Juan Alberto Alcántara-Cárdenas

The new requirements for materials with improved properties and resistance to hazardous aggressive environments is very important in industrial incinerators and stoves. Thus, the present manuscript is dedicated to the study of the chemical interaction between Fe-Cr alloys at high temperatures (500–600 °C). Four alloys with different Al, Si, and Mo chemical composition were tested to determine their resistance to active laboratory conditions. The conditions were established based in those inside waste disposal incinerators. Laboratory equipment was set up to reproduce an enclosed aggressive but controlled atmosphere. Cylinders filled with N₂ and O₂ generated an 8% vol, and other containers produced a 220 vppm of HCl, 360 Vppm of H₂O, and 200 vppm of SO₂. The exposition was not continuous because the goal was to analyze the material response along different exposition times. The corrosion products that resulted after chemical etching were characterized using Scanning Electron Microscopy (SEM), X-ray diffraction (XRD), and taking an average of various thermo-gravimetric measurements. The main products were Cr₂O₃, Fe₂O₃, Fe_0.6Cr_0.4, and Fe and Cr. The alloy with the best performance was found and theoretical principles of corrosion were analyzed to understand the corrosion mechanisms, which were driven by the formation of non-protective oxides.

Steel is the most used metallic material in the world and the demand for new improved high-quality steel products due to modern performance requirements has been increased. Steel is produced in small and big bulks in accordance with the necessities inside the secondary refining process such as Electric Arc Furnaces (EAF), Basic Oxygen Furnaces and AOD converters where pig-iron or scrap steel are mixed and recycled. Here steel is foundry, and additional elements like carbon and other ferrous-alloys or metals are added to obtain the chemical composition required; then, oxidation and reduction eliminate some undesirable inclusions. Moreover, these lances also blow gases towards the AOD converter to generate twirlings that move the melting steel inside. Therefore, it is so important to understand hydrodynamic behavior to improve industrial practices. In this work, different fine meshes were solved to guarantee the good concordance and fidelity of the results regarding the fluid flow dynamic in the melting bath inside an AOD converter under the influence of a blowing system. The results refer to the finest mesh which had the best fit and lower fluctuations. Then, this work focuses on the simulation of a configuration of seven nozzles disposed beside the first conic inverted wall, which are used to blow a mix of argon and oxygen to promote the movement of the melting steel inside and drag those undesirable materials up towards the slag. Initially in this work an approaching analysis was done by comparing the penetration of the gas blown to the melting bath. After verification a hydrodynamical analysis is done by comparing vertical and horizontal cut views of velocity fields and streamlines, contributing to the understanding of hydrodynamic behavior. Furthermore, a kinetic energy analysis was also done to support the profiting and dissipation of the energy inside the fluid.

Contamination of agricultural soil by potentially toxic elements (PTEs) can be caused by volcanic emissions and the use of agrochemicals; this threatens human food security, as PTEs can be transferred from the soil to plant tissues. Sorghum is the fifth most important cereal crop worldwide, and Mexico is one of the countries with the highest sorghum production. However, these crops are vulnerable to pests; thus, agrochemicals are applied to eliminate them. In this study, the identification and translocation of PTEs into sorghum plants grown in urban and volcanic areas of central Mexico were evaluated. Sorghum plants and soil samples were collected at four sites (S1, S2, S3, and S4) in these areas. The concentrations of PTEs in the soil samples and in the different tissues of the sorghum plants were determined by inductively coupled plasma optical emission spectroscopy. It was found that these sites are contaminated with PTEs, which were attributed to volcanic emissions and anthropogenic activities. In addition, the translocation factor values for zinc, nickel, and manganese showed that these PTEs were retained in the roots of the sorghum plants; however, the average concentrations of these PTEs in the grains of the plants were higher than the translocation factor values. This result indicates that the aerial parts of the sorghum plants could have been contaminated with PTEs from the air, which could then enter humans throughout the food chain.

Understanding the corrosion mechanism inside waste incinerators is very important in order to prevent possible damage due to high operational temperatures in chemical reactions for burning raw hazardous materials. Moreover, it is critical to understand the corrosion mechanisms to identify whether the oxides formed are protective or not, enabling us to prevent mass change on the steel walls of heat exchangers in waste incinerators. Thus, the present work comprises a high-temperature corrosion study on four Ferritic alloys with different contents of Al, Si, and Mo which are capable of replacing expensive materials such as stainless steel. The corrosion behavior was evaluated in atmospheres with H₂O_(g), HCl_(g), and an additional mixture of both atmospheres at 500 and 600 °C over 300 h. A thicker but porous heterogeneous oxide scale was formed in the HCl atmosphere, mainly composed of Fe₂O₃ and Cr₂O₃. Under the water vapor atmosphere, the presence of (Fe0.6Cr0.4)₂O₃ was observed. Meanwhile, in the mixed atmosphere, the presence of FeCr₂O₄, Cr₂SiO₄, and (CrFe)₂O₃ was observed. The biggest mass loss was measured inside the water vapor atmosphere. In comparison, inside the mixed atmosphere, the oxide scale was thinner. Finally, it was concluded that the alloy with the best corrosion resistance in HCl and H₂O atmospheres was Fe9Cr1.5AlSi3Mo steel.

La implementación de estrategias eficientes para un manejo integral de los residuos sólidos urbanos está basada en el diagnóstico de la generación de residuos que permiten identificar, cuantificar y evaluar los residuos sólidos generados por las actividades humanas. Algunas herramientas que sirven para llevar a cabo este análisis se fundamentan en normas locales nacionales, como la NMX-AA-015-1985 y la NADF-024-AMBT-2013, de las cuales se obtienen datos sobre la clasificación, cantidad y origen de los residuos. Asimismo, como información complementaria, se pueden identificar cuáles son las empresas predominantes responsables de la generación de los empaques plásticos encontrados durante la auditoría de marcas, la cual sirve para asignar responsabilidades a las compañías que contribuyen a la generación de este tipo de desechos. La implementación de este tipo de estrategias permite tomar mejores decisiones en política pública y regulaciones; también contribuye a sensibilizar a la población sobre la importancia de una correcta gestión de residuos, e invita a los consumidores a tomar conciencia al elegir productos de empresas comprometidas con la sostenibilidad.

Los residuos peligrosos del sector de hidrocarburos (RPSH) en México representan riesgos significativos para el medioambiente y la salud. En la región petrolera conocida como la Faja de Oro, que incluye Tamaulipas, Veracruz y Tabasco, no existe un control ni inventario actualizado sobre la generación y disposición de estos residuos. Se generan en diversas etapas, como la exploración, producción y refinación, y su manejo es deficiente. Este análisis aborda la clasificación, manejo y disposición de los RPSH, y compara el marco legal vigente con la realidad de las operaciones en el sector. Se concluye que las leyes mexicanas en esta área no se ajustan a las prácticas actuales de la industria, y algunas normativas son obsoletas. Además, los residuos varían según la operación, siendo distintos los producidos en perforación y fracking. Finalmente, se propone una clasificación más precisa de los residuos basada en el tipo de operación, con el fin de mejorar su gestión y reducir los impactos negativos.

This study presents the synthesis, crystal structure determination and luminescence properties of three novel mononuclear europium (III) complexes constructed from sodium benzoate and the three different isomers of biphenylcarboxylic acid (2-, 3-, and 4-). All complexes share a common structural core; consisting of a single europium (III) ion coordinated by three bidentate benzoate ligands and two monodentate biphenylcarboxylate ligands. The synthesis followed a two-step strategy: first, a benzoate-based precursor complex was prepared by displacing the chloride and water molecules from europium (III) chloride hexahydrate with sodium benzoate by chelating process. The remaining water ligands were substituted with each biphenylcarboxylic acid isomer yielding solvent-free luminescent complexes. The structural characterization involved thermogravimetric analysis (TGA) to confirm the complete elimination of water molecules. The crystal structures of the europium (III) complexes were solved from X-ray powder diffraction data using the EXPO2014 software; and were deposited in the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers 2477668, 2477667 and 2476992. The photoluminescence properties, including excitation, emission, decay time, and color purity, were studied. The influence of each biphenylcarboxylate isomer on the symmetry of the europium coordination sphere was assessed by calculating the asymmetry ratio, R = (I⁵D₀ → ⁷F₂/I⁵D₀ → ⁷F₁), revealing clear differences in emission intensity and symmetry distortion, directly correlated to the ligand isomer used. These findings demonstrate the antenna effect and tunable luminescence enabled by ligand design, offering potential applications in optoelectronics, bio-imaging and others.

Metallic materials are formed with grain structures which are naturally formed during solidification or modified after any manufacturing process, such as rolling, cutting, machining, welding, etc. Grains with different sizes and geometrical morphologies have a strong influence on the micro- and macro properties of metallic materials. This is the reason why many authors have worked on computer simulations based on numerical methods, applying chaos theory and using graphical techniques for its reproduction. Thus, this manuscript is focused on the comparison between grain structures obtained computationally with grains in real metallic samples. The analyzed structures in this work were polygonal and equiaxed, they resulted from a dynamic evolution in which nucleation and growth procedures were simulated. Then, computational algorithms and standardized procedures were used for characterization. Thus, in order to demonstrate the geometrical similarities and differences in mathematical terms, similarities between sample features were calculated, measuring sizes and populations along different directions which could be used to establish rules and parameters for the appropriate control of nucleation and growth. Furthermore, the influence of the computational methods for simulation and characterization are also described in detail.