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300 results on '"Muñoz-Saldaña, J."'

6. Effect of pre-oxidation treatments on the structural, microstructural, and chemical properties of (Ni,Pt)Al systems

Author

Garcia-Herrera, J. E., Espinosa-Arbelaez, D. G., Caceres-Diaz, L. A., Mondragon-Rodriguez, G. C., Ruiz-Luna, H., Gonzalez-Hernandez, J., Munoz-Saldana, J., and Alvarado-Orozco, J. M.

Subjects
Condensed Matter - Materials Science
Abstract

The effect of isothermal pre-oxidation treatments on the \b{eta}-(Ni,Pt)Al + Ren\'e N5 system degradation is here reported. The oxidation treatments were carried out from 900 (mostly {\theta}-Al2O3 growing conditions) to 1200{\deg}C (mainly {\alpha}-Al2O3 growing conditions) for 5 h, under a purified Ar-stream with a fixed pO2= 1 x 10-5 atm. Results are discussed based on the correlation between the structural, microstructural and chemical properties of the \b{eta}-(Ni,Pt)Al BC showing that pre-oxidation parameters have an important effect on the multi-elemental counter diffusion phenomena along BC. For instance, a significant BC+IDZ thickness increase of 55% at 1200 {\deg}C was observed with respect to as-received sample just after 5 h of oxidation resulting in a severe BC degradation., Comment: 18 pages, 7 Figures

Published
2018

7. Influence of HVOF parameters on HAp coating generation: An integrated approach using process maps

Author

Hermann-Muñoz, J. A., Rincón-López, J. A., Clavijo-Mejía, G. A., Giraldo-Betancur, A. L., Alvarado-Orozco, J. M., De Vizcaya-Ruiz, A, and Muñoz-Saldaña, J.

Subjects
Physics - Applied Physics
Abstract

An experimental approach based on design of experiments, process maps and the analysis of deposition first stages to improve the biocompatibility of High-Velocity Oxygen Fuel (HVOF) hydroxyapatite (HAp) coatings is here presented. A two-level design of three factors (23) was performed using the stand-off distance (SOD), the fuel-oxygen ratio (F/O) and the powder feed rate (PFR). The effect of these experimental factors on the first stages of the coating formation was investigated to study the physical state of the particles before and after impacting the substrate. This study allowed the selection of the most suitable deposition parameter combinations to obtain HAp coatings with optimal crystallinity (> 45%), Ca/P ratio (approx. 1.67), phase content (> 95% of HAp), which guarantee the coatings mechanical stability and biocompatibility. The behavior of the coating within simulated body fluid (SBF) and cell culture (hFOB) was studied to analyze the apatite layer formation and the extracts cytotoxicity on human osteoblasts, respectively. The results show that the F/O ratio is the most influential factor on temperature and velocity on the in-flight particles and therefore on the coating properties. The SBF results confirmed the formation of an apatite layer after 14 days of immersion. Finally, the mitochondrial activity, measured by the MTS assay, and cell membrane integrity measures by LDH liberation assays, show that the coating released material does not induce toxicity on the exposed cells., Comment: Keywords: HAp coatings, HVOF, Process maps, Design of experiments, in vitro behavior

Published
2018
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34. Top–Down Approach for the Deposition of Photoactive (Na0.5Bi0.5)TiO3-Based Heterojunctions by Flame Spray: Analysis of Deposition Parameters.

Author

Gutiérrez-Pérez, A. I., Ayala-Ayala, M. T., Mora-García, A. G., Hernández-Navarro, C., Pérez, S., Diaz-Real, J. A., González Hernández, J., and Muñoz-Saldaña, J.

Subjects
PHOTOELECTROCHEMISTRY, COATING processes, FLAME spraying, GAS flow, ENVIRONMENTAL remediation, LIGHT absorption, REDSHIFT, FLAME
Abstract

Visible-light photoactive (Na0.5Bi0.5)TiO3 (NBT)-based heterojunctions have demonstrated their applicability in environmental remediation. The photocatalytic properties of NBT-based coatings are here reported. NBT-based materials were deposited by oxyacetylene flame spray (FS). The physicochemical properties were analyzed as a function of the spraying parameters: fuel/oxygen ratio (F/O), stand-off distance (SOD), and total gas flow (TF). A flame with reducing characteristics promotes the formation of TiO2 (anatase and rutile) and Bi4Ti3O12, while an oxidizing flame results in coatings rich in NBT and Bi4Ti3O12. The SOD mainly influences the degree of crystallinity, which is higher at shorter distances. Optical properties estimated by UV–VIS diffuse reflectance confirmed an increase in light absorption after the FS process, with an Eg red shift from 3.32 eV of the NBT powder to 2.63-2.96 eV of the coatings. These values are dependent on the F/O, with a significant Eg narrowing under reducing conditions. Photoelectrochemical measurements revealed that faster electron collection is obtained due to the transformations occurring throughout the FS process while still retaining nearly 70 and 88% of the photocurrent density (jph) at UV and visible light, respectively. These results suggest the great potential of the FS methodology to produce multiphase photocatalytic coatings by tuning the processing parameters. [ABSTRACT FROM AUTHOR]

Published
2023
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