Microstructural characterisation of porous TiO 2 ceramic coatings fabricated by plasma electrolytic oxidation of Ti

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Abstract

This study aims at providing a thorough examination of compositional and microstructural heterogeneities in the porous oxide ceramic surface layers formed on Ti by plasma electrolytic oxidation (PEO). The PEO-titania layers of up to 5μm thick were produced using 0.02...0.04M NaH 2 PO 4 electrolyte solutions in the voltage range of 450...500V DC. Advanced methods of X-ray diffractometry (XRD), scanning electron microscopy (SEM) and field-emission transmission electron microscopy (FE-TEM) were employed to observe the surface layer morphology and characterise its crystal structure across the whole coating thickness. As revealed by XRD analysis, the surface layers consist of both anatase and rutile evenly distributed across the layer thickness. Detailed TEM studies showed that a continuous amorphous layer exists at the top of the PEO coating, the layer comprises mainly TiO 2 , with some phosphorus incorporated from the electrolyte. Underneath, there is a porous crystalline layer with uniformly distributed nano-scale pores (<50nm), anatase nanocrystallites (<100nm) and submicrometer-scale (0.1 to 1μm) rutile crystallites. Large micrometre size pores (about 1...3μm in diameter) surrounded by nanocrystalline anatase are found to exist at the bottom of the porous crystalline layer, adjacent to the thin interfacial barrier layer. Correlations between thermal-physical properties of the coating material, heat dissipation conditions and microstructural evolution in the surface layer during coating formation are discussed.

Bibliographical metadata

Original languageEnglish
Title of host publicationAdvanced Ceramic Coatings and Materials for Extreme Environments III - A Collection of Papers Presented at the 37th International Conference on Advanced Ceramics and Composites, ICACC 2013
Pages117-127
Number of pages11
Volume34
Edition3
Publication statusPublished - 13 Jan 2014
EventAdvanced Ceramic Coatings and Materials for Extreme Environments III - 37th International Conference on Advanced Ceramics and Composites - Daytona Beach, United States
Event duration: 27 Jan 20131 Feb 2013

Conference

ConferenceAdvanced Ceramic Coatings and Materials for Extreme Environments III - 37th International Conference on Advanced Ceramics and Composites
Abbreviated titleICACC 2013
CountryUnited States
CityDaytona Beach
Period27/01/131/02/13