Browsing by Author "Sancy, Mamie"

Now showing 1 - 11 of 11
  • No Thumbnail Available
    Item
    Alumoxane film for corrosion protection of 2024 aluminum alloy
    (2023) Vejar, Nelson; Rojas, Javier; Alvarado, Claudia; Solis, Roberto; Pineda, Fabiola; Sancy, Mamie; Munoz, Lisa; Paez, Maritza
    Alumoxane film on anodized 2024 was obtained using stearic acid to prevent corrosion in a chloride medium. A cleaning pretreatment was applied to the metal surface to improve the adhesion and formation of the alumoxane film using three different sprays, ethanol, water, and NaOH. Then a molten stearic acid was applied to form an alumoxane. The obtained films were characterized by X-ray photoelectron spectroscopy and glow discharge optical emission spectroscopy, and electrochemical techniques, such as linear sweep voltammetry and electrochemical impedance spectroscopy, evaluated the corrosion protection. The surface analyses suggested an interaction between the boehmite and stearic acid to form alumoxane, and the electrochemical results revealed that alumoxane film using ethanol significantly improved the protection against corrosion due to the formation of compact and homogeneous films with a hydrophobic characteristic for the 2024-T3 alloy. & COPY; 2023 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
  • No Thumbnail Available
    Item
    Applicability of Paper and Pulp Industry Waste for Manufacturing Mycelium-Based Materials for Thermoacoustic Insulation
    (2024) Munoz, Hugo; Molina, Paulo; Urzua-Parra, Ignacio A.; Vasco, Diego A.; Walczak, Magdalena; Rodriguez-Grau, Gonzalo; Chateau, Francisco; Sancy, Mamie
    Cellulose and paper produce significant waste such as ash, activated sludge, and sludge from the pulp and paper industry. Depending on the raw material, legislation, and subprocesses, these sludges contain around 30-50% organic matter, mainly composed of less than 0.02 mm cellulose fibers and hemicellulose and lignin. This work used sludge from the pulp and paper industry as a substrate for manufacturing mycelium-based biomaterials using the white rot fungus Trametes versicolor. Chemical and surface analyses revealed the formation of new materials. Acoustic impedance analyses revealed that these materials have a noise reduction coefficient and sound absorption average comparable to extruded polystyrene and polyurethane. In addition, the material's thermal conductivity was near that of sheep wool. Therefore, the biomaterials fabricated using sludge and Trametes versicolor have the potential to be a game-changer in the industry as promising thermoacoustic insulators.
  • Thumbnail Image
    Item
    Biotribocorrosion of implants
    (Springer, 2016) Magdalena Walczak; Sancy, Mamie
    Biotribocorrosion can be broadly defined as all the aspects of tribocorrosion, i.e. the degradation of surfaces by the combined effect of corrosion and wear, related to biological systems. Whereas tribology alone, also known as frictioncorrosion, corrosion-wear, wear-corrosion or (micro) abrasion-corrosion, is concerned with the phenomena occurring at the interface of surfaces in mutual motion (friction, lubrication and wear), corrosion is the science and engineering of chemical and electrochemical reactions at the interface between a material and the environment it is exposed to. In the case of biotribocorrosion, the environment is necessarily that of a living organism or a combination of living organisms (biofilm). Although all materials may suffer biotribocorrosion it is especially pronounced in case of metallic alloys due to the electrochemical nature of their interaction with aqueous media such as the interior of a human body. Both corrosion and wear result in the weight loss over the exposed surface; however, the total weight loss of a tribosystem immersed in a corrosive environment is larger than a simple sum of the losses caused by corrosion and wear alone. In this chapter the principles of biotribocorrosion are presented and discussed for the specific case of alloys typically used in replacement of large joints. Since all the involved processes occur at the surface of the metal, first, the description of technical and natural surfaces is provided. The various interactions with environment and third bodies are then discussed, followed by a review of the methods of testing and mitigation of surface damage applicable for medical implants.
  • No Thumbnail Available
    Item
    Effect of Plasma Argon Pretreatment on the Surface Properties of AZ31 Magnesium Alloy
    (2023) Montero, Cecilia; Ramirez, Cristian Gino; Munoz, Lisa; Sancy, Mamie; Azocar, Manuel; Flores, Marcos; Artigas, Alfredo; Zagal, Jose H.; Zhou, Xiaorong; Monsalve, Alberto; Paez, Maritza
    Climate change has evidenced the need to reduce carbon dioxide emissions into the atmosphere, and so for transport applications, lighter weight alloys have been studied, such as magnesium alloys. However, they are susceptible to corrosion; therefore, surface treatments have been extensively studied. In this work, the influence of argon plasma pretreatment on the surface properties of an AZ31 magnesium alloy focus on the enhancement of the reactivity of the surface, which was examined by surface analysis techniques, electrochemical techniques, and gravimetric measurements. The samples were polished and exposed to argon plasma for two minutes in order to activate the surface. Contact angle measurements revealed higher surface energy after applying the pretreatment, and atomic force microscopy showed a roughness increase, while X-Ray photoelectron spectroscopy showed a chemical change on the surface, where after pretreatment the oxygen species increased. Electrochemical measurements showed that surface pretreatment does not affect the corrosion mechanism of the alloy, while electrochemical impedance spectroscopy reveals an increase in the original thickness of the surface film. This increase is likely associated with the high reactivity that the plasma pretreatment confers to the surface of the AZ31 alloy, affecting the extent of oxide formation and, consequently, the increase in its protection capacity. The weight loss measurements support the effect of the plasma pretreatment on the oxide thickness since the corrosion rate of the pretreated AZ31 specimens was lower than that of those that did not receive the surface pretreatment.
  • Thumbnail Image
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    On the validation and applicability of multiphysics models for hydrogen SOFC
    (2024) Diaz, Brayn; Celentano, Diego; Molina, Paulo; Sancy, Mamie; Troncoso, Loreto; Walczak, Magdalena
    Solid oxide fuel cells (SOFC) are a viable alternative for environmentally-friendly conversion of hydrogen into energy and multiphysics simulation can be used to diminish the experimental effort to improve their efficiency. However, an appropriate model of the involved processes and their parameters must be chosen. This paper studies the effects of choice between Maxwell-Stefan and Fick's law models, and uncertainty of electrode ionic conductivity sigma(ion) ion and anodic reference exchange current density i(0,ref,f), on cell performance as implemented in the COMSOL Multiphysics (R) software. In the case of Maxwell-Stefan, peak average power output increased by 21.9% as sigma(ion) varies from 10(-3) to 10(-1) S/cm, while the model based on Fick's law shows an increase of 55.2%. The Maxwell-Stefan model exhibits an increase in peak power of 6% as i(0,ref,f) ranges from 0.4 to 0.8 A/cm(2), and the Fick's law model an increase of 8.2%. The dependence of the Maxwell-Stefan model on sigma(ion) is characterized as logarithmic in the studied range. The Maxwell-Stefan model is deemed preferable because its lower sensitivity to the studied parameters helps mitigate uncertainty. It is concluded that despite its limitations, multiphysics modeling is a useful tool for directing research on SOFC materials owing to its descriptive potential.
  • No Thumbnail Available
    Item
    Simulation of the Influence of the Radial Graded Porosity Distribution on Elastic Modulus of γ/β Phase Ti-Based Alloy Foams for Bone Implant
    (2023) Aguilar, Claudio; Alfonso, Ismeli; Gonzalez, Daniel; Pio, Edgar; Neves, Guilherme Oliveira; De Barbieri, Flavio; Sancy, Mamie; Munoz, Lisa
    This research aims to examine how a radial graded porosity distribution affects the elastic modulus by conducting simulations on Ti-based alloy foams with face-centered cubic and body-centered cubic crystal structures. Four types of foams were analyzed; commercially pure-Ti, Ti-13Ta-6Mn (TTM), Ti-13Ta-(TT) and Ti-13Ta-6Sn (TTS), (all in at.%). Four radial graded porosity distribution configurations were modeled and simulated using the finite element analysis (FEA). The radial graded porosity distribution configurations were generated using a Material Designer (Ansys) with a pore range of 200 to 600 mu m. These radial graded porosity distributions had average porosity values of 0, 20, 30 and 40%. The consolidated samples that were obtained through a powder metallurgy technique in two step samples were synthesized using a powder metallurgy technique, with the elastic moduli values of the aforementioned Ti based alloys being measured by ultrasound using similar to 110, similar to 69, similar to 61 and similar to 65 GPa, respectively. The results showed that the modulus decreased as a function of porosity level in all simulated materials. The TTM, TT and TTS foams, with average porosities of 20, 30 and 40%, exhibited an modulus smaller than 30 GPa, which is a requirement to be used as a biomaterial in human bones. The TT foams showed the lowest modulus when compared to the other foams. Finally, certain theoretical models were used to obtain the modulus, the best being; the Gibson-Ashby model (alpha = 1 and n = 2.5) for the cp-Ti foams and Knudsen-Spriggs model (b = 3.06) for the TTM, TT and TTS foams.
  • No Thumbnail Available
    Item
    The Effect of the Addition of Copper Particles in High-Density Recycled Polyethylene Matrices by Extrusion
    (2022) Arcos, Camila; Munoz, Lisa; Cordova, Deborah; Munoz, Hugo; Walter, Mariana; Azocar, Manuel I.; Leiva, Angel; Sancy, Mamie; Rodriguez-Grau, Gonzalo
    In this study, the effect of the recycling process and copper particle incorporation on virgin and recycled pellet HDPE were investigated by thermo-chemical analysis, mechanical characterization, and antibacterial analysis. Copper particles were added to pellet HDPE, virgin and recycled, using a tabletop single screw extruder. Some copper particles, called copper nano-particles (Cu-NPs), had a spherical morphology and an average particle size near 20 nm. The others had a cubic morphology and an average particle size close to 300 nm, labeled copper nano-cubes (Cu-NCs). The thermo-chemical analysis revealed that the degree of crystallization was not influenced by the recycling process: 55.38 % for virgin HDPE and 56.01% for recycled HDPE. The degree of crystallization decreased with the addition of the copper particles. Possibly due to a modification in the structure, packaging organization, and crystalline ordering, the recycled HDPE reached a degree of crystallization close to 44.78% with 0.5 wt.% copper nano-particles and close to 36.57% for the recycled HDPE modified with 0.7 wt.% Cu-NCs. Tensile tests revealed a slight reduction in the tensile strength related to the recycling process, being close to 26 MPa for the virgin HDPE and 15.99 MPa for the recycled HDPE, which was improved by adding copper particles, which were near 25.39 MPa for 0.7 wt.% copper nano-cubes. Antibacterial analysis showed a reduction in the viability of E. coli in virgin HDPE samples, which was close to 8% for HDPE containing copper nano-particles and lower than 2% for HDPE having copper nano-cubes. In contrast, the recycled HDPE revealed viability close to 95% for HDPE with copper nano-particles and nearly 50% for HDPE with copper nano-cubes. The viability of S. aureus for HDPE was lower than containing copper nano-particles and copper nano-cubes, which increased dramatically close to 80% for recycled HDPE with copper nano-particles 80% and 75% with copper nano-cubes.