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Nanocomposites for Use in Sliding Electrical Contacts
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Tekniska sektionen, Institutionen för teknikvetenskaper, Tillämpad materialvetenskap.
2011 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

In this thesis nanocomposite materials for use in high performance electrical contacts are tested. Self mating silver as coatings on cupper substrates are the most used material combination in power connectors today. In this work two new concepts were tested. The first one was to change one of the mating surfaces to a hard thin coating and keep the other surface made of silver. Tested coatings were nanocomposites with hard carbides in a matrix of amorphous carbon. TiC/a-C and  Ti-Ni-C/a-C were tested both electrically and tribologically. The total amount of carbon and the amount of carbon matrix was important, both for the electrical and the tribological properties. The Ti-Ni-C coating also showed that substituting Ti in TiC with the weak carbide former Ni changed the stability of the carbides. The substitution resulted in more a-C matrix and less C in the carbides. Thin coatings of nc-TiC/a-C and  Ti-Ni-C/a-C showed high potential as material candidates for use in electrical contacts.

The other tested concept was to modify the used silver instead of replacing it. This was done by embedding nanoparticles of solid lubricant IF-WS2 in the silver. The results from reciprocating sliding displayed low friction and high wear resistance. The modified silver surfaces lasted for 8000 strokes with a friction of about 0.3 while at the same time allowing for a low contact resistance. The results for surfaces of pure silver coating displayed a friction of 0.8-1.2 and that the silver was worn through already after 300 strokes.

A new method to investigate inherent hardness and residual stress of thin coatings, on complex geometries or in small areas, was also developed. An ion beam was used to create stress free coating as free standing micro pillars. Hardness measured on the pillars and on as-deposited coating were then used to calculate the residual stress in the coatings.

sted, utgiver, år, opplag, sider
Uppsala: Acta Universitatis Upsaliensis , 2011. , s. 49
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 879
Emneord [en]
tribology, materials science
HSV kategori
Forskningsprogram
Materialvetenskap; Teknisk fysik med inriktning mot materialvetenskap; Teknisk fysik med inriktning mot tribomaterial
Identifikatorer
URN: urn:nbn:se:uu:diva-160809ISBN: 978-91-554-8219-0 (tryckt)OAI: oai:DiVA.org:uu-160809DiVA, id: diva2:453060
Disputas
2011-12-09, Siegbahnsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Polacksbacken, Uppsala, 10:15 (svensk)
Opponent
Veileder
Tilgjengelig fra: 2011-11-18 Laget: 2011-11-01 Sist oppdatert: 2011-11-23bibliografisk kontrollert
Delarbeid
1. Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
Åpne denne publikasjonen i ny fane eller vindu >>Industrialisation Study of Nanocomposite nc-TiC/a-C Coatings for Electrical Contact Applications
Vise andre…
2009 (engelsk)Inngår i: Plasma Processes and Polymers, ISSN 1612-8850, Vol. 6, nr S1, s. S928-S934Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Nanocomposite nc-TiC/a-C coatings were prepared by non-reactive magnetron sputtering in industrial scale equipment, under varying deposition conditions in order to investigate upscaling and possible industrialisation. The coatings were found to have similar microstructure and performance compared to previous laboratory scale experiments. The samples were characterised with XRD, XPS and SEM as well with ball-on-disc, nanoindentation and electrical measurements. Coatings containing a small fraction of a-C matrix phase were found to have promising both electrical properties (rho < 400 mu Omega cm and contact resistances down to 0.34 m Omega at 40 N) and tribological properties (f < 0.3 for 10 000 laps).

sted, utgiver, år, opplag, sider
WILEY-VCH Verlag GmbH & Co, 2009
Emneord
conductivity, inorganic materials, nanocomposites, thin films, tribology
HSV kategori
Forskningsprogram
Oorganisk kemi; Kemi med inriktning mot oorganisk kemi
Identifikatorer
urn:nbn:se:uu:diva-109022 (URN)10.1002/ppap.200932303 (DOI)000272302900178 ()
Tilgjengelig fra: 2009-10-07 Laget: 2009-10-07 Sist oppdatert: 2016-04-14
2. Synthesis, structure and properties of Ni-alloyed TiCx-based thin films
Åpne denne publikasjonen i ny fane eller vindu >>Synthesis, structure and properties of Ni-alloyed TiCx-based thin films
Vise andre…
2010 (engelsk)Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, nr 28, s. 5950-5960Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

By using non-reactive sputter deposition at low temperatures metastable solid solution phases in the Ti–Ni–C system were synthesized. Produced thin films were either single phase carbides or nanocomposite of nanocrystalline carbide and amorphous C. In the Ni-containing samples a supersaturated solid solution phase (Ti1−xNix)Cy was identified, and was present either as single phase or in a nanocomposite with amorphous C. By modification of the chemical stability of the carbide phase, the addition of Ni was found to strongly promote the formation of amorphous carbon phase in the coatings. Samples have been microstructurally analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Mechanical properties have been evaluated through nanoindentation and pin-on-disc measurements; electrical properties were determined by measurement of the resistivity and the contact resistance. Alloyed nanocomposite coatings were also found to exhibit enhanced tribological and electrical properties, with a decreased resistivity and friction. This makes these thin films very interesting for application in sliding electrical contacts. The mechanisms responsible for the reductions remain to be determined.

HSV kategori
Forskningsprogram
Kemi med inriktning mot oorganisk kemi
Identifikatorer
urn:nbn:se:uu:diva-109034 (URN)10.1039/c0jm00592d (DOI)000279565900025 ()
Tilgjengelig fra: 2009-10-08 Laget: 2009-10-08 Sist oppdatert: 2017-12-13bibliografisk kontrollert
3. Friction and contact resistance of nanocomposite Ti-Ni-C coatings
Åpne denne publikasjonen i ny fane eller vindu >>Friction and contact resistance of nanocomposite Ti-Ni-C coatings
2011 (engelsk)Inngår i: Wear, ISSN 0043-1648, E-ISSN 1873-2577, Vol. 270, nr 9-10, s. 555-566Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Ceramic nanocomposite coatings in the Ti-Ni-C were deposited using PVD and studied with respect to tribological properties and contact resistance. It was shown that coatings could be deposited combining of a low contact resistance and a low friction coefficient against silver, making them suitable for use in high performance electrical contacts.Nine coatings with different amounts of C and Ni were deposited. Coatings on flat Ni plated copper substrates were tested in a tribological ball-on-disc setup against ball bearing steel balls. Depending on primarily the amount of carbon the coatings showed very different friction coefficient and wear rate. The coatings were also deposited on cylindrical Ni plated copper substrates. Using geometrically identical silver plated cylinders as counter surface these were evaluated in a test setup better resembling a real life electrical contact. For most coatings a low electrical contact resistance was measured. The evolution of friction coefficient and contact resistance was correlated to wear marks and contact tracks, with their generated tribofilms, as examined after testing using electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy.

Emneord
TiC, TiNiC, Friction, Tribofilm, Electrical contacts, Contact resistance
HSV kategori
Forskningsprogram
Oorganisk kemi; Teknisk fysik med inriktning mot materialvetenskap
Identifikatorer
urn:nbn:se:uu:diva-109425 (URN)10.1016/j.wear.2010.12.006 (DOI)000290132500001 ()
Tilgjengelig fra: 2009-10-15 Laget: 2009-10-15 Sist oppdatert: 2017-12-12
4. Nanoindentation on micro pillars for determination of intrincic hardness and residual stress in coatings deposited on complex geometries
Åpne denne publikasjonen i ny fane eller vindu >>Nanoindentation on micro pillars for determination of intrincic hardness and residual stress in coatings deposited on complex geometries
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Emneord
nanoindentation, hardness, residual stress, focused ion beam, coating, PVD
HSV kategori
Forskningsprogram
Materialvetenskap; Teknisk fysik med inriktning mot tribomaterial; Teknisk fysik med inriktning mot materialvetenskap
Identifikatorer
urn:nbn:se:uu:diva-160807 (URN)
Tilgjengelig fra: 2011-10-31 Laget: 2011-10-31 Sist oppdatert: 2016-04-22
5. Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles
Åpne denne publikasjonen i ny fane eller vindu >>Performance and Tribofilm Formation of a Low-Friction Coating Incorporating Inorganic Fullerene Like Nano-Particles
2012 (engelsk)Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 206, nr 8-9, s. 2325-2329Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

A new tribological coating with potential as a coating for components for low-friction applications is tested and compared to three, state of the art, commercial low-friction PVD coatings. The new coating is an electrodeposited coating composed by a Ni-P matrix incorporating fullerene like nanoparticles of WS2. The performance of the new coating is compared with three reference coatings in a ball-on-disc setup. The tribological tests involved ball bearing steel balls slid on coated discs, under different conditions of humidity and also with or without oil lubrication. Both mating surfaces were closely investigated in a scanning electron microscope and the low-friction tribofilms formed were further analysed. The correlations found between coefficient of friction, surface roughness of the wear scar, tribofilm formation and contact conditions are discussed. The new coating exhibits a very low coefficient of friction at low humidity, a behaviour closely resembling that of the MoS2-based commercial reference, whereas the carbon based PVD coatings tested exhibit the reversed dependence of humidity. The low-friction behaviour of the new coating is correlated to the formation of a WS2 tribofilm with a superficial alignment of the basal planes parallel to the sliding direction. When lubricated with a base oil, the beneficial tribofilm is not formed and the coefficient of friction is much higher. The results show that even though the coating is an electrodeposited coating it can compete with state of the art commercial PVD coatings.

Emneord
Friction, Wear, Tungsten disulphide, Nanoparticles, Fullerene, Tribofilm
HSV kategori
Forskningsprogram
Teknisk fysik med inriktning mot tribomaterial; Teknisk fysik med inriktning mot materialvetenskap
Identifikatorer
urn:nbn:se:uu:diva-160806 (URN)10.1016/j.surfcoat.2011.10.012 (DOI)000300458500038 ()
Tilgjengelig fra: 2011-10-31 Laget: 2011-10-31 Sist oppdatert: 2017-12-08
6. Enhancing silver through embedding of fullerene like WS2 for sliding electrical contacts
Åpne denne publikasjonen i ny fane eller vindu >>Enhancing silver through embedding of fullerene like WS2 for sliding electrical contacts
(engelsk)Manuskript (preprint) (Annet vitenskapelig)
Emneord
friction, wear, electrical, contacts, tungsten, disulfide, silver
HSV kategori
Forskningsprogram
Materialvetenskap; Teknisk fysik med inriktning mot materialvetenskap; Teknisk fysik med inriktning mot tribomaterial
Identifikatorer
urn:nbn:se:uu:diva-160808 (URN)
Tilgjengelig fra: 2011-11-01 Laget: 2011-11-01 Sist oppdatert: 2012-05-08

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