Sharif Digital Repository

In this study, titanium substrates which previously oxidized through Micro arc oxidation method, was coated by Hydroxyapatite (HAp) coating once more by means of the same method. Morphology, topography and chemical properties as well as phase composition and thickness of layers were studied to reveal the effect of the electrolyte concentration on coating features. According to results, the obtained coatings are consisted of HAp and titania as the major phases along with minor amounts of calcium titanate and α-tri calcium phosphate. Ca and P are present on surface of obtained layers as well as predictable Ti and O based on the XPS results. Thickness profile of coatings figured out that by... 

Simple synthesis of silver doped TiO2 nanostructured layers by micro arc oxidation process is reported for the first time. The layers consisted of anatase and rutile phases whose characteristic XRD-peaks shifted toward lower diffraction angles when compared to the pure micro arc oxidized TiO 2 layers. Silver-doping was confirmed by XPS technique. The anatase phase crystalline size was determined as 27.6 and 21.8 nm for the layers grown under the voltages of 350 and 500 V. Employing a UV-Vis spectrophotometer, a red shift in the absorption edge of the layers was observed when silver was incorporated into the titania lattice  

Micro arc oxidation was employed to grow TiO2/hydroxyapatite composite layer on titanium substrate. The correlation between electrolyte concentration, diameter and density of the pores in fabricated layers was investigated. Therefore, the effect of electrolyte concentration on composition and morphology of grown layers was studied using SEM, EDX, XRD and XPS techniques. Samples were coated in electrolytes containing 5, 10 and 15 g/l calcium acetate and 1, 3 and 5 g/l β-glycerophosphate, at optimized voltage for 3 min. Pore size variations obey a similar pattern by the addition of both calcium acetate and β-glycerophosphatein various concentrations based on SEM observations. However,... 

Micro Arc Oxidation (MAO) process was utilized to fabricate nano bioceramic TiO 2-hydroxyapatite coatings on titanium substrates. Samples were produced in electrolytes contained 1 g/l β-glycerophosphate and 5, 10 and 15 g/l calcium acetate for 3, 6 and 10 min at 350 V. The techniques including XRD, XPS, SEM, FESEM and EDX were employed to study the effect of processing parameters. Hydroxyapatite, anatase, α-tri calcium phosphate and calcium titanate phases as well as 30-60 nm-size crystals were detected in the coating layer. It was also observed that the pore volume would increase by increasing the electrolyte concentration. The growth time was also found to influence the total pore volume.... 

Very recently, we fabricated (WO3)x-(TiO 2)1-x layers via micro-arc oxidation process under different applied voltages. Morphological and topographical studies, accomplished by SEM and AFM techniques, revealed that the pores size as well as the surface roughness increased with the voltage. Phase structure and chemical composition of the layers were also investigated by XRD and XPS and the results showed the grown layers consisted of titanium and tungsten oxides. It was found that WO3 dispersed in the TiO2 matrix and also doped into the TiO2 lattice. In addition, optical properties of the synthesized layers were studied employing a UV-vis spectrophotometer. Band gap energy of the layers was... 

S-doped TiO2 layers were grown on titanium substrates by MAO process. SEM results revealed a porous morphology with a pore size of 40-100 nm. Our XRD analysis showed that the anatase relative content reached its maximum value at the voltage of 500 V. The existence of sulfur in the states of S 4+ and S6+ which substituted Ti4+ in the titania crystalline lattice was confirmed by XPS results; meanwhile, no S 2- was detected. That is, a cationic doping was observed. EDS results showed that sulfur concentration in the layers increased with the voltage. The band gap energy was also calculated as 2.29 eV employing a UV-Vis spectrophotometer  

V2O5-TiO2 porous layers were synthesized via micro-arc oxidation for the first time. The effect of the applied voltage on morphology, composition, and photo-activity of the layers was investigated. The layers, which consisted of anatase, rutile, and vanadium pentoxide phases, revealed an enhanced photo-activity. About 93% of methylene blue solution was degraded on the synthesized layers after 120 min UV-irradiation with a reaction rate constant of k = 0.0228 min-1. The band gap energies of the vanadia-titania and pure titania layers were calculated as 2.56 and 3.39 eV, respectively  

Sulfur doped TiO2 layers containing nano/micro-sized pores were synthesized by micro-arc oxidation process. Effect of the applied voltage and the electrolyte composition on physical and chemical properties of the layers was investigated using SEM, AFM, XRD, XPS, and EDS techniques. A UV-vis spectrophotometer was also used to study optical properties of the layers. It was found that the doped layers were porous with a pore size of 40-170 nm. They consisted of anatase and rutile phases with varying fraction depending on the applied voltage and electrolyte concentration. Our XPS investigations revealed the existence of sulfur in the forms of S4+ and S6+ states which substituted Ti4+ in the... 

TiO2 layers were grown via pulse type microarc oxidation process under different applied voltages, frequencies, and duty cycles. Surface chemical composition and phase structure of the synthesized layers were studied utilizing X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Furthermore, scanning electron microscope (SEM) and atomic force microscope (AFM) were employed to investigate surface morphology and topography of the layers. It was revealed that the layers had a porous structure with both anatase and rutile phases. The anatase relative content in the layers increased with the applied frequency; meanwhile, it decreased with duty cycle at low applied voltages, but... 

WO3-TiO2 nano porous layers were synthesized by micro arc oxidation (MAO) process under different applied voltages in electrolytes containing sodium tungstate and phosphate salts with various concentrations. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and energy dispersive X-ray spectroscopy (EDS) techniques were employed to study phase structure and chemical composition of the layers. According to our data analysis, the nano porous layers consisted of anatase, rutile, and tungsten oxide phases with a varying fraction depending on the voltage and electrolyte concentration. Moreover, it was found that WO3 not only dispersed in the TiO2 matrix, but also doped into the TiO2... 

In this research, the effect of applied voltage and electrolyte concentration on structure, chemical composition, optical properties, and especially photo-catalytic activity of the TiO2 layers containing micro/nano-sized pores are discussed. TiO2 layers were synthesized by micro arc oxidation (MAO) process using different electrolyte concentrations and applied voltages. Surface structure of the layers was studied by scanning electron microscope (SEM); furthermore, energy dispersive spectrophotometry (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were employed to determine phase structure and chemical composition of the layers. Photo-activity of the...