Formation and Properties of Oxide Coatings with Immobilized Zeolites Obtained by Plasma Electrolytic Oxidation of Aluminum

Abstract

In this paper, we employed plasma electrolytic oxidation (PEO) of aluminum in a water solution of sodium tungstate (Na2WO4∙2H2O) with the addition of the pure and Ce-loaded zeolites clinoptilolite and 13 X for the preparation of oxide coatings. The obtained coatings were characterized with respect to their morphologies and chemical and phase compositions using scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, atomic force microscopy, and X-ray diffraction. The prepared coatings contained γ-alumina, WO3, and metallic tungsten. The surface morphologies of the obtained coatings strongly depended on the PEO processing time; the roughness of all coatings increased with PEO time, while porosity decreased with PEO processing time as a result of microdischarge coalescence and growth. All coatings contained elements originating from the substrate and from the electrolytes. Coatings containing zeolites with Ce showed higher photoactivity than those with immobilized pure zeolites. The highest photocatalytic activity levels were observed for coatings containing immobilized Ce-exchanged clinoptilolite processed for 10 min. It was observed that both clinoptilolite and 13X zeolites improved the features of the PEO coatings in a similar manner, making natural and abundant clinoptilolite an excellent candidate for various applications.

Plasma Electrolytic Oxidation (PEO) Coating on γ-TiAl Alloy: Investigation of Bioactivity and Corrosion Behavior in Simulated Body Fluid

“…Thus, the trend in the Rct of the samples was: uncoated TiAl (49.6 kΩ m 2 ) < 400 V (280.1 kΩ m 2 ) < 450 V (380.2 kΩ m 2 ) < 500 V (456.7 kΩ m 2 ). In this regard, some researchers [80][81][82][83][84][85][86][87][88][89][90][91] have suggested that the substantial corrosion resistance in PEO coatings stems from the thickness of the oxide layer. Therefore, as the voltage rose, a thicker PEO film formed, which causes the penetration rate of the corrosive solution into the substrate to decrease; hence the chemical reactions culminating in the coating formation deaccelerated kinetically and thermodynamically.…”

Oxide coatings with immobilized Ce-ZSM5 as visible light photocatalysts

“…it entirely depends on content of Ce 3+ ions incorporated into PEO coatings, it can be concluded that Ce is present in all coatings (with Ce concentration increasing with PEO time) but quantification was not possible because of its low content. 19 Furthermore, from Figure 4 it can be observed that PL intensity of the broad 440 nm emission peak increases with PEO processing time, thus suggesting that the number of oxygen vacancy related defects increases with PEO processing time. This is also in line with the observed phase transformation from andalusite to sillimanite (Fig.…”