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The influence of oxygen in TiAlOxNy on the optical properties of colored solar-absorbing coatings
Department of Chemical and Materials Engineering, Hefei University, China. (Materials Science)
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Inorganic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
2012 (English)In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 98, p. 179-184Article in journal (Refereed) Published
Abstract [en]

Low cost and ease of fabrication are important factors for solar-thermal applications in energy-efficient buildings. This contribution reports the influence of oxygen on structure, optical properties and chromaticity of TiAlOxNy thin films prepared by DC magnetron sputtering. It is an extension of a previous study on colored solar-thermal absorbers based on titanium-aluminum nitride. The purpose is to investigate the possibility of using TiAlOxNy as middle layer to achieve a gradient effect. The results reveal that the structure and optical properties of the TiAlOxNy coatings are sensitive to the oxygen content under certain sputtering conditions.  The ratio of oxygen/nitrogen of 0.7:10 is the most appropriate to form the crystalline structure of TiAlON.  The optical constants of TiAlN and TiAlON were deduced by fitting the experimental data. It shows that both the refractive index (n) and the extinction coefficient (k) are decreased when oxygen is introduced to form titanium-aluminium nitro-oxide. The gradient effect can be achieved and controlled by adjusting the ratio of oxygen/nitrogen flow during the process to enhance solar absorptance while keeping the desired color appearance.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2012. Vol. 98, p. 179-184
Keyword [en]
Titanium-aluminum nitride/nitro-oxide; colored solar-thermal absorber; optical properties; chromaticity.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Solid State Physics
Identifiers
URN: urn:nbn:se:uu:diva-164134DOI: 10.1016/j.solmat.2011.11.001ISI: 000300536500023OAI: oai:DiVA.org:uu-164134DiVA: diva2:466689
Available from: 2011-12-19 Created: 2011-12-16 Last updated: 2017-12-08Bibliographically 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. p. 98
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)
Opponent
Supervisors
Available from: 2017-05-18 Created: 2017-04-18 Last updated: 2017-06-07

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