Browsing by Author "Guerra, Carolina"

Now showing 1 - 13 of 13
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    A novel optimization framework for minimizing the surface roughness while increasing the material processing rate in the SLM process of 316L stainless steel
    (2023) La Fe-Perdomo, Ivan; Ramos-Grez, Jorge Andres; Quiza, Ramon; Jeria, Ignacio; Guerra, Carolina
    Purpose - 316 L stainless steel alloy is potentially the most used material in the selective laser melting (SLM) process because of its versatility and broad fields of applications (e.g. medical devices, tooling, automotive, etc.). That is why producing fully functional parts through optimal printing configuration is still a key issue to be addressed. This paper aims to present an entirely new framework for simultaneously reducing surface roughness (SR) while increasing the material processing rate in the SLM process of 316L stainless steel, keeping fundamental mechanical properties within their allowable range.
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    A Tribological and Ion Released Research of Ti-Materials for Medical Devices
    (2021) Silva, Daniela ; Montero, M. Cecilia ; Guerra, Carolina ; Martinez Ugalde, Carola ; Li, Xuejie ; Ringuedé, Armelle ; Cassir, Michel ; Ogle, Kevin ; Guzman, Danny ; Aguilar, Claudio ; Paez, Maritza ; Sancy, Mamié
    The increase in longevity worldwide has intensified the use of different types of prostheses for the human body, such as those used in dental work as well as in hip and knee replacements. Currently, Ti-6Al-4V is widely used as a joint implant due to its good mechanical properties and durability. However, studies have revealed that this alloy can release metal ions or particles harmful to human health. The mechanisms are not well understood yet and may involve wear and/or corrosion. Therefore, in this work, commercial pure titanium and a Ti-6Al-4V alloy were investigated before and after being exposed to a simulated biological fluid through tribological tests, surface analysis, and ionic dissolution characterization by ICP-AES. Before exposure, X-ray diffraction and optical microscopy revealed equiaxed alpha-Ti in both materials and beta-Ti in Ti-6Al-4V. Scratch tests exhibited a lower coefficient of friction for Ti-6Al-4V alloy than commercially pure titanium. After exposure, X-ray photoelectron spectroscopy and surface-enhanced Raman spectroscopy results showed an oxide film formed by TiO2, both in commercially pure titanium and in Ti-6Al-4V, and by TiO and Al2O3 associated with the presence of the alloys. Furthermore, inductively coupled plasma atomic emission spectroscopy revealed that aluminum was the main ion released for Ti-6Al-4V, giving negligible values for the other metal ions.
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    Effects of laser surface modification on stainless steel 316L thin annular discs under radial and cartesian scans
    (2023) Gonzalez, Matias; Ramos Grez, Jorge; Jeria, Ignacio; Guerra, Carolina; Solis, Roberto; Carvajal, Linton
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    Electrochemical analysis of carbon steel embedded in mortars with pretreated copper tailings as supplementary cementitious material
    (2024) Sepulveda-Vasquez, Carlos; Carrasco-Astudillo, Nicolas; Munoz, Lisa; Molina, Paulo; Ringuede, Armelle; Guerra, Carolina; Sancy, Mamie
    The cement industry, responsible for 8% of global greenhouse gas emissions, necessitates developing sustainable materials to replace cement partially. This investigation examined the feasibility of using copper tailings, a byproduct of mining, as alternative materials for cement within mortars and reinforced mortars (0-15 wt%). The microstructural composition of the tailings was analyzed using scanning electron microscopy and X-ray diffraction. The corrosion resistance of mortars reinforced with copper tailings was elucidated through opencircuit potential measurements and electrochemical impedance spectroscopy. The results showed that incorporating 5 and 10 wt% of sieved copper tailings improved the mechanical strength and significantly enhanced the electrochemical stability, as indicated by more noble open-circuit potential values. Specifically, the sieved tailings played a crucial role in forming a more stable oxide film, which was confirmed by higher impedance values, suggesting a reduced corrosion rate. In contrast, mortars with 5 wt% of milled tailings exhibited properties like those of the control group. This electrochemical understanding highlights the potential of processed copper tailings in mitigating the environmental impact of cement production and enhancing the durability of cementitious composites.
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    Evolution of corrosion products on ASTM A36 and AISI 304L steels formed in exposure to molten NaNO3-KNO3 eutectic salt: Electrochemical study
    (2022) Pineda, Fabiola; Walczak, Magdalena; Vilchez, Franco; Guerra, Carolina; Escobar, Rodrigo; Sancy, Mamie
    Thermal energy storage uses molten salt as a heat transfer fluid implies a high corrosion risk. In this work, ASTM A36 and AISI 304L steel, exposed to solar salt at 390 degrees C for 21 days, were studied by electrochemical impedance spectroscopy. The results were validated by mass gain and the characterization of corrosion products. Carbon steel revealed a porous behavior related to the formation of corrosion products based on iron oxides, as described the De Levies theory, whereas stainless steel showed the formation of a passive multilayer of iron and chromium oxides, which was adjusted to the Power-law model.
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    Influence of Bacillus safensis and Bacillus pumilus on the electrochemical behavior of 2024-T3 aluminum alloy
    (2022) Vejar, Nelson; Gutierrez, Sebastian; Tareelap, Napachat; Alvarado, Claudia; Solis, Roberto; Guerra, Carolina; Pineda, Fabiola; Sancy, Mamie; Paez, Maritza
    In this work, electrochemical techniques were employed to evaluate the contribution to the corrosion and corrosion inhibition of 2024-T3 aluminum alloy by two Gram-positive bacteria. In addition, polarized impedance was used to determine the microbial effect on the cathodic and anodic reactions. These microorganisms were collected from a tropical environment due to the favorable bacterial growth of this kind of climate. The alloy was exposed to the sterile medium and inoculated for up to 12 days evaluating the microbiological and electrochemical behavior. The results by linear scanning voltammetry showed that the B. safensis and B. pumilus caused a dual effect of increase and decrease currents, and through electrochemical impedance spectroscopy, showed in some cases, inductive loop, which could be associated with local corrosion and another case, an increasing impedance could be related to protection. In addition, a morphological characterization was performed by scanning electron microscopy before and after exposure, showing an increase in copper precipitation in the vicinity of the intermetallic phases by bacteria, attributed to local corrosion, but, in general, a significant effect of damages was not observed. (C) 2021 Elsevier B.V. All rights reserved.
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    Microstructure and Mechanical Properties of Cu-11Al-5Ni-4Fe wt% Manufactured by LPBF
    (2023) Guerra, Carolina; Ramos Grez, Jorge; La Fe-Perdomo, Ivan; Castillo, Alejandro; Walczak, Magdalena
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    Microstructure simulation and experimental evaluation of the anisotropy of 316 L stainless steel manufactured by laser powder bed fusion
    (2023) Omar Barrionuevo, German; Ramos Grez, Jorge; Walczak, Magdalena; Sanchez-Sanchez, Xavier; Guerra, Carolina; Debut, Alexis; Haro, Edison
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    On the effect of simulated contamination of chlorides and sulfates on steel rebar corrosion: Electrochemical behavior and surface analysis
    (2022) Melo, Paula; Echague, Matias; Guerra, Carolina; Jin, Qingxu; Sancy, Mamie; Paul, Alvaro
    To understand the effect of sulfate ions on the chloride-induced corrosion of reinforced concrete, this study focuses on the electrochemical behavior and surface analysis of standarded carbon steel that was exposed to simulated pore solutions, with different combinations of high and low chloride and sulfate concentrations. Linear scanning voltammetry and electrochemical impedance spectroscopy were used to monitor the corrosion reaction. Steel surface was characterized by X-ray photoelectron spectroscopy and field emission scanning electron mi-croscopy. Results indicate that the presence of sulfate affects the electrochemical behavior of steel corrosion at a low and high chloride concentration, where the capability of the corrosion protective layer was influenced by the increase of the sulfate and chloride content. Calcium carbonate deposits were observed at the surface of corroded samples, where higher precipitation of calcium carbonate crystals on carbon steel surface is associated with higher rates of localized corrosion.
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    Practical issues concerning the use of optical coherence tomography in multiple sclerosis in Latin America: Discussion from 19 centres on behalf of the Foro Latam EM study group
    (Elsevier, 2025) Ciampi Diaz, Ethel Leslie; Garcia, Lorena; Carcamo Oyarzo, Claudio Marcelo; Soler León, Bernardita María; Becker, Jefferson; Carra, Adriana; Correa-Diaz, Edgar; Cortes, Fernando; Garcia Bonitto, Juan; Guerra, Carolina; Macias, Miguel Angel; Martinez, Alejandra; Novarro, Nelson; Rivera-Sarabia, Linda; Rocha, Valeria; Rodriguez, Virginia; Sato, Douglas; Steinberg, Judith; Trevino Frenk, Irene; Vasquez, Guido; Pena, Luis
    The 2024 McDonald Criteria now include the optic nerve as the fifth topography for dissemination in space. Optical coherence tomography (OCT) is a valuable biomarker for the diagnosis, prognosis and monitoring of multiple sclerosis (MS). A panel of MS neurologists from 19 centres across 9 Latin American (LATAM) countries discussed OCT use, access, standardized protocols and research potential. They found inequities in OCT access between private (80%) and public healthcare (44%). Only 9 centres had standardized protocols, 50% of which followed the OSCAR-IB consensus criteria for retinal OCT quality assessment and 53% had a neuro-ophthalmologist. The panel concluded that OCT should be available in all MS centres and that standardized acquisition and reporting, as well as improved knowledge of OCT use, in clinical practice are necessary. OCT has significant research potential in LATAM that requires further development and implementation.
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    Practical issues concerning the use of optical coherence tomography in multiple sclerosis in Latin America: Discussion from 19 centres on behalf of the Foro Latam EM study group
    (2025) Ciampi Diaz, Ethel Leslie; Garcia, Lorena; Carcamo Oyarzo, Claudio Marcelo; Soler León, Bernardita María; Becker, Jefferson; Carra, Adriana; Correa-Diaz, Edgar; Cortes, Fernando; Garcia Bonitto, Juan; Guerra, Carolina; Macias, Miguel Angel; Martinez, Alejandra; Novarro, Nelson; Rivera-Sarabia, Linda; Rocha, Valeria; Rodriguez, Virginia; Sato, Douglas; Steinberg, Judith; Trevino Frenk, Irene; Vasquez, Guido; Pena, Luis
    The 2024 McDonald Criteria now include the optic nerve as the fifth topography for dissemination in space. Optical coherence tomography (OCT) is a valuable biomarker for the diagnosis, prognosis and monitoring of multiple sclerosis (MS). A panel of MS neurologists from 19 centres across 9 Latin American (LATAM) countries discussed OCT use, access, standardized protocols and research potential. They found inequities in OCT access between private (80%) and public healthcare (44%). Only 9 centres had standardized protocols, 50% of which followed the OSCAR-IB consensus criteria for retinal OCT quality assessment and 53% had a neuro-ophthalmologist. The panel concluded that OCT should be available in all MS centres and that standardized acquisition and reporting, as well as improved knowledge of OCT use, in clinical practice are necessary. OCT has significant research potential in LATAM that requires further development and implementation.
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    Simultaneous Optimization of Surface Roughness and Mechanical Properties of 316L Produced by LB-PBF Using Grey Relational Analysis Complemented by Residual Stress Analysis
    (2023) La Fe-Perdomo, Ivan; Ramos Grez, Jorge; Jeria, Ignacio; Guerra, Carolina; Zambrano-Robledo, Patricia