Ugas Carrión, Ruperto A. (2010)
Investigation of Stabilizing Agents in Thin Sol-Gel Zirconium Oxide Anti-corrosion Coatings on Iron Materials.
Technische Universität Darmstadt
Dissertation, Erstveröffentlichung
Kurzbeschreibung (Abstract)
Abstract Thin protective zirconium oxide coatings prepared via sol-gel with zirconium propoxide and acetyl acetone (acac) or hydroxypropyl cellulose as stabilizers have been successfully deposited onto iron substrates at low temperature. Electrochemical current density vs. potential scans showed a reduction of the iron dissolution current density and coating porosity in comparison to uncoated iron, with a strong decrease of these parameters around 5 orders of magnitude for a HPC concentration = 0.004 g/l. This result is expected as the steric effect of HPC. A mixed oxide layer of zirconium and iron was observed in SIMS depth profiles. The mixed oxide layer thickness showed a dependence on the acac molar ratio. Increases of acac shorted the overall film thickness, while the mixed oxide layer was thicker. ZrO2-HPC coatings displayed however, a thicker mixed oxide layer and additional increases of the zirconium intensity direct onto substrate surface. So a higher interdiffusion of zirconium into deeper layers and of iron towards coating surface was reached. XRD revealed that the mixed oxide layer is localized between the substrate and coating surface and possess crystalline structure. At a HPC concentration = 0.004 g/l no ZrO2 reflexes could be detected. ZrO2 crystals of 70 nm size were identified by TEM in ZrO2-acac coatings. However, ZrO2-HPC films showed an amorphous structure constituted of ZrO2 and iron oxide containing nanocrystalline zirconium oxide particles immersed in the mixed oxide layer. The crystals (monoclinic 112) size was between 5 and 10 nm. This result explains why there were not zirconium oxide reflexes visible in the XRD analysis. Obviously the ZrO2 crystalline particles are too small (less than 10 nm) to be detected by XRD so they appear as amorphous material [83]. The particles are immersed in a compact and amorphous mixed oxide matrix. The correlation between growth of the mixed oxide phase and decrease of dissolution current density suggests that it is the mixed oxide phase with zirconium nanoparticles that is responsible for the reduction of film porosity and the good corrosion protection properties of the films.
| Typ des Eintrags: | Dissertation | ||||
|---|---|---|---|---|---|
| Erschienen: | 2010 | ||||
| Autor(en): | Ugas Carrión, Ruperto A. | ||||
| Art des Eintrags: | Erstveröffentlichung | ||||
| Titel: | Investigation of Stabilizing Agents in Thin Sol-Gel Zirconium Oxide Anti-corrosion Coatings on Iron Materials | ||||
| Sprache: | Englisch | ||||
| Referenten: | Ensinger, Prof. Dr. Wolfgang ; Albert, Prof. Dr. Barbara | ||||
| Publikationsjahr: | 4 November 2010 | ||||
| Ort: | Darmstadt | ||||
| Datum der mündlichen Prüfung: | 18 Oktober 2010 | ||||
| URL / URN: | urn:nbn:de:tuda-tuprints-23186 | ||||
| Kurzbeschreibung (Abstract): | Abstract Thin protective zirconium oxide coatings prepared via sol-gel with zirconium propoxide and acetyl acetone (acac) or hydroxypropyl cellulose as stabilizers have been successfully deposited onto iron substrates at low temperature. Electrochemical current density vs. potential scans showed a reduction of the iron dissolution current density and coating porosity in comparison to uncoated iron, with a strong decrease of these parameters around 5 orders of magnitude for a HPC concentration = 0.004 g/l. This result is expected as the steric effect of HPC. A mixed oxide layer of zirconium and iron was observed in SIMS depth profiles. The mixed oxide layer thickness showed a dependence on the acac molar ratio. Increases of acac shorted the overall film thickness, while the mixed oxide layer was thicker. ZrO2-HPC coatings displayed however, a thicker mixed oxide layer and additional increases of the zirconium intensity direct onto substrate surface. So a higher interdiffusion of zirconium into deeper layers and of iron towards coating surface was reached. XRD revealed that the mixed oxide layer is localized between the substrate and coating surface and possess crystalline structure. At a HPC concentration = 0.004 g/l no ZrO2 reflexes could be detected. ZrO2 crystals of 70 nm size were identified by TEM in ZrO2-acac coatings. However, ZrO2-HPC films showed an amorphous structure constituted of ZrO2 and iron oxide containing nanocrystalline zirconium oxide particles immersed in the mixed oxide layer. The crystals (monoclinic 112) size was between 5 and 10 nm. This result explains why there were not zirconium oxide reflexes visible in the XRD analysis. Obviously the ZrO2 crystalline particles are too small (less than 10 nm) to be detected by XRD so they appear as amorphous material [83]. The particles are immersed in a compact and amorphous mixed oxide matrix. The correlation between growth of the mixed oxide phase and decrease of dissolution current density suggests that it is the mixed oxide phase with zirconium nanoparticles that is responsible for the reduction of film porosity and the good corrosion protection properties of the films. |
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| Alternatives oder übersetztes Abstract: |
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| Freie Schlagworte: | Stabilizing agents, sol-gel, corrosion, porosity, zirconium oxide, electrochemistry, thin films, nanocrystal | ||||
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| Sachgruppe der Dewey Dezimalklassifikatin (DDC): | 500 Naturwissenschaften und Mathematik > 500 Naturwissenschaften 500 Naturwissenschaften und Mathematik > 540 Chemie 600 Technik, Medizin, angewandte Wissenschaften > 620 Ingenieurwissenschaften und Maschinenbau 600 Technik, Medizin, angewandte Wissenschaften > 600 Technik 600 Technik, Medizin, angewandte Wissenschaften > 660 Technische Chemie |
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| Fachbereich(e)/-gebiet(e): | 11 Fachbereich Material- und Geowissenschaften 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft 11 Fachbereich Material- und Geowissenschaften > Materialwissenschaft > Fachgebiet Materialanalytik 07 Fachbereich Chemie |
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| Hinterlegungsdatum: | 05 Nov 2010 13:18 | ||||
| Letzte Änderung: | 05 Jan 2024 09:41 | ||||
| PPN: | |||||
| Referenten: | Ensinger, Prof. Dr. Wolfgang ; Albert, Prof. Dr. Barbara | ||||
| Datum der mündlichen Prüfung / Verteidigung / mdl. Prüfung: | 18 Oktober 2010 | ||||
| Schlagworte: |
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