metallurgical Coatings and Thin Films, APR 28-MAY 02, 2014, San Diego, CA
Funder
Swedish Foundation for Strategic Research Swedish Research Council
Available from: 2015-01-08 Created: 2015-01-08 Last updated: 2016-08-29Bibliographically approved
3. Structure and properties of Cr-C/Ag films deposited by magnetron sputtering
Open this publication in new window or tab >>Structure and properties of Cr-C/Ag films deposited by magnetron sputtering
Show others...
2015 (English)In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 281, 184-192 p.Article in journal (Refereed) Published
Abstract [en]

Cr-C/Ag thin films with 0-14 at% Ag have been deposited by magnetron sputtering from elemental targets. The samples were analyzed by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) to study their structure and chemical bonding. A complex nanocomposite structure consisting of three phases; nanocrystalline Ag, amorphous CrCx and amorphous carbon is reported. The carbon content in the amorphous carbide phase was determined to be 32-33 at% C, independent of Ag content Furthermore, SEM and XPS results showed higher amounts of Ag on the surface compared to the bulk. The hardness and Young's modulus were reduced from 12 to 8 GPa and from 270 to 170 GPa, respectively, with increasing Ag content. The contact resistance was found to decrease with Ag addition, with the most Ag rich sample approaching the values of an Ag reference sample. Initial tribological tests gave friction coefficients in the range of 0.3 to 0.5, with no clear trends. Annealing tests show that the material is stable after annealing at 500 degrees C for 1 h, but not after annealing at 800 degrees C for 1 h. In combination, these results suggest that sputtered Cr-C/Ag films could be potentially applicable for electric contact applications.

Place, publisher, year, edition, pages
Elsevier, 2015
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-247276 (URN)10.1016/j.surfcoat.2015.09.054 (DOI)000366072200024 ()
Funder
Swedish Foundation for Strategic Research , RMA11-0029Swedish Research Council, 621-2011-3492
Available from: 2015-03-16 Created: 2015-03-16 Last updated: 2016-08-29Bibliographically approved
4. The influence of nanoeffects on the oxidation of magnetron sputtered Cr-C/Ag thin films containing silver nanoparticles
Open this publication in new window or tab >>The influence of nanoeffects on the oxidation of magnetron sputtered Cr-C/Ag thin films containing silver nanoparticles
(English)Article in journal (Other academic) Submitted
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-302060 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29
5. Passive films on nanocomposite carbide coatings for electrical contact applications
Open this publication in new window or tab >>Passive films on nanocomposite carbide coatings for electrical contact applications
(English)Article in journal (Other academic) Submitted
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-302061 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29
6. Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings
Open this publication in new window or tab >>Optical methods to quantify amorphous carbon in carbide-based nanocomposite coatings
(English)Article in journal (Other academic) Submitted
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-302062 (URN)
External cooperation:
Available from: 2016-08-29 Created: 2016-08-29 Last updated: 2016-08-29

Open Access in DiVA

fulltext(2415 kB)12 downloads
File information
File name FULLTEXT01.pdfFile size 2415 kBChecksum SHA-512
56859ff0536db7850c97ce45be0229421bb6b6d21766d6630573e861c42886fb82fd37a1f93b4b7e9276bea4dc81ba9dba762ce1c436fc49cf15d4612c93acb8
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Nygren, Kristian
By organisation
Inorganic Chemistry
Materials ChemistryInorganic ChemistryCeramicsNano TechnologyComposite Science and EngineeringCorrosion Engineering

Search outside of DiVA

GoogleGoogle Scholar
Total: 12 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 90 hits
ReferencesLink to record
Permanent link

Direct link