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Nanoscaled Structures in Ruthenium Dioxide Coatings
Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
2009 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

An essential ingredient in the generation of environmentally compatible pulp bleaching chemicals is sodium chlorate. Chlorate is produced in electrochemical cells, where the electrodes are the key components. In Sweden the so-called DSA !R electrodes with catalytic coatings have been produced for more than 35 years. The production of chlorate uses a large amount of electric energy, and a decrease of just five percent of this consumption would, globally, decrease the consumption of electrical energy corresponding to half a nuclear power reactor. The aim of this project is to improve the electrode design on the nanoscale to decrease the energy consumption. The success of the DSA!R depends on the large catalytic area of the coating, however, little is known about the actual structure at the nanometer level. To increase the understanding of the nanostructure of these coatings, we used a number of methods, including atomic force microscopy, transmission electron microscopy, X-ray diffraction, porosimetry, and voltammetric charge. We found that the entire coating is built up of loosely packed rutile mono-crystalline 20 − 30 nm sized grains. The small grain sizes give a the large area, and consequently, lower cell-voltage and reduced energy consumption. A method to control the grain size would thus be a way to control the electrode efficiency. To alter the catalytically active area, we made changes in the coating process parameters. We found a dependency of the crystal-grain sizes on the choice of ruthenium precursor and processing temperature. The use of ruthenium nitrosyl nitrate resulted in smaller grains than ruthenium chloride and lowering the temperature tended to favour smaller grains. A more radical way would be to create a totally different type of electrode, manufactured in another way than using the 1965 DSA !R recipe. Such new types of electrodes based on, for example, nanowires or nanoimprint lithography, are discussed as future directions.

Place, publisher, year, edition, pages
Sundsvall: Mid Sweden University , 2009.
Series
Mid Sweden University licentiate thesis, ISSN 1652-8948 ; 36
Keyword [en]
Bleaching chemicals, sodium chlorate, ruthenium dioxide, electrodes, crystallites, nanowires, microscopy, diffraction, electrocatalytic area, reduced energy consumption
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:miun:diva-8728ISBN: 978-91-86073-33-6 (print)OAI: oai:DiVA.org:miun-8728DiVA, id: diva2:208709
Presentation
(English)
Supervisors
Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2013-11-01Bibliographically approved
List of papers
1. Nanoscale characterisation of crystallinity in DSA coating
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2008 (English)In: PROCEEDINGS OF THE 17TH INTERNATIONAL VACUUM CONGRESS/13TH INTERNATIONAL CONFERENCE ON SURFACE SCIENCE/INTERNATIONAL CONFERENCE ON NANOSCIENCE AND TECHNOLOGY, Institute of Physics (IOP), 2008, Vol. 100, no 052026, p. 4-4Conference paper, Published paper (Refereed)
Abstract [en]

Dimensionally Stable Anodes (DSA (R)) are used for industrial production of e. g. chlorine and chlorate. It is known that the superior electrocatalytical properties of DSA (R) is due to the large effective area of the porous coating. However, this knowledge is mainly found from in situ electrochemical measurements. Here, we used ex situ methods, AFM, TEM and gas porosimetry, for characterization at the nanoscale. The DSA (R) coating was found to consist of mono-crystalline grains with a size of 20-30 nm and with pores of about 10 nm in diameter. Using a simple geometrical model an effective area was calculated. For a typical coating thickness, an increase of about 1000 times in the effective surface area was found, which is consistent with in situ estimations. These results suggest that the dominating source of surface enlargement is due to nano-crystallinity.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2008
Series
Journal of Physics Conference Series, ISSN 1742-6588 ; 100
Keyword
nanoteknik nanotechnology
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-4291 (URN)10.1088/1742-6596/100/5/052026 (DOI)000275655200122 ()2-s2.0-77954381591 (Scopus ID)5088 (Local ID)5088 (Archive number)5088 (OAI)
Conference
17th International Vacuum Congress/13th International Conference on Surface Science/Internatinal Conference on Nanoscience and Technology, Jul 02-06, 2007, Stockholm, Sweden
Available from: 2008-09-30 Created: 2009-03-19 Last updated: 2017-10-09Bibliographically approved
2. Nanocrystallinity in RuO2 coatings - influence of precursor and preparation temperature
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2010 (English)In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 518, no 14, p. 3615-3618Article in journal (Refereed) Published
Abstract [en]

The effects of precursor and calcination temperature on the nano morphology of ruthenium dioxide on titanium, prepared from thermal decomposition of aqueous salt solutions were investigated. Transmission electron microscopy. X-ray diffraction, gas porosimetry and cyclic voltammetry showed that lower calcination temperature yielded smaller crystallites. The crystallites were between 6 and 22 nm in diameter. When using ruthenium nitrosyl nitrate the firing temperature had a large impact on the grain size, but for chloride there was only a minor effect in the temperature range 350-550 degrees C.

Keyword
Materials Science, Multidisciplinary; Materials Science, Coatings & Films; Physics, Applied; Physics, Condensed Matter
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-8725 (URN)10.1016/j.tsf.2009.09.065 (DOI)000278064600004 ()2-s2.0-77950543416 (Scopus ID)
Available from: 2009-03-19 Created: 2009-03-19 Last updated: 2017-12-13Bibliographically approved

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Malmgren, Christine

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